University of Delaware uses solar reactor to make hydrogen

A University of Delaware doctoral student recently traveled to the Swiss Federal Institute of Technology in Zurich to test the device that he’s developed to convert water into hydrogen for use as a fuel. The device uses thermal energy from concentrated sunlight and a catalyst, in this case zinc oxide, to split hydrogen from water, producing a fuel that could be used for a variety of purposes, like a replacement for gas.

Doctoral candidate Erik Koepf designed the device, which involved multiple disciplines and is likely the most complicated device built by a graduate student at the university, according to his advisor, Professor Ajay Prasad, of the Department of Mechanical Engineering and director of UD’s Center for Fuel Cell Research. The making of the device included high-temperature ceramics and customized mechanics, fluid dynamics, heat transfer, reaction kinetics and experimental design, all of which was designed by Koepf.

Koepf left for the Swiss university on April 5 to test the 1,750 pound device under the simulated power of 10,000 suns. The device is a the first step in a two-step process to produce hydrogen, superheating zinc oxide, converting it to zinc. The second step is introducing steam and reacting that with the zinc to produce hydrogen and zinc oxide, which can be cooled and reused in the process.

The device will heat the zinc oxide to more than 3,000 degrees Fahrenheit. “Erik’s device is to accomplish step 1 of the two-step zinc oxide thermochemical cycle. Erik’s reactor decomposes zinc oxide to zinc and oxygen using highly concentrated sunlight. The hydrolysis step [i.e., converting water to hydrogen] actually happens in Step 2, which is after the zinc is produced in Step 1,” he said. The oxygen stripped from the zinc in the first step is vented into the atmosphere.

In the second step steam is introduced to the zinc at temperatures below 1,000 degrees Fahrenheit. “The oxygen that comes from the water is simply recombined with zinc to recover zinc oxide, which is then transferred back to step 1. All of the water…combines with zinc to make zinc oxide…in a closed loop. In the process, hydrogen is generated from water. The only inputs are water and sunlight, and the only (useful) product is hydrogen,” Prasad said.

The reactor that Koepf is testing is testing is a proof-of-concept reactor, according to Prasad. If it works effectively it could be scaled up in the future to larger scales, he said.

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