Sun-free photovoltaics powered by heat

August 1, 2011

Silicon chip micro-reactors developed by the MIT team. Each of these contains photonic crystals on both flat faces, with external tubes for injecting fuel and air and ejecting waste products. Inside the chip, the fuel and air react to heat up the photonic crystals. (Credit: Justin Knight)

A new photovoltaic energy-conversion system has been developed by researchers at MIT, powered solely by heat, generating electricity with no sunlight at all.

The researchers made a button-sized power generator fueled by butane that can run three times longer than a lithium-ion battery of the same weight. The device can then be recharged instantly, just by snapping in a tiny cartridge of fresh fuel.

The researchers designed a thermal emitter that radiates only the wavelengths that the PV diode can absorb and convert into electricity, while suppressing other wavelengths.  They used a slab of tungsten, creating billions of tiny pits on its surface.

When the slab heats up, it generates bright light with an altered emission spectrum because each pit acts as a resonator, capable of giving off radiation at only certain wavelengths.

A related device designed by the researchers, powered by a radioisotope that steadily produces heat from radioactive decay, could generate electricity for 30 years without refueling or servicing — an ideal source of electricity for spacecraft headed on long missions away from the sun.

Ref.: Peter Bermel, et al., Design and global optimization of high-efficiency thermophotovoltaic systems, Optics Express, 2010; 18 (S3): A314 [DOI: 10.1364/OE.18.00A314]

Ref.: Ivan Celanovic, Natalija Jovanovic, and John Kassakian, Two-dimensional tungsten photonic crystals as selective thermal emitters, Applied Physics Letters, 2008; 92 (19): 193101 [DOI: 10.1063/1.2927484]

Ref.: M. Ghebrebrhan, et al., Tailoring thermal radiation from metallic photonic crystal slabs via coupled-mode theory, Physical Review A, 2011; 83: 033810

Ref.: Pilawa-Podgurski, et al., Low-power maximum power point tracker with digital control for thermophotovoltaic generators, Proceedings of the Twenty-Fifth Annual IEEE Applied Power Electronics Conference, APEC 2010, February 2010