Hydrogen Fuel Made with Sunlight and Zinc
Hydrogen is the most abundant element on Earth. And it’s potential as a fuel could revolutionize the energy market because using it doesn’t produce any emissions. Zero. Unfortunately, it’s lightweight gas and rises into the atmosphere, which means its rarely found in its pure form. And making making it produces emissions.
Erik Koepf, a mechanical engineering PhD student at the University of Delaware, may have found a way to make hydrogen fuel cheaply, using only sunlight, zinc oxide and water.
He built a device that has a mirror and chamber, which holds the zinc oxide. The mirror concentrates the sunlight into the chamber holding the zinc oxide. The concentrated light is so intense, with temperatures hitting up to 3,500 degrees Fahrenheit, that when it hits the zinc oxide the heat separates the zinc and oxygen, and the zinc becomes a vapor.
In a large facility, the zinc vapor would be added to water, which reacts with it and turns into zinc oxide again, releasing the hydrogen. Koepf’s apparatus doesn’t perform that second step, which is actually simpler.
It’s the first step that’s more challenging, “because it requires very high temperatures,” said Ajay Prasad, a professor of mechanical engineering at the University of Delaware and Koepf’s PhD adviser.
Since the product is zinc oxide, the same chemical the reaction started with, it can be used over and over again. The only waste produced is oxygen. Since the power source is sunlight, it eliminates the problem of the vast amounts of electricity needed in other hydrogen-producing reactions, such as electrolyzing water.
The device is being tested at the Swiss Federal Institute of Technology, and there are still questions about whether it can be scaled up. Thus far the amounts of hydrogen and zinc produced have been small, and the reaction chamber Koepf designed only takes care of the first step, making the zinc vapor. The next stage will be setting up the water-zinc reaction to more efficiently produce the hydrogen.
Koepf will also be testing a reflector designed to concentrate the sunlight. Initially he used an existing mirror at the Institute to concentrate the sunlight, but to run this next set of tests he’ll be using a water-cooled version of his own design to reach the temperatures necessary to drive the reaction.
Credit: University of Delaware / Kathy F. Atkinson and courtesy of Erik Koepf