MTPV Readying Micron-Gap Thermal Photovoltaics
By David Lammers
Much of the world’s energy is wasted, streaming out of smokestacks rather than being captured and turned into usable electricity. MTPV LLC (Austin) is not far from commercializing a series of modules which turn heat into electricity, at much higher rates of conversion efficiency than previously thought possible from thermal photovoltaics or thermoelectrics, said David Mather, president and chief operating officer.
David Mather
Mather was one of the original angel investors in MTPV, after working in senior management positions at Compaq, H-P, and others. The market for electronics used in alternative energy systems is “a new market, one that will be as big as IT for semiconductors,” Mather said in a presentation to SEMI Austin members.
Micron-gap thermal photovoltaics converts heat into electricity. The initial opportunity, Mather said, is in industrial markets, such as glass making, where huge amounts of 1000-plus-degree heat are generated. Mather said MTPV has been working closely with Saint-Gobain, the French glass producer, to apply the MTPV technology. With the partnership with Saint-Gobain in hand, and other technology development agreements with both identified and as-yet-unnamed partners in the works, Mather said the dawn of commercial micron-gap thermal photovoltaics is upon us.
Last October, the company was named Best Venture by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) at its 23rd Industry Growth Forum, which attracted some 500 people to Denver.
The MTPV technology has been more than 15 years in the making.
Bob DiMatteo
Bob DiMatteo, the CEO and chairman of MTPV, has spent three decades in the energy field. DiMatteo questioned the conventional wisdom of thermal PV, dating back to Planck’s Law, which had prescribed limits for the relatively large gaps thought to be needed between the black body emitter and the photovoltaic device.
In mid life, DiMatteo went to M.I.T. to gain graduate degrees and to prove (or disprove) his hypothesis that a much smaller gap, in the sub-micron dimension, would yield far more electrical energy. As Mather told the SEMI Austin audience, “if the gap is reduced to the 100nm-and-below range, the physics change.” Rather than waste photons by having them bounce around, at sub-micron dimensions they exhibit a tunneling effect referred to as “evanescent coupling.”
Working at the Charles Stark Draper Laboratory over a period of five years, DiMatteo and colleagues developed the concepts that became MTPV, which now has small teams in Austin, Boston, and Wuhan, China. The company has developed modules which deliver 10-50 times more power than earlier thermal photovoltaics, Mather said.
The silicon-based MEMS emitter takes heat, ranging in temperature from 100 to 1400°C, and transfers radiation to the germanium-based photovoltaic device. Mather said the emitter prototypes now being made in Boston will be manufactured soon at SVTC’s fab in Austin in relatively modest commercial quantities. Later, production will be transferred to a foundry for higher-volume manufacturing.
While germanium has the advantage of being low in cost, Mather said MTPV, with government research support, has been developing second-generation photovoltaic devices that take advantage of the bandgap properties of other semiconductor materials. Working with MIT professor Peter Hagelstein, MPTV is developing a second-generation technology that delivers more energy, using quantum dots and quantum wells which promise to be more efficient at relatively low source temperatures, in the 100-degree Centigrade range.
“There is a tremendous amount of waste heat generated by industries now,” Mather said, adding that in the long run “MTPV technology has application anywhere where there is waste heat exceeding 100 degrees C.”
Mather said the company “is about 12 months away from the start of selling commercial products.” The “quad” module (pictured below) could be inserted into the gas flow of an industrial plant or the methane burn-off at a coal mine. It will generate about 300 Watts, about one-fourth the power needed to power a small home. Smaller modules are also in development.
“We will be entering the market at 1 Watt per square centimeter, and we believe we are about two years away from perfecting our second-generation technology capable of more than 40-50 Watts per square centimeter,” Mather said.
Tags: alternative energy, MTPV, Saint-Gobain, thermal photovoltaics