IN Brief:
- Seven Stream 2 prototypes completed the LoDES demonstration programme.
- Technologies covered electricity, heat, hydrogen, hydro, and compressed-air storage.
- A separate Stream 1 project demonstrated a 7MW/30MWh vanadium-flow system.
The Department for Energy Security and Net Zero has completed seven prototype projects under the second stream of its Longer Duration Energy Storage demonstration programme.
Running from 2021 to 2026, the programme provided around £70m of capital support across two delivery streams. Its projects were designed to move a range of storage technologies beyond laboratory development through larger prototypes and operational demonstrations.
The seven Stream 2 projects covered domestic and network-scale thermal storage, hydrogen held in metal hydrides, lithium-sulphur flow batteries, high-density pumped hydro, pumped thermal energy storage, and a system combining thermal and compressed-air storage.
Sunamp’s EXTEND project received approximately £9.25m to develop thermal batteries and controls for trials across 100 homes, while the University of Sheffield’s ADSorB project received about £2.6m for modular thermal storage tested at the Creative Energy Homes facility.
EDF R&D UK led the £7.73m HyDUS project, which stored hydrogen in depleted-uranium metal hydride with partners including the University of Bristol, UK Atomic Energy Authority, and Urenco. StorTera’s £5.02m SLIQ programme developed a 200kW/1.6MWh single-liquid lithium-sulphur flow battery in Midlothian.
RheEnergise received £8.24m for a 250kW/1MWh high-density hydro demonstrator, while SynchroStor received £9.44m for a grid-connected, megawatt-scale pumped-thermal system designed for ten-hour operation. Cheesecake Energy’s £9.45m FlexiTanker project combined thermal and compressed-air storage, with demonstrations in Nottingham and at microgrid sites in Colchester.
Different technologies address different duties
Rather than selecting one universal replacement for lithium-ion batteries, the programme examined technologies with distinct combinations of duration, response time, efficiency, siting requirement, material demand, and operating life.
Thermal systems can serve buildings or industrial processes where heat is required directly, avoiding some of the losses involved in converting stored electricity back into heat. Pumped hydro and compressed-air systems can support larger energy volumes but depend on suitable sites, civil infrastructure, or pressure equipment.
Flow batteries separate power equipment from stored electrolyte volume, allowing duration to increase without scaling every component proportionally. Lower energy density can increase site area, although long cycle life and reduced fire risk may suit stationary applications.
Hydrogen-based systems can retain energy over extended periods but require conversion equipment, storage infrastructure, safety controls, and a defined route for using the hydrogen or converting it back into electricity. Their lower round-trip efficiency makes the intended duty particularly important.
Demonstration must lead to repeatable projects
A separate Stream 1 programme supported actual-environment demonstrations, including the 7MW/30MWh vanadium-flow battery hub delivered by Invinity in East Sussex.
Completing a prototype does not establish commercial readiness because developers must still demonstrate manufacturing repeatability, warranty performance, degradation behaviour, maintenance requirements, grid compliance, and financeable project economics across several installations.
Revenue remains a central constraint for long-duration projects. Assets designed for infrequent but extended operation can provide substantial system value, yet many existing markets reward short-term response or daily energy trading.
A technology may therefore meet an identified system requirement without securing sufficiently predictable income to support construction finance. Contract design, market reform, or long-term procurement may be needed where revenue cannot be assembled from existing services.
Connection arrangements also shape project viability. Storage may charge when electricity is abundant and discharge during tighter periods, but import and export capacity, network charges, losses, curtailment, and operational restrictions affect the value available at each site.
The demonstrations provide engineering data from repeated cycling, standby periods, changing temperatures, partial load, and real network operation. Those results are more useful for commercial specification than laboratory efficiency alone.
The programme therefore ends with a portfolio of tested options rather than a preferred technology. Progress now depends on which developers can standardise their systems, secure appropriate sites, establish reliable manufacturing, and obtain contracts suited to the duration and services their assets provide.
