Skip to comments.Nano-breakthrough: Dramatic Increase In Thermoelectric Efficiency
Posted on 03/21/2008 5:08:59 AM PDT by saganite
Researchers at Boston College and MIT have used nanotechnology to achieve a major increase in thermoelectric efficiency, a milestone that paves the way for a new generation of products -- from semiconductors and air conditioners to car exhaust systems and solar power technology -- that run cleaner.
The team's low-cost approach, details of which are published in the journal Science, involves building tiny alloy nanostructures that can serve as micro-coolers and power generators. The researchers said that in addition to being inexpensive, their method will likely result in practical, near-term enhancements to make products consume less energy or capture energy that would otherwise be wasted.
The findings represent a key milestone in the quest to harness the thermoelectric effect, which has both enticed and frustrated scientists since its discovery in the early 19th century. The effect refers to certain materials that can convert heat into electricity and vice versa. But there has been a hitch in trying to exploit the effect: most materials that conduct electricity also conduct heat, so their temperature equalizes quickly. In order to improve efficiency, scientists have sought materials that will conduct electricity but not similarly conduct heat.
Using nanotechnology, the researchers at BC and MIT produced a big increase in the thermoelectric efficiency of bismuth antimony telluride -- a semiconductor alloy that has been commonly used in commercial devices since the 1950s -- in bulk form. Specifically, the team realized a 40 percent increase in the alloy's figure of merit, a term scientists use to measure a material's relative performance. The achievement marks the first such gain in a half-century using the cost-effective material that functions at room temperatures and up to 250 degrees Celsius. The success using the relatively inexpensive and environmentally friendly alloy means the discovery can quickly be applied to a range of uses, leading to higher cooling and power generation efficiency.
"By using nanotechnology, we have found a way to improve an old material by breaking it up and then rebuilding it in a composite of nanostructures in bulk form," said Boston College physicist Zhifeng Ren, one of the leaders of the project. "This method is low cost and can be scaled for mass production. This represents an exciting opportunity to improve the performance of thermoelectric materials in a cost-effective manner."
"These thermoelectric materials are already used in many applications, but this better material can have a bigger impact," said Gang Chen, the Warren and Towneley Rohsenow Professor of Mechanical Engineering at MIT and another leader of the project.
At its core, thermoelectricity is the "hot and cool" issue of physics. Heating one end of a wire, for example, causes electrons to move to the cooler end, producing an electric current. In reverse, applying a current to the same wire will carry heat away from a hot section to a cool section. Phonons, a quantum mode of vibration, play a key role because they are the primary means by which heat conduction takes place in insulating solids.
Bismuth antimony telluride is a material commonly used in thermoelectric products, and the researchers crushed it into a nanoscopic dust and then reconstituted it in bulk form, albeit with nanoscale constituents. The grains and irregularities of the reconstituted alloy dramatically slowed the passage of phonons through the material, radically transforming the thermoelectric performance by blocking heat flow while allowing the electrical flow.
In addition to Ren and six researchers at his BC lab, the international team involved MIT researchers, including Chen and Institute Professor Mildred S. Dresselhaus; research scientist Bed Poudel at GMZ Energy, Inc, a Newton, Mass.-based company formed by Ren, Chen, and CEO Mike Clary; as well as BC visiting Professor Junming Liu, a physicist from Nanjing University in China.
Thermoelectric materials have been used by NASA to generate power for far-away spacecraft. These materials have been used by specialty automobile seat makers to keep drivers cool during the summer. The auto industry has been experimenting with ways to use thermoelectric materials to convert waste heat from a car exhaust systems into electric current to help power vehicles.
This research will be published online in Science Express on March 20, 2008. The research was supported by the Department of Energy and by the National Science Foundation
Does this mean better Peltier devices?
I don’t know. It looks like it will have an application in utilizing any industrial waste heat to generate electricity though. There’s no discussion of the efficiency of the process but I’m guessing anything that produces waste heat will see some benefit.
Also check out ENECO and Power Chips PLC.
