Using pumped storage to solve the challenge of intermittent renewables

What researchers are calling seasonally pumped hydropower storage (SPHS) could provide an affordable way to store renewable energy over the long-term, filling a much-needed gap to support the transition to intermittent renewables, according to a study from scientists with the International Institute for Applied Systems Analysis.

According to IIASA, SPHS means pumping water into a deep storage reservoir, built parallel to a river, during times of high water flow or low energy demand. When water is scarce or energy demand increases, stored water is released from the reservoir to generate electricity.

Per a press release, SPHS, an already established yet infrequently used technology, could be an affordable and sustainable solution to store energy and water on an annual scale. The study, published in the journal Nature Communications, says that compared with other mature storage solutions such as natural gas, there is considerable potential for SPHS to provide highly competitive energy storage costs.

“The energy sectors of most countries are undergoing a transition to renewable energy sources, particularly wind and solar generation,” says IIASA postdoc Julian Hunt, the study lead author. “These sources are intermittent and have seasonal variations, so they need storage alternatives to guarantee that the demand can be met at any time. Short-term energy storage solutions with batteries are underway to resolve intermittency issues, however, the alternative for long-term energy storage that is usually considered to resolve seasonal variations in electricity generation is hydrogen, which is not yet economically competitive.” 

Researchers assessed the theoretical global potential for storing energy and water seasonally with SPHS, focusing on the locations with the highest potential and lowest cost. They also analyzed scenarios where the storage of energy and water with SPHS could be a viable alternative. The study included topographical, river network and hydrology data, infrastructure cost estimation, and project design optimization to identify technically feasible candidate sites. 

The study shows that water storage costs with SPHS plants vary from US$0.007 to US$0.2/m3, long-term energy storage costs vary from $1.8 to $50/MWh and short-term energy storage costs vary from $370 to $600/kW of installed power generation capacity, considering dam, tunnel, turbine, generator, excavation and land costs. The estimated world energy storage potential below a cost of $50/MWh is 17.3 PWh, which is about 79% of the world electricity consumption in 2017.

Researchers found that significant potential exists for SPHS around the world, in particular in the lower part of the Himalayas, Andes, Alps, Rocky Mountains, northern part of the Middle East, Ethiopian Highlands, Brazilian Highlands, Central America, East Asia, Papua New Guinea, the Sayan, Yablonoi and Stanovoy mountain ranges in Russia.

“Concerns about the intermittency and seasonality of wind and solar can be valid, but are also sometimes exaggerated,” says IIASA researcher Edward Byers, a study coauthor. “This study demonstrates that there is an extremely high potential for SPHS to be used across much of the world, providing a readily-available, affordable, and sustainable solution to support the transition to sustainable energy systems and overcome real and perceived barriers to high shares of renewable generation.”

The study also addresses some of the potential environmental concerns related to hydropower. Because SPHS reservoirs are deep and constructed parallel to, rather than within, the course of a river, the environmental and land use impacts can also be up to 10 to 50 times smaller than traditional hydropower plants. 

The upcoming HYDROVISION International event, this July in Minneapolis, Minn., in the U.S., features a five-session summit track on the topic of Energy Storage (including Pumped Storage). Click here to learn more about what will be discussed.

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