Thermoelectric Materials Key to Savings

The research is based on the principle of thermoelectric cooling and heating, which was first discovered in the early 19th century and was advanced into some practical applications in the 1960s by MIT professor Paul Gray, among others.

MIT Institute Professor Mildred S. Dresselhaus and colleagues are now applying nanotechnology and other cutting-edge technologies to the field.

Thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage. Conversely, when a voltage is applied to them, they become hotter on one side, and colder on the other. The process works with a variety of materials, and especially well with semiconductors. But it always had one big drawback: it is very inefficient.

The fundamental problem in creating efficient thermoelectric materials is that they need to be very good at conducting electricity, but not heat. That way, one end of the apparatus can get hot while the other remains cold, instead of the material quickly equalizing the temperature. In most materials, electrical and thermal conductivity go hand in hand. So researchers had to find ways of modifying materials to separate the two properties.

The key to making it more practical, Dresselhaus explains, was in creating engineered semiconductor materials in which tiny patterns have been created to alter the materials’ behavior. This might include embedding nanoscale particles or wires in a matrix of another material. These nanoscale structures interfere with the flow of heat, while allowing electricity to flow freely. “Making a nanostructure allows you to independently control these qualities,” Dresselhaus says.; Source: Massachusetts Institute of Technology