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“Let it rain, let it rain, let it rain…” What if our beloved Irish rain was actually a national energy asset? Following on from my last post about piezoelectricity generated from foot and car traffic, brilliant minds at CEA/Leti-Minatec, an R&D institute in Grenoble, France, have recently developed a system that can harvest energy from falling raindrops.  “Our work could be considered as a good alternative to power systems in raining outdoor environments where solar energy is difficult to exploit,” Thomas Jager told PhysOrg.com, and he could be speaking specifically to Ireland, where, especially in winter, we can’t guarantee the sun, but can expect a healthy dose of rain.

For those of you with a technical bent, this is how it works: the scientists use a polyvinylidene fluoride (PVDF) 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, thus converting the raindrop’s mechanical energy into electrical energy.

Slow falling, large raindrops generate the most energy because raindrops falling at high speeds often lose some energy due to splash.  The scientists haven’t yet developed the mechanism for storing this energy, but surely with developments in wind and wave power surely this can’t be far behind?

A number of other organizations are working on piezoelectric devices as well: Zhong Lin Wang at the Georgia Institute of Technology has devised a sensor that can harvest mechanical energy by bending zinc oxide nanowires: he wants to put it in a shoe, so as you walk you generate power. There’s also Trevor Baylis, inventor of the wind-up radio, who designed and used a piezoelectric boot to power his mobile phone during a hike across the Namib desert.  TEXON International is looking to raise £1m to further develop these electric shoes.

One of the beauties of piezoelectricity is that the tools involved are not beyond the reach of a clever diy inventor: while not everyone has PDVF lying around, the essence of piezoelectricity is a copper wire, that when bent produces a negative/positive charge; when the pressure on the wire is relieved, an electrical current can be detected.  So who’s up for singing in the rain?

Imagine generating electricity with every step you take; that every time you drive or cycle, energy is sent to the national grid; and that even your workout is powering the lights and heat of the gym, replacing fossil fuel – sounds great, right?  Well, piezoelectricity is here.

Piezoelectricity is basically the use of certain materials to transform kinetic energy into electricity.  I wrote in another blog about the development of piezoelectric floor tiles that turn foot traffic into electricity; now the first practical installation of this kind is in place at a Sainsbury’s supermarket in Gloucester, England, where “kinetic road plates” are being used to produce 30 kW of electricity every hour. The company’s press release describes the process as a more physical process (plates are pushed down by passing cars to create rocking motions that turn generators) than a piezoelectrical one, but the broader concept of using transient motion to generate electricity is the same.

There’s no reason why this simple, cheap and sustainable type of energy conversion can’t be used in businesses and homes all over Ireland.  And genius scientists are also working on an even more Irish-friendly form of energy conversion: raindrops into electricity, in my next post!