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Tenneco/Gentherm showcasing prototype of thermoelectric generator for waste heat recovery; targeting 5% fuel economy improvement

TEG component (cartridge) and TEG architecture concept. Source: Crane (2013).Click to enlarge.

Tenneco and Gentherm (formerly BSST/Amerigon) are part of a US Department of Energy (DOE) consortium actively developing a thermoelectric generator (TEG) for capturing waste exhaust heat in vehicles and converting it to electrical energy to be used to power electrical systems within the vehicle. The first rapid prototype of their Thermoelectric Generator (TEG) for light vehicle applications is on display at Tenneco’s booth at the 2013 Frankfurt IAA Motor Show.

Partnering with Tenneco and Gentherm are BMW and Ford, as well as CalTech and NREL. Gentherm is supplying modular, cylindrical-shaped thermoelectric cartridges that convert waste heat from the exhaust into electricity. Tenneco then integrates the cartridges inside a thermoelectric generator (TEG) that includes a unique heat exchanger.

Among the objectives of the project is delivering a 5% fuel economy improvement by direct conversion of engine waste heat to useful electric power for light-duty vehicle application. For light duty passenger vehicles, the fuel economy improvement must be measured over the US06 cycle. Total funding for the 4-year project, which started in October 2011, is $15,794,813; DOE’s share is $9,553,950.

Thermoelectric material is sandwiched together within the cartridges that are exposed to hot exhaust gas on one side and to engine coolant on the other side. The temperature gradient over the thermoelectric material results in a continuous electrical current flow, which is then redistributed to the vehicle. The modular design of the TEG enables packaging scalability depending on vehicle design, making it more cost-effective to integrate into the vehicle’s exhaust system.

Our new TEG cartridge design is the result of several years of research with the DOE and other important partners. We believe it is a breakthrough technology that has applications in a variety of global industries, but especially for automobiles in terms of reducing CO2 emissions, improving fuel economy and providing a new source of much-needed electricity. We are now working closely with Tenneco to integrate our thermoelectric cartridges into a new and innovative exhaust system design.

—Gentherm President and CEO Daniel R. Coker

Tenneco is responsible for the overall system layout and integration, including validation testing for the project. TEGs must undergo rigorous durability testing, using a wide range of exhaust gas temperatures. The test process must also simulate harsh operating conditions on the underbody of the vehicle, such as road bumps, salt corrosion and other examples of severe conditions.

Testing and validation for the TEG is being conducted at Tenneco’s global emissions technical centers in Edenkoben, Germany and Grass Lake, Michigan. The consortium anticipates that initial demonstrators will be available in early 2014.




for heavy trucks , maybe, for car forget it, unless they can get 10% fuel economy, it isn't worth it


If they could design the TEG stack so that it also served as a muffler that would be quite crafty and possibly push the system that much closer to being economically viable.

Locating the TEG stack very close to the exhaust header outlet and using a ceramic coating on the inside of the exhaust header to minimize heat loss would improve the thermodynamics of the whole system (hotter hot side, cooler cold side).


Interesting potential, specially for HEVs and PHEVs. A 5% fuel saving for early models would be acceptable if the price is right.


It's all about the cost, and about incentives. A full sized pickup or SUV (15 MPG) consumes US$40,000 worth of fuel in a 150,000 mile life. 5% of that is $2000. There could be maintenance costs that cut into the benefit, and we know that the first purchaser of a vehicle does not get 100% of the lifetime fuel savings, and finally there is the time value of money. But if the installed cost is below $400, you have to believe there is a business case for this.


Over the life of a mid sized vehicle it may burn 25,000 liters of fuel, so 5% savings would be 1250 l. At $1.20 /l the overall savings might be $1500. Not much potential for savings by individual buyers but if you look at it from a national perspective, the US supplies about 13 million barrels per day (EIA) of diesel and gasoline so if all vehicles were required to have a TEG as they are catalytic converters, the reduced petroleum demand would be 650,000 bpd. The losers would be the refiners and the winners would be whoever makes the TEG. A bit like the ethanol mandate.


This begs the question, what's the scrap value of the TEG?  If it has a second career as an electricity-generating water heater (or more than one), this could be a pure win for the vehicle buyer.


