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Pump it Up: The case for Pumped Hydro Storage

18 Feb 2021

There are many challenges to be overcome on the road to net zero but a big one is how we move to a 100% green electricity system to power our homes, businesses, EVs and more.

Whilst we know that renewables will end up generating most of the power the country needs, we also know that wind and solar are not always available.

In Great Britain today, we mainly rely on gas power stations to balance the grid but that has carbon emissions associated with it. We also know there are already periods during the year when renewables are providing more electricity than the country needs and whilst we can store very small amounts and export some; some is going to waste.

A big part of the solution is energy storage, which comes in many forms. In terms of electricity storage, there are of course lithium ion batteries. These are great for rapid, short term system response but are not cost effective for longer durations.

The benefit of long duration storage 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 the long term innovative forms of storage like hydrogen and compressed air may well play an important role but today there is a proven renewable long duration storage technology which has been around for decades – pumped hydro storage.

In addition to the ability for pumped storage schemes to provide huge volumes of energy storage capability, they are also able to provide key support services to assist the efficient running of the electricity system, particularly frequency response and operating reserves, while enhancing system inertia.

This video explains how it works:

At Coire Glas in Scotland’s Great Glen, SSE has a pumped storage hydro project ready to go.  If built, it would have capacity to generate up to 1500MW of electricity and have 30GWh of storage – more than all of the UK’s current pumped storage capacity combined.

At SSE Renewables we have been convinced of the case for the country needing more pumped storage for a while. So we asked independent researchers from SSE’s academic partner, Imperial College London, to model what the value of additional long duration pumped storage would be on the pathway to reaching net zero by 2050.

The research, by flexibility modelling expert Dr Goran Strbac and his colleagues, found that 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. That is the equivalent to 3 Coire Glas projects.

The study found that 75% of the savings to the energy system would be from the avoided capital expenditure in higher cost electricity generation technologies, such as new nuclear, that would otherwise be needed to meet the UK’s target of carbon neutrality by 2050 whilst also meeting security of supply.

It also found that we would waste a lot less of the renewable power we generate because more of it could be stored in pumped hydro reservoirs ready to be used when needed.

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

In the next few months, BEIS and Ofgem will publish a proposed update to their Smart System and Flexibility Plan, including how to address barriers to long duration storage. We believe this offers an excellent opportunity to consult specifically on the need for long duration storage and the most cost-effective policies to bring those technologies to market.

Coire Glas, along with other possible new pumped storage sites, have a vital role in the transition to net zero.  They can also create thousands of jobs at a time when they will be most needed, as our economy looks to recover from the COVID pandemic.

Download the final report here.