Energy harvesting

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 cantadvantages over battery-powered
solutions: virtually inexhaustible sources and little or no adverse environmental effects.
Macro-scale harvesting technologies differ in manyways 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 forelectronic 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 fromsolar,
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 toultra-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.
Now, designers are sizingup ULP not just from the consumption side but from the production
perspective as well. Understanding ULP from the sourcing side will be every bit as
challenging as it wasfrom the consumption side not that many years ago. Primary reason:
harvested power is derived from ambient sources so it tends to be unregulated, intermittent
and small.