Purdue engineer's research
of solar power may benefit NASA financially
By Luis Jiménez
Summer
Reporter
A Purdue engineer has devised a method of testing
a new satellite solar-power system on Earth instead of in space, which
could save NASA astronomical amounts of money.
Shripad Revankar, an associate professor of nuclear
engineering, said solar-energy satellites with a geosynchronous orbit
follow a pattern much like Earth does with a day-night cycle. He said
conventional power systems store the sunlight received during the day
in bulky rechargeable batteries. However, new power systems generate
electricity by using the heat-transfer properties of some liquids.
Experiments to test the new power systems are usually
conducted in the space shuttle, thus, the method Revankar designed to
test these new systems on Earth could save the National Aeronautical
and Space Administration millions of dollars.
Revankar said that an experiment that usually costs
$1 or $2 million can be done with under $100,000 with the added benefits
of having a controlled testing environment.
The main difference between conventional and experimental
power systems is the way power is generated. Conventional systems store
energy in rechargeable batteries while the new systems generate electricity
by using the heat released when "phase-change" materials inside the
satellite melt, Revankar said.
Phase-change materials encapsulated in the satellite
stay in a liquid phase during the daylight hours of a satellite's day-night
cycle. At night, the phase-change material freezes releasing heat in
the process. The heat released then drives small steam turbines called
thermoelectric units.
Revankar said the new technology has a lot of potential
uses. The satellites would generate three times more energy than batteries
of comparable size, Revankar said. The same concept could be applied
to space vehicles and even to commercial heating and energy applications.
The major obstacle, however, is getting the phase-change
material to freeze uniformly inside the capsules, Revankar said. When
the phase-change materials freezes, bubble-like cavities or voids form
against the wall, making the heat transfer process more difficult.
He has been working around this problem by trying
different capsule shapes and sizes. He has made it possible to experiment
with different capsule shapes and different phase-change materials on
Earth by designing transparent capsules and low-temperature melting
materials.
This way researchers can visually see the cavities
as they form and can come up with solutions to avoid them.
The research is funded by the NASA.
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