5599 lines
126 KiB
Plaintext
5599 lines
126 KiB
Plaintext
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\pdf_title "Net-zero Cable Repair Ship"
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\pdf_author "Andy Pack"
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Andy Pack
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January 2021
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Sustainable Cable Ship - Group 1
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\begin_layout Section
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Introduction
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\begin_layout Subsection
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Sustainability
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\end_layout
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Sustainability defines operating such that the needs of the present can
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be satisfied without compromising the needs of the future,
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key "BrundtlandReport"
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literal "false"
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.
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Although colloquially associated with environmental concerns, sustainability
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is a wide field with 3 pillars,
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key "un-assembly-sustainability-pillars"
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literal "false"
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,
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Economic
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Social
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\begin_layout Itemize
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Environmental
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\end_layout
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\begin_layout Standard
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Environmental sustainability includes consideration of concepts such as
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energy usage and production, emissions, water usage and quality, food and
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land usage.
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\end_layout
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\begin_layout Standard
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The social aspect includes consideration for the effects of war, labour
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standards, social justice and poverty among others.
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\end_layout
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\begin_layout Standard
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Economic sustainability can define economic growth that takes into account
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the above concepts.
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For example, economic development is typically measured in gross domestic
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product (GDP), however this metric does not include social aspects such
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as equality, a population's average wage or access to healthcare.
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\end_layout
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\begin_layout Standard
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There are many formal initiatives and goals for sustainable development,
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the main strategies with which this project aligns itself are the United
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Nation's Sustainable Development Goals.
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\end_layout
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\begin_layout Part
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Vessel Study
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\end_layout
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\begin_layout Section
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Propulsion
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\end_layout
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\begin_layout Subsection
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Power Requirements
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\end_layout
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\begin_layout Subsubsection
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Hotel Load [AP]
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\end_layout
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\begin_layout Standard
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The hotel load is defined as the energy usage not related to the propulsion
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including lighting and power outlets.
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An estimation of this load for the vessel was modelled and a breakdown
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can be seen in figure
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\begin_inset CommandInset ref
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reference "fig:hotel-load"
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plural "false"
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\end_inset
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.
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The total load was estimated at 680 kWh per day.
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As can be seen, the oven and food refrigeration make up the majority and
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so 3 methods for refrigeration were investigated in order to find the most
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energy efficient solution with SDG 7 in mind.
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These included a collection of standard upright fridges, all-in-one cold
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rooms and a bespoke cold room.
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All-in-one cold-rooms were the most energy efficient and were selected
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as a result.
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\begin_layout Plain Layout
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Breakdown of hotel load energy for the surface vessel, totals to
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680 kW
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name "fig:hotel-load"
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\end_layout
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\begin_layout Section
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Efficiency Investigations
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\end_layout
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\begin_layout Subsection
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Solar [AP]
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\end_layout
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\begin_layout Standard
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The scope of the vessel's solar energy capabilities were investigated with
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the intention of supplementing the chemical energy of the ammonia fuel
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cells.
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The capabilities of photovoltaic cells covering an area of the vessel's
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footprint are considered and compared with both the financial and carbon
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cost in an effort to determine whether the proposal would be effective
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in achieving the goal of net-zero operations and SDG 9 specifically.
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\end_layout
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\begin_layout Standard
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The expected available area capable of hosting photovoltaic cells was estimated
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to be 26m x 30m or 780 m
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\begin_inset script superscript
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2
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\end_layout
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.
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Using the same solar panel modelling of GEORGE, this would equate to 441
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panels with a max power of 176 kW, an order of magnitude smaller than the
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ammonia fuel cell capabilities.
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This would represent 123 tonnes of embodied carbon which could be reduced
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to 65 tonnes by recycling following decommission.
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\end_layout
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\begin_layout Standard
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As a result of this projection, it is proposed that the vessel is not fitted
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with solar panels.
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As the other energy being generated via the ammonia cells is already carbon-zer
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o (assuming the use of
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\emph on
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green ammonia
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\emph default
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), the embodied carbon of the panels would not be offset through their own
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use.
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This carbon cost would need to be offset via the project-level offsetting
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processes, see JASON.
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The benefits would be limited to the financial savings of reducing fuel
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usage, limiting carbon cost is more of a priority for this project.
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\end_layout
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\begin_layout Section
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Energy Storage [AP]
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\begin_inset CommandInset label
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LatexCommand label
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name "sec:Energy-Storage"
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\end_inset
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\end_layout
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\begin_layout Standard
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The use of ammonia fuel cells for power generation on the vessel provides
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the opportunity to eliminate direct CO
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\begin_inset script subscript
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\begin_layout Plain Layout
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2
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\end_layout
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\end_inset
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emissions from the vessel; when produced using renewable energy (
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\emph on
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green ammonia
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\emph default
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), the entire fuel supply chain from production to use can be made carbon-neutra
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l.
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From an electrical perspective, however, the current-voltage characteristics
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of such a system must be considered.
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\end_layout
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\begin_layout Standard
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Figure
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reference "fig:fuel-cell-iv"
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plural "false"
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caps "false"
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noprefix "false"
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\end_inset
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presents the I-V characteristics for a typical fuel cell, it can be seen
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that drawing more current from a cell reduces its voltage.
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As
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\begin_inset Formula $P=IV$
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\end_inset
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, this inverse relationship results in an optimum current draw to operate
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with the highest efficiency or power density.
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Operating outside of this area will accentuate losses, the dominant effects
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of each operating region can be seen in figure
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\begin_inset CommandInset ref
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reference "fig:fuel-cell-iv-losses"
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plural "false"
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caps "false"
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noprefix "false"
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\end_inset
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.
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Comparing the two graphs, it can be seen that the optimum operating state
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would be in R-2 (figure
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "fig:fuel-cell-iv-losses"
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plural "false"
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caps "false"
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noprefix "false"
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\end_inset
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); in fact drawing excess current and pushing into R-3 can damage the cell,
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\begin_inset CommandInset citation
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key "elec-a2z-fuel-cell-iv"
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literal "false"
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.
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filename fuel-cell-i-v.gif
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width 60col%
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\begin_layout Plain Layout
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\begin_inset Caption Standard
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\begin_layout Plain Layout
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Current-Voltage characteristics for a typical fuel cell, rated operating
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point highlighted,
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\begin_inset CommandInset citation
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LatexCommand cite
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key "strathclyde-fuel-cell-efficiency"
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literal "false"
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\end_inset
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LatexCommand label
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name "fig:fuel-cell-iv"
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wide false
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filename fuel-cell-iv-a2z.jpg
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lyxscale 50
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width 60col%
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\end_inset
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.
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\end_layout
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\begin_layout Plain Layout
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\begin_inset Caption Standard
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\begin_layout Plain Layout
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Current-Voltage characteristics for a fuel cell with dominant losses highlighted
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in each operating region,
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\begin_inset CommandInset citation
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LatexCommand cite
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key "elec-a2z-fuel-cell-iv"
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literal "false"
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\end_inset
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\begin_inset CommandInset label
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LatexCommand label
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name "fig:fuel-cell-iv-losses"
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\end_inset
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\end_layout
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\end_inset
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\end_layout
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\begin_layout Plain Layout
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\end_layout
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\end_inset
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\end_layout
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\begin_layout Standard
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From these figures, fuel cells could be described as being sensitive to
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a noisy or dynamic load such as changes in thrust and therefore the required
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power can vary quickly.
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For example, when using dynamic positioning in a high sea state.
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Ideally, the use of more cells operating in their optimum state would be
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preferred over increasing the draw on a smaller population
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\begin_inset Flex TODO Note (Margin)
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status open
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\begin_layout Plain Layout
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Is this valid?
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\end_layout
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\end_inset
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.
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However, this increase in active cells is not an instantaneous operation
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and cells require time to reach their optimum state.
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To allow this focus on efficiency, the load including hotel and propulsion
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power should be decoupled from the fuel cells with an electrical storage
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buffer in between.
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This will allow the buffer to absorb spikes in load draw and allow the
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fuel cells to increase power output by increasing active cells instead
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of individual draw.
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This initiative was conducted with SDGs 7 (Affordable and clean energy)
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|
and 12 (Responsible consumption and production) in mind, although goal
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14 (Life below the water) is also important due to the materials involved
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in the considered solutions.
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\end_layout
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\begin_layout Standard
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The following section outlines solutions for this described buffer, rechargeable
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batteries are the natural option and as such this is considered first.
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Other, innovative solutions are also outlined before the implementation
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of a suitable solution is presented along with the safety and financial
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implications of such a system.
