UK: Storage need intensifies as wind curtailment costs hit £400m

• 10 per cent of the UK’s wind power was curtailed in 2024 
• Inadequate grid infrastructure, as well as lack of storage, key factors
• More storage could save UK up to £3.5 billion per year, says one study
• Orsted’s incorporation of storage into Hornsea 3 offshore wind project is ‘blueprint for future’

“Without large-scale energy storage and grid upgrades, we will continue wasting clean energy and paying the price for it.” This was the verdict of Dr Iain Staffell of Imperial College London last week as pumped storage hydro company Drax published data showing that 8.3 terrawatt hours of wind power, around 10 per cent of the total produced in the UK, had to be curtailed due to grid congestion in 2024, costing consumers nearly £400 million. Drax said this was enough energy to power more than two million homes.

Of particular concern is the fact that, in just one year, the rate of wind curtailment has approximately doubled – from 5.5 per cent to more than 10 per cent, largely due to Scotland’s wind farms producing more energy than the grid can carry south to demand centres in England.

Inadequate grid infrastructure and lack of energy strorage

Drax highlighted how the productivity of the wind sector is being hampered by inadequate grid infrastructure as well a lack of much-needed energy storage facilities. Wind capacity in Scotland had risen more rapidly in recent years, however, the transmission links that carry output down to demand centres in England are now heavily congested. As Scottish Government statistics show, Scotland’s renewable electricity capacity – the vast majority of which is onshore and offshore wind – more than doubled in the period 2013 to 2023 (see chart below), and increased by 10 per cent to 15.3GW in one year alone (from 2022 to 2023).

Source: Scottish Government (www.gov.scot)

The problem for the wind sector is that statistics on curtailment are being used by sections of the media to paint a picture of wind sector inefficiency, despite the problem actually being an underdeveloped grid that is not being expanded sufficiently to accommodate new wind power generation projects. For example, some reports have focussed on the 1GW SeaGreen wind farm – off the coast of Angus in Scotland – which came online late in 2023, but last year had 70 per cent of its electricity wasted due to grid congestion.

How storage could reduce the cost of reaching net zero 

In response, Drax has called for the rapid scaling up of storage facilities such as long-duration energy storage (LDES) and battery energy storage systems (BESS), alongside better grid infrastructure, to allow more wind power to be stored and released when needed, preventing the grid from relying too heavily on gas during ‘dunkelflaute’ [a German term for low wind and solar output] periods.

The case for incorporating more storage in wind projects is compelling. Studies have shown that implementing medium-duration energy storage (10 to 100 hours) could significantly reduce the cost of reaching net zero. One study projected that energy storage could save the UK between £500 million and £3.5 billion per year, with “greater annual savings the sooner storage is implemented”. The report also concluded that energy storage could increase the UK’s wind capacity by 11 TWh per year, without any curtailment costs.

Source: Storelectric (storelectric.com)

While grid upgrades would certainly reduce curtailment, the wind sector knows that incorporating energy storage into wind projects is part of the solution. To date, the energy storage industry has found itself more naturally aligned with the solar sector than the wind industry. This phenomenon is particularly evident in the US where, according to statistics supplied by the Lawrence Berkeley National Laboratory (Berkeley Lab), 571 GW of solar hybrids (primarily solar and battery), compared to just 48 GW of wind hybrids, are currently in US interconnection queues. Berkeley Lab has also said that solar and battery storage are, by far, the fastest growing resources in the queues – combined, they accounted for more than 80 per cent of new capacity entering the queues in 2023.

Storage at Hornsea 3: A ‘blueprint for the future’

Yet the wind industry is making more progress in terms of maximising the benefits of energy storage systems. For example, Ørsted’s Boudica project, which is owned by Ørsted ICENI Energy Storage UK Ltd, will include a 300MW / 600MWh battery energy storage system (BESS) on the same site as Ørsted’s Hornsea 3 Offshore Wind Farm Onshore Substation in the UK. Bridgit Hartland-Johnson, chief specialist, system integration at Ørsted, has described the project as a “blueprint for the future”. The Boudica project is a pathfinder project designated by the UK Government’s Offshore Transmission Network Review (OTNR). UK energy minister Michael Shanks has previously emphasised the need to store more renewable energy, and has highlighted the Boudica project as a prime example of the steps being taken to achieve this objective. Shanks said that innovative battery storage projects, such as Boudica will help the UK fulfil its objectives of making the most of its “clean, homegrown power and reducing our exposure to volatile fossil fuel markets”.

More wind projects need to include energy storage facilities. Successfully doing so will do more to combat accusations of wasting wind power, while also maintaining the wind sector’s position as a viable alternative to solar energy. For its part, the offshore wind industry says more could be done to encourage more battery and green hydrogen projects to co-locate with offshore wind farms. For example, RenewableUK published a report last month calling for reform of Contracts for Difference (CfD) auctions to encourage the co-location of energy storage and offshore wind, as well as improvements to the efficiency of the planning system that would enable developers to seek consent for offshore wind and energy storage projects simultaneously rather than separately. Enacting such reforms must now be a priority.