Thermoelectrics could capture currently wasted heat to boost overall vehicle efficiency from 38% to 57%. A 50% efficient free-piston engine could be boosted to 65% overall efficiency A regular 30% gas engine would be boosted to 51% overall efficiency.
Scientists at RTI are teaming up with several leading universities and a major aerospace company to develop the next generation of thermoelectric materials – revolutionary technologies that can efficiently convert heat differentials or waste heat into electrical energy for a wide range of applications.
The project will be funded up to $5.8 million and the RTI-led team will develop new materials and devices that operate across a broad temperature range – from 0o C to about 700 degrees C, to achieve the goal of near 30 percent energy conversion efficiencies.
Such a technology can pave the way for improving the fuel-efficiency of automobiles by almost 20 percent and can also lead to efficient energy harvesting for electronics.
Sufficiently advanced thermoelectrics could also help increase the efficiency of smaller powerplants.
The 30% energy efficiency is triple the efficiency of todays common thermoelectrics and double most advanced systems and would get to range of using solid state thermoelectrics to replace refrigerators [thermoelectrics can help cool as well as convert heat to electricity] and many small car sized engines. Typical conversion systems become less efficient as they are scaled down to small size. This means there is a crossover point: below some power level thermoelectric technology will tend to be more efficient. Increasing ZT will move the crossover point to higher power levels, increasing the range of applications where thermoelectrics compete. Thus the ZT of 3 to compete with current best car size and refridgerator mechanical systems.
Thermoelectrics for cars would place thermoelectric chips around heat sources like the tailpipe to capture heat for power
This site has had extensive coverage of thermoelectric systems in the past and believes that advanced thermoelectrics will be deployed over the next few years and will be widespread by 2020.
A goal of the US Department of Energy is the 60% efficient diesel engine which would use advanced thermoelectrics to capture currently wasted heat. [this powerpoint presentation describes all the areas where advanced thermoelectrics would help]
- Capture waste heat in aluminum manufacturing to allow widespread usage of aluminum which would reduce the weight of cars. Lighter cars are more fuel efficient. Currently Jaguar, Aston Martin and Audi A-8 have aluminum frames and bodies which reduce vehicle weight by about 500 pounds. Oak Ridge National Laboratory has empirically developed a rule of thumb that a 10 percent reduction in vehicle weight improves fuel economy by 5 to 7 percent.
- Improve refrigerators and eliminate the use of harmful gases (R-134a)
RTI Thermoelectric research
Effect of nanodot areal density and period on thermal conductivity in SiGe/Si nanodot superlattices, Feb 2008