Closed-circuit pumped hydroelectric

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Researchers at the Center for Strategic Energy Analysis at the National Renewable Energy Laboratory (NREL) have conducted pioneering research on closed-loop pumped hydropower (PHES). Their results have been published in the journal Environmental Science and Technology.

Advantages of the pumped hydroelectric system
Pumped hydropower is an established and widely used technology in the global power grid , representing a large share of the energy storage market.

Its operation is simple : two water tanks are used, one higher than the other. When water is released from the upper reservoir to the lower one, it passes through turbines generating electricity. Then, to “recharge” the system, water from the lower reservoir is pumped back to the upper one. Thanks to this design, pumped hydroelectric plants can provide several hours of energy storage .

However, its construction requires specific land and represents a large engineering project, which can prolong its implementation compared to other storage technologies, such as lithium-ion batteries.


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Comparison with other storage technologies
The NREL study focused Buy Email Database specifically on the closed-loop PHES system, that is, one that is not permanently connected to a naturally flowing body of water. This variant was compared with other technologies such as compressed air energy storage (CAES), large-scale lithium-ion batteries, lead acid batteries and vanadium flow batteries.



The results showed that closed-loop PHES has a lower global warming potential (GWP) compared to the other technologies. This system was determined to have a GWP between 58 g and 502 g of CO 2 per kWh stored.

The resurgence of PHES in the world
Today, due to the growing need to store renewable energy, PHES plants are gaining ground again . Currently, there are projects in development or already operational in countries such as India, England , Australia, China, Portugal and Spain. In fact, another recent NREL report noted that Alaska has the potential to host up to 1,800 pumped hydroelectric storage sites.

Diverse applications for different technologies
Each storage technology has its niche. Lithium-ion batteries are excellent for high-power applications with fast response times, while PHES is ideal for storing large amounts of energy for long periods.

The NREL team acknowledged these differences, but highlighted that, in terms of emissions, PHES has approximately four times less impact than CAES .

For those interested in delving deeper into the study, the full report is available under the title “ Life cycle assessment of closed-loop pumped hydropower in the United States .”

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