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\end_layout
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\begin_layout Subsection
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Rechargeable Battery Chemistry
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\end_layout
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\begin_layout Standard
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There are many different methods for constructing a traditional rechargeable
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battery or
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\emph on
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secondary cell
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\emph default
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|
; the chemistry of the reactants determines the characteristics of the system
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|
as well as having drastic implications on the safety and sustainability.
|
|
Secondary cells are a consumable item, their components degrade with usage
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|
and this lifespan will be reduced if not constructed and maintained correctly.
|
|
This only accentuates the importance of the solution's sustainability as
|
|
it constitutes a significant amount of material which will periodically
|
|
require replacing and disposal.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="8" columns="7">
|
|
<features tabularvalignment="middle">
|
|
<column alignment="center" valignment="middle" width="15col%">
|
|
<column alignment="center" valignment="middle" width="10col%">
|
|
<column alignment="center" valignment="middle" width="10col%">
|
|
<column alignment="center" valignment="middle" width="10col%">
|
|
<column alignment="center" valignment="middle" width="10col%">
|
|
<column alignment="center" valignment="middle" width="10col%">
|
|
<column alignment="center" valignment="middle" width="10col%">
|
|
<row>
|
|
<cell alignment="center" valignment="top" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
NiCd
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
NiMH
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
Lead Acid
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
Li-ion
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
Li-ion Polymer
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
Reusable Alkaline
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Gravimetric Energy Density
|
|
\begin_inset Newline newline
|
|
\end_inset
|
|
|
|
|
|
\series bold
|
|
(Wh/kg)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
45 - 80
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
60 - 120
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
30 - 50
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
110 - 160
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
100 - 130
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
80 (initial)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Cycle Life
|
|
\begin_inset Newline newline
|
|
\end_inset
|
|
|
|
|
|
\series bold
|
|
(to 80% of initial)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1500
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
300 - 500
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
200 - 300
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
500 - 1000
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
300 - 500
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
50
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Self-discharge / Month
|
|
\begin_inset Newline newline
|
|
\end_inset
|
|
|
|
|
|
\series bold
|
|
(room temperature)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20%
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
30%
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5%
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10%
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
~10%
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0.3%
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Load Current
|
|
\begin_inset Newline newline
|
|
\end_inset
|
|
|
|
|
|
\series bold
|
|
(Peak)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
>2C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
>2C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0.5C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Load Current
|
|
\begin_inset Newline newline
|
|
\end_inset
|
|
|
|
|
|
\series bold
|
|
(Ideal)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Formula $\leq$
|
|
\end_inset
|
|
|
|
0.5C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0.2C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Formula $\leq$
|
|
\end_inset
|
|
|
|
1C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Formula $\leq$
|
|
\end_inset
|
|
|
|
1C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Formula $\leq$
|
|
\end_inset
|
|
|
|
0.2C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Operating Temperature
|
|
\begin_inset Newline newline
|
|
\end_inset
|
|
|
|
|
|
\series bold
|
|
(discharge only)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-40 - 60°C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-20 - 60°C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-20 - 60°C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-20 - 60°C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0 - 60°C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="middle" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0 - 65°C
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Commercial Use Since
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1950
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1990
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1970 (sealed lead acid)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1991
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1999
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1992
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset VSpace smallskip
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "battery-uni-chemistry-types"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Comparison of physical characteristics for common rechargeable battery chemistry
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "tab:battery-chemistry-stats"
|
|
|
|
\end_inset
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\end_layout
|
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\end_inset
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\end_layout
|
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|
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\end_inset
|
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\end_layout
|
|
|
|
\begin_layout Standard
|
|
Table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "tab:battery-chemistry-stats"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
outlines the relevant characteristics for the most common configurations
|
|
of rechargeable battery.
|
|
As can be seen, Lithium-ion technology leads the other solutions in most
|
|
of the categories.
|
|
While Nickel-Cadmium has a higher lifespan than Li-ion there are other
|
|
factors that led to this being discounted.
|
|
NiCd suffers from the
|
|
\emph on
|
|
memory effect
|
|
\emph default
|
|
, where frequent charge/discharge cycles lead to the battery
|
|
\emph on
|
|
remembering
|
|
\emph default
|
|
the point at which charging began and experiencing a drop in voltage past
|
|
this point.
|
|
Additionally, Cadmium is a highly toxic heavy metal, requiring specialist
|
|
containment; in fact, many types of Cadmium battery are now banned in the
|
|
EU.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Lithium-ion batteries are a mature domain and one of active research; they
|
|
are essentially the standard for portable electronics and the growing electric
|
|
vehicle market.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Innovative Solutions
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Traditional rechargeable batteries of varying chemistry are currently the
|
|
standard for this domain.
|
|
However, other systems utilising different technologies were also considered.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Flow Battery
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
A redox flow battery is a type of electrochemical cell where the energy
|
|
is stored in two chemicals brought together at a membrane in order to facilitat
|
|
e ion exchange and create a potential difference or voltage.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This can be structured to function like a rechargeable battery as the chemical
|
|
reaction is reversible.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are a number of advantages to a system like this, for example it is
|
|
less sensitive than Lithium-ion to overcharge and overdischarge with no
|
|
need for equalisation charging.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
wide false
|
|
sideways false
|
|
status open
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|
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|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
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\begin_inset Tabular
|
|
<lyxtabular version="3" rows="11" columns="3">
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<features tabularvalignment="middle">
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<column alignment="center" valignment="top">
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<column alignment="center" valignment="top">
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<column alignment="center" valignment="top">
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<row>
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<cell alignment="center" valignment="top" bottomline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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\end_layout
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\end_inset
|
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</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Energy Density (WhL
|
|
\begin_inset script superscript
|
|
|
|
\begin_layout Plain Layout
|
|
-1
|
|
\end_layout
|
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\end_inset
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)
|
|
\end_layout
|
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|
\end_inset
|
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</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
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|
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\begin_layout Plain Layout
|
|
Power Density (WL
|
|
\begin_inset script superscript
|
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|
|
\begin_layout Plain Layout
|
|
-1
|
|
\end_layout
|
|
|
|
\end_inset
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)
|
|
\end_layout
|
|
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|
\end_inset
|
|
</cell>
|
|
</row>
|
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<row>
|
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
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\begin_layout Plain Layout
|
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Bromine-polysulphide
|
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\end_layout
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\end_inset
|
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</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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20 - 35
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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60
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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Vanadium-vanadium
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\end_layout
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\end_inset
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</cell>
|
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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20 - 35
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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60 - 100
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\end_layout
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\end_inset
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</cell>
|
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</row>
|
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<row>
|
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
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\begin_layout Plain Layout
|
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Iron-chromium
|
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\end_layout
|
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|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
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\begin_layout Plain Layout
|
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20 - 35
|
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\end_layout
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\end_inset
|
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</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
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\begin_layout Plain Layout
|
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6
|
|
\end_layout
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\end_inset
|
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</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
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Vanadium-bromine
|
|
\end_layout
|
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|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
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\begin_layout Plain Layout
|
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20 - 35
|
|
\end_layout
|
|
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|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
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|
\begin_layout Plain Layout
|
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50
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Zinc-/bromine
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20 - 35
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
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40
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Zinc-cerium
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20 - 35
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
50
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Soluble lead-acid
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20 - 35
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
25
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Conventional lead-acid
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
60 - 80
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
230
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Lithium-ion
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
150 - 200
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
275
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Nickel-metal-hydride
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
100 - 150
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
330
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Energy and power densities for typical redox flow battery chemistry (top)
|
|
compared to traditional rechargeable cells (bottom),
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "flow-battery-energy-density"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "tab:flow-battery-energy-density"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The main disadvantage relevant to the required applications is the required
|
|
space and weight.
|
|
Flow batteries typically have a much lower energy and power density than
|
|
traditional rechargeable batteries, a comparison of values for various
|
|
structures can be seen in table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "tab:flow-battery-energy-density"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
Both values are critical for the vessel; as a buffer for absorbing large
|
|
peaks from the propulsion, it is key that a high power can be drawn from
|
|
the solution.
|
|
From the presented values, Lithium-ion can provide between about 3 and
|
|
7 times as much power draw than redox flow batteries.
|
|
Looking to energy or capacity density, Li-ion is roughly 4 to 10 times
|
|
higher.
|
|
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Sentence on energy density
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
To achieve the capacity and power requirements defined by the propulsion
|
|
system, a flow battery would likely need vastly more space and weigh significan
|
|
tly more.
|
|
The weight penalty would prove more damaging as this would require more
|
|
fuel for propulsion and lower the efficiency of the vessel.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Although flow batteries have found applications in large-capacity applications
|
|
including grid services from load balancing to peak shaving, these are
|
|
typically stationary without as much of a volume restriction.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Solid-State
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The previously described traditional rechargeable batteries have a liquid
|
|
electrolyte in which the electrodes are submerged.
|
|
This solution allows ions to pass between the electrodes during charge
|
|
and discharge.
|
|
Systems in which this liquid electrolyte is instead a solid are called
|
|
solid-state batteries (SSB).
|
|
This provides an advantage in that these liquid electrolytes are typically
|
|
one of the key causes of safety concerns as they are flammable and sometimes
|
|
toxic.
|
|
These are important considerations for this domain.
|
|
With less of a concern regarding high operating temperatures, this also
|
|
allows SSBs to be charged faster.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Additionally, the system has the opportunity to increase energy density,
|
|
thereby reducing the required space while increasing the available capacity.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Unfortunately, however, there are a number of considerations that, currently,
|
|
make it unsuitable for the required application.
|
|
As an active area of research without much commercial availability, the
|
|
price of solid-state batteries is much higher than that of other formats,
|
|
for comparison, the
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Price
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
Additionally, concerns associated with Lithium-ion batteries including
|
|
overheating and explosion are not completely removed by transitioning to
|
|
an SSB.
|
|
Dendrites are structures of Lithium that can form during charging and dischargi
|
|
ng as a result of electrodeposition.
|
|
While this should occur evenly across the electrode, if uneven it can cause
|
|
columns to grow towards the separator, figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:Dendrites"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
As these grow they can penetrate through this separator and make contact
|
|
with the cathode.
|
|
This will cause a short circuit, rapidly increasing heat and potentially
|
|
causing fire and explosion.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename dendrite.jpg
|
|
width 40col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Dendrites growing between the Lithium battery electrodes,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "mse-supplies-dendrite"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:Dendrites"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "4-ssb-challenges-article"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
summarises four current challenges to scaling up solid-state batteries
|
|
as investigated by
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "SSB-challenges-paper"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
:
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
Stability of the electrode-electrolyte interface
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
Characterising and analysing this interface in a now opaque structure
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
Sustainable manufacturing processes
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
Designing for recyclability
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
These last two are critical for the project objectives.
