While solar, wind, hydro, geothermal, tidal, bio-energies are widely known, there are also other sources which are, now, less reliable as both research and technology in those fields are still in their initial stages. Evaporation is one such source and scientists are saying that it could become the world’s largest renewable energy source.
Though it is theoretically a known fact that during every energy transformation, it is possible to capture and store energy, in practical, with our today’s technology, we succeeded with only a few sources. Now, evaporation has also lost the game.
The story of evaporation’s becoming a renewable source of energy picked up a pace in 2010 with the study conducted by Brazilian scientists at the University of Campinas, which found that the atmospheric water vapour, instead of remaining neutral, picks up a charge.
Later, in 2012, a study, which was conducted by Dr. Ozgur Sahin, Associate Professor of Biological Sciences and Physics at Columbia University, and his team, and was published in the Journal of the Royal Society Interface, discovered how a soil bacterium called Bacillus subtilis, which typically exists in dry places, not only dries up to become a tough, wrinkled, dormant spore, but can also restore its original shape immediately once water is introduced.
To prove it, Dr. Sahin had even created prototype electrical generators that respond to changes in humidity. The bacterium is so sensitive to humidity that a tiny, flexible silicon plank, coated with a solution of spores, started to bend and straighten in cycles in reaction to the humidity in Dr. Sahin’s breath – before he could even get the plank under a microscope. The team discovered that the spore coated plank, when subjected to humidity, varying from dry to moist, could generate a force which is equivalent to 1000 times the force of human muscle. In other words, by moistening one pound of dry spores we could generate enough force to lift a car 3.2 feet off the ground.
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Now researchers at the Columbia University have taken another leap by utilizing the same Bacillus subtilis spores and creating two devices that can harness renewable energy from evaporation. The latest research paper, lead authored by the same Dr. Sahin, was published in Nature Communications.
The first device, Evaporation engine, is made up of thin plastic tapes on which spores were deposited. These tapes, thus, contract in the dry environment and expand with the increase in humidity and act as muscles. When water is introduced in the evaporation engine, the shutters that are coupled with these tapes, open and close due to the force exerted by the tapes. When the tapes build up enough force to push open the shutters, the accumulated humidity would be released causing the tapes to shrink and thus closing the shutters. Thus, the energy captured from evaporation would be converted into mechanical energy, which can then be stored and utilized in a regulated way.
The second device, Moisture mill, consists of a wheel, around which the spore coated tapes are fixed. The arrangement is such that a half of the wheel lies in a humid environment while the other half lies in a dry environment. The difference in humidity makes the spore coated tapes to continuously expand and contract. The movements, along with a tiny mass imbalance on the wheel, make the wheel rotate forward as long as the difference is maintained.
The researchers are suggesting many possible applications of the devices which include an evaporation-driven car, off the grid applications, batteries, robots, and prostheses.
Some studies also say that the climate change, which, on one hand, is threatening the world today, would lead to increase in evaporation rates and result in more moisture in the troposphere. Dr. Sahin is positive that this technology could harness energy without threatening the water security – perhaps like how the biofuels are posing a threat to food security. They hope that if this technology could be brought into practice, the enormous water potential on earth could become the ever renewable source for all our energy needs.