Water is an extraordinary resource not only for sustaining life on the planet, but also for producing energy. We can turn it into steam, use its force in dams and mills, or apply electrolysis to it to obtain hydrogen, but there is something we have not fully managed to exploit: its evaporation. At Columbia University, researchers have taken on this challenge, and the result is two systems based on spores that use water evaporation to generate energy.
Slightly more than 70 percent of the Earth's surface is covered by water. More than 95 percent is found in the oceans, and only about 2.5 percent is 'fresh', although that does not necessarily make it 'safe' for human consumption. Regardless of its situation, the water evaporates, and that process generates energy. To tell the truth, it is not an option that enjoys high priority these days. It is more useful to convert water into steam to spin turbines, or extract hydrogen from it via electrolysis, but evaporation does not seem so useful at first glance. Still, we must insist: it covers most of the planet, and it evaporates. Now, imagine a mechanism capable of tapping into the energy of evaporation...
That concept is being explored by a group of researchers at Columbia University. According to Dr. Ozgur Sahin, the first step was to invent a new material they have named HYDRA, acronym for "HYgroscopy-DRiven Artificial muscle". As its name indicates, the material behaves like an artificial muscle, composed of spores that react to the presence of humidity. Each spore expands when it accesses a minimum amount of humidity, and contracts if the environment is drier. Working together, the spores reproduce this behavior on the substrate, entering a cycle of expansion and contraction with a little water. The team developed two motors from that cycle: one inspired by shutters that pull a cable and spin a miniature generator, and the other in the format of a "moisture mill", with one of its halves covered. When humidity rises in that space, the HYDRAs cause a loss of balance in the wheel, making it turn.
Needless to say, the energy levels generated are very low. The shutter motor is in the order of 50 microwatts. However, what matters here is not the maximum energy value, but the continuity. Extracting energy from a puddle of water that does nothing sounds absurd, but this proof of concept demonstrates exactly the opposite. Another interesting point is that the shutter motor should not cost more than five dollars, including the HYDRAs. If within some years we manage to develop a series of synthetic spores, and increase the scale of the design... the applications could be much broader.
