Modernizing a Technology From the Vacuum Tube Era to Generate Cheap Power

Estimated reading time: 4 minutes

The work function is basically a measure of how tightly a material clings to its electrons. “In thermionics you take two materials that have very different work functions, put plates next to each other, make one plate hotter than the other, and magically, electricity comes out,” Schmid said. “When they explained this to me and showed me the efficiency can be as high as 30 percent or more, which is comparable to the best thermal-to-electricity conversion methods that exist, this was a huge surprise for me.”

Riley and Schwede, who were introduced to Schmid soon after coming to Berkeley Lab as part of Cyclotron Road, were equally excited to collaborate with Schmid.

“His microscope was built for exactly what we wanted to do,” Schwede said. “Historically studying thermionics was like a black box. You would have current voltage characteristics, and based on the shape of those curves, you would have to reason about complicated interrelated parameters. This basically allows us to crack open that black box and study precisely what’s going on and compare that to our device results.”

The ARPA-E award will allow the team to develop compelling prototypes. Riley and Schwede have founded a startup company, Spark Thermionics, to pursue their portion of the project and drive its commercialization. Ultimately they envision a small device that can fit on a desk and easily scale depending on the application. “Just like solar cells, where you can string many of them together to make a module,” Schwede said, “we believe that our thermionic devices can scale in modules from watts to megawatts.”

In addition to being useful in developing countries, their thermionic power generator could be used in a combined heat and power (CHP) system for a single home. “When you heat water in your home, you’re actually taking a 2,000-plus degree flame—a natural gas flame can be that hot—and all you’re doing is heating water to 80 degrees Celsius. From the thermodynamic perspective, all of that is going to waste,” Riley said. “Our thermionic device can generate electricity in the home and use the waste heat to warm it, increasing the overall efficiency and dramatically reducing carbon emissions at the same time.”

Added Schmid: “These guys have something that will be a revolution in how we make electricity.”

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