UK Pioneers Long-Duration Energy Storage to Smooth Renewable Energy Output

The UK is at the forefront of a new era in energy storage, with the government and industry leaders working together to develop "super batteries" that can store energy for extended periods. This long-duration energy storage (LDES) technology is crucial for smoothing the output from wind and solar power as the country transitions towards net-zero emissions.

The UK's energy regulator, Ofgem, has identified 16 LDES projects that it is considering supporting under a new "cap-and-floor scheme". These projects include a range of technologies, such as pumped hydro, lithium-ion batteries, flow batteries, and compressed-air storage, which can store energy for long periods in the form of gravity, chemical processes, or electrical charge.

## What is Long-Duration Energy Storage?

Long-duration energy storage refers to a broad category of technologies that can store energy for anywhere from four hours up to years. The UK government defines it as technologies that can store energy for at least four hours, while Ofgem uses a slightly different threshold of eight hours and upwards.

The diversity of LDES technologies reflects the range of roles it is expected to play in the electricity system in the UK. This could be meeting short-term surges, helping to utilize surplus renewable energy generation, or providing longer-term flexibility.

## Types of Long-Duration Energy Storage

There are numerous types of energy storage technology, although most fall into four main categories: mechanical; thermal; chemical; and electrochemical. For example, a pumped-hydro project uses surplus energy to pump water uphill to a reservoir, while thermal storage could be a tank of gravel that is heated up, then later used to warm up water.

A key consideration for each LDES technology is the amount of energy it can store, measured in watt-hours (Wh). For example, a 1MW battery with four hours of storage contains 4MWh of electricity. Another consideration is whether the energy can be stored for long periods before use - and whether it is economic to do so.

The UK is working to expand the capacity and duration of storage available through LDES, as well as the range of technologies this system is based on. For example, in May 2026, the UK's largest vanadium "flow battery" site opened, co-located with a 3MW solar farm in Uckfield, East Sussex.

| Technology | Storage Duration | Energy Capacity | | --- | --- | --- | | Pumped Hydro | Up to 50 years | Up to 10 hours | | Lithium-ion Batteries | Up to 12 hours | Up to 10 MWh | | Vanadium-Redox Flow Batteries | Up to 12 hours | Up to 10 MWh | | Compressed-Air Energy Storage | Up to 12 hours | Up to 10 MWh |

The use of LDES technologies is expected to cut energy system costs in the UK by more than £24bn between 2030 and 2050. The UK is leading the charge on technology diversity, with experts predicting that a handful of LDES technologies will do the heavy lifting over the next decade.

As the UK's electricity system becomes increasingly dominated by variable renewables, the need for LDES to manage peaks and troughs of generation is growing. George Martin, principal for power system modelling at analytics company LCP Delta, tells Carbon Brief that wind power creates a particular need for LDES, saying: "LDES is really important for the system, particularly in a wind-driven system. You get more peaks and troughs in your renewable output and, [while] short duration [storage] can obviously help with that, with things like 'dunkelflaute', long-duration storage is what is needed."

The UK is working to expand the capacity and duration of storage available through LDES, as well as the range of technologies this system is based on. By investing in LDES technologies, the UK is taking a crucial step towards a more sustainable and resilient energy future.