Pumped hydroelectric energy storage systems (PSH) improve grid flexibility in several key ways:
- Bidirectional grid frequency support with faster response times: Modern pumped hydro plants, especially those with new technologies like variable speed capabilities, can quickly respond to grid frequency fluctuations by either generating power (turbine mode) or consuming power to pump water (pump mode). This two-way frequency regulation enhances the stability and reliability of the grid.
- Large-scale energy storage capacity: PSH is the dominant form of grid-scale energy storage globally, accounting for over 94% of storage capacity and stored energy. It can store energy for daily, weekly, or even seasonal cycles, providing flexible timing for energy release based on grid demand.
- High round-trip efficiency: Pumped hydro systems convert energy to gravitational potential and back with approximately 80% efficiency, which is favorable compared to many other storage technologies. This efficiency makes it a cost-effective method for grid balancing over long time periods.
- Supporting renewable energy integration: By storing excess electricity generated from variable renewable sources like wind and solar, PSH helps smooth out the intermittency of renewables and balance supply and demand on the grid. Optimization models for PSH operation increase profitability and reduce total system costs, supporting greater renewable penetration.
- Provision of multiple grid services: Beyond energy storage, PSH plants provide a variety of grid services formerly managed by fossil fuel plants, including reactive power support, synchronous or virtual inertia, frequency control, and black-start capability. These services are delivered more quickly and without CO2 emissions, aiding the transition to cleaner power systems.
In sum, pumped hydroelectric energy storage enhances grid flexibility by serving as a highly efficient, large-scale, and fast-reacting “water battery” that stabilizes grid frequency, supports renewable energy integration, and provides multiple ancillary services critical to modern power systems.
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