PHES

PHES refers to Pumped Hydro Energy Storage. It is a type of large-scale energy storage that involves pumping water from a lower reservoir to an upper reservoir when electricity is cheap or abundant, and then releasing the water to flow back down through turbines to generate electricity when demand is high or prices are high. This process effectively stores potential energy in the elevated water.

The basic components of a PHES system include two water reservoirs at different elevations, a connecting waterway or pipe, and a pump-turbine unit. During periods of surplus electricity, the pump-turbine unit uses this energy to move water from the lower reservoir to the upper reservoir, thus storing energy. When electricity is needed, the water is allowed to flow from the upper reservoir back to the lower one, passing through the pump-turbine unit which now acts as a generator, producing electricity.

PHES is the most established and widely deployed form of large-scale energy storage globally, with a significant installed capacity. Its advantages include long operational life, high efficiency, and the ability to provide grid services such as frequency regulation and voltage support. However, the construction of new PHES facilities can be complex, requiring specific geographical conditions with suitable elevation differences and land availability for reservoirs. Environmental considerations, such as impact on local ecosystems and water resources, are also important factors in the planning and development of these projects.