27-09-2012, 12:52 PM
Energy Harvesting
INTRODUCTION
Energy harvesting has been around for centuries in the form of windmills, watermills and passive
solar power systems. In recent decades, technologies such as wind turbines, hydro-electric
generators and solar panels have turned harvesting into a small but growing contributor to
the world’s energy needs. This technology offers two signifi cant advantages over battery-powered
solutions: virtually inexhaustible sources and little or no adverse environmental effects.
Macro-scale harvesting technologies differ in many ways but have one thing in common:
they “feed the grid,” typically adding kilowatts or megawatts to the power distribution system.
As such, they are not game changers for electronic designers whose mission in life is to snip
the wires – including power cords and even battery-powered systems where the perpetual
device is the ultimate design goal.
For this second goal, micro-energy harvesting systems are the answer. Energy harvesting’s
new frontier is an array of micro-scale technologies that scavenge milliwatts from solar,
vibrational, thermal and biological sources. A few years ago, micro-harvesting could have
been called a scientifi c curiosity. But the design community’s long march to ultra-low-power
(ULP) technology has had the unexpected result of pushing micro-scale energy harvesting out
of the lab and onto the designer’s bench.