|
|
With these considerations it is suggested that solid-state batteries will
|
|
not be ready at the time of construction to supply the scale of storage
|
|
array required.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Proposed Solution
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "subsec:Proposed-UUV-Battery-Solution"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For this project, Lithium-ion chemistry was proposed as the solution for
|
|
the vessel energy storage.
|
|
As previously mentioned, the domain is an area of fervent research as a
|
|
result of its importance to consumer electronics and electric vehicles.
|
|
An important factor in the decision is the scale of system required, this
|
|
will have significant impacts on the ability to source and dispose of a
|
|
system as well as the financial and safety implications.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are a variety of chemical compositions for Lithium-ion batteries depending
|
|
on the other materials used in the electrodes including Lithium Manganese
|
|
Oxide and Lithium Cobalt Oxide.
|
|
Each have specific benefits and associated applications, for our purposes
|
|
Lithium Nickel Manganese Cobalt Oxide will be used as it is a common chemistry
|
|
with high specific energy,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "batt-uni-lithium-chemistry"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are many standard Lithium-ion standard cell formats from flat pouches
|
|
and prismatic cells designed for mobile phones, to the more standard cylindrica
|
|
l cells.
|
|
For this application, cylindrical cells are a suitable choice as compactness
|
|
and thinness are not critical design parameters.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The 18650 cell is a mature cylindrical cell with good reliability records
|
|
and high rates of use among medical equipment, drones and electric vehicles;
|
|
Tesla uses battery packs composed of 18650 cells.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As with other battery cells, the voltage is a characteristic of the chemistry,
|
|
for Lithium this is around 3.6 V.
|
|
The key parameters that vary amongst producers are the capacity and charge/disc
|
|
harge C-rates.
|
|
In order to estimate the cell specification for use in this project, the
|
|
existing range of available cells was taken into account.
|
|
Typical, mid-range 18650 cells can vary between 2500 - 3000 mAh capacity;
|
|
the highest energy density can currently extend this to 3500 - 3600 mAh.
|
|
As technology improves, it is expected that by the point of construction
|
|
this higher range will be more accessible and reliable, and as such, 3500
|
|
mAh is used as the cell capacity for further calculations.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The 18650 cell specifications being used herein are described in table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "tab:18650-specs"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="6" columns="2">
|
|
<features tabularvalignment="middle">
|
|
<column alignment="center" valignment="top">
|
|
<column alignment="center" valignment="top">
|
|
<row>
|
|
<cell alignment="center" valignment="top" bottomline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
18650 Cell
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Voltage, (
|
|
\begin_inset Formula $V$
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3.6
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Capacity, (
|
|
\begin_inset Formula $mAh$
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3500
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Ideal Discharge C-Rate, (
|
|
\begin_inset Formula $h^{-1}$
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Ideal Charge C-Rate, (
|
|
\begin_inset Formula $h^{-1}$
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0.5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Weight, (
|
|
\begin_inset Formula $g$
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
48
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
General specifications for 18650 Lithium-ion cells
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "tab:18650-specs"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Configuration
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The quantity of required cells for the battery system was calculated using
|
|
the expected propulsion power requirements in conjunction with the expected
|
|
generation capabilities of the ammonia fuel cells.
|
|
The specifics for the calculations can be seen in appendix
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sec:Battery-Cell-Calculations"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
; to summarise, the quantity of required cells was calculated from the required
|
|
power draw of the battery and the characteristics of the 18650 Lithium
|
|
cell being used.
|
|
The result was 193,600 cells.
|
|
These cells are arranged into a matrix of parallel and series blocks, all
|
|
the series blocks connected in parallel must be of the same length
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Figure?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The balance of parallel to series blocks is not a critical parameter for
|
|
the application and can instead be tuned for efficiency; as the propulsion
|
|
units require AC power, transformers can be used to select a desired voltage
|
|
and current from a given power value.
|
|
For high power applications high voltage is typically preferred to high
|
|
current which corresponds to a higher weighting of series length.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Challenges
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Self-discharge
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Flex TODO Note (inline)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Self discharge per month, 1-10%?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Limited Lifespan
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Traditional rechargeable battery cells are a consumable item with the capacity
|
|
and performance decreasing over extended use for a number of reasons.
|
|
These include electrode corrosion, reduced porosity or a reduction in Lithium
|
|
ions as a result of side reactions,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "li-ion-degradation"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
When the cells begin to perform below a defined acceptable level, they will
|
|
require replacement.
|
|
This poses both financial and environmental implications.
|
|
As will be discussed in section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "subsec:Extending Lifespan"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
this is a significant amount of money.
|
|
Additionally, the scale of required cells means that the disposal protocols
|
|
are critical.
|
|
Options for such disposal procedures are discussed as part of the life
|
|
cycle analysis in section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "subsec:Life-cycle-Analysis"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Safety
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Although Lithium-ion batteries are typically safe and stable if stored and
|
|
used correctly, abuse can cause severe safety issues.
|
|
As previously mentioned, the liquid organic electrolyte is flammable, and
|
|
combined with the high energy density of Li-ion batteries can lead to thermal
|
|
runaway and eventually fire if not handled correctly.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are a couple of causes for such a thermal runaway, these include physical
|
|
damage, short circuits, overcharging and exposure to high temperature,
|
|
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "washington-lithium-safety"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Multiple measures must be implemented to ensure safety,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "washington-lithium-safety"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Reputable manufacturers must be used as defects during construction can
|
|
cause or exacerbate faults.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
The battery system should be located far from combustible materials
|
|
\end_layout
|
|
|
|
\begin_deeper
|
|
\begin_layout Itemize
|
|
Contextually this would primarily be the fuel tanks.
|
|
|
|
\end_layout
|
|
|
|
\end_deeper
|
|
\begin_layout Itemize
|
|
The cell's temperature should be monitored and controlled.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Cells of the same age must be grouped and used together
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Cells should be charged intelligently in order to mitigate overcharge and
|
|
implement equalisation charging, see
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "subsec:Safety-Circuitry"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
The battery system should be stored in an water/air-tight container
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
This container should be able to safely vent gases
|
|
\end_layout
|
|
|
|
\begin_deeper
|
|
\begin_layout Itemize
|
|
In the event of an emergency, cells can release toxic gases (CO
|
|
\begin_inset script subscript
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, CO, HF)
|
|
\end_layout
|
|
|
|
\end_deeper
|
|
\begin_layout Standard
|
|
With regards to the described container, as previously outlined, standard
|
|
shipping containers will be used
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Container spec?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
This provides a good base to modify in order to meet the above, i.e.
|
|
air/water-tight and venting.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Charging & Safety Circuitry
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "subsec:Safety-Circuitry"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As previously described, Lithium-ion cells are sensitive to stressful electrical
|
|
conditions such as overcharging, deep discharging and excessive current
|
|
draw.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In order to protect and enforce operating conditions for the Lithium cells,
|
|
a battery management system or BMS is used.
|
|
A BMS implements safety protocols to mitigate the above effects as well
|
|
as providing information to the load and other monitoring services such
|
|
as state-of-charge information (remaining capacity),
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "batt-uni-bms"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Extending Lifespan
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "subsec:Extending Lifespan"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Lithium-ion cells are a consumable item that degrades.
|
|
The environmental and financial cost of replacement creates a significant
|
|
incentive to extend this as much as possible as long as this does not inhibit
|
|
the operating capabilities beyond the specification.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As previously mentioned, the temperature of the cells is a key parameter
|
|
affecting both performance and lifespan,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "batt-uni-discharge-temp"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
Although operating at a higher temperature increases performance it also
|
|
decreases lifespan.
|
|
Temperature control is already critical for safety purposes.
|
|
20°C provides the ideal temperature for prolonging lifespan and as such
|
|
will be set as the target temperature,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "batt-uni-discharge-temp"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Another important aspect to the lifespan of Lithium-ion batteries is the
|
|
depth-of-discharge (DOD) which determines the number of charge cycles that
|
|
the battery will last for.
|
|
The depth-of-discharge describes the amount of capacity used each cycle
|
|
before recharging.
|
|
Lithium batteries are able to handle moderate DOD without significantly
|
|
affecting the lifespan, however, frequent deep discharge cycles, completely
|
|
emptying the battery, will shorten its life,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "bat-uni-prolong-liion"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Similar to frequently completely discharging the battery, storing a battery
|
|
fully charged for long periods of time can also shorten its lifespan.
|
|
This can be seen presented in figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:charge-lifespan"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
where higher cell charge voltages can be seen to reduce capacity much faster
|
|
as time or charge cycles increases
|
|
\begin_inset Foot
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Worth noting that the capacity is initially higher for higher voltages,
|
|
it is the lifespan that can be extended by picking a more reserved value.
