John Scrimgeour, Non-Executive Chairman of the Board at Archer Knight

"Currently, the UK’s total energy storage capacity is around 18 GWh, which would power about one-sixth of the UK for around three hours. If the storage were spread across the whole country, it would last only 30 minutes."

Earlier this month, I came across an article about the new government agency, National Electricity System Operator (NESO), tasked with improving energy security, reducing energy costs, and advancing the clean power supply. The goal is to source all electricity from renewable sources by 2030. One of NESO's key priorities is to identify energy storage technologies that can store sufficient power during periods of high renewable generation to cover times of low generation (e.g. low wind, high wind, or lack of sunlight). However, the example technology of giant flywheels, mentioned in the article, seemed inadequate for mass storage, highlighting how far we are from achieving workable, large-scale energy storage solutions.

So, what is the current UK energy storage situation, and what new generation capacity would be needed to deliver all our electricity from renewable sources by 2030?

Most of the current energy storage comes from Pumped Hydro Storage (PHS), including large projects at Dinorwig in Wales and Cruachan in Scotland. PHS supplies around 90% of the UK’s storage capacity, with batteries contributing another 8%, and the remainder from thermal and compressed air. Hydrogen is currently supplying only experimental capacity.

A challenge arises in that PHS project sizes are often stated in terms of their deliverability, such as Dinorwig’s 1.7 gigawatts (GW), which refers to the size of the generating engine rather than the reservoir's usable storage capacity. Dinorwig’s reservoir can store over 10 gigawatt-hours (GWh) of pumped water, meaning it can deliver its nominal 1.7 GW capacity for around six hours. This is at the higher end of existing storage capacity, with PHS typically delivering energy for 4-6 hours and batteries for 1-4 hours.

Currently, the UK’s total energy storage capacity is around 18 GWh, which would power about one-sixth of the UK for around three hours. If the storage were spread across the whole country, it would last only 30 minutes!

This hypothetical situation shows that during periods of low renewable generation (e.g., low or too strong wind, no sun), the country would soon face blackouts without electricity from other sources such as gas, nuclear, or imports. Current storage levels can help stabilise grid voltage and frequency, but they cannot sustain the electricity supply during extended periods of low generation.

Globally, PHS accounts for over 90% of energy storage capacity, and although the UK has relatively high storage capacity per capita, the rest of the world is not moving as quickly toward 100% renewable electricity generation.

The government has set a target to increase the UK’s electricity storage capacity to 30 GW by 2030, which is seven times the current level. However, electricity demand is expected to rise from an average of 35 GW today to between 50 and 60 GW by 2030, mainly due to the electrification of transport and heating. This would provide enough stored power to keep the country going for 3-4 hours. Without gas generation, the UK would face significant shortages, relying only on nuclear power (currently with a 6 GW capacity, increasing to 9 GW when Hinkley Point comes online in 2031). As a result, large-scale imports—potentially up to 50 GW—would be required by 2030. However, it’s unlikely that neighbouring countries would have sufficient surplus electricity to supply the UK, especially if they experience similar low renewable generation conditions.

Looking further ahead, as the UK continues to electrify transportation and heating, electricity demand could increase from the current 35 GW average to around 100 GW by 2050.

In conclusion, the UK is far from being able to store sufficient electricity to cover extended periods of low renewable generation. While PHS can help bridge short-term gaps, it cannot support the country’s needs for more than a few hours. The UK will need to maintain its gas-powered generation or prepare for regular blackouts and increased reliance on imports to maintain grid stability.

About the Author: John Scrimgeour is an experienced C-suite leader in the international energy sector, currently serving as the Non-Executive Chairman of the Board at Archer Knight. With an extensive background in offshore energy and a reputation for driving strategic growth, John brings a wealth of knowledge to the company. His career has spanned senior roles in both the private and public sectors, focusing on energy transitions, innovation, and sustainable practices.

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