How does pumped storage hydropower work and what are its benefits and drawbacks?

1 How PSH works

PSH consists of two reservoirs at different elevations, connected by pipes and turbines. When there is excess electricity in the grid, water is pumped from the lower reservoir to the upper one, storing potential energy. When there is a peak demand for electricity, water is released from the upper reservoir to the lower one, driving the turbines and generating electricity. The cycle can be repeated as needed, depending on the grid conditions and the water availability.

2 Benefits of PSH

PSH has several benefits for the electricity system and the environment. First, it can provide fast and flexible response to fluctuations in demand and supply, enhancing grid stability and reliability. Second, it can integrate more variable renewable energy sources, reducing greenhouse gas emissions and fossil fuel dependence. Third, it can offer ancillary services, such as frequency regulation, voltage control, and black start capability, improving grid quality and resilience. Fourth, it can improve the economics of electricity generation, by arbitraging the price differences between peak and off-peak periods, and by avoiding curtailment of excess renewable energy.

3 Drawbacks of PSH

PSH also has some drawbacks that limit its widespread adoption. First, it requires large land and water resources, which may conflict with other uses, such as agriculture, recreation, and ecology. Second, it involves high capital and operational costs, which may not be recovered by the current market mechanisms and regulations. Third, it faces technical and environmental challenges, such as water losses, evaporation, leakage, sedimentation, erosion, and impacts on aquatic habitats and biodiversity. Fourth, it faces social and political barriers, such as public acceptance, permitting, licensing, and coordination among multiple stakeholders.

4 Types of PSH

There are different types of PSH, depending on the configuration of the reservoirs and the connection to the grid. The most common type is conventional PSH, which uses two natural or artificial reservoirs that are connected to the grid at both ends. Another type is closed-loop PSH, which uses two artificial reservoirs that are not connected to any natural water body, reducing the environmental impacts. A third type is seawater PSH, which uses the ocean as the lower reservoir, avoiding the need for freshwater resources. A fourth type is underground PSH, which uses underground caverns or mines as the upper reservoir, saving land space.

5 Examples of PSH

PSH is not a new technology. It has been used for decades in many countries around the world. Some of the largest and oldest PSH plants are in the United States, China, Japan, and Europe. For example, the Bath County PSH plant in Virginia, USA, has a capacity of 3,003 megawatts (MW) and can store up to 24 gigawatt-hours (GWh) of energy. The Three Gorges PSH plant in Hubei, China, has a capacity of 1,836 MW and can store up to 9.2 GWh of energy. The Okutataragi PSH plant in Hyogo, Japan, has a capacity of 1,932 MW and can store up to 8 GWh of energy. The Vianden PSH plant in Luxembourg has a capacity of 1,290 MW and can store up to 5.1 GWh of energy.

6 Future of PSH

PSH has a significant potential to expand and improve its performance in the future. According to the International Hydropower Association (IHA), there are currently about 127 gigawatts (GW) of PSH capacity in operation worldwide, and another 78 GW in development or planning stages. The IHA estimates that PSH could provide up to 450 GW of additional capacity by 2050, if the technical, economic, environmental, and social barriers are overcome. Some of the key drivers for PSH development are the increasing demand for electricity, the growing share of variable renewable energy sources, the need for grid flexibility and reliability, and the climate change mitigation goals.

7 Here’s what else to consider

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