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename lithium-overcharge-capacity.jpg
|
|
width 55col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
The lifespan of Lithium-ion cells described by the max capacity as charge
|
|
cycles increase for various charge voltages,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "bat-uni-prolong-liion"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:charge-lifespan"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Both of the above points, tempering DOD and charge voltage rely on the BMS.
|
|
To prevent deep discharges, more ammonia fuel cells should start up as
|
|
the capacity decreases in order to balance the workload meaning that the
|
|
ammonia management system will need to interface with the BMS.
|
|
Additionally, it would be the responsibility of the BMS to charge cells
|
|
to a reasonable voltage, 3.9 - 4.1 V can provide a balance between higher
|
|
capacity and longer lifespan,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "bat-uni-prolong-liion"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename discharge-voltage-temperature.jpg
|
|
lyxscale 60
|
|
width 60col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Voltage-Capacity characteristics for a 18650 Li-ion cell at varying temperatures
|
|
,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "batt-uni-discharge-temp"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:temperature-characteristics"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Flex TODO Note (inline)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Define a replacement interval
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Financial
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "subsec:batteryFinancial"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As described, a battery array lasts approximately 2.3 years, after which,
|
|
a new set must be sourced.
|
|
18650 cells vary in price across manufacturers and distributors, a range
|
|
of RRPs were taken from UK distributors,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "18650-ecolux,18650.uk,18350-fogstar"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
In general, a cell's RRP ranged between £4 and £7, and so it is assumed
|
|
that a procurement department would secure a unit price at the lower end
|
|
of this for the scale of order required, £5 is used.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
A set of 193,600 cells at this cost totals to £968,000 which averages to
|
|
£420,869 a year for modelling purposes.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Costing a battery management system is complicated by the scale of battery
|
|
being proposed.
|
|
A mega-watt scale battery will require a complex BMS without publicly available
|
|
prices and an estimation must be made.
|
|
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "bms-cost-article,bms-cost-report"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
suggests that cells constitute 60% of the total system price.
|
|
Using this estimate the BMS and pack is estimated to cost £645,000.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Life-cycle Analysis
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "subsec:Life-cycle-Analysis"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The life-cycle analysis (LCA) of Lithium-ion batteries is a complicated
|
|
process for a couple of reasons.
|
|
As repeatedly stated, Li-ion batteries have been critical to the explosion
|
|
of mobile consumer electronics; the development of the fabrication process
|
|
and the associated environmental effects has changed dramatically.
|
|
More recent LCAs and meta-analyses of previous data are considered in order
|
|
to account for this.
|
|
Additionally, as a global product the values for various greenhouse gas
|
|
(GHG) and other emissions is contingent on the country within which the
|
|
cells are made.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Both the cumulative energy demand (CED) and the GHG emissions are considered.
|
|
Cumulative energy demand allows abstraction of the specific method of energy
|
|
production and the associated emissions.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Many of the LCA studies on Lithium-ion batteries consider a cradle-to-gate
|
|
scope without including use or end-of-life.
|
|
Two end-of-life procedures are considered as well as practices to improve
|
|
usage lifetime.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Cradle-to-Gate
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename battery-breakdown-mj-kwh.png
|
|
lyxscale 50
|
|
width 75col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
CED breakdown for a NCM11 battery pack (MJ/kWh),
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "circular-energy-li-lca,argonne-li-ion-lca"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:battery-ced-breakdown"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:battery-ced-breakdown"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
outlines the cumulative energy demand for the major elements of a Nickel/Cobalt
|
|
/Manganese cathode (NCM11) battery.
|
|
As
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "circular-energy-li-lca"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
points out, cathodes are tending towards a higher cathode composition of
|
|
Nickel, however the general proportions are relevant to other chemistry.
|
|
It can be seen that the production of the cells constitutes the majority
|
|
of the required CED at 75% of the total.
|
|
As this is also the element of the battery that requires periodic replacement
|
|
following degradation, a closer look at the contributing stages should
|
|
be considered.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename cell-breakdown-mj-kwh.png
|
|
lyxscale 50
|
|
width 75col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
CED breakdown for a NCM11 cell without BMS or pack (MJ/kWh),
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "circular-energy-li-lca,argonne-li-ion-lca"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:cell-ced-breakdown"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This further breakdown can be seen in figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:cell-ced-breakdown"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
The precursors, Li
|
|
\begin_inset script subscript
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
CO
|
|
\begin_inset script subscript
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and cathode production constitute almost 50% of the cell's CED, these are
|
|
the Lithium intensive processes.
|
|
By using recycled Lithium, this major contributor can be reduced.
|
|
As such, a cell manufacturer using recycled Lithium should be identified
|
|
and used.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename battery-breakdown-c02e-kwh.png
|
|
lyxscale 40
|
|
width 75col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Equivalent carbon breakdown for a NCM11 battery pack (kg CO2e/kWh),
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "circular-energy-li-lca,argonne-li-ion-lca"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:battery-co2e-breakdown"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The contributions of each stage to the embodied carbon can be seen in figure
|
|
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:battery-co2e-breakdown"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
As previously shown, the Lithium-containing NCM powder constitutes the
|
|
largest contributor.
|
|
The 73 kg CO2e/kWh quoted value is dependent on the location of manufacture,
|
|
a slightly more conservative 80 kg CO2e/kWh will be used for calculating
|
|
the battery systems embodied carbon from production.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Using this value, a set of cells represents 191 tonnes of embodied carbon.
|
|
This will be included in the total embodied for the project requiring offset.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Use
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The use of Lithium batteries does not inherently incur a Carbon cost; the
|
|
associated cost of energy stored is accounted for by the source of this
|
|
energy, in this case ammonia fuel cells
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
solar panels?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The use of the batteries does require analysis, however.
|
|
The source and end-of-life procedures for a battery pack is a carbon intensive
|
|
operation and the ability to extend the time in-between replacement will
|
|
improve the environmental impact overall.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are a number of ways to increase the lifespan of a battery pack, these
|
|
have been outlined in section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "subsec:Extending Lifespan"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
and are critical for reducing the environmental impact of the system.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
End-of-Life
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are two main approaches to sustainable end-of-life processing for
|
|
Lithium-ion processing, second-use and recycling.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Second-use describes the use of a battery for new applications after the
|
|
performance is deemed too low for the vessel's buffer.
|
|
By doing so the lifespan of the batteries can be extended and reducing
|
|
the amount being constructed.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are many methods for recycling Lithium batteries, and it is important
|
|
to identify a process that will not use more energy than that required
|
|
to mine virgin materials.
|
|
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "circular-energy-li-lca"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
summarises that up to 48% of the CED and CO
|
|
\begin_inset script subscript
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
e could be saved.
|
|
They identify
|
|
\emph on
|
|
direct recycling
|
|
\emph default
|
|
as the best option for this.
|
|
This method allows the electrodes to retain their composition as opposed
|
|
to breaking it down into constituent parts,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "li-direct-recycling"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
This has applicability across Lithium-ion chemistry including the form
|
|
used herein, NCM.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For the vessel battery, the use of an intelligent BMS and tight integration
|
|
with the ammonia cells should allow it to be treated well such that it
|
|
is kept in comparably good condition.
|
|
As such it is proposed that they would be well suited for second-use applicatio
|
|
ns such as energy storage.
|
|
The battery will not be used until failure but instead until it cannot
|
|
be used for the high-draw requirements of the buffer.
|
|
They would likely have good applicability to purposes without such focus
|
|
on high draw but that will make use of the remaining capacity.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Sustainability
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "subsec:SurfaceVesselBatterySustainability"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Although many of the important environmental aspects of sustainability are
|
|
covered by a life-cycle analysis, there are other elements to consider
|
|
regarding sustainability.
|
|
One of the most important aspects is a social one, that of the mining of
|
|
Lithium and Cobalt.
|
|
The majority of both minerals are located in two areas of the global south
|
|
where resource shortages and unethical mining practices lead to dangerous
|
|
and damaging results both socially and environmentally.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Lithium
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The majority of global Lithium deposits can be found in an area of South
|
|
America referred to as the
|
|
\emph on
|
|
Lithium Triangle
|
|
\emph default
|
|
covering areas of Chile, Argentina and Bolivia.
|
|
The area has been estimated to constitute between 54 and 70% of the world's
|
|
deposits,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "wired-lithium,resourceworld-54-lithium"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
The extraction is a water-intensive process in an area already without
|
|
an adequate supply; in Chile this is as much as 65% of the area's water
|
|
or 500,000 gallons per tonne of Lithium,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "wired-lithium"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The processing can also include dangerous chemicals including various acids
|
|
that can pollute local water supplies as a result of leaks, leaching and
|
|
emissions,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "wired-lithium"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Cobalt
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Over half of the world's Cobalt deposits are found in the Democratic Republic
|
|
of Congo,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "wired-lithium,ethical-consumer-conflict-materials"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Although not officially designated as such, there are efforts to class Cobalt
|
|
as a conflict mineral as its importance grows to one of the most notorious
|
|
countries for other such minerals including Gold and Tungsten.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
20% of the exported cobalt has been estimated to come from artisanal mines,
|
|
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "ethical-consumer-conflict-materials"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
These are small-scale mines known for a lack of safety standards including
|
|
minimal personal protective equipment, structural requirements and child
|
|
labour,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "wef-cobalt-mining"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Summary
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The above emphasises the need to identify Lithium cell manufacturers using
|
|
recycled materials in order to reduce the amount of virgin material being
|
|
mined and assembled.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Time-dependent Modelling
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In order to validate the buffer configuration, a model was constructed to
|
|
visualise the capacity of the battery system while in use.
|
|
Explanations as to the specific behaviour and assumptions made can be seen
|
|
in appendix
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sec:Time-dependent-Power-Modelling"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
An example model describing the vessel's dynamic positioning above a cable
|
|
fault can be seen in figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:dyn-pos-power-model"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename ../maths/final_report_res/dynpos1.png
|
|
lyxscale 20
|
|
width 80col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Power model describing the vessel dynamic positioning on mission
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:dyn-pos-power-model"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The top sub-figure describes the power in from the ammonia fuel cells and
|
|
the load power drawn from the hotel and propulsion systems.
