Exploiting Nature’s secret stash

Published in Compound Semiconductor, 1 Apr 2009

Phone-charging shoes? Wireless light switches? Photovoltaics that harness the warmth of radioactive isotopes? Energy harvesting is starting to gain momentum, finds Jon Cartwright.

We are, by most accounts, a wasteful bunch. If you are sitting in an office, the chances are that most of the energy produced by the heaters is disappearing outside rather than keeping you warm. If you have your computer switched on, it could be frittering four-fifths of its maximum power consumption simply doing nothing. Just by reading to the end of this article you could expend around 100 kJ of energy – though beware that doing anything else will almost certainly be a bigger drain.

Most people rarely acknowledge the energy that is lost to the environment. Rather than chase it, we have opted to generate more. The past 35 years have seen a tripling of world electricity demand, which has predominantly been met through the burning of additional fossil fuels. With less than a 3% contribution to global energy production, those technologies that exploit what is already around us – solar, wind and tidal power, for example – barely feature.

Recently, however, and partly in response to the drive for lower carbon footprints, scientists have started to rethink the possibilities for salvaging wasted energy – what they term “energy harvesting”. They are finding ways to capture the heat lost from buildings, the idle power drain of computers or the motions of the human body, and to convert it into useful, clean electricity. But that is not all: energy harvesting permits devices that are free from a battery or an external power source. With these restrictions removed, the devices can be placed or moved anywhere, scaled to dimensions smaller than ever and designed to exist without maintenance. […]

The rest of this article is available here.