Could Evaporating Water Be the Next Big Thing in Renewable Energy?
Each day, our Sun pours its energy down onto the Earth’s surface, turning vast expanses of open water into vapor. New research shows the surprising degree to which this clean and renewable process could be used to produce electricity—enough, perhaps, to meet 70 percent of US energy needs. But before this energy solution makes it to prime time, we’ll need to know a lot more about its potential environmental effects.
Open bodies of water across the continental United States—excluding the Great Lakes—have the potential to produce 325 gigawatts of power each year through natural evaporation, according to new research published today in Nature Communications. That’s about 87 percent of the electric power produced by all the world’s nuclear power plants combined.
At the same time, the new research also suggests that water evaporation farms, though still hypothetical, could provide power densities three times greater than wind power, and significantly reduce the amount of water lost to evaporation. The lead author of the new paper, Ozgur Sahin from Columbia University, says natural evaporation could serve as a reliable renewable energy source, and that the time has come to develop the materials and technologies required to make it happen. The study marks a “first stab” at this potential new power source, but many questions remain—including any negative effects this technology might have.
Nearly half of the Sun’s energy that reaches the Earth’s surface drives evaporation, influencing ecosystems, water resources, and climate. Recent studies have considered the various ways in which we might be able to harness the power of evaporation, a prime example being a floating, piston-driven engine that can generate enough electricity to cause a light to flash and power the engine of a miniature car.
In the future, a scaled-up version could produce electricity from giant floating power generators installed over bays or reservoirs, or huge rotating machines similar to wind turbines that sit above water. The basic idea is that materials are made to perform work through a cycle of absorbing and expelling water through evaporation.
But while slow progress is being made to develop the materials and devices required to pull this off, even less is known about the availability, reliability, and potential for this currently unexploited resource. Sahin and his colleagues are the first to estimate the total potential power available from natural evaporation in US lakes and water reservoirs, while also providing a model to predict how these energy harvesters could actually work in the natural environment and how they could impact water resources and energy reliability.
Their model shows that 325 gigawatts of power is potentially available from evaporation via existing lakes and reservoirs larger than 0.1 square kilometer (not including the Great Lakes). That’s around 70 percent of the US electric energy generation rate in 2015. The states with the highest evaporation-energy potential include Utah (47,200 Megawatt (MW) potential), California (27,550 MW), Minnesota (19,251 MW), and Louisiana (14,353 MW). In total, the US boasts 95,000 square kilometers (36,680 square miles) of potentially available water bodies for the task.