Posted by: garispang | June 26, 2009

Producing Clean Energy From Falling Raindrops

heavey_downpour.jpgPiezoelectrics is a really cool science. Basically, energy is produced when a certain object is bent, deformed, or stressed in some way. Scientists at the CEA/Leti-Minatec in Grenoble are looking at this technology as a way to harness the vibrations caused by falling raindrops. According to the article, the system works with raindrops ranging in diameter from 1 to 5 mm, and simulations show that it’s possible to recover up to 12 milliwatts from one of the larger ‘downpour’ drops.

When a raindrop impacts a surface, it produces a perfectly inelastic shock. The amount of energy generated by the impact can then be estimated using a mechanical-electric model. To capture the raindrops’ mechanical energy, the scientists used a PVDF (polyvinylidene fluoride) polymer, a piezoelectric material that converts mechanical energy into electrical energy. When a raindrop impacts the 25-micrometer-thick PVDF, the polymer starts to vibrate. Electrodes embedded in the PVDF are used to recover the electrical charges generated by the vibrations.

Apparently, slow, fat raindrops produce the most energy — since those accelerating at high speeds lose energy due to splash. A single large drop might generate up to 12 milliwatts of energy. This technology is still in the research stage, but it presents another interesting piece of the future energy puzzle. Imagine skyscrapers located in rainy (or windy) areas with piezoelectric materials creating energy for a portion of the building. Or how about a basketball court producing energy based on the vibrations of the players feet above? Any number of applications could be invested to harness vibration. It’s amazing to believe that even rain could prove useful in powering your life.


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