Vandervelde Wins NSF CAREER Award for Thermophotovoltaic Research
Professor of Electrical and Computer Engineering
has been awarded an early-career award from the National Science
Foundation for promising research on the conversion of heat to
Vandervelde, the John A. and Dorothy M.
Adams Faculty Development Professor in the Department of Electrical
and Computer Engineering, received a NSF CAREER Award for his
research on thermophotovoltaics (TPVs)—cells that convert thermal
radiation, or heat, into electricity—with implications for a new
class of green energy technologies.
"Right now, thermophotovolatics are used when the heat source is
very hot," says Vandervelde, citing that generally heat sources have
to be in excess of 1500°C for TPVs to work efficiently. His goal is to make TPVs more efficient at lower
temperatures, and ultimately, convert heat to electricity at a cool
37°C—or the temperature of the human body. This could have
implications for medical devices, such as a pacemaker that keeps a
charge from the electricity generated by one's own body heat.
In a TPV system, when a photon—an energy packet of light or heat—strikes the TPV, a
charge carrier pair is created that generates an electron and
subsequently electricity. But if the charge carriers recombine, a
photon is re-emitted and is lost as light or heat. "Every time that
recombination happens, that's less energy you get out and in the end
that lowers your overall efficiency," says Vandervelde.
By using recent advances in
infrared photodetectors, Vandervelde
will investigate the use of a
novel photodiode structure to enhance the efficiency of current TPV devices. The new photodiode structure
contains a barrier that
prevents the recombination of the charge carriers, while allowing
them to flow out of the cell as unimpeded electrical current.
"By putting the barriers in, we end up separating where those charge
carriers are so they end up not spending a lot of time near each
other," says Vandervelde. "It makes recombination far less likely to
occur, which means that you end up getting out a lot more current
for the same amount of light coming in."
More efficient TPVs could also be used to recoup the heat lost to
keep massive computer data server farms cool. "The realization of
cooler-running, more energy-efficient, server farms— which occupy
20% of energy consumption off the energy grid in some locations—alone will change
the very nature of our nation's energy needs in a positive way," he
At higher temperatures, like the heat thrown from a car's engine,
more efficient thermophotovoltaics could capture the more than 60%
of power lost to waste heat in the engine compartment or out the
tailpipe. "In electric cars, lithium ion batteries put out a lot of
heat. If you could harness even a little bit of that heat and put it
toward recharging the batteries, you could extend the life of the
battery and the drive time," Vandervelde says.
In Vandervelde's Renewable Energy and Applied Photonics (REAP) Labs,
he and his graduate students have engineered a test chamber for this
new class of TPV cell samples that can measure the samples' end
"The ability to harness the ubiquitous waste heat represents a
significant jump forward to our becoming a truly green society,"