Thermal photovoltaics exploit nanostructuring for higher efficiency

MIT researchers developed a photovoltaic system that relies on heat to generate electricity without mechanical parts. The material’s nano-surface engineering enables it to convert heat into precisely tuned light wavelengths, which are then transmitted onto matched photovoltaics cells.

August 12, 2011 — MIT researchers developed a photovoltaic energy-conversion system that relies on heat, not sunlight, to generate electricity without any moving parts. The material’s unique surface engineering enables it to convert heat into precisely tuned light wavelengths, which are then transmitted onto matched photovoltaics cells.

The material is etched with billions of nanoscale pits that radiate energy from heat at tuned wavelengths. The heat source could be the sun, or a hydrocarbon fuel, decaying radioisotope, etc.

The research is a continuation of the thermophotovoltaics (TPV) concept, which couple a PV cell with any heat source via a thermal emitter. This new design is more efficient with less waste, MIT claims. The thermal emitter radiates only the wavelengths that the PV diode can absorb and convert into electricity, suppressing other wavelengths. The team made a photonic crystal on a slab of tungsten (W) with nanoscale features patterned on its surface to control light behavoir. Each nanostructure acts as a resonator, capable of giving off radiation at only certain wavelengths. It is a manufacturing technique that has been used to improve lasers and light emitting diodes (LEDs) previously.

The researchers at MIT built 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 by snapping in a tiny cartridge of fresh fuel. This micro-TPV power generator has a “micro-reactor” designed by Klavs Jensen, the Warren K. Lewis Professor of Chemical Engineering, and fabricated in the Microsystems Technology Laboratories. Further work could triple the current energy density. Another device, powered by a radioisotope that steadily produces heat from radioactive decay, could generate electricity for 30 years without refueling or servicing, opening up deep space applications. The MIT team, supported in part by a seed grant from the MIT Energy Initiative, is now working with collaborators to create several novel electricity-generating devices.  

The team includes Ivan Celanovic ScD ’06, research engineer in MIT’s Institute for Soldier Nanotechnologies (ISN); Marin Solja?i?, professor of physics and ISN researcher; Peter Bermel, research scientist in the Research Laboratory for Electronics (RLE); Peter Fisher, professor of physics; and Michael Ghebrebrhan, a postdoc in RLE.

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Also read: Polymer solar photovoltaic thermal device provides heat, saves money

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