In the case of Antora Energy’s thermophotovoltaic (TPV) energy storage technology, what’s old is new again. And Myles Steiner, a researcher at the National Renewable Energy Laboratory (NREL), is helping the company to reinvigorate it.
TPV—a technology that harvests electricity not from visible light, but from heat—has been on the back burner for several years. It has been 15 years since NREL (led by retired scientists Tim Coutts and Mark Wanlass) conducted research for the U.S. Navy with regards to nuclear submarines; at the time, NASA also studied it for deep space missions.
“The efficiencies were good, and it had potential for power generation and waste heat collection,” Steiner says, “but the Navy chose to go a different route.”
Antora Energy is one of three companies in the inaugural class of the Shell GameChanger Accelerator Powered by NREL (GCxN). For Antora’s research project, Steiner and colleagues have even dusted off the equipment used for the original tests, now refurbished with new computer controls.
“We’ve learned how to make TPV cells better than we did 20 years ago,” Steiner says. “We’ve learned how to manage photons better, and put reflectors behind cells to recycle all that sub-band-gap light.”
Antora’s technology stores energy cheaply in the form of carbon blocks, insulated to retain temperatures up to 2,000ºC. TPV cells, which convert heat to electricity, draw off the power when needed on the grid.
“Energy storage is a huge area of research and is one of the key enablers of renewable penetration,” he says. “Getting the cost down is very important. You have to have high efficiencies and a low cost for the materials.”
One of the other major advances since the last go-around is that Antora’s batteries will be far hotter. The Navy project looked at energy storage materials kept at temperatures of 1000-1200ºC; industrial waste heat applications are even cooler, around a “low” 600-800ºC.
But, with energy storage materials that are insulated and kept at 2000ºC, “you can use better high band-gap materials like gallium arsenide, and the efficiencies and power densities really go up,” Steiner says. That is precisely the kind of TPV cell that Antora and NREL researchers will be growing at the lab.