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