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How Britain’s biggest natural battery can help deliver net zero

SSE wants to double the nation’s flexible electricity storage capacity.

After previous delays and false starts, governments and businesses across the world are pushing towards the common goal of net zero. The energy sector is arguably the area with the biggest responsibility to work towards this target, and there is no time for complacency.

Ensuring clean, renewable energy sources such as hydrogen, wind and solar power become a larger part of the grid will be critical for the sector in its push towards net zero. A key facet of the clean energy drive will be having sufficient storage for each renewable power source kept in reserve, to be used as and when required as a crucial back-up mechanism. In last spring’s energy security review the government outlined its commitment to support long duration storage projects.

Energy company SSE wants to build Britain’s biggest pumped hydro storage facility at Coire Glas, in the Scottish Highlands. The £1.5bn+ project would help maintain supplies of clean, secure and flexible renewable energy, when other sources of renewable energy supplies – if it isn’t particularly windy, or sunny, for example – are in short supply.

Coire Glas could become Britain’s largest natural battery and if built, the proposed water battery would double Britain’s current flexible electricity storage capacity and could power three million homes across the country for up to 24 hours.

“At a group level, SSE’s strategy is completely focused on delivering the decarbonisation of the energy system,” said Finlay McCutcheon, the director of onshore renewables at SSE Renewables. “What Coire Glas provides is an extraordinary level of flexibility to support a larger penetration of wind and solar energy, because it has massive storage potential.”

Coire Glas could function in a variety of ways, McCutcheon continued. “It can be used for days; you can run it at full maximum load for over 24 hours, or it could run day after day through the evening peak hours. But at the same time, it could run for minutes. You can go from zero output to full output within five minutes. So the grid can use it in a whole range of ways. It is a genuinely renewable decarbonised form of flexibility that enables the grid to support more and more wind and solar to displace oil and gas provision.”

Subject to the outcome of ongoing exploratory works at the site as well as the prevailing policy environment for long duration electricity storage, SSE stands ready to unlock investment in the project, which it believes could be operational by 2031. SSE is calling on the UK government to help it commit to building the Coire Glas storage facility by providing one simple policy decision that will send a clear signal as to how government intends to support the deployment of long duration electricity storage. The project doesn’t need subsidising, SSE states, but it would benefit from revenue stabilisation, and clarity on such support sooner rather than later.

“We have a clear government target to have a decarbonised net zero power system by 2035, and I’m convinced that’s possible,” said McCutcheon. “Pumped hydro storage has a massive potential to enable that,” he continued. “But, these are large, complex projects… if Coire Glas is going to play its part, it needs to be getting a final investment decision in the next couple of years, and it needs to be being built in the 2020s.”

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In March this year, SSE announced it would be investing upfront an extra £100m as a “down payment” towards the Coire Glas project and its development. Around half of the money will be spent on initial exploratory site work, which will contribute additional information about the project, ahead of an expected final investment decision on the full £1.5bn+ plan in 2024. Gregor Alexander, SSE’s finance director, said that the early £100m funding for Coire Glas research “signals a significant down-payment by SSE to keep this critical project moving forwards”.

He added: “Our ability to reach a positive final investment decision will clearly depend on the prevailing policy environment for long duration electricity storage and long-term infrastructure projects more broadly.”

In May, SSE announced plans to convert its existing hydro power station in Sloy, located on the west bank of Loch Lomond in Scotland, into a new pumped hydro storage facility aimed at bolstering energy security. Humza Yousaf, First Minister of Scotland, visited the site to mark the 80th Anniversary of the 1943 Hydro Electric Development (Scotland) Act and said Scotland is one of the “world leaders” in renewables.

“Hydro power was the country’s original source of renewable energy and it has the potential to play a significantly greater role in the transition to net zero – both on a small scale in cooperation with local communities, and on a larger scale to help to ensure a continued resilient and secure electricity supply,” said Yousaf.

The First Minister added: “We will continue to call for the UK government to provide an appropriate market mechanism for hydro power and other long duration energy storage technologies, to ensure this potential is fully realised.”

The case for committing to support pumped hydro projects such as Coire Glas is “urgent”, says McCutcheon. “We’re going through an amazing transition into a decarbonised energy system, and there are lots of things that we don’t know for sure right now,” he said. “But we’re in a climate crisis – so we need to get building and operating the things we do know will work and play a leading role in delivering a decarbonised and secure energy system.

“That starts with investing in wind, solar and long duration energy storage,” McCutcheon continued. “Pumped hydro storage can play a huge role in the UK’s decarbonised power sector. So, we need to unlock the potential and get this new generation of pumped storage hydro built through the 2020s and early 2030s. We need to crack on and get it done.”

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