Q&A: What is ‘long-duration energy storage’ – and why does the UK need it?

The United Kingdom is advancing efforts to develop "long-duration energy storage" (LDES), a critical technology aimed at stabilizing the national electricity grid as renewable energy sources like wind and solar become more prominent. The UK's energy regulator, Ofgem, has identified 16 potential LDES projects that it is considering supporting under a new financial mechanism known as the "cap-and-floor scheme." These projects are designed to store energy over extended periods, sometimes lasting days or even weeks, to bridge supply gaps when renewable sources are insufficient due to weather conditions. This approach addresses challenges associated with "dunkelflaute," a term borrowed from German referring to prolonged periods of low renewable energy production. The UK currently operates 2.8 gigawatts (GW) of LDES capacity, primarily composed of four pumped-hydro energy storage facilities located in Scotland and Wales. Among these, the Dinorwig power station in North Wales stands out as the largest, with a capacity of 1,728 megawatts (MW). Opened in the 1980s, this facility plays a crucial role in managing sudden increases in electricity demand, such as during major sporting events. For instance, during a high-profile football match in July 2026, electricity demand surged significantly, reaching levels comparable to the combined consumption of Glasgow and Leeds. Pumped storage systems, along with battery technologies, have historically helped maintain grid stability during such peak times. Long-duration energy storage encompasses a variety of technologies capable of storing energy for durations ranging from four hours up to several years. According to definitions provided by both the UK government and Ofgem, LDES includes methods such as gravity-based storage, chemical processes, and electrical charge. Technologies under consideration range from traditional pumped hydro to newer innovations like large lithium-ion batteries, flow batteries with unique chemistries, and compressed-air storage solutions. These diverse options offer flexibility in addressing varying energy demands and environmental considerations. The importance of LDES is underscored by the increasing reliance on variable renewable energy sources, particularly wind power. George Martin, a principal in power system modeling at LCP Delta, emphasizes that wind energy introduces greater variability in generation patterns, necessitating robust storage solutions. While short-duration storage can assist with immediate fluctuations, LDES provides essential support during prolonged periods of low renewable output. This capability ensures that the electricity supply remains reliable despite intermittent generation from wind and solar sources. The implementation of LDES is anticipated to yield substantial economic benefits for the UK. Experts predict that these advancements could reduce energy system costs by more than £24 billion between 2030 and 2050. By mitigating the risks associated with unpredictable renewable energy production, LDES contributes to a more resilient and cost-effective electricity infrastructure. As the UK progresses toward its net-zero emissions targets, the integration of advanced storage technologies will play a pivotal role in achieving sustainable energy goals while maintaining grid reliability. The push for LDES aligns with broader global initiatives aimed at enhancing energy security and sustainability. Countries worldwide are exploring similar strategies to address the intermittency of renewable resources and ensure continuous power supply. In the context of the UK, the focus on developing innovative storage solutions reflects a commitment to leveraging technological advancements for a transition to cleaner, more efficient energy systems. With ongoing research and investment in LDES, the UK aims to position itself as a leader in the global shift toward renewable energy integration.