The majority of methods we use for generating electricity convert mechanical energy into electrical energy in some fashion. We may utilize nuclear power or burning coal or rushing water or wind but we end up spinning a turbine to create electricity. Over time, we have developed numerous ways to initiate the motion in a generator.
Recently, researchers at Harvard have come up with a scheme that uses changes in humidity to drive an electrical generator. Water evaporation is an enormous power source in nature – just think of the energy it takes to move water from lakes and rivers to the top of Mount Everest.
Harvard’s prototype device uses the movement of a sheet of rubber coated on one side with spores. The spores – a particular kind of soil bacterium – wrinkle up like a raisin when they dry up and almost instantly restore themselves when they take in water. As a result, the rubber sheet bends when it dries out and straightens out when humidity rises. Genetic engineering of the bacterium has already yielded strains that double the amount of energy stored in the spores.
This flexing is the basis of an actuator that moves the magnets of an electrical generator. While it is strictly in the prototype stage at this point, the concept could be scaled up into a viable source of renewable electricity that could be harnessed day and night. The water evaporation cycle is an enormous storehouse of energy and clever microengineering has the potential to provide ways of tapping into it.
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Getting a charge from changes in humidity
Photo, posted July 9, 2011, courtesy of Jenny Downing via Flickr.
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Earth Wise is a production of WAMC Northeast Public Radio.