|
|
The middle figure describes the effect this has on the capacity of the
|
|
battery.
|
|
The bottom figure describes the efficiency of this system, the
|
|
\emph on
|
|
unused
|
|
\emph default
|
|
power describes when more fuel cells than required are turned on and power
|
|
is drawn below the most efficient state.
|
|
The
|
|
\emph on
|
|
unavailable
|
|
\emph default
|
|
power describes when the fuel cells in their most efficient state and the
|
|
battery combined cannot meet the requirement.
|
|
As a result, extra power would be drawn from both pulling them into an
|
|
inefficient or damaging state.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
second
|
|
\begin_inset Graphics
|
|
filename ../maths/final_report_res/mission3.png
|
|
lyxscale 20
|
|
width 80col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Power model describing one mission including travelling and dynamic positioning
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:mission-power-model"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This model was extended to simulate an entire mission as described in section
|
|
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
NICKS SECTION
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:mission-power-model"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
) including:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Outbound journey (3 days)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Manoeuvring to the fault (1 day)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Dynamic positioning while completing the first splice (2 days)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Manoeuvring to the other half of the cable (1 day)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Dynamic positioning while completing the second splice (2 days)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Homeward journey (3 days)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Probably covered by Nick
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
From these models, the amount of battery charge cycles was estimated to
|
|
be 2 per day.
|
|
Extrapolating this to a yearly usage value using the expected vessel usage,
|
|
a battery array was estimated to last 2.3 years.
|
|
This is a typical value for the lifespan of Lithium-ion batteries.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Summary
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The proposed buffer solution includes 193,600 NCM Lithium-ion cells requiring
|
|
replacement every 2.3 years.
|
|
As a result of this replacement rate, it is stipulated that the battery
|
|
be re-appropriated for second-use such as energy storage following decommission
|
|
in order to extend their life and reduce the environmental impact.
|
|
Manufacturers using recycled materials should also be identified in order
|
|
to reduce the impact of mining virgin materials.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
It is worth noting that this is the proposed solution based on the current
|
|
state of energy storage.
|
|
One of the only advantages of rechargeable batteries being a consumable
|
|
item requiring replacement is that when this occurs, it is an opportunity
|
|
to re-evaluate the system design.
|
|
With an expected project lifespan of 30 years, it is highly unlikely that
|
|
the use of Li-ion cells will remain the best option.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Systems based on a solid-state chemistry will likely become more stable
|
|
and less expensive to the point that the advantages in safety and energy
|
|
density can be fully utilised without the heavy downsides.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Mission Ops
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Grapnel-based Operations [AP]
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Possibly covered by Nick
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
While the use of robotics has made sub-sea cable repair operations more
|
|
efficient, there are situations where this is not available and it is worth
|
|
briefly outlining how grapnels are used in repair operations.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Grapnels are specialised tools attached to lengths of chain which trail
|
|
the stern of the ship.
|
|
For cable repair operations, a cut & hold grapnel is used
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "cut-and-hold-paper,cut-and-hold-eta-product"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
With knowledge of the path of the subject cable and the location of the
|
|
fault, the grapnel is lowered before the boat makes a pass perpendicular
|
|
to the cable.
|
|
As the grapnel makes contact it is able to both cut and grip the cable
|
|
before being raised to the surface vessel.
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Disadvantages
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Unmanned Underwater Vehicle Operations [AP]
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The following section outlines how the use of an unmanned underwater vehicle
|
|
(UUV) can make mission operations more efficient and precise.
|
|
The state of current UUV usage throughout cable repair operations is outlined
|
|
in order to identify the critical capabilities, requirements and advantages
|
|
over traditional grapnel operations.
|
|
The future of the domain is then explored and the challenges in applying
|
|
these developments to sub-sea cable repair are identified before exploring
|
|
how these can be overcome in order to meet the determined requirements.
|
|
Prior to this, the domain of UUVs as a whole is described in order to outline
|
|
the scope of available vehicles.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The developments are aligned with UNSDGs 9 (Industry, Innovation and Infrastruct
|
|
ure) and 12 (Responsible consumption and production) for the ability to
|
|
reduce required fuel usage of the surface vessel.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
UUV Classes
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
ROVs and AUVs
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
UUVs can be divided into two categories based on their control scheme.
|
|
Remotely operated underwater vehicles (ROV) and autonomous underwater vehicles
|
|
(AUV) are distinguished by whether a human is controlling the vehicle or
|
|
whether it operates independently; as such they have different applications.
|
|
ROVs have been the vehicle class of choice where complex intervention and
|
|
actuation is required such as offshore oil and gas operations and cable
|
|
repair.
|
|
A human operator controls the vehicle from the surface vessel; bi-directional
|
|
communication including data, control, video and power are transmitted
|
|
through an umbilical cord tether between the two vessels.
|
|
AUVs on the other hand have primarily been used for survey and research
|
|
purposes.
|
|
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
No umbilical cord?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This distinction in responsibilities is not static, however.
|
|
Like other robotics domains such as auto-mobiles and ships, autonomy is
|
|
a rapidly developing area of research and development; newer vehicles are
|
|
able to complete more complex operations without human intervention and
|
|
with longer endurance.
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Physical Configuration
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The physical layout of a UUV can generally be described by one of two classes,
|
|
box frames or torpedo shaped.
|
|
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
determined by the size and range of the vehicle.
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
Box frame UUVs are typically larger with more space for instruments and
|
|
actuators but are not expected to make longer distance journeys as a result
|
|
of their poor hydrodynamic profile.
|
|
Torpedo shaped vehicles tend to be smaller without actuators; their hydrodynami
|
|
c profile makes them well suited for faster, longer distance missions however
|
|
this comes at the cost of reduced stability and control.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Current ROV Usage
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Cable repair operations are currently undertaken, where possible, with human-con
|
|
trolled ROVs.
|
|
With visual contact and direct actuation at the seabed, the ROV is used
|
|
to identify, cut and grip the cable for retrieval to the surface-vessel.
|
|
In doing so the need for repeated motions of the ship across the cable
|
|
is removed, saving time and fuel.
|
|
Instead, the surface vessel uses dynamic positioning in order to maintain
|
|
its position above the ROV and cable.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
While this finer control is a key benefit for ROV use over grapnels, one
|
|
of the most important benefits is the ability to bury repaired cables in
|
|
the sea floor using high-powered water jets.
|
|
70% of cable damage is caused by man-made activity, of which over a third
|
|
is a result of fishing activity; another quarter is as a result ship anchors
|
|
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "ultra-map-cable-damage-causes"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
As such, the ability to protect sub-sea cables in shallower waters by burying
|
|
them from human intervention is a key parameter in protecting cables from
|
|
further damage and extending the time between repairs.
|
|
While this can be completed with a separate plough, this would require
|
|
more deck space and motion of the surface vessel.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The need for fine movement control and actuators with which to manipulate
|
|
cables has led to box frame vehicles dominating this field, figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:The-HECTOR-7-ROV"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
shows SIMEC Technology's HECTOR-7 ROV, a typical design for sub-sea cable
|
|
repair vehicles.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename hector-7.jpg
|
|
lyxscale 50
|
|
width 50col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
SIMEC Technology's HECTOR-7 ROV used on Orange Marine's Pierre de Fermat,
|
|
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "rov-hector-7-datasheet"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:The-HECTOR-7-ROV"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
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\begin_inset Tabular
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<lyxtabular version="3" rows="8" columns="5">
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<features tabularvalignment="middle">
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<column alignment="center" valignment="top">
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<column alignment="center" valignment="top">
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<column alignment="center" valignment="top" width="0pt">
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<column alignment="center" valignment="top">
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<column alignment="center" valignment="top">
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<row>
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<cell alignment="center" valignment="top" bottomline="true" usebox="none">
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\begin_layout Plain Layout
|
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\end_layout
|
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\end_inset
|
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</cell>
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
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\series bold
|
|
HECTOR-7
|
|
\end_layout
|
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|
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\end_inset
|
|
</cell>
|
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
Atlas
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
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\begin_layout Plain Layout
|
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|
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\series bold
|
|
ST200
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
QTrencher 600
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
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|
|
|
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|
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|
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|
|
Company
|
|
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|
|
|
|
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|
|
</cell>
|
|
<cell alignment="center" valignment="top" leftline="true" usebox="none">
|
|
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|
|
|
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|
|
SIMEC Technology
|
|
\end_layout
|
|
|
|
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|
|
</cell>
|
|
<cell multicolumn="1" alignment="center" valignment="top" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Global Marine
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell multicolumn="2" alignment="center" valignment="top" leftline="true" usebox="none">
|
|
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|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
SMD
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell multirow="3" alignment="center" valignment="middle" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
Vessel
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell multirow="3" alignment="center" valignment="middle" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Pierre de Fermat
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Wave Sentinel
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell multirow="3" alignment="center" valignment="middle" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Cable Innovator
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell multirow="3" alignment="center" valignment="middle" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
N/A
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell multirow="4" alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
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\begin_layout Plain Layout
|
|
|
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\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell multirow="4" alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
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|
|
\end_layout
|
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|
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\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
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\begin_layout Plain Layout
|
|
C.S Sovereign
|
|
\end_layout
|
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|
|
\end_inset
|
|
</cell>
|
|
<cell multirow="4" alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
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|
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\end_layout
|
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\end_inset
|
|
</cell>
|
|
<cell multirow="4" alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
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\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
Depth Rating
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3,000 m
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2,000 m
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2,500 m
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3,000 m
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
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|
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\series bold
|
|
Weight in Air
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
9 t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10.6 t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
6.5 t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
11 t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\series bold
|
|
Power
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
300 kW
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
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|
|
|
|
\begin_layout Plain Layout
|
|
300 kW
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
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|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
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|
|
|
|
\begin_layout Plain Layout
|
|
450 kW
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
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|
|
|
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|
|
|
|
\series bold
|
|
Burial Depth
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
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|
|
|
|
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|
|
2 m
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
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|
|
|
|
\begin_layout Plain Layout
|
|
2 m
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1.5 m
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3 m
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset VSpace smallskip
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "rov-hector-7-datasheet,global-marine-atlas-data-sheet,glboal-marine-st200-datasheet,smd-qtrencher-600-datasheet"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Relevant specifications and operating capabilities for sub-sea cable repair
|
|
ROVs
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "tab:ROV-specs"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "tab:ROV-specs"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
lists the specifications for the ROVs currently being used as part of the
|
|
ACMA cable repair agreement along with similarly classed vehicles from
|
|
other providers.
