Breathing new life into an old idea, MIT Institute Professor Mildred S. Dresselhaus and co-workers are developing innovative materials for controlling temperatures that could lead to substantial energy savings by allowing more efficient car engines, photovoltaic cells and electronic devices.
Novel thermoelectric materials have already resulted in a new consumer product: a simple, efficient way of cooling car seats in hot climates. The devices, similar to the more-familiar car seat heaters, provide comfort directly to the individual rather than cooling the entire car, saving on air-conditioning and energy costs.
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 (and former president) Paul Gray, among others.
Dresselhaus and colleagues are now applying nanotechnology and other cutting-edge technologies to the field. She'll describe her work toward better thermoelectric materials in an invited talk on Monday, Nov. 26 at the annual meeting of the Materials Research Society in Boston.Thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage.
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 - just a few billionths of a meter across - interfere with the flow of heat, while allowing electricity to flow freely. “Making a nanostructure allows you to independently control these qualities,” Dresselhaus says.
She and her MIT collaborators started working on these developments in the 1990s, and soon drew interest from the US Navy because of the potential for making quieter submarines (power generation and air conditioning are some of the noisiest functions on existing subs). “From that research, we came up with a lot of new materials that nobody had looked into,” Dresselhaus says.
After some early work conducted with Ted Harman of MIT Lincoln Labs, Harman, Dresselhaus, and her student Lyndon Hicks published an experimental paper on the new materials in the mid 1990s. “People saw that paper and the field started,” she says. “Now there are conferences devoted to it.”
Her work in finding new thermoelectric materials, including a collaboration with MIT professor of Mechanical Engineering Gang Chen, invigorated the field, and now there are real applications like seat coolers in cars. Last year, a small company in California sold a million of the units worldwide.OTHER POTENTIAL APPLICATIONS
The technology could also be used in cars to make the engines themselves more efficient. In conventional cars, about 80 percent of the fuel's energy is wasted as heat. Thermoelectric systems could perhaps be used to generate electricity directly from this wasted heat. Because the amount of fuel used for transportation is such a huge part of the world's energy use, even a small percentage improvement in efficiency can have a great impact, Dresselhaus explains. “It's very practical,” she says, “and the car companies are getting interested.”
The same materials might also play a role in improving the efficiency of photovoltaic cells, harnessing some of the sun's heat as well as its light to make electricity. The key will be finding materials that have the right properties but are not too expensive to produce.
Dresselhaus and colleagues are continuing to probe the thermoelectric properties of a variety of semiconductor materials and nanostructures such as superlattices and quantum dots. Her research on thermoelectric materials is presently sponsored by NASA.
Elizabeth A. Thomson | MIT News Office
Did you know that the wrapping of Easter eggs benefits from specialty light sources?
13.04.2017 | Heraeus Noblelight GmbH
To e-, or not to e-, the question for the exotic 'Si-III' phase of silicon
05.04.2017 | Carnegie Institution for Science
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy