Heat-Based Photovoltaics Created at MIT

Researchers at the Massachusetts Institute of Technology (MIT), in Cambridge, announce the creation of a new type of photovoltaic device, that relies solely on heat to create electricity, rather than sunlight.

Though it may seem like a stretch to associate the term photovoltaic to any technology not having to do with the Sun directly, the researchers assure that their new device is in fact an energy-conversion device of the photovoltaic class.

The way the system works is very simple. The idea is quite old, but thus far experts found no way of applying it into practice at an affordable price. The main innovation is developing a new approach to engineering the surface of a material.

What this does is allow the material to convert the heat it collects into light of a specific wavelength. That wavelength is selected specifically to meet the highest conversion efficiency rates of standard photovoltaic devices, such as solar cells.

By eliminating wavelengths that are absorbed inefficiently to begin with, researchers basically managed to feed solar cell with only the best type of light. Details of this research appear in the latest issue of the esteemed journal Physical Review A.

In order to develop the new material, the MIT group turned to nanotechnology, and fashioned a device that features countless nanoscale pits embedded in its texture. By varying the size and disposition of the pits, experts can fine-tuned the wavelength of light the surface emits.

This device can be fueled from a variety of sources, including for example decaying isotopes such as uranium, hydrocarbon fuels such as methane or ethane, and of course the Sun. Conceivably, other methods could be converted for use as well.

The button-sized power generator the group developed based on its innovative technique is fueled by butane, and provides electricity for three time longer than the most advanced lithium-ion battery on the market today.

It can be recharged with utmost ease, simply by snapping a cartridge containing a fresh supply of the fuel into place. MIT experts also created a version of the generator that is powered by radioactive decay, just to prove that the concept is feasible.

“Being able to convert heat from various sources into electricity without moving parts would bring huge benefits, especially if we could do it efficiently, relatively inexpensively and on a small scale,” says MIT Institute for Soldier Nanotechnologies research engineer Ivan Celanovic says.

“By choosing how we design the nanostructure, we can create materials that have novel optical properties. This gives us the ability to control and manipulate the behavior of light,” adds Marin Soljačić.

The expert holds an appointment as a researcher at ISN, and is also a professor of physics at MIT.