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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 a city that is completely green - not just ecologically sound and sustainable, but literally, visibly, green as far as the eye can see?  This fantasy is becoming a reality around the world.   The movement known as vegitecture, or vegetated architecture, is taking off,  and is not just beautiful, but is also an environmentally friendly way to literally add life to a city.
The Musee du Quai Branly in Paris has an 8,600 square foot vertical garden featuring more than 170 different plant species.  The walls use a combination of sunshades, solar panels, and ventilation to catch water, making them self-sustaining ecosystems. The benefits aren’t just aesthetic — the walls reduce noise and provide natural cooling for the surrounding buildings because they soak up noise and heat, whereas concrete just reflects those things. Architects imagine people one day being able to grow and harvest food from vertical gardens.

One of the main leaders in the field is Ken Yeang, a Malaysian-born architect and writer who first designed the Tropical Skyscraper in 1992.  Examples of his visionary work can be viewed here. The technology required to create and sustain a vertical garden is rather complex, but considering it can reintroduce biodiversity to urban areas and even cut down on air conditioning and air purification costs, maybe Ireland’s urban planners could start including vertical gardens to their designs - we certainly have enough rain to water them!