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Investing in pumped hydro storage could save up to £690m a year on pathway to net zero

18 Feb 2021

An artist's impression of Coire Glas, south west of Laggan Locks near Loch Lochy, Highland

A new study by independent researchers from Imperial College London has found that just 4.5GW of new long duration pumped hydro storage with 90GWh of storage could save up to £690m per year in energy system costs by 2050, as the UK transitions to a net-zero carbon emission system.

Commissioned by SSE Renewables via Imperial Consultants the report focused on the benefits of new long-duration pumped hydro storage in Scotland, as the current most established long-duration energy storage technology. The main benefit of long duration storage compared to short duration batteries is being able to continuously charge up the storage with excess renewables and also discharge power to the grid for several hours or days when wind and solar output is low.

In its recent Energy White Paper, the UK Government set out that long-duration storage technologies like pumped hydro, would play an essential role in decarbonising UK’s electricity supply by integrating renewable energy and maintaining security of supply.

In October, SSE Renewables received a revised consent from the Scottish Government for what would be the UK’s largest pumped hydro energy storage scheme – Coire Glas – located near Loch Lochy in the Scottish Highlands.

The proposed 1.5GW (30GWh) Coire Glas scheme would more than double the current amount of pumped hydro storage capacity in Great Britain, providing an invaluable low carbon resource to help cost effectively manage the fluctuations of the electricity system.

The study, by Imperial’s researchers, found that 75% of the savings to the energy system from projects like Coire Glas would be from the avoided capital expenditure in higher cost electricity generation technologies that would otherwise be needed to meet the UK’s target of carbon neutrality by 2050 whilst meeting security of supply.

Importantly, the report highlighted that despite all of the benefits which new pumped hydro storage projects would bring, the current policy and market framework is unlikely to bring forward investment in many new projects because the long duration and low carbon capability of pumped hydro storage is not sufficiently valued.

Professor Goran Strbac, from Imperial’s Faculty of Engineering led the study. He explained:

“The analysis carried out demonstrated that new Long Duration Pumped Hydro Energy Storage located in Scotland, can reduce system costs by providing a number of services to the GB net-zero emission energy system.”

“These are:

- reduced wind curtailment by storing excess renewable production and discharging it when needed;

- provision of critical ancillary services needed for integrating a high penetration of renewable generation, particularly frequency response and operating reserves, while enhancing system inertia.

- reducing system emissions by displacing operation of some conventional (fossil-fuel based) mid-merit and peaking plant.


- supporting network congestion management and reducing the need for transmission network reinforcement between Scotland and England.”

Mike Seaton, Director of Development at SSE Renewables welcomed the report and said:

“The findings in this report support our view – that pumped hydro storage projects like Coire Glas have a huge role to play in the UK achieving its ambition of net zero carbon emissions by 2050 in the most cost-effective way possible.”

“Following the recent reconsent of Coire Glas we are now progressing the project through further refinement and studies and believe it could come online by the end of the decade, generating thousands of jobs in the process”

“However, there are commercial hurdles that we still need to overcome if such a large civil engineering project is to become a reality. The current policy and market framework are not yet suitable for attracting investment in such large-scale storage projects, although the UK Government has set out its intention to address those barriers to investment."

Paul Wheelhouse MSP, Scotland’s Minister for Energy, Connectivity and the Islands, said:

“I warmly welcome this report from the researchers at Imperial College London, and the spotlight it shines on the value of pumped hydro storage in a net zero power system. The Scottish Government has long been supportive of pumped hydro storage for its role in ensuring resilience in our electricity supplies, and for the tremendous opportunity it provides to unlock the potential of renewable energy and support Scotland’s net zero ambitions.

“Scotland is a leader in this field, with excellent hydro-electric power heritage built over the last century. As we add more renewable electricity generation across Scotland, investing in pumped hydro storage will be key to balancing our electricity demand with supply and keeping the system secure, as well as creating high quality, green jobs and enabling a green recovery from the COVID-19 pandemic. That is why we continue to call on the UK Government to take urgent steps which are essential to provide investors with improved revenue certainty and unlock potentially significant investment in new pumped storage capacity in Scotland.”

Download the full report: Whole-System Value of Long-Duration Energy Storage in a Net-Zero Emission GB Energy System

For more information about Coire Glas go to: