Renewable energy from evaporation

Researchers from Columbia University claim that evaporating water could be used to generate clean, renewable electricity that could help power robots, sensors and vehicles. The additional benefit with evaporation is that, unlike solar or wind power, it happens continuously throughout the day and night.

"The biggest form of energy transfer in nature is evaporation," said Ozgur Sahin, associate professor of biological sciences and physics at Columbia. "Our climate is powered by evaporating water from the oceans, and we have no direct way of accessing this energy."

The basis of Sahin's research is the bacteria Bacillus, microorganisms commonly found in soil. When starved, Bacillus forms a rigid, dormant spore, a survival mechanism to protect its genetic material. In humid conditions the spores absorb moisture from the air, expanding up to 40% in volume.

"Changing size this much is highly unusual for a material that is as rigid as wood or plastic," explained Sahin. "The expanding and contracting spores can act like a muscle, pushing and pulling other objects. We noticed that we could harness the motion of spores and convert it to electrical energy."

In a paper published in Nature Nanotechnology on 26th January, Sahin and his team, including collaborators from Harvard University and Loyola University Medical Centre, showed that these spores produced a thousand times more force than human muscles, and that even a little bit of moisture from evaporation could cause a movement strong enough to be harvested.