THERMOELECTRIC DREAMS

The generation of electric currents from temperature differentials is more than “another one of those wild ideas.” Detroit automakers and NASA are seriously interested.

Related idea: Some hypothesize that a current can be obtained from the temperature differential between the upper and the deep ocean.

Thermoelectric materials are one key to energy savings
November 20, 2007 (MIT via Science Daily)

WHO
MIT Professor Mildred S. Dresselhaus, former MIT professor/president Paul Gray, Ted Harman, MIT Lincoln Labs, Dresselhaus student Lyndon Hicks, MIT professor of Mechanical Engineering Gang Chen,

Schematic of the concept. (click to enlarge)

WHAT
Dresselhaus and co-researchers are developing thermoelectric materials based on the principle of thermoelectric cooling and heating: certain materials, when heated, generate electrical voltage. When voltage is applied to them, they become hotter on one side, colder on the other.

WHEN
- The research is based on a principle first discovered in the early 19th century and advanced in the 1960s by Gray and others.
- Dresselhaus and colleagues did work for the Navy in the 1990s to more quietly cool submarines.
- 2006: The thermoelectric carseat sold 1 million units
- Dresselhaus and colleagues are now developing nanotech applications. She will present her work Nov. 26 at the annual Materials Research Society meeting in Boston.

WHERE
A thermoelectric material presently is used in car seats to cool passengers and spare auto air conditioning demands. Uses are foreseen in car engines, photovoltaic cells and electronic devices.

WHY
- The process works with a variety of materials and especially well with semiconductors (the material used in computer chips and photovoltaic (solar) panels.
- Dresselhaus breakthrough: Thermoelectric materials had been inefficient. The charge quickly passed through the material, heating the material uniformly. The temp differential and insulating effect were lost. The Dresselhaus team is embedding obstacles (nanoscale particles, wires or patterns) in semiconductors to impede the flow of current and sustain the temp differential.
- By embedding the obstacles in computer chips or solar panels, temperatures can be controlled, making functions more efficient.
- In cars, if the engine’s heat can be translated into electricity, that power can be incorporated.
- In solar arrays, if the temperatures of the panels can be turned into electricity, it would the system’s output.
- Dresselhaus and colleagues, now sponsored by NASA, are working with semiconductor materials and nanostructures like superlattices and quantum dots.

In this hypothetical application, a tiny device could capture a current from the temperature difference between an air duct and the room ambient. (click to enlarge)

QUOTES
Dresselhaus: "Making a nanostructure allows you to independently control [electrical and temperature conduction] qualities…It's very practical…and the car companies are getting interested."