1,500 pumped hydro plants of storage needed, says Royal Society

The equivalent of 1,500 pumped hydro plants would be required to provide the minimum amount of storage to enable the UK’s transition to a wind and solar powered grid, the vice-president of the Royal Society has estimated.

Giving evidence to the House of Lords Science and Technology Committee, Sir Peter Bruce outlined the findings of the society’s new report on long duration energy storage.

He said the report had concluded that the cheapest way of decarbonising the UK’s power system would be to prioritise solar and wind power.

In order to cope with the intermittent supply of electricity from these weather-reliant technologies, Bruce said the report backed the use of hydrogen produced using renewable sources when there is excess generation.

But he said that up to 100 terawatt hours (TWhrs) of electricity storage may be required to meet demand when there is little or no wind for days and weeks at a time.

Even with a mix of nuclear and gas-fired CCS (carbon capture and storage) plants added to the mix, at least 30 TWhrs of storage would be required, said Bruce, who is also the Physical Secretary of the august natural sciences academy.

This, he told the committee, would be equivalent of about 1,500 new pumped hydro storage power stations.

Only a handful of these plants, which work by pumping water from a lower to a higher reservoir when electricity is cheap and then releasing it through turbines to generate electricity, have been built in the UK.

Bruce said that building 1,500 pumped hydro plants is “not practical” given how big each one is.

The most cost-effective long-term storage option, according to the report, is to exploit the low cost of excess renewable electricity by producing hydrogen, which can then be stored in salt caverns and used to generate electricity when required.

While the price of the hydrogen generated electricity would be more than £100/MWhr, it would only be required for around 14% of the time, pushing up the overall power price in a renewable dominated system to £55-85/MWhr, it says.

This is higher than the average of £45/MWhr in the decade leading up to 2021, Bruce added.

However he told the committee that the society’s researchers had estimated that the upper end of this range would be lower than the cheapest estimates for a system relying on nuclear energy.

Earlier Caroline Still, senior associate at Aurora Energy Research; had told the committee that hydrogen-powered generation would play a “small but important part” in the generation mix.

In the consultancy’s net zero scenario, hydrogen would provide 1.5% of total generation, she said: “It’s the only technology that can provide power at that last minute point” because all gas fired plants will have been decommissioned.

However Still estimated that only 5% to 10% of total hydrogen demand would be likely to come from the power sector because there will be greater need for the gas from harder to decarbonise parts of the economy.