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.

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.

Conclusions

De-carbonisation is changing the way we generate, distribute and use electricity. As some of the technologies are developed and get cheaper, the opportunities as well as the need for successful deployment of electricity storage will increase. Electricity storage will be able to help achieve de-carbonisation targets provided that it is charged from surplus low-carbon electricity.

At present, pumped hydroelectric is the mature and dominant energy storage technology. Of many other technologies that have potential to make a significant contribution, battery technologies are advancing the most rapidly; costs are coming down and the rate of installation (mostly lithium-ion) is increasing quickly.

None of the challenges noted above should be regarded as reason to hold back on the deployment and growth of energy storage. The need for change is not confined to electricity. In all aspects of the built environment, engineers must seek to reduce whole-life greenhouse gas emissions in line with targets. See also ICE’s briefing sheet on heat.

Further reading

• Electricity storage: Realising the potential, ICE, 2015
• The rise of electricity storage: something for everybody, Brookings, 2015
• Is large-scale energy storage dead?
• The Catch-22 of Energy Storage
• Energy Storage Association
• The Electricity Storage Network
• Status, Role and Costs of Energy Storage Technologies, Store, March 2012
• Energy Storage: The Missing Link in the UK’s Energy Commitments, IMechE (2014)
• DOE [Dept. of Energy, USA] Global energy storage database, Sandia National Laboratories, accessed December 2017
• Energy storage – technologies and applications, Zobaa, Ahmed Faheem, InTech. ISBN 978-953-51-0951-8, January 2013 (open access)
• Energy Storage: Opportunities & Challenges, AXIS and Renewables Consulting Group, August 2017
• Government of South Australia, 2017^[1]