|
|
As can be seen, current ROVs for this domain have a maximum working depth
|
|
of about 3 km.
|
|
This poses a problem to cable repair operations where, further out to sea,
|
|
the sea floor can extend much further, see figure
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
bathymetry chart?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
While ROVs could be capable, in theory, of reaching lower depths it is
|
|
important to balance these working capabilities with other considerations
|
|
such as price and weight.
|
|
In practice, while this working depth is a reasonable range to work within,
|
|
it could be argued that the most important capability of current ROVs is
|
|
their ability to re-bury the cable post-repair.
|
|
As described previously, this is in order to protect the cable from human
|
|
intervention including fishing and anchor operations.
|
|
These incidents are more prevalent in shallower waters within the operating
|
|
range of the ROV, therefore it is acceptable to use a grapnel outside of
|
|
this operating range where burying the cable is less important.
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Requirements Specification
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Using this information, the requirements for a cable repair UUV could be
|
|
described as the following,
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
The UUV should have actuators in order to both cut and grip cables
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
The UUV should be able to operate to at least 2 km of depth
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
The UUV should be able to locate the cable without visual information i.e.
|
|
electromagnetically
|
|
\end_layout
|
|
|
|
\begin_deeper
|
|
\begin_layout Enumerate
|
|
In shallower water the cable is buried and will not be able to be visually
|
|
identified
|
|
\end_layout
|
|
|
|
\end_deeper
|
|
\begin_layout Enumerate
|
|
The UUV should be able to re-bury the cable in shallower waters
|
|
\end_layout
|
|
|
|
\begin_deeper
|
|
\begin_layout Enumerate
|
|
This should provide more protection to the cable from interference including
|
|
fishing operations
|
|
\end_layout
|
|
|
|
\end_deeper
|
|
\begin_layout Subsubsection
|
|
Current AUV Usage
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Autonomous underwater vehicles are well suited to survey and research operations
|
|
; without human intervention they sweep a given area collecting data for
|
|
analysis.
|
|
This can include bathymetry
|
|
\begin_inset Foot
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Measurement of the depth of a body of water
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, surveys and chemical composition investigations such as pH and toxin levels.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename hugin-superior.jpg
|
|
lyxscale 30
|
|
width 60col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Kongsberg Maritime's HUGIN Superior AUV,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "auv-hugin-superior-datasheet"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Advantages
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
An advantage of using an autonomous vehicle would be the lack of need for
|
|
the surface vessel to maintain position directly above the ROV and fault;
|
|
instead the surface vessel would stay within a larger area only to maintain
|
|
contact with the UUV.
|
|
This could reduce the required power directed to dynamic positioning which
|
|
in higher sea states can become a significant draw.
|
|
Additionally, as the UUV can move independently, the surface vehicle would
|
|
not need to directly track the vehicles movement; for example, when the
|
|
UUV is re-burying the repaired cable in shallower waters.
|
|
This would, again, lower the required propulsion power used by the surface
|
|
vessel.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Another advantage could be a reduction in risk during mission operations.
|
|
With a traditional tethered ROV, should the umbilical cable be broken the
|
|
vehicle would likely lose functionality and require specialist recovery.
|
|
This break could occur as a result of a fault in the tether management
|
|
system, high storm activity causing too much tension on the system, or
|
|
in less likely scenarios, animal intervention.
|
|
An autonomous vehicle has no tether to break and a hybrid ROV/AUV could
|
|
likely be instructed to take control and return home should the tether
|
|
break during missions involving direct human control
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
No longer valid, battery is removable when using TMS
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Domain Challenges
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Navigation
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As mentioned, one of the main advantages of using an autonomous vehicle
|
|
for sub-sea cable repairs would be the physical de-coupling of the vehicles,
|
|
however this also poses the most significant challenge.
|
|
In typical ROV operations, the operator has knowledge of the location of
|
|
the ROV relative to the surface vessel.
|
|
As the surface vessel is GNSS
|
|
\begin_inset Foot
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Global Navigation Satellite System, the generic term for satellite aided
|
|
global navigation of which the American GPS, Russian GLONASS and European
|
|
Galileo systems are examples
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
-enabled (Likely GPS) it has knowledge of its position in world co-ordinates
|
|
and the operator can use this to reduce the ROV's cable search space.
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Diagram?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Decoupling the vehicles introduces complications that are not necessarily
|
|
typical to the existing use cases for AUVs.
|
|
The frequency of EM waves used by GNSS systems do not penetrate deep through
|
|
the water and an AUV must be able to operate without world co-ordinates
|
|
provided in this manner.
|
|
As such, navigation systems used by AUVs are typically
|
|
\emph on
|
|
dead reckoning
|
|
\emph default
|
|
systems.
|
|
This is a form of navigation that operates relative to a known fixed point
|
|
(where a UUV is deployed for example) as opposed to one relative to world
|
|
co-ordinates.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
With an accurate system, this will satisfy many surveying and research use
|
|
cases where relative location data can be transformed to world-coordinates
|
|
after the fact.
|
|
This will prove less effective when the vehicle is expected to autonomously
|
|
navigate to a specific location (the cable fault).
|
|
A dead reckoning system as described above uses relative sensors to measure
|
|
speed and infer the current location however these relative sensors have
|
|
associated measurement errors which accumulate over time.
|
|
This would be more pronounced under the water where sea currents are liable
|
|
to accentuate these errors, the efficacy of an AUV's fault location capabilitie
|
|
s may be reduced to the point of unacceptability.
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
Kalman filter now?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Launch & Recovery
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
By allowing the UUV to operate untethered underwater, complications are
|
|
introduced to the method by which it is launched and recovered to the surface
|
|
vessel.
|
|
A tethered ROV of the size being considered typically has a top-hat tether
|
|
management system (TMS) responsible for controlling the slack in the umbilical
|
|
cable, an example can be seen in figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:top-hat-tether"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
Smaller vehicles can also use a garage-style TMS where the tether attaches
|
|
to a box-like cradle that houses the UUV within.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename tophat.png
|
|
lyxscale 50
|
|
width 40col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
A top-hat tether management system attached to the top of an ROV,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "tophat-tms"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:top-hat-tether"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This results in the UUV being under control by the surface vessel as it
|
|
is being lifted from the water, especially during the
|
|
\emph on
|
|
splash zone
|
|
\emph default
|
|
, the area surrounding the average water level.
|
|
As the UUV is lifted or dropped through this area and it beings to make
|
|
contact with the water, the weight load on the crane can change dramatically,
|
|
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "splash-zone"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
During this period, the UUV is most at risk of damage as wind and sea forces
|
|
can make it swing towards the surface vessel.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The TMS and LARS system together aim to protect both vessels as the UUV
|
|
descends through the splash zone by dampening the lateral movement of the
|
|
UUV and by limiting the amount of umbilical slack; this keeps it away from
|
|
the surface vessel's thrusters,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "rov-tms-splash-zone"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
These methods are effective in protecting tethered UUVs during launch and
|
|
recovery, the challenge comes in defining how the UUV will be deployed
|
|
when operating autonomously without a tether.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Proposed Design
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The vehicle will be designed for hybrid ROV/AUV operations.
|
|
The vehicle should be able to complete missions independently of the surface
|
|
vessel with the ability to operate in a similar fashion to existing ROVs
|
|
(human controller, tethered power and data connection).
|
|
This will have a number of benefits, primarily that the vehicle should
|
|
be able to benefit from autonomous operation where possible with the ability
|
|
for direct human control in missions deemed too complex for autonomous
|
|
control.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The existing remit of AUV operations is primarily survey, inspection and
|
|
light intervention, it is likely that the autonomous capabilities of this
|
|
vehicle would not be capable of conducting all existing cable repair missions
|
|
which involve more intervention.
|
|
It is important that enabling autonomous operations does not ultimately
|
|
reduce its operating capabilities.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As previously described, box frame UUVs are well suited to sub-sea cable
|
|
operations where fine movement control and space for actuators are critical.
|
|
As such a box frame of similar specifications to those currently used,
|
|
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "global-marine-atlas-data-sheet,rov-hector-7-datasheet"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
will be used.
|
|
The vehicle will likely be at the larger and heavier end of existing ROVs
|
|
as the vehicle must now have the onboard energy capabilities to complete
|
|
a mission without a constant power supply from the surface vessel.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Communication
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As the UUV is now expected to operate independently of the surface vessel,
|
|
it should have the ability to bi-directionally, wirelessly communicate
|
|
with the surface vessel.