It did not do so when similar work was done in 1990-1994 under NASA JPL funding for the SP-100 program.
Do a quick search in the MRS and NASA databases as well as a simple Google search and see all the patents and publications in this area.
If someone is at MIT they can get away with this kind of thing.
I am surprised Earth First isn’t bombing the facility. This new technology will encourage the enslavement of Mother Earth because cheap power will expand consuption! Woe is us!
Only if the value of the generated electricity exceeds the cost of the equipment. I would think that if they had seen good cost efficiency, they would have put some numbers into the press release
We didn’t even get in the NIT. sigh
This is just an improvement on old tech so I expect it will see lots of new uses since it’s already in use. As for the article not saying much, that’s pretty typical of the stories on ScienceDaily. They just present a brief synopsis of new tech and science with a note at the end saying when the paper will be published and in what publication. This paper should already be published since it says 20 March is the pub date.
“This research will be published online in Science Express on March 20, 2008. The research was supported by the Department of Energy and by the National Science Foundation”
Great news! I wonder what the conversion efficiency is though and how much power can be generated per degree/m2 or cm3?
This has staggering applications - rooftops and building faces, roads, cars - anything with thermal imbalances can be made to generate power. The same car sitting under the hot sun can be made to generate power to cool down its interior without depleting its battery or fuel. In short, a solid-state and much simpler thermal-electric system than geothermal or any other conventional electricity generator.
If the figure of merit is only increased by 40%, the efficiency will still be rather dismal. The figure of merit needs to be increased by at least an order of magnitude to see reasonable increases in efficiency.
This should improve the efficiency of thermoelectric nuclear power supplies for space missions also. One of the major drawbacks for exploration right now is the lack of electricity, especially during deep space missions, to power larger and more capable instruments. Since putting an actual nuclear power plant on board spacecraft has been nixed the next best method is putting nuclear material on board and using the heat from nuclear decay to power instruments. This should make that process more efficient.
So...an engine that puts out an enormous amount of heat, say during propulsion of a car, can be cooled and provide its own electricity by this new technology?
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Here’s a little more info that might help answer your question from another article.
One promising application for the improved material is transforming waste heat from car engines into electricity to help power the vehicles. The US Department of Energy (DOE) has set a goal of demonstrating a 10% increase in vehicle fuel economy through waste heat capture by 2014, according to John Fairbanks of the DOE.
No commercially available vehicle uses the technology today, but tests by car manufacturers including BMW suggest a 6-8% fuel efficiency increase is possible, Fairbanks says.
“Adding a 40% efficiency increase in thermoelectrics to that might meet that target,” Jeff Snyder, of the California Institute of Technology in Pasadena, US, says.
The same approach could harvest human body heat to power medical implants although designing less power hungry devices is important too, Snyder notes.
Alternatively the improved alloy could be used in reverse for solid state cooling, without bulky pipes of gas or liquid coolant, in new areas. “We’re not yet at the point where we will see air conditioning systems or large refrigerators with solid state cooling, but it’s a significant advance,” says Snyder.
I design Thermoelectric refrigerators .... I’d love a 40% improvement!
Yeah, it would be good for you but I’m wanting a thermoelectric car and or backup generator for my house.
40% doesn’t get me there.
If this is your field, what do you think of ENECO? It seems to be a rather straight forward improvement in technology but I have heard nothing about product out the door.
Let me clarify.
A 40% improvement in figure of merit would not significantly improve the effiency of a thermo electric refrigerator, or thermo electric car.
Yes a 40% improvement in effiency would be great for you but I don’t think that is what they are talking about.
I haven’t done the calculations in a couple of decades but if memory serves the figure of merit affects the carnot effiency in a rather minimal way.
A 40% improvement of a low efficiency is still low. The Carnot efficiency is the maximum possible efficiency and is dependent on the temperatures of the heat source and sink.
In low grade heat applications, which these mostly are, the Carnot (theoretical) maximum efficiency is still very low. Not good enough to build an economy on, but it is a good way to obtain useful energy when there is no other way.