Water evaporating from lakes and rivers could become a new source of renewable energy, according to a new study.
Evaporation is a natural process driven by solar heat. Nearly half of the Sun’s energy that reaches Earth’s surface powers the evaporation of water from lakes, rivers, and reservoirs. This process plays a major role in regulating ecosystems, water resources, and climate. Scientists now suggest that the energy contained in this evaporating water could potentially be captured and converted into electricity.
Researchers from Columbia University estimate that the theoretical potential of evaporation energy is enormous. In a study published in Nature Communications, they calculate that evaporation from lakes and reservoirs in the United States alone could generate up to 325 gigawatts of power. This is roughly equivalent to about 70 percent of the total electricity generated in the U.S. in 2015.
The researchers also suggest that future evaporation-based energy systems could achieve power densities up to three times greater than wind power, while simultaneously reducing water lost to evaporation.
“We have the technology to harness energy from wind, water, and the sun, but evaporation is just as powerful,” said study lead author Ozgur Sahin, Associate Professor of Biological Sciences at Columbia University. “Now we can begin to estimate its potential.”
To explore this idea, the research team has developed small experimental machines powered entirely by evaporation. These devices regulate humidity using tiny shutters that open and close, allowing moisture in the air to interact with special materials.
At the heart of the system are thin plastic strips coated with bacterial spores. These spores naturally expand when they absorb moisture and contract when humidity decreases. As they expand and shrink, they create mechanical motion—similar to the movement of biological muscles.
The researchers refer to these devices as HYDRAs (hygroscopy-driven artificial muscles). The concept was first introduced in 2015, but the new study focuses on estimating the large-scale energy potential of evaporation.
According to the team’s models, capturing evaporation energy from existing U.S. lakes and reservoirs larger than 0.1 square kilometers—excluding the Great Lakes—could theoretically produce the estimated 325 gigawatts of electricity.
The next step is to develop materials that can be manufactured on a large scale and to test the technology on larger bodies of water.
If successful, evaporation power could become a significant new renewable energy source. After all, about 70 percent of Earth’s surface is covered by water, providing vast potential for harnessing this largely untapped energy.
Reference:
Cavusoglu, A.-H., Chen, X., Gentine, P., & Sahin, O. “Potential for natural evaporation as a reliable renewable energy resource.” Nature Communications. DOI: 10.1038/s41467-017-00581-w