|
|
Uses for such a communications channel include the UUV reporting its mission
|
|
status and the surface vessel providing high-level instructions such as
|
|
|
|
\emph on
|
|
return home
|
|
\emph default
|
|
orders.
|
|
When operating underwater, acoustic signals are the primary medium for
|
|
wireless communication.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Navigation
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "subsec:Navigation"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As previously described, the navigation system will primarily be built on
|
|
the principle of
|
|
\emph on
|
|
dead reckoning
|
|
\emph default
|
|
using an inertial navigation system (INS).
|
|
An INS uses input from many types of sensor such as accelerometers and
|
|
gyroscopes to measure the movement of the vehicle and hence infer its location.
|
|
None of these could individually provide an accurate determination of location
|
|
and as such
|
|
\emph on
|
|
sensor fusion
|
|
\emph default
|
|
is employed.
|
|
Each sensor has an associated measurement uncertainty which compounds over
|
|
time, sensor fusion allows all the sensor measurements to be combined in
|
|
such a way as to produce a single output measurement with an uncertainty
|
|
smaller than any of each sensor individually.
|
|
A common method for implementing sensor fusion is using a
|
|
\emph on
|
|
Kalman filter
|
|
\emph default
|
|
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
reference, explain?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
However, despite the use of a Kalman filter allowing more precise approximations
|
|
of the vehicle's relative location, the lack of external calibration means
|
|
that the overall uncertainty will still increase over time.
|
|
In land-based robotics this is mitigated through the use of periodic GPS
|
|
measurements which have low, constant uncertainty and help to place an
|
|
upper bound on the overall error.
|
|
As previously mentioned, GNSS systems do not work deep underwater and as
|
|
such, another method for providing these external updates must be used.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The following proposes methods for providing global positioning to the UUV
|
|
without a traditional GNSS system.
|
|
This will be completed in two stages, the first being to provide the UUV
|
|
with the ability to measure the location of a fixed point relative to itself.
|
|
In parallel, the global co-ordinates of this fixed point will be communicated
|
|
to the UUV in order to infer its own global location.
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Underwater Acoustic Positioning
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Alongside the use of acoustic signals for communications it will also be
|
|
employed for positioning.
|
|
One application for this is underwater acoustic positioning which employs
|
|
the use of time-of-flight measurements to beacons of a known location to
|
|
triangulate an object's location.
|
|
There are different configurations for such a system depending on how these
|
|
beacons are laid out,
|
|
\emph on
|
|
long-baseline
|
|
\emph default
|
|
(LBL) systems involve beacons located on the sea floor.
|
|
Spreading these beacons around the working area of an ROV widens the baseline
|
|
of the system and provides higher accuracy when triangulating.
|
|
This configuration is best suited to static areas of research such as ship
|
|
wrecks where an initial time devoted to deploying and calibrating these
|
|
underwater beacons is a reasonable expense to pay for the required high
|
|
accuracy.
|
|
This is not the case for sub-sea cable repairs where the deployment, calibratio
|
|
n and recovery of beacons on the seabed would be prohibitively complex and
|
|
add significant time to the duration of a mission.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
|
|
\emph on
|
|
Short-baseline
|
|
\emph default
|
|
(SBL) systems involve a number of beacons placed at the furthest corners
|
|
of the surface vessel, this has the benefit of requiring little set-up
|
|
and pack-down at the cost of reduced accuracy.
|
|
Relative to the UUV these beacons are all on a similar bearing when operating
|
|
at a distance, as a result changes in the vehicle's location would be reflected
|
|
in similar changes to the measurements from all of the beacons.
|
|
Previously, with a long-baseline, the beacons are ideally surrounding the
|
|
UUV's working area and changes in its location are reflected in different
|
|
distance deltas for each beacon allowing tighter triangulation.
|
|
Accuracy can be improved by extending the beacons away from the vessel
|
|
to extend the baseline as far as possible.
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
such as on a boom?
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
One method to mitigate the drawbacks of both described methods is by using
|
|
GPS Intelligent Buoys (GIBs).
|
|
This configuration, also referred to as an
|
|
\emph on
|
|
inverted long-baseline
|
|
\emph default
|
|
, allows a much wider baseline than the surface-vessel-mounted beacons by
|
|
deploying a group of
|
|
\emph on
|
|
smart buoys
|
|
\emph default
|
|
around the expected working area of the UUV.
|
|
The use of buoys as opposed to beacons on the sea-floor significantly decreases
|
|
the preparation and clean-up mission phases.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Of these methods it is proposed that the surface vessel be equipped with
|
|
a short-baseline beacon array as well as a population of GIBs.
|
|
This will allow the choice between higher accuracy or faster mission turnaround
|
|
be decided by mission conditions as well as providing redundancy for either
|
|
system.
|
|
In shallower waters, the accuracy of the onboard SBL may be deemed sufficient
|
|
however in deeper water where the UUV is operating far further from the
|
|
surface vessel, the compactness of the SBL baseline may require the higher
|
|
accuracy of the GIBs
|
|
\begin_inset Foot
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
In practice the two could be used in conjunction for efficiency.
|
|
As the UUV is deployed it initially uses the onboard SBL array while the
|
|
surface vessel makes a pass around the working area deploying GIBs for
|
|
use as the UUV gets deeper
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
The GIBs would be considered additional accuracy, the SBL would be used
|
|
alongside the GIBs and act as an extra node in the array.
|
|
Additionally the weather and sea conditions could play a factor in the
|
|
decision.
|
|
In higher sea states and stormy weather, the deployment and recovery of
|
|
GIBs may be deemed too risky and the SBL could be used alone.
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Global Calibration
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The above underwater acoustic positioning system will allow the UUV to keep
|
|
track of its position relative to known points at the surface, however
|
|
this alone will not provide the UUV with its global location.
|
|
In order for the UUV to calibrate its local map to global co-ordinates,
|
|
the global position of these surface points must be provided.
|
|
This will be conducted over the previously described acoustic communication
|
|
channel.
|
|
As it could be expected that this channel has a low bandwidth, these updates
|
|
need not be excessively frequent.
|
|
\end_layout
|
|
|
|
\begin_layout Paragraph
|
|
Acoustic Doppler Current Profiling
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
While accelerometers and gyroscopes would be expected components of any
|
|
mobile dead reckoning navigation system, additional sensors well-suited
|
|
to sub-sea localisation will allow the vessel's movement to be more precise.
|
|
One such sensor is a
|
|
\emph on
|
|
Doppler velocity log
|
|
\emph default
|
|
(DVL) which estimates the vessel's velocity by tracking the seabed.
|
|
DVLs apply the broader concept of
|
|
\emph on
|
|
acoustic Doppler current profiling
|
|
\emph default
|
|
which measures the velocity of water by measuring the change in frequency
|
|
caused by the Doppler effect.
|
|
Combined with depth measurements calculated from the signal's echo time,
|
|
this can be used to estimate the vessel's velocity.
|
|
DVLs are crucial to a sub-sea INS as, like GPS, their error does not grow
|
|
when employed correctly unlike other relative sensors.
|
|
As described in section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "subsec:Navigation"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
, a sensor who's measurement error does not compound and grow but stays
|
|
constant is important as it places an upper bound on the overall error
|
|
and allows the system to maintain accuracy over time.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Power
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The ability to operate autonomously without an umbilical cord implies that
|
|
the UUV must have an onboard power supply.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As mentioned, much of the vehicle specification is being inherited from
|
|
existing ROV technology and this would include expected operating power.
|
|
The expansion of the UUV's capabilities to include autonomous operation
|
|
would primarily be completed through software and not significantly alter
|
|
the required power.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
300 kW was used as the required max power to calculate the energy storage
|
|
capabilities, an operating time of 10 hours was also defined.
|
|
An average draw of 50% max power was used to calculate 1.5 MWh of required
|
|
storage.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The previously described 18650 cells (section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "subsec:Proposed-UUV-Battery-Solution"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
) will be used for the UUV's battery pack, this will allow a single process
|
|
for sourcing and end-of-life processing and increase efficiency by utilising
|
|
the economy of scale.
|
|
As such, the previously mentioned notes on sustainability including processes
|
|
for second-use and recycling would apply to the UUVs battery pack.
|
|
\begin_inset Flex TODO Note (Margin)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
As described in the sustainability, operating at scale has allowed the carbon
|
|
cost of cells to go down, this is the same thing
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
Lithium-polymer batteries have found usage in AUVs as a result of their
|
|
lighter weight than Lithium-ion batteries.
|
|
While this will increase efficiency, it is proposed that the use of a single
|
|
supply chain will improve sustainability, a key parameter for this project.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The cell voltage (3.6 V) and capacity (3.5 Ah) were multiplied for 12.6 Wh
|
|
of power capacity per cell.
|
|
This would require 119,048 cells to meet the capacity requirements.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The battery system constitutes an extra 5,700 kg of extra weight for the
|
|
UUV, it is important that the battery be removable for tethered operation
|
|
in order to increase efficiency when independent operation is not required.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As this battery array will experience less usage than the surface vessel's
|
|
set, it is expected that it will last longer.
|
|
Despite undergoing less charge cycles, Lithium-ion cells still have a finite
|
|
lifespan and would not be expected to last beyond 4 years.
|
|
As such this is defined as the battery replacement time period.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
LARS
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The proposal for hybrid AUV/ROV capabilities somewhat simplifies the required
|
|
LARS methods.
