This is an excerpt from EERE Network News, a weekly electronic newsletter.
Will Electrokinetics Yield a New, Clean Energy Source?
A team of researchers from the University of Alberta in Canada announced Monday that they have discovered a new method of generating electricity. The researchers forced water through a filter made of porous glass, causing an electrical charge to build up on the filter via the electrokinetic effect?the physical separation of charges within a liquid, such as water, due to its interaction with a solid surface, such as glass. Using the pressure caused by a 30-centimeter column of water (a column about one foot high), the researchers were able to draw a current of 1.5 micro-amps from the glass filter. That's an extremely small current, but the researchers believe that using saltier water and a greater number of "microchannels"?the miniature channels existing in the pores of the glass filter?could yield a practical power source.
Although the authors described the technique as possibly "a new alternative energy source to rival wind and solar power," it suffers from a potentially fatal flaw, namely, its low conversion efficiency. According to the authors' paper, published Monday in the Journal of Micromechanics and Microengineering (a publication of the Institute of Physics), the amount of electrical energy produced by the technique is expected to be less than 0.05 percent of the mechanical flow energy consumed by the pressure drop across the microchannels?at least, for dilute solutions. That suggests that for any natural source of flowing water, such as a river, a conventional turbine-generator would yield far more electricity than would an electrokinetic device. However, the devices should be more efficient when driven by salt water, and may have an application in tidal or wave energy devices that aim to convert the energy in flowing seawater into electricity. See the announcement from the Institute of Physics and the University of Alberta press release.