The Royal Society has published a report exploring large scale electricity storage. The Executive Summary begins with a useful clarification of the problem we face:

The UK Government has a stated ambition to decarbonise the electricity system by 2035 and is committed to reaching net zero by 2050. As Great Britain’s electricity supply is decarbonised, an increasing fraction will be provided by wind and solar energy because they are the cheapest form of low-carbon generation. Wind and solar supply vary on time scales ranging from seconds to decades. However high the average level of supply might be, there will be times when wind and solar generation is close to zero and periods when there is enough to meet part of but not all demand, as well as times when it exceeds demand.

To ensure that demand is always met, the volatile wind and solar generated electricity that is fed directly into the grid must be complemented by other flexible low-carbon sources, and / or using excess wind and solar energy that has been stored. The excess could be stored in a variety of ways, for example electrochemically in batteries, gravitationally by pumping water into dams, mechanically by compressing air, chemically by making hydrogen, or as heat.

There is a useful Policy Brief which has easily accessible data and graphic information.

The overall message is that we have seriously underestimated the need for energy storage. Its ‘major conclusions’ are:

In 2050 Great Britain’s demand for electricity could be met by wind and solar energy supported by large-scale storage.

• The cost of complementing direct wind and solar supply with storage compares very favourably with the cost of low-carbon alternatives. Further, storage has the potential to provide greater energy security.

• Wind supply can vary over time scales of decades and tens of TWhs of very long duration storage will be needed. The scale is over 1000 times that currently provided by pumped hydro in the UK, and far more than could conceivably be provided by conventional batteries.

• Meeting the need for long-duration storage will require very low cost per unit energy stored. In GB, the leading candidate is storage of hydrogen in solution-mined salt caverns, for which GB has a more than adequate potential, albeit not widely distributed. The fall-back option, which would be significantly more expensive, is ammonia.

• The demand for electricity in GB in 2050 is assumed to be 570 TWh/year in most of this report. In principle it could all be met by wind and solar supply supported by hydrogen, and some small-scale storage that can respond rapidly, which is needed to ensure the stability of the transmission grid. With the report’s central assumptions, this would require a hydrogen storage capacity ranging from around 60 to 100 TWh (depending on the level of wind and solar supply). The average cost of electricity that is available to meet demand varies very little over this range as the rising cost of wind and solar supply is offset by the decreasing cost of the storage that is needed. Although some hydrogen (or ammonia) storage will be needed, it is quite likely that a portfolio of different types of storage would lower the average cost of electricity.

• Including steady nuclear (‘baseload’) supply would increase costs, unless the cost of nuclear is near or below the bottom of the range of projections made by the Department for Business, Energy and Industrial Strategy (BEIS) and / or the costs of storage are near the top of the range of estimates in this report. The addition of bioenergy with carbon capture and storage generation (BECCS) would lower the cost if it attracts a carbon credit of order £100 / (tonne CO2 saved) or more, but it could not provide GB with more than 50 TWh/year without imports of biomass.

• Using natural gas generation equipped with carbon capture and storage (CCS) to provide flexibility, instead of storage, would lead to unacceptable emissions of CO2 and methane, and also to higher costs. Used as baseload, it would only lower costs appreciably if added in amounts that would lead to unacceptable emissions; the future price of natural gas is lower than expected; and storage costs are high.

• Using a combination of storage and gas plus CCS to provide the flexibility required to match wind and solar supply could lower costs significantly, without necessarily leading to unacceptable emissions. Whether it would lower costs depends on the costs of storage, wind and solar power, and gas plus CCS, the price of gas and the carbon price. It would not remove the need for large-scale long-term storage, although it would reduce the required scales of storage and wind plus solar supply. While it would provide diversity, it would expose GB’s electricity costs to fluctuations in the price of gas, and increasing reliance on imports as GB’s gas reserves decline.


The publication explores the issues surrounding these vitally important issues for our futures.

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