|
|
As the vehicle must still be able to operate while tethered, from the surface
|
|
vessel's perspective a traditional LARS system with a top-hat TMS will
|
|
be used.
|
|
When operating as an ROV, the underwater vehicle will not have the battery
|
|
system mounted on the top and the tether will directly connect to the vehicle.
|
|
In these scenarios the LARS processes will be as previously described,
|
|
see figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:tethered tms"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename tms-lars.png
|
|
lyxscale 50
|
|
width 40col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
TMS and UUV structure when operating tethered
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:tethered tms"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
When operating autonomously, the battery system will be mounted on the top
|
|
of the vehicle.
|
|
It is proposed that the battery system have an interface for the top-hat
|
|
TMS on the top, see figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:untethered tms"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
An acoustic location and communication beacon will be mounted on the underside
|
|
of the TMS in order to provide a reference to the UUV for navigating towards
|
|
and docking,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "hugin-lars-article"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename tms-lars-auv.png
|
|
lyxscale 50
|
|
width 30col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Graphics
|
|
filename tms-lars-disconnected.png
|
|
lyxscale 50
|
|
width 50col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
TMS and UUV structure when operating autonomously, indicating mount point
|
|
for re-housing
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:untethered tms"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This allows the actual LARS processes to be conducted in the traditional
|
|
secure manor through the splash zone and then allow detachment for autonomous
|
|
operation when safely under the water.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Sustainability
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
With regards to the battery system, the same principles as described for
|
|
the surface vessel battery in sections
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "subsec:Life-cycle-Analysis"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "subsec:SurfaceVesselBatterySustainability"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
apply including procurement, and lifespan extension.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
However, the difference in usage patterns for the UUV may make the battery's
|
|
applicability to second-usage less viable.
|
|
This would be because it would be expected to sustain higher depth-of-discharge
|
|
without the ability to activate more ammonia cells and keep the capacity
|
|
higher.
|
|
As such the direct recycling processes previously described may be more
|
|
appropriate as an end-of-life procedure.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Using the previous per kilowatt embodied carbon value, a UUV battery set
|
|
represents 120 tonnes of carbon requiring offset to achieve net-zero.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Financials
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
UUVs and TMSs are typically bespoke, purpose-built projects without publicly
|
|
available prices.
|
|
As such estimations were made in order to cost the entire system.
|
|
UUVs with publicly available prices tend to be light intervention and autonomou
|
|
s survey vehicles with a max depth of 300m,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand cite
|
|
key "price-amron-rov,price-deep-trekker"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
These vehicles tend to cost between £24,000 and £50,000.
|
|
The proposed vehicle is far more powerful and is not the same class of
|
|
vehicle.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Including the advancements of autonomous capabilities it is proposed that
|
|
an industrial vehicle of the requirements described would cost £2,000,000.
|
|
Additionally it is proposed that the tether management system would cost
|
|
£400,000.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As described, a single type of Lithium cell are being used in order to benefit
|
|
from the economy of scale.
|
|
Using the previously specified £5 unit price, a set of UUV battery cells
|
|
will cost £595,240.
|
|
Modelling this across its lifespan averages to £148,810 per year.
|
|
For costing the associated BMS, the previously mentioned 60% cell cost
|
|
contribution would suggest a price of £397,000.
|
|
\end_layout
|
|
|
|
\begin_layout Subsubsection
|
|
Summary
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The proposed UUV describes an extension to existing ROV capabilities by
|
|
allowing untethered autonomous operations.
|
|
This requires a wireless communication channel between the surface and
|
|
underwater vessel which will be completed using acoustic waves.
|
|
The UUV will effectively be GNSS-enabled by proxy from the surface vessel,
|
|
allowing it to navigate to the fault locations.
|
|
In order to operate autonomously, the UUV will require onboard power, a
|
|
battery system of suitable scale was described along with protocols for
|
|
decommissioning sustainably.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Onboard Systems
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Flex TODO Note (inline)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
nav, comms systems
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Part
|
|
Digitalisation
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Before discussing how this project aims to leverage
|
|
\emph on
|
|
digitalisation
|
|
\emph default
|
|
it is worth defining the term and the adjacent term
|
|
\emph on
|
|
digitisation
|
|
\emph default
|
|
.
|
|
Digitisation describes the transforming of data or a process from an analogue
|
|
system to a digital one,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "workingmouse-digitalisation"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
It is a value-neutral term in of itself and could have positive or negative
|
|
effects.
|
|
A simple example would be transitioning from working with pen-and-paper
|
|
forms to digital documents and PDFs.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Digitalisation describes the use of digitisation to increase efficiency
|
|
and access new value-producing business opportunities,
|
|
\begin_inset CommandInset citation
|
|
LatexCommand citep
|
|
key "workingmouse-digitalisation,gartner-digitalization"
|
|
literal "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
To follow the above example, digitalisation could include using groupware
|
|
in order to collaboratively work on a cloud document as opposed to delivering
|
|
hard copy revisions of a document between locations.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As a broad concept, there are many ways that the concept of digitalisation
|
|
could be applied to this project, as a whole, though, the initiative could
|
|
be described as a
|
|
\emph on
|
|
smart ship
|
|
\emph default
|
|
.
|
|
Many of the features rely on interconnected sites, the internet network
|
|
topology can be seen in figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:Network-topology"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The surface vessel will be connected to the internet via two gateways.
|
|
While berthed, the vessel should be able to connect to the depot via Ethernet
|
|
which can be run alongside the shore power line.
|
|
For internet connectivity while at sea, the vessel will be equipped with
|
|
satellite internet apparatus.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\noindent
|
|
\align center
|
|
\begin_inset Graphics
|
|
filename ../network/NetworkDiagramJointDepot.png
|
|
lyxscale 30
|
|
width 75col%
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption Standard
|
|
|
|
\begin_layout Plain Layout
|
|
Network topology across the depot, vessel and cloud environment; main services
|
|
highlighted
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:Network-topology"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
With a fully connected environment, head-office and the depot will be able
|
|
to monitor and control aspects of the vessel.
|
|
In theory, head-office would be able to remotely command both the vessel
|
|
and UUV, although proper authorisation, safety and business practices would
|
|
need to be defined for where this is appropriate.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Live access will be available for information about the vessels including
|
|
location data, course information, battery capacity information and remaining
|
|
fuel levels.
|
|
This could be used in order to sync depot operations with the vessels mission
|
|
status, for example by preparing the local electrical supply for cold-ironing
|
|
the vessel.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Within the vessels, machine learning (ML) and AI will have varying applicability.
|
|
The UUV, for example, would likely apply both for applications such as
|
|
image recognition from the visual cameras.
|
|
Kalman filters have already been discussed for calculating the vessel's
|
|
location.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset bibtex
|
|
LatexCommand bibtex
|
|
btprint "btPrintCited"
|
|
bibfiles "references"
|
|
options "bibtotoc"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
\start_of_appendix
|
|
Battery Cell Calculations
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Battery-Cell-Calculations"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Flex TODO Note (inline)
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
C rates
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Time-dependent Power Modelling
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Time-dependent-Power-Modelling"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Power In
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As described in the premise for why a buffer is needed (section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sec:Energy-Storage"
|
|
plural "false"
|
|
caps "false"
|
|
noprefix "false"
|
|
|
|
\end_inset
|
|
|
|
), the power from the ammonia fuel cells will primarily be varied by changing
|
|
the population of active cells as opposed to drawing varied power from
|
|
each individually.
|
|
This allows the cells to operate as much as possible in their most efficient
|
|
state.
|
|
However, cells require time to turn on and reach this efficient state,
|
|
about 20 minutes.
|
|
This was modelled by having the input power move in discrete steps as cells
|
|
are turned on and off.
|
|
This step value was defined as 200kW, the most efficient state for a single
|
|
fuel cell.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As time increases, every twenty minutes the amount of active cells can be
|
|
incremented or decremented.
|
|
This over-simplifies the actual behaviour as this would, in reality, be
|
|
a gradual process as opposed to one of discrete steps, however, it was
|
|
deemed acceptable in order to enforce the time penalty in changing the
|
|
number of powering cells.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Power Out
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In order to model the load draw from the propulsion and hotel load, a random
|
|
differential was applied each second.
|
|
This was done in order to provide a dynamic environment, were the load
|
|
power to stay the same the battery would either charge or discharge entirely
|
|
and then stay in this state.
|
|
A random change each second more closely matches the expected power requirement
|
|
s as the wind and currents are also dynamic.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The max load differential was defined as 10 kW.
|
|
This means that each second the load could change by a maximum of
|
|
\begin_inset Formula $\pm$
|
|
\end_inset
|
|
|
|
10kW as a random number between -1 and 1 was generated and used as a coefficient.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The different stages of a mission were defined as having a maximum and minimum
|
|
load power which the random function was able to fluctuate between.
|
|
When dynamic positioning it could be expected that more power would be
|
|
used than when completing either the out or home-bound journey.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Efficiencies
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The charging and discharging of the battery is not a completely efficient
|
|
process.
|
|
In order to take this into account, both processes were treated as 80%
|
|
efficient.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Validity
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In terms of applicability, the model provides a good high-level approximation
|
|
of the relationship between the fuel cells and the battery usage.
|
|
In reality, however, the system would be far more complex.
|
|
For example, the model only increments or decrements the active fuel cells
|
|
by one at each twenty minute interval when in reality many could be activated
|
|
or deactivated simultaneously.
|
|
\end_layout
|
|
|
|
\end_body
|
|
\end_document
|