Thermal Energy-Harvesting Research Gets $1.5M Boost

The potential of harvesting thermal energy doesn't get nearly the attention that taking energy from wind andsolar sources does. But that all could soon change with a grant awarded to a researcher at a UK university to pursue a method in harvesting energy from thermal sources that leverages synthetic diamond as the electrical converter.

"Thermal energy is all around us," Neil Fox, a senior lecturer in the University of Bristol's School of Chemistry, who was awarded nearly $1.5 million by the Engineering and Physical Sciences Research Council to pursue his thermal-energy harvesting work, told Design News. "The major portion of the solar energy (insolation) reaching the surface of the earth is in the infrared bands. Other terrestrial sources include geothermal, as well as man-made waste-heat from industrial processes."

If energy could be harvested from these sources more efficiently and effectively, thermal could figure prominently on the list of global renewable energy sources, he said.

The project for which Fox received the funding is called "Beta-enhanced thermionic energy converters and nuclear batteries employing nanostructured diamond electrodes." Work on the project began in April and will run for 42 months. The project will continue the work initiated by E.ON's International Research Initiative, "Diamond nanoparticle energy converter for highly efficient solar generation."

Specifically, Fox won the grant to pursue his work using synthetic diamond made by chemical vapor deposition to create thermionic energy converters and nuclear batteries that can harvest and store thermal energy. "Diamond has already been shown to operate thermionically in the target temperature range," Fox told us. "Up until now, most efforts have been focused on thermoelectric devices built back in the 1950s and 1960s before semiconductors to build thermoelectrics were available."

Researchers also have been looking at a vacuum electronic-valve technology called thermionic energy converters. These convert sources of concentrated heat into electrical power by transferring hot electrons from a thermally heated electrode to a cooled electrode, Fox said. But the key problems with these converters was that the materials were not available to make a device that operated in the temperature range of 300C to 900C, which is needed for tapping into the terrestrial sources of thermal heat.

As a result, "thermoelectric was pursued for heat scavenging," which doesn't begin to unlock its potential the way a thermionic method using diamond could, Fox said. "Thermionics is capable of much higher theoretical efficiencies -- up to 60 percent -- compared with thermoelectrics, which is why thermionics was pursued for space applications," he told us.

Specifically, Fox will work to test a method of incorporating Carbon 14 reclaimed from decommissioned nuclear reactors into thermionic diamond to overcome the traditional problem of electrical transport. This also should achieve the power-conversion efficiencies needed to demonstrate a prototype thermal-energy harvesting device, he said.

There are several key objectives to the funded research, Fox told us. They are:

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