RTI International Developing Higher Efficiency Thermoelectric Materials, Applications

01 October 2008

Researchers at RTI International, led by Dr. Rama Venkatasubramanian, in collaboration with several universities and United Technologies Research Corporation are working on higher efficiency thermoelectric materials for the conversion of heat differentials or waste heat into electrical energy for a wide range of applications. The research is funded by two separate contracts with the US Department of Defense.

For the first effort, funded by the Defense Sciences Office of the Defense Advanced Research Projects Agency (DARPA), RTI has received $1 million for the initial 12 months of work. The total value, if all phases of the development program are completed, could be up to$5.8 million. As part of this project, the RTI-led team will develop new materials and devices that operate across a broad temperature range—from 0° to about 700°C—to achieve a goal of near 30% energy conversion efficiencies.

Such a technology could pave the way for improving the fuel-efficiency of automobiles by almost 20%, according to RTI, and can also lead to efficient energy harvesting for electronics.

(The Department of Energy FreedomCar project is sponsoring research by four teams attempting to develop a thermoelectric generator that can improve overall fuel economy through waste heat recovery by 10% and can be in production in the 2011-2014 timeframe. DOE has also sponsoring research in thermoelectric applications for vehicle heating and air conditioning. Earlier post.)

Since about 60 percent of the world’s energy from fossil fuels is wasted as heat, there is a considerable interest in converting even a fraction of this heat into useful electric power for significant savings in overall fuel-efficiency. We are excited about the opportunity to collaborate with several outstanding research universities in this new DARPA program to make further advancements in nanoscale thermoelectric materials.

—Dr. Rama Venkatasubramanian, principal investigator for the project at RTI and director of RTI’s Center for Solid State Energetics

RTI’s research partners on this project include California Institute of Technology, North Carolina State University, Purdue University, Ames Lab of Iowa State, University of California Riverside and University of Delaware as well as United Technologies Research Corporation.

This effort builds on a previously DARPA-funded initiative called Direct Thermal Energy Conversion (DTEC) in which RTI scientists achieved improvements in device efficiencies and power densities for thermoelectric power conversion as well as demonstrated several early-stage applications of the technology.

The second project, worth \$1.3 million over three years, seeks to improve the fuel-efficiency of the US Army’s portable diesel generators using thermoelectric technologies. It is sponsored by the Strategic Environmental Research and Development Program (SERDP). SERDP is the Department of Defense’s environmental science and technology program, which is planned and executed in partnership with the US Environmental Protection Agency and the US Department of Energy.

RTI is targeting a fuel-efficiency improvement of up to 10% in diesel generators in the SERDP program, according to Dr. Chris Caylor of RTI, the principal investigator of this SERDP project.

RTI’s previous research in nanoscale superlattice materials, developed with DARPA support, resulted in a spin-off of the thermoelectric technology company, Nextreme Thermal Solutions, in December 2004. As part of the transaction, Nextreme acquired certain intellectual property rights in thin film thermoelectric from RTI. Since 2004, Nextreme has developed manufacturing methods and begun sampling thin-film thermoelectric modules with a variety of commercial customers in optoelectronics, electronics cooling and power generation applications.

Resources

• Rama Venkatasubramanian, Edward Siivola, Thomas Colpitts, Brooks O’Quinn (2001) Thin-film thermoelectric devices with high room-temperature figures of merit. Nature 413, 597 - 602 doi: 10.1038/35098012

Great application in power amplifiers. Typical 100W basestation transmitter is sucking down more than 250W input power and creating quite a bit of heat. If their device functions down at 60 degrees celsius there are quite a few cell towers that could make use of this.

Depending on cost, size, weight, etc, this could have wide-sweeping ramifications. HEVs could use this to add more recharge to battery charging approaches. Power plants could capture significant energy currently being lost. This is very early in the process, however, especially considering this is a DARPA effort, so I guess we'll hear more in 5+ years...

Skip all the marketing hype about the future and just print the data on a graph of temperature vs. energy conversion efficiency they have measured in the lab today.

Bet you find you need 500-700 degC above ambient to get anything worthwhile at all. Works for traditional heat engines, does nothing at all for data centers, cell towers, or anything else where the heat rejected by the cooling systems are maybe 100degF above ambient.

Just show the data please. Otherwise you sound like a Wall Street bank looking for a bailout of bad assets you won't qunatify?

If it is power dense and 30% efficient, why not just use it as a range extender in a PHEV? Couple gallons of fuel, a heat exchanger...

Because you can use such a material as a bottoming cycle for a piston engine and get 45-50% efficiency instead, that's why.

This might be good heat recovery in an SOFc. 50% efficient stack 10% more on the output gas turbine and even more on the heat out of the turbine.

Organic Rankine cycle - useful power from a 20oC difference.

@EP

The fuel efficiency game is about more than TE, no? If the range extender for a PHEV can be shrunk down to a ~10l package weighing ~20kg, would that not allow for a smaller/lighter/more aerodynamic vehicle that requires less energy to move? I'm trying to think a little bit like Amory Lovins here...

Organic Rankine Cycle?? Useful power? And those mean what? Just show real, verified data -- skip allusions to science fiction.

Comments about turbines and bottoming cycles are excatly the point -- high temperature is needed.

Look up the website for this company and you will see it is micro devices located at heat cources of individual components -- where you have high temp available to use. Possible to hook all this up to take a few watts out of an electronic box and lighten load on coolers. Marginal efficiency arbitrage games most likely.

They don't show any plans for low temp waste heat recovery.

We need tons more research -- but when you report on it just show the numbers -- people here can understand them and what they mean quite well.

Temperatures coming out of a turbine on the output side of an SOFC can be 1000f. That is hot enough to recover some energy.