Researchers have come up with an unusual, highly efficient and possibly less expensive way of turning the sun’s heat into electricity.
Researchers at the Massachusetts Institute of Technology in
Cambridge, Mass., and their collaborators have come up with an unusual, highly
efficient and possibly less expensive way of turning the sun’s heat into
Their system, described in a paper published online in the
journal Nature Materials, produces power with an efficiency roughly eight times
higher than ever previously reported for a solar thermoelectric device such as
one that produces electricity from solar heat. It does so by generating and
harnessing a temperature difference of about 392°F (200°C) between the interior
of the device and the ambient air.
The concept “is very radical,” says Gang Chen, MIT’s Carl
Richard Soderberg Professor in Power Engineering and director of the Pappalardo
Micro and Nano Engineering Laboratories, who co-authored the paper with MIT
doctoral student Daniel Kraemer and collaborators from Boston College and GMZ
Energy. The work is funded by the Solid-State Solar-Thermal Energy Conversion
Center, an Energy Frontier Research Center at the U.S. Department of Energy.
While solar thermal electricity systems are not a new idea,
they typically involve vast arrays of movable mirrors that track the sun and
focus its rays on a small area. The new approach uses flat stationary panels
similar to traditional solar panels, eliminating the need for tracking systems.
Like the silicon photovoltaic cells that produce electricity
when struck by sunlight, Chen’s system is a solid-state device with no moving
parts. A thermoelectric generator, placed inside a vacuum chamber made of
glass, is covered with a black plate of copper that absorbs sunlight but does
not re-radiate it as heat. The other side of the generator is in contact with
ambient temperatures. Placed in the sun, the entire unit heats up quickly, even
without facing the sun directly.
The device requires much less material than conventional
photovoltaic panels and could therefore be much less expensive to produce. It
also can be integrated into solar hot water systems, allowing the expenses of
the structure and installation to serve two functions at once. Such solar water
heaters are rarely seen in the United States, but are already a highly
successful mass-market product in China and Europe where they provide
households with hot water and in some cases space heating as well.
The materials used to build such solar thermoelectric
generators, made through a nanostructured process, were developed jointly a few
years ago in Chen’s MIT lab and in co-author Zhifeng Ren’s lab at Boston
College. Their teams have continued to work on improving these materials and
integrating them into complete systems.
Chen points out that the DOE has programs to develop
thermoelectric systems, mostly geared toward harnessing waste heat from car and
truck engines. He says that solar applications for such devices also can have
an important role to play in reducing carbon emissions.
The system would not be a substitute for solar
photovoltaics, Chen says, but offers another way of tapping into the enormous
amount of solar energy that bathes the Earth every day. And because it can be
piggybacked onto the existing solar hot-water industry, the thermoelectric
device could be a relatively inexpensive addition, with no subsidies required,
Solar Power with a Side of Hot Running Water
September 6, 2011