Depending on who you ask, pumped hydro energy storage is either the future of the clean energy industry and the key to decarbonizing the global economy, or it’s an ecological disaster that needs to be stopped. The truth, of course, lies somewhere in between – but friends and enemies of pumped hydro tend to espouse either one narrative or the other with inadequate attention to the nuanced trade-offs and potential synergies that pumped hydro storage presents to the renewable energy industry.
The issue is this: building dams is good for clean energy storage, which is good for the environment; but on the other hand, the dams themselves tend to be extremely bad for the environment and the surrounding communities. We’re talking about massive dams that flood whole valleys, irreversibly changing the ecological balance of the area and often displacing humans as well as animals. These dams can seriously harm or eradicate crucial habitats for birds, fish, and plants.
On the other hand, supporters will say the risk posed by climate change is much bigger than the risk of damaging local ecosystems. These supporters argue that if global greenhouse gas emissions are left unchecked, a flooded river valley here and there will be a molehill next to the mountain of disastrous ecological impacts created by warming temperatures, rising sea levels, acidifying oceans, and increased intensity and incidence of extreme weather events, among other results of warming past 1.5º.
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In an effort to curb global emissions in time to avoid these devastating results, any and every kind of clean energy innovation should be considered and tested. And one of the most promising such innovations, river valleys be damned, is pumped hydro. It’s an elegant and relatively simple solution to a complex problem inherent to renewable resources including solar and wind. Wind and solar are variable, which means that their productivity depends on factors outside of human control – the weather and the time of day or year. This creates an issue for the grid, as demand for energy tends to peak when supply is lowest – we all turn our lights on when the sun goes down on our houses as well as on the community’s nearest solar farm.
This dynamic means that energy storage is an essential part of the renewable energy sector. In fact, a net-zero energy future will require a whopping 6TWh of energy storage. It is needed to capture excess energy captured when production is high and then release that stored energy back to the grid when demand outweighs production. This could mean that energy is stored for a few hours – but it could also mean that energy is stored for whole seasons. This rules out lithium-ion batteries, which currently dominate the energy storage sector but which can only hold energy short-term. What’s more, the production of lithium-ion batteries requires finite, non-renewable rare Earth elements which are going to become increasingly scarce in the future. China has a chokehold on many rare Earth element supply chains, including lithium, presenting a major geopolitical minefield if the industry doesn’t pivot to alternative and long-term storage options.
This is where pumped hydro comes in. It’s a long-term energy storage solution in which water is pumped uphill using excess energy at peak production times and then released downhill to spin turbines to create electricity when energy is needed. While some projects are building massive new dams for the purpose of energy storage alone, others are hoping to incorporate storage into existing hydropower dams, recycling some of the water lost in the hydropower process to use for pumped storage. “We will change them into something better suited for the future,” Ivar Arne Borset, a senior vice president at Norwegian hydro leader Statkraft, was quoted by the New York Times.