If the thermoelectric elements are made from elements like Indium, the scrap value might be quite high, or even be higher than the purchase value if precious metal prices keep going up. Then again, it probably wouldn't cost less than 1500$ then.


The Turbosteamer from BMW had better cost/benefit numbers.


Can this produce enough electricity to make the alternator redundant?


Most ICE are less than 30% efficient. Recovering a rather small part of the other 70% could certainly replace the alternator and more?


If the vehicle uses 30% of the fuel to generate on average say 25 kw then 5% is 1/6 of 30 or about 4kw. Does that make sense? Also curious how much energy goes out the exhaust as opposed to through the coolant system,friction, drag and other losses?


If I recall correctly, a typical split used to be 30% crankshaft, 30% cooling system, 40% exhaust.  Peak engine efficiencies have improved, but most don't reach 40% and averages are much lower with idling, etc.

Some years ago there was talk of piezoelectric mufflers to recover exhaust impulse energy as electricity.  A thermoelectric generator could be used in addition to that.


"If the vehicle uses 30% of the fuel to generate on average say 25 kw then 5% is 1/6 of 30 or about 4kw. Does that make sense?"


A 30% efficient heat engine produces 70% waste heat. 100 kWh of fuel becomes 30 kWh of mechanical energy and 70 kWh of heat. 5% of 70 kWh is 3.5 kWh. 30 kWh of mechanical energy might take the car 100 miles, but 100 kWh of gasoline would be about 3 gallons.

So you might be getting 30 MPG and with this maybe 33 MPG under ideal conditions. The BMW Turbosteamer created 15 HP peak output, so a direct cost/benefit comparison would be valid. The hope here is that some day the costs for this will come down. Key word phase are "hope" and "some day".



"targeting 5% fuel economy improvement"

So now you get 31.5 MPG instead of 30 MPG. This makes a recovery of 2.5% of the heat energy, not a lot of energy recovered for an unstated price.


The presentation specifies a "5 percent fuel economy improvement" so... 30*1.05=31.5 (%effic or mpg) sounds like the right definition here. If this is a 30kW passenger car, 1.5% would be 450W, and they specify a 500W TEG. so that seems right.

This has been in R&D for quite some time, with a lot of good progress being made. But the last couple comments reflect the same confusion on definitions that always comes about with these programs.

5%. but 5% what? Efficiency improvement? Additional fuel economy? Waste heat recovery? Waste heat conversion? TE Conversion efficiency? I've seen presentations where they claim 5% improvement and then use the above terms interchangably on different slides...

If you have a 100kW engine, and get 30kW of useful work, that's 30% efficiency. lets say that equals 30mpg (so efficiency generally equals mpg).

Now, all the ways the math 'could work' depending on how the goal is stated:

same work out for 5% less energy in:
30kW out, 95kW input = = 31.58% effic., or +1.58% effic. increase. (a 5% fuel economy improvement)

OR 5% improvement in work out for same input:
31.5kW out, 100kW in = 31.5% effic, or 1.5% increase.

OR, additional 5% fuel efficiency
35% of 100kW = 35kW out, or 5% effic increase.

OR, 'recover' 5% of fuel energy
5% of 100kW = 5kw, for 35kW total out, so same as 35%

OR 'recover' 5% of wasted energy (100-30=70kW)
70kw * 5%= 3.5kW. 30+3.5 = 33.5kW out = 33.5% or 3.5% effic increase

OR 'recover' 5% of exhaust energy (~40kW)
40kW * 5% = 2kW, 30+2=32kW out = 2% effic increase...

I'm sure I could come up with some others.

OH, and lets not forget these are heat engines. TE conversion efficiency ranges from 3-15%. Let's be generous with 10%. to get 500W out, they need to grab 5000W of heat from the exhaust (where there's 40% of 30kW = 12kW available), force it through the TE, and then 4.5kw goes out with the engine coolant. The coolant had 9kW (~30% of 30kW) of fuel heat, it now has 45% (9+4.5=13.5kW), or the cooling system now has to handle a 50% heat increase. Hopefully, it takes less that 1.5% of fuel energy to get that extra heat out the radiator, or you have a net loss.


Hey it is true that now a days a large amount of heat is wasted, it is very nice if we can recover them and can make use of it. And thermoelectric generators are the best for that.

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