UD doctoral student Erik Koepf (left) and Ajay Prasad, professor of mechanical engineering, inspect the novel solar reactor. Photo: University of Delaware, Evan Krape
Producing hydrogen from non-fossil fuel sources is a problem
that continues to elude many scientists, but University of Delaware’s
Erik Koepf thinks he may have discovered a solution.
Hydrogen is traditionally made from natural gas. Unfortunately,
natural gas is a fossil fuel that releases carbon dioxide, a greenhouse gas,
when converted to hydrogen.
Koepf, a doctoral candidate in mechanical engineering, has designed a
novel reactor that employs highly concentrated sunlight and zinc oxide powder
to produce solar hydrogen, a truly clean, sustainable fuel with zero emissions.
His advisers are Ajay Prasad, professor of mechanical engineering and
director of UD’s Center for Fuel Cell Research, and Suresh Advani, George W. Laird
Professor of Mechanical Engineering.
“People have been trying for years to generate hydrogen
renewably from sunlight, and Erik’s reactor takes us closer to that goal,”
explained Prasad, principal investigator of the University’s fuel cell bus
project, which uses hydrogen fuel to power its fleet.
A unique design
The reactor, which resembles a large cylinder, is comprised of layers of
advanced, ultrahigh-temperature insulation and ceramic materials. It measures
roughly 2 ft by 3 ft and weighs a hefty 1,750 lbs.
The conical geometry of the reactors’ design uses gravity to feed
zinc oxide powder (the reactant) into the system through 15 hoppers perched on
top of the device using special gears and a custom built control assembly Koepf
developed at UD. Cooling blocks embedded in the structure keep the motors, a
quartz window and the aperture ring, where the sunlight enters, cool.
“The idea is to create a small, well-insulated cavity and
subject it to highly concentrated sunlight from above,” explained Koepf.
Koepf has been testing the main control systems for his reactor
in Spencer Laboratory for months. The missing ingredient, however, has been
sunlight. Beginning April 5, he will spend six weeks testing the prototype’s
effectiveness for the first time at the Swiss Federal Institute of Technology
“We will measure the temperature and the production of oxygen
inside the reactor in real time, which will tell us how much solar fuel or zinc
we are actually producing,” Koepf explained.
During testing, light concentrated to simulate the energy of
10,000 suns will be focused down into the reactor, sending the temperature within
soaring to over 3,000 F, nearly one-third the temperature of the sun’s surface.
Once hot, the hoppers will feed zinc oxide powder (a benign substance
resembling baking soda) onto the ceramic layer, causing a reaction that
decomposes the powder into pure zinc vapor. In a subsequent step, the zinc will
be reacted with water to produce solar hydrogen.
“Essentially, we take zinc oxide powder and thermochemically
store the energy of the sun in it, then bottle it,” explained Koepf, whose work
is funded mainly through the Federal Transit Administration, a part of the U.S.
Department of Transportation. “Zinc in and of itself is a very valuable fuel
that can be used in batteries and fuel cells, among other things, even if you
don’t create hydrogen.”
Koepf calls his research a “potentially sustainable energy path
for the future” and he is working to patent his design through the University’s
Office of Economic Innovation and Partnerships (OEIP).
“Doctoral students typically specialize in one area, but Erik’s
reactor involves many different branches of mechanical engineering; notably
fluid mechanics, heat transfer, reaction kinetics, and experimental design,”
One interesting feature of the reactor is that, in theory, the
zinc oxide byproduct created during the reaction will be re-usable, making the
“This is probably the most complex device built by a graduate
student in the history of our department,” added Prasad. “If he is successful,
one day, we can imagine a huge array of mirrors out in the desert concentrating
sunlight up into a large central tower containing a larger version of Erik’s
reactor and making hydrogen on an industrial scale.”