The question of where to put panels for new large-scale solar projects is up for debate but we know it’ll take a lot of them to create enough energy so that the world can decarbonize. Solar power requires over 20 times more area than fossil fuel plants to produce one gigawatt (GW) of energy. By 2050, the US alone might need to devote up to 61,000 square kilometers to solar panels -- land that could be used for agriculture or conservation.

In response, some experts advocate for an innovative, albeit controversial solution for scaling up the world’s solar capacity: floating photovoltaic solar panels -- or floatovoltaics -- that would cover 10% of the world’s reservoirs and provide 4,000 GW of capacity, equal to the output of all fossil fuel plants worldwide. But, these water-based panels could have unintended consequences, such as potentially harming wildlife and lowering local property prices.

Why This Matters

When installing renewable energy, there are always potential drawbacks that must be taken into account. Wind turbines on land, for example, can threaten migratory birds, while those installed offshore interfere with whale migrations and fisheries. Still, preventing climate change will require a lot more renewable energy capacity, particularly in the solar sector.

The Biden Administration intends to install 30GW of offshore wind capacity throughout the US by 2030. The president has even invoked the Defense Production Act to speed domestic solar panel production. The unprecedented move was made in response to an investigation by the Department of Commerce that threatened to impose debilitating tariffs on solar manufacturers and grind US solar projects to a halt. Should the industry still risk instability, floatovoltaics could help expand the world’s solar energy capacity.

Unique Challenges For Floating Panels

Solar panels on reservoirs currently contribute 3 GW of electricity globally, a tiny fraction of renewable energy. There are already plans to install solar panels over 16 square kilometers of a reservoir in Batam, Indonesia, that is expected to generate “2,600 GW hours of electricity, and potentially offset more than 1.8 million metric tons of carbon, per annum.”

But floatovoltaics may threaten reservoir ecosystems, as panels could block sunlight, making water bodies less hospitable to photosynthetic organisms and upsetting natural food chains. Moreover, less photosynthetic organisms means less oxygen contributed to the water, allowing methane-producing bacteria to flourish, potentially outweighing decarbonization efforts.

Similarly, extreme weather could affect the solar panel functionality. For example, a 2019 typhoon hit a floatovoltaic project on the Yamakura Dam in Japan, causing panels to pile up and catch fire. Other potential issues include panels placed on reservoirs in drought-prone areas, where water is needed for drinking and irrigation and water levels are less stable.

In any case, more studies must be done to understand the potential effects -- both positive and negative -- of a wider implementation of floatovoltaics. As an article in Nature put it: “The floatovoltaic industry is poised to expand rapidly. Science and policy must move equally fast to ensure that this use of the world’s reservoirs is sustainable and equitable.”