It can transform excess electrical energy during periods of low grid load into high-value electrical energy during peak grid periods. It is also suitable for frequency and phase regulation, stabilizing the frequency and voltage of the power system, and is suitable for emergency backup. It can also improve the efficiency of thermal and nuclear power plants in the system.
Working principle of pumped storage power station
Pumped-storage power stations are equipped with dual-purpose pumping and power generation units, capable of both pumping water and generating electricity. During the day and the first half of the night, water is released from the reservoir, and the high-level water flows through the dual-purpose units, which act as generators, converting the mechanical energy of the high-level water into electrical energy, which is then supplied to the power grid. This addresses power shortages during peak hours. Later at night, when the power grid is in a low-demand period and cannot store electrical energy, the dual-purpose units are used as pumps (these units can rotate in opposite directions), utilizing excess electrical energy from the grid to pump water from the low-level reservoir to a higher level, injecting it into the reservoir. In this way, during periods of low demand, excess electrical energy from the grid is converted into the mechanical energy of the water and stored in the reservoir.
During peak electricity demand, the reservoir releases water, converting the water's mechanical energy into electrical energy via generators, which is then fed into the power grid. The water in the reservoir is used multiple times, working with the two generating units to complete multiple energy conversions. The high-water level reservoir stores a large amount of water at low water levels, effectively storing excess electrical energy from the grid, thus solving the problem of insufficient electricity storage. Because electricity prices differ between peak and off-peak periods—higher during peak times and lower during off-peak times—the economic benefits of pumped-storage power stations are significantly improved.
In addition, there are wind-powered pumped-storage power stations.
Its main functions are: firstly, daily peak shaving, which involves using electricity from the grid to pump water during periods of low electricity demand and generating electricity from the water to supply the grid during periods of high demand. Secondly, annual regulation, which involves using electricity to pump water to high-level reservoirs during the wet season when there is a surplus of electricity, and releasing the water to generate electricity to supply the grid during the dry season.
Pumped storage power stations are the most reliable, economical, long-life, large-capacity, and technologically mature energy storage devices in the power system, and are an important component of new energy development. By constructing pumped storage power stations, the operating and maintenance costs of nuclear power units can be reduced, and their lifespan extended; the impact of wind farm grid connection on the power grid can be effectively reduced, and the coordination between wind farm and power grid operation can be improved, as well as the safety and stability of power grid operation.
