Scientists Turns Waste Heat Into Electricity

Engineers from The Ohio State University have found a way to convert heat into electricity by applying their technique to capture "waste heat," the byproduct of electrical and mechanical devices like car engines.

The study of solid-state thermoelectrics has been growing since its main purpose was to capture the waste heat inside specially designed materials to produce power and add to overall energy efficiency.

"Over half of the energy we use is wasted and enters the atmosphere as heat," shared Stephen Boona, a postdoctoral researcher at Ohio State. "Solid-state thermoelectrics can help us recover some of that energy. These devices have no moving parts, don't wear out, are robust and require no maintenance. Unfortunately, to date, they are also too expensive and not quite efficient enough to warrant widespread use. We're working to change that."

Previous research by Joseph Heremans, a professor of mechanical and aerospace engineering and the Ohio Eminent Scholar in Nanotechnology, in 2012 with the same Ohio State research group showed that magnetic fields could boost a quantum mechanical effect called the spin Seebeck effect. This will enhance the voltage output of thin films made from exotic nano-structured materials from a few microvolts to a few millivolts.

The recent development increases the output for a composite of two very common metals, nickel with a sprinkling of platinum, from a few nanovolts to tens or hundreds of nanovolts. This could be incorporated into a more basic device that requires no nanofabrication and could easily be scaled up for industry.

"Basically, classical thermodynamics covers steam engines that use steam as a working fluid, or jet engines or car engines that use air as a working fluid.

Thermoelectrics use electrons as the working fluid. And in this work, we're using quanta of magnetization, or 'magnons,' as a working fluid," Heremans said.

Though the research has yet to produce a real-world device, Heremans knows that the proof-of-principle established by their research will eventually be used in common waste heat generators, including car and jet engines.