Should Solar Power Replace Our Hydroelectric Dams?


Hydroelectric power produces just 6% of electricity in the U.S., and the dams used to generate that power are aging and environmentally problematic. Dams also block migratory fish like salmon from swimming upstream to spawn, causing these fish populations to diminish over time.

But what if we replaced that hydropower with solar energy production? What if we used solar panels to recoup the energy generated by hydroelectric power plants? How much land would that require?

The answer: less than 0.1 percent of U.S. land, which is smaller than the size of Delaware, according to a study published in Nature Sustainability. The study was written by Professor John Waldman (Queens College, The Graduate Center), Balazs Fekete (formerly of City College of New York), Ph.D. graduate Shahab Afshari, and Shailesh Sharma, who previously worked as a postdoctoral researcher in Waldman’s lab.

“Decades of unsuccessful restorations predicated on engineered fishways, the rapid aging of our dams … and the advent of other, increasingly cost-effective forms of alternative energy all suggest that there is a way both to reopen our rivers and to replace the energy production they so long provided,” wrote Waldman in a “Behind the Paper” article.

The authors also laid out other concerns about hydroelectric dams: They stop sediment from reaching river deltas, they cause rivers to warm, and they could become more of a liability as they age and are strained by climate change-related weather events.

Of course, the authors caution, the reality of switching to solar is more complex than the numbers suggest. Reservoirs that were built to retain water in a dam system often serve other purposes—storage for irrigation or drinking water, and support for flood control. And some dams are built on waterfalls that fish cannot pass. Solar farms, meanwhile, can contribute to biodiversity loss and require batteries to store energy for later use.

But battery technology is advancing, the authors say, and in places where dams have been removed, migratory fish populations have grown dramatically. Solar panels could be placed on the land reclaimed from drained reservoirs, or on already damaged areas such as landfills. Alternatively, solar could be combined with wind power or hydrokinetic turbines that don’t block waterways.

Waldman and Sharma are now conducting a detailed analysis of how the suggested replacement would work in Maine, which has the third most hydroelectric dams of any state in the U.S.

Beyond SUM

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John Waldman (Professor, Earth and Environmental Sciences) | Profile 1 | Profile 2
Balazs Fekete (Assistant Professor, Civil Engineering) | Profile 1