Energy from evaporating water could power 70 percent of the U.S.

evaporating water
Central Arizona Project

With very good reason, there is a big drive to promote sustainable energy sources around the world, but could one of the most efficient possible renewables be being ignored? That is what a new study carried out by researchers at Columbia University suggests. Based on their calculations, the United States could harvest 325 gigawatts of power — around 70 percent of the power it currently produces — by using evaporating water from U.S. lakes and reservoirs.

“Evaporation is a fundamental process taking place in nature,” Ozgur Sahin, a biophysicist at Columbia who served as the study’s senior author, told Digital Trends. “Wet surfaces and open bodies of water release the heat coming from the sunlight via evaporation. It is an important part of the water cycle. In principle, one could capture energy from evaporation occurring in nature by, for example, using materials that respond to water vapor by changing size. We wanted to determine theoretically how much energy can be captured from evaporation by taking into account the weather conditions. Understanding its energy generation potential could help motivate development of new technologies to harness energy from this important natural phenomenon.”

One of the researchers’ main findings is that the amount of power which can be generated from a given area of water surface is comparable to the current state of other sustainable energy methods, such as wind and solar power. However, what gives evaporation-based renewables the edge is the fact that it is less intermittent than other sustainable energy types — meaning that it can generate power when they are unable to.

Of course, for evaporation to really take off (no pun intended) as a renewable energy source, it’s necessary to have the right technology to harvest it. Fortunately, Sahin’s team can help there, too, since it has spent the past several years developing a muscle-like material called HYDRA (short for hygroscopy-driven artificial muscles) that’s able to capture energy from evaporating water. To do this, it uses plastic bands strategically imbued with bacteria spores, which expand when they are exposed to moisture and contract when dried out.

“These are micron-sized dormant cells that respond to changes in relative humidity particularly strongly, which makes them good candidates for creating materials that harness energy from evaporation,” Sahin said. “Our goal is to create these spore-based materials. If these materials are sufficiently efficient and durable, then the technology might be ready to transition to industry.”

A paper describing the research was recently published in the journal Nature Communications.