How much energy do we waste in America? A little over half of
it, says Arun Majumdar, the Almy and Agnes Maynard professor of
mechanical engineering at UC Berkeley. The U.S. consumes about
100 quads of energy a year, he said. A quad is a quadrillion
BTUs. A BTU is equivalent to the energy produced by a match. "Of
the 100 quads, about 55 to 60 go into waste heat," he said.
"Fifty or 60 percent of the energy is wasted as heat." The
culprit is waste heat, the heat that is emitted into the
atmosphere by everything from nuclear power plants and factories
to car engines and that power brick on your laptop. A new crop
of startups, however, are tinkering with ways to make this
useful. The companies can be divided into two categories. On one
hand, there are the companies with mechanical systems, which
capture heat, compress it and exploit the pressure to crank a
turbine. ElectraTherm, for instance, recently raised $2.6
million to further test out its low-heat converter. ElectraTherm
uses captured heat to boil a liquid