From: Clay Dillow, Fast Company
Published May 22, 2009 09:29 AM

Pumping Green Power from Fake Plastic Trees

With all the potential good wind power could do for the carbon economy, one of the objections hindering its implementation is aesthetic; people simply don't want massive turbines dotting the landscape and marring their views. The Dutch founder of London's Solar Botanic Ltd. was wrestling with that very issue in 2002 when the idea began to blossom: why not redesign the technology to blend into the natural world?

Founded last year, Solar Botanic's ambitious goal involves layering existing technologies three-fold into the natural form of a leaf and producing fake power-producing trees that individually could power an entire home. Each "nanoleaf" would incorporate photovoltaics for collecting solar power, thermoelectrics for converting the sun's heat to electricity, and piezoelectric nanogenerators in the leaves' petioles (the stalk connecting the leaf to the branch) that capture the kinetic energy from the wind rustling the leaves.

Solar Botanic estimates that a single tree with a canopy 20 feet in diameter could power an average home, producing about 120,000 kilowatt-hours over two decades. Forests, on the other hand, could power entire population centers. But a more reasonable deployment scenario involves greening up parking lots while providing power to charge electric vehicles or planting the "trees" along highways to capture the turbulence of passing traffic.

Though the final materials have not been determined, the leaves would likely rely on thin-film photovoltaics to collect sunlight. The company is looking into molding the trunks of the "trees" from recycled plastic and tires, as well as a liquefied waste biomass produced from wood itself. The company is also exploring a handful of designs, from palm trees to shrubbery, to see what might be most efficient.

The idea is not without its detractors. For one, black leaves would be the most efficient solar conductors, but would render the aesthetic argument moot. Also, placing thin-film photovoltaics and thermoelectrics on a single leaf presents a spatial problem, especially if the leaf is to remain light enough to flutter in the wind. Current thermoelectrics also require higher temperatures than the average green leaf can achieve from sunlight alone.

Then there's the problem of the market: at an estimated cost between $12,000 and $20,000 per tree, each kilowatt hour would cost around 13.5 cents, not particularly competitive with current sources that cost around five cents. Even so, the idea of a wind generator that is home to birds rather than a menace to them, or a solar plant with the footprint of a tree trunk (and minus the ugly black panels) is a pleasant thought. If technology and design can meet in the right places, Solar Botanic could have a working prototype in three years.