Why Energy Storage? | Grant Wilson

1. Why Energy Storage ?
Dr Grant Wilson
The University of Sheffield
EPSRC’s Energy Storage for Low Carbon Grids consortium
grant.wilson@sheffield.ac.uk
#driagwilson

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• The talks this morning have provided details on
several different uses and technologies of
energy storage
• They all have a common goal to provide a
buffer, a balance between the supply of energy
and the demand of that energy – the differences
are in the scale, type of energy transformation or
final energy use, and the timeframes that the
energy is expected to be stored for

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• This has always been the case - energy
networks have always depended on energy
storage to help match supply with demand over
different timescales
• It is a question of where the boundary is drawn
for analysis – this presentation considers grid
level energy flows
• So rather than imagine that a large amount of
energy storage is something novel – let us
rather imagine that the tasks we wish energy
storage to fulfill are changing

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• The ‘Why Energy Storage ?’ question may be
easy to answer - we have always had it – and
will always need it – but it depends
• Energy systems are changing, and that change
is providing some challenges that different types
of energy storage may help to mitigate

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• Main driver for change: to decarbonise the
electrical network – the UK seems likely to have
a combination of Nuclear, Onshore and Offshore
Wind, Coal & Gas with Carbon Capture
• Nuclear, Coal & Gas are dispatchable to a
degree, but dependent on the technology and
the carbon capture process too
• On electrical demand – lets have a look at
recent history for some indication of the
challenges for balancing within a day
Electrical network

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GB electrical load curve

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GB electrical load curve

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GB Daily energy graph
Each box on the grid is ~ 6,000
GWh = 600 Dinorwigs
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leum products for inland consu mption from DECC website
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3000 GWh
GB Daily energy graph
Each box on the grid is ~ 6,000
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• Energy storage has vastly different types of
scale. At the 1000s of GWh size – (fossil) fuels
are the usual choice for stored energy
• Immensely useful – risks are well known
• However, they cause greenhouse gas emissions
when combusted and are finite
• Can be thought of as pre-conversion storage
(electricity or indeed heat)
A matter of scale

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Total existing
(30GWh) and
potential (60GWh)
would be less than
100 GWh of
electrical energy
storage
Currently Scotland
has nearly 60% of
GB’s energy
capacity of PS,
and if schemes
are built – it would
have over 85%

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One Q-Max class LNG tanker
has an energy capacity of > 1,600 GWh (£16million for each
1p/kWh)
@ 50% conversion efficiency CCGT equates to 800 GWh
~ 29 times all GB pumped storage (80 Dinorwigs)
Pictures sourced from www.gcaptain.com
A matter of scale

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A matter of scale
Mild winter caused
less draw down on
coal stocks ?

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• GB’s electrical demand follows a daily cycle
• Within day storage/balancing is a focus for much
research and pilot stage activity
• Any mention of seasonal storage is well into the
TWh region – which suggests fuels or thermal
storage rather than electrochemical storage
• 1 GWh of storage at £300 per kWh is
£300million
• 1 TWh of storage at $100 per kWh is $100billion
A matter of timescale

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A matter of timescale
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Each box on the grid is ~ 6,000
GWh

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A matter of timescale
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Each box on the grid is ~ 6,000
GWh

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A matter of timescale
Purple line is gas to gas storage
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Each box on the grid is ~ 6,000
GWh

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EV sales in UK
Plug-In Car Grant: Since the launch of the Plug-In Car Grant in January 2011
there have been 14,274 eligible cars registered
There are approximately 29 million cars registered in the UK
What about electric vehicles ?
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• Lets take 1/10th of a round figure of 30 million
vehicles = 3 million vehicles
• Lets take an average battery pack of 33 kWh
• This gives a value of 99 GWh – in daily terms a
sizeable manageable demand but in weekly or
seasonal terms – not very much at GB level
• Also – this presumes that each battery would
require charging every day (unlikely) e.g. if 20%
of the charge was used each day on average –
the figure would be even lower at 20 GWh
What about electric vehicles ?

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A matter of timescale
99 GWh per day is half of the difference between a
week day and a weekend or roughly half the UK’s
nuclear output (before the drop off this August)
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Each box on the grid is ~ 6,000
GWh

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• Cheapest post conversion storage is pumped
hydro
• Coire Glas suggested price of £800 million
equates to <£30 per kWh installed
• Order of magnitude less than battery based
systems
A matter of cost

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• If storage is providing a service of matching
demand and supply – what else can help ?
• And what are the comparative advantages and
disadvantages ?
• Does it compete or complement
• Interconnection to enlarge the network (same
energy carrier)
• Demand side management
• Interconnection (change of energy carrier)
A matter of what else is available

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Scotland gas transit
Each rectangle on the grid is ~ 6,000 GWh

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• Up to 800 GWh per day transmitted to England,
equating to equivalent power of 33 GW
• Electrical connection between Scotland and
England is thought to be 3.3 GW – but
increasing to 6.5 GW by end of 2015
A matter of what else is available

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GB electrical load curve

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GB electrical load curve
Each rectangle on the grid is ~ 100 MWh

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• We have not mentioned frequency control or
distributed energy storage – which are both
likely to be major areas of growth
• Also – if an energy system is to be
decarbonised, it needs low-carbon energy
sources and low carbon balancing
• Finally, there is the question of access to any
large storage scheme – maybe lessons to be
learnt from interconnectors ?