Energy Storage

Electricity storage will play an increasingly important role in supply and distribution. This paper is a summary of the relevance of electricity storage at ‘utility level’ and ‘grid level’ (say 10 to 1000 MW), the technologies, the potential costs and benefits, and some issues to do with facilitating implementation.

Energy Storage options include pumped hydro storage lakes
Energy Storage options include pumped hydro storage lakes

Electricity storage will play an increasingly important role in supply and distribution. This paper is a summary of the relevance of electricity storage at ‘utility level’ and ‘grid level’ (say 10 to 1000 MW), the technologies, the potential costs and benefits, and some issues to do with facilitating implementation.

Roles and benefits of electricity storage

In the context of large-scale storage of electricity (from say 10 MW upwards), two main roles and their benefits are considered here.

  • Ancillary services: until recently, the UK electricity system was characterised by a relatively small number of massive rotating generators feeding power ‘one way’ to consumers via the transmission and distribution networks. The diverse and highly distributed nature of renewable generation, often using power electronics, can result in power flows and fluctuations at variance with the original designs of networks. Electricity storage can help maintain stability and optimise use of networks.
  • ‘Time-shifting’: outputs from wind and solar generation are variable and/or unpredictable and cannot be adjusted to match demand. As demand increases at peak times, increasingly expensive and inefficient fossil-fuelled generators are called. Low carbon energy stored at off-peak times could ‘fill the gaps’ in intermittent renewable generation and displace peaking plant, reducing costs, helping to meet carbon reduction targets and increasing capacity margins.

Both the above may help postpone or avoid enhancement or replacement of existing infrastructure.

Electricity storage can generally respond to changes in demand more quickly than generation, whether storing or exporting. Comparing some sources of electricity generation and storage: the output from nuclear power stations tends to be varied slowly and is used to serve ‘base load’; coal-fired stations can ramp up or down by about 5% of their installed capacity per minute; gas turbine power stations can respond more quickly; Dinorwig pumped storage station can take up 1,320 MW of load in 12 seconds if synchronised in ‘spinning reserve’; batteries can respond to load fluctuations within say 1 second. Keep in mind that installed capacities of thermal generation are typically up to 2,000 MW; the biggest battery installation at November 2017 is 100 MW[1].

Therefore, well designed and implemented electricity storage systems may help address the energy ‘trilemma’, that is the simultaneous achievement of decarbonisation, security of supply and affordability.

Storage offers further particular benefits; see ‘Further reading’ below.

Storage technologies

In practice, electricity is converted to potential, kinetic or chemical energy from which it is converted back to electricity on demand. Technologies are listed in roughly decreasing level of maturity and scale.


[1] Government of South Australia, 2017, http://ourenergyplan.sa.gov.au/battery.html

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