Long-duration energy storage (LDES)
Storage able to discharge at rated power for roughly 8 hours or more, covering multi-day lulls and seasonal imbalances that 2–4 hour batteries cannot.
Long-duration energy storage has no single legal definition; the US DOE and the LDES Council generally use 10 hours or more, while many studies use 8 hours. Inter-day storage (10–100 hours) bridges calm, overcast periods; seasonal storage (weeks to months) shifts summer solar to winter demand.
Technologies include:
- Pumped hydro: about 90% of global storage energy capacity, typically 6–20 hours
- CAES and liquid air storage
- Flow batteries and iron-air batteries (about 100-hour discharge)
- Thermal storage, including molten salt in CSP
- Hydrogen in salt caverns, the main candidate for seasonal storage
Required energy (MWh) = power (MW) x duration (h)
The economics differ from short-duration batteries: an LDES asset cycles fewer times per year, so it needs very low energy-capacity cost (studies such as Sepulveda et al. 2021, Nature Energy, suggest below about 20 USD/kWh for significant system value) and can tolerate lower round-trip efficiency. LDES becomes valuable as variable renewable shares exceed roughly 60–80%.
Related terms
All terms →- Pumped hydro storage
Energy storage that pumps water to an upper reservoir when electricity is cheap or abundant and releases it through turbines when power is needed; the largest form of grid storage worldwide.
- Flow battery
An electrochemical battery storing energy in liquid electrolytes held in external tanks, so power (stack size) and energy (tank volume) scale independently.
- Compressed air energy storage (CAES)
A storage technology that compresses air into caverns or vessels with surplus electricity and expands it through a turbine to regenerate power.
- Thermal energy storage
Storing energy as heat or cold, in sensible, latent (phase-change) or thermochemical form, for later use as heat or for power generation.
- Green hydrogen
Hydrogen produced by splitting water in an electrolyser powered by renewable electricity, with near-zero direct CO2 emissions.
- Variable renewable energy (VRE)
Renewable generation whose output varies with weather and time of day, mainly wind and solar PV, and cannot be fully dispatched.