Investing in pumped hydro storage in Scotland could save up to £690mn a year in energy system costs by 2050, according to researchers from Imperial College London.
On 18 February, the results of the SSE Renewables-commissioned study were published, revealing that these savings could be realised from just 4.5GW of new long duration pumped hydro energy storage with 90GWh of storage. In contrast to short duration batteries, long duration storage is able to continuously charge up the storage with excess renewables while discharging power to the grid for several hours a day, during periods of low wind or solar output.
Around 75% of the savings would be achieved from the avoided capital cost in low carbon electricity technologies that would otherwise be needed to meet decarbonisation and security of supply objectives. Wider benefits include reduced wind curtailment, between 3TWh and 11TWh a year, by storing excess renewable output and discharging it when needed, as well as providing critical ancillary services that are needed for integrating a high penetration of renewable generation.
It would also lead to a reduction in system emissions by displacing some conventional mid-merit and peaking plant; supporting network congestion management with it able to reduce the need for up to 2GW of transmission between Scotland and England in 2050, saving £2bn; and its ability to complement other storage and flexible technologies, such as cutting the need for hydrogen storage by up to 10%, or 110GWh, given the close interactions between hydrogen and electricity systems.
However, despite the benefits, the report found the current policy and market framework is unlikely to bring forward investment in many new projects. This is due to the long duration and low carbon capability of pumped hydro storage not being sufficiently valued. While developing the right framework is in need of further analysis, it could include a real-time carbon price market that captures the investment and operating cost of the system to meet the carbon target. This would provide an appropriate economic signal and incentive for long duration pumped hydro energy storage to support the integration of renewables and reduce the required capacity of high-cost firm low-carbon technologies.
Further analysis was also recommended on how the cross-sector technology benefits, such as the integration between hydrogen infrastructure and the electricity system, can be recognised to maximise potential cost savings to energy consumers.