Pumped-storage hydropower
The quiet giant of energy storage: pump water uphill when power is cheap or in surplus, then release it through turbines at peak demand. Pumped storage still holds the vast majority of the world's grid storage capacity, far ahead of batteries. It is the proven way to store energy for hours to days.
The main families
Two reservoirs, one head
An upper and a lower reservoir linked by a penstock. Pumping happens off-peak (abundant power), generation at peak demand. Round-trip efficiency reaches about 70 to 80%.
Reversible pump-turbines
Reversible pump-turbines (often Francis-type), and variable-speed machines (DFIM) that regulate power even while pumping. Underground STEP and seawater STEP widen the set of possible sites.
Arbitrage & ancillary services
Arbitrage between off-peak and peak hours, power reserve, mechanical inertia, frequency control and black-start capability after a grid collapse.
Key challenges
- Storage scale — pumped hydro is by far the largest grid storage in the world: it accounts for the bulk of installed capacity, a scale no other technology matches today.
- Efficiency & sizing — round-trip efficiency (~70-80%) and stored energy depend on head and reservoir volume: site geometry sets the power and the duration.
- Ancillary services — frequency regulation, mechanical inertia and black-start: services that batteries struggle to match at this scale and duration, and that pumped storage has provided for decades.
- Siting constraints — it needs the right geography — head, water, two reservoirs — and faces long construction times and sometimes difficult local acceptance.
- Variable-speed machines — variable-speed DFIM machines allow power and frequency regulation even in pumping mode, which fixed-speed machines cannot do.
See also
Pumped-storage-specific standards
- IEC 61362 — Guide to the specification of hydraulic turbine governing systems (governors, power and frequency control).
- IEC 60193 — Model acceptance tests for hydraulic turbines, pump-turbines and storage pumps (efficiency measurement).
- IEC 62933 — Electrical energy storage systems: terminology, performance parameters and requirements for grid-connected storage.
- IEC 61850 — Digital substations and automation: communication protocols for the control of electrical installations.
Related standard pages on IndustryHub
Major players
Reversible turbines & equipment
GE Vernova, Voith Hydro, Andritz Hydro, Toshiba.
Operators
EDF, Iberdrola, China Yangtze Power, Drax (Cruachan).
Control systems
ABB, Siemens, Emerson.
Engineering
AFRY, Stantec, Mott MacDonald.
Landmark facts
| Fact | Year | Source | Lesson |
|---|---|---|---|
| "The world's largest battery" | 1985 | Bath County (Virginia, USA) | Long described as the world's largest pumped-storage station, nicknamed "the world's largest battery" — it illustrates the GW-scale, multi-hour role of pumped storage. |
| Domination of global storage | — | Global grid storage | Pumped hydro still represents the large majority of grid energy storage worldwide, far ahead of lithium batteries despite their rapid growth. |