NREL Supports Caterpillar Thermoelectric Project to Recovering Waste Heat from Heavy-Hybrids
NREL is conducting key tests to verify progress by Caterpillar Inc. in developing advanced thermoelectric (TE) materials. Under a 21st Century Truck Partnership subcontract, Caterpillar is developing new boron-carbide TE thin films to capture waste heat in truck exhaust to generate electricity. NREL recently provided sophisticated chemical composition data and verified electrical conductivity for the materials and is continuing its support by testing thermal conductivity and measuring composition for new versions of the TE films.
NREL scientists used Auger electron spectroscopy to measure variation in boron and carbon concentrations in a multilayer film. The measurements verified that the Caterpillar sputter deposition process had successfully produced a quantum well structure with alternating boron and carbon concentrations on the nanometer scale. Recently deposited boron carbide films have incorporated nickel and aluminum dopant atoms to successfully increase the electrical conductivity of the thermoelectric material. NREL is now determining the atomic concentration of these dopant atoms in the films. This information will provide important feedback on the dopant incorporation effectiveness and will be correlated with thermoelectric property measurements.
NREL also measured electrical conductivity of the boron carbide films. NREL used the van der Pauw technique, which compliments the four-point-resistivity measurement used at Caterpillar. NREL's conductivity measurements agreed with the electrical conductivity values obtained by Caterpillar, giving them increased confidence in their in-house measurement setup. In addition, NREL is measuring thermal conductivity of the TE material by the 3-omega method in parallel with Caterpillar's efforts to setup a thermal conductivity measurement apparatus.
Caterpillar Inc. was awarded one of four 21st Century Truck Partnership cost-shared subcontracts from the Advanced Heavy Hybrid Propulsion System Project to develop thermoelectric generators as a way to recover waste heat from and provide electric power for hybrid-electric heavy vehicles. Under the $2-million, two-year subcontract, Caterpillar is exploring use of advanced thin-film semiconductors for the TE elements and contracted with NREL to characterize the boron-carbide materials to better understand their nature to help in developing an effective system.
If dissimilar metals or semiconductors at different temperatures are joined in an electrical circuit, they will generate an electrical current proportional to the temperature difference. Such thermocouple or thermoelectric generators have historically been relatively inefficient, but recent research shows promise for making them far more efficient. And the high temperature difference between a heavy vehicle exhaust system and the passing air as it goes down the highway is an ideal opportunity. An estimated 30%-40% of heavy vehicle fuel energy is lost as exhaust waste heat. The goal of the Caterpillar project is a 1-kw system 20% efficient in capturing that heat loss. This could lead to 8% reduction in fuel use for heavy hybrids if used for driveline power only and 13% reduction if also used for auxiliary systems in place of an alternator.
Heavy Hybrid Vehicles Aid New Orleans Relief Effort
Providing power to critical facilities and shuttling locals to safety, heavy hybrid buses and trucks are helping with relief resources to the areas devastated by Hurricane Katrina.
Hybrid buses are temporarily on loan to local officials from General Motors Corp. (GM) to help the relief effort by transporting hundreds of hurricane victims to various relief centers around Houston. These hybrids use significantly less fuel (up to a 60% reduction) compared to a conventional urban transit bus—providing another form of relief to the nation's increasing fuel prices and demand. The GM demonstration buses are using hybrid technologies originally developed in partnership with the U.S. Department of Energy (DOE) and the Defense Advanced Research Projects Agency. Currently, these hybrid technologies are being further improved for performance and reliability under the DOE's Advanced Heavy Hybrid Propulsion Systems Project (AH2PS), with technical guidance and testing by the DOE's National Renewable Energy Laboratory.
Millions of heavy trucks and buses are driven on U.S. streets and highways each day. Their sheer numbers, coupled with our nation's fuel supply issues highlighted by Hurricane Katrina, means that improving their fuel economy and emissions is essential to the nation's safety, security, and environmental well being. The AH2PS project focuses on improving these vehicles by developing advanced heavy hybrid propulsion systems that are projected to increase the fuel efficiency of trucks (Class 3-8) and buses by as much as 100%, and improve emissions to meet or exceed the Environmental Protection Agency's 2007-2010 emission standards. A project goal is to overcome cost and durability challenges to make these heavy hybrid technologies cost-effective before the end of this decade. Overall, AH2PS-developed technologies are projected to save over 2 million barrels/year of oil by 2020, depending upon the rate of technology implementation and the cost of fuel that drives that rate.
In The News: AH2PS/DOE Backs Eaton
August 29, 2005, Fleets & Fuels Newsletter reports: "DOE Backs Eaton: Funding by Energy Department's National Renewable Energy Lab Allows Aggressive Hybridization & Electrification of Class 6 Truck Eaton Corp and AH2PS partner International Truck and Engine are
working on an aggressive hybridization and indeed electrification of a Class 6 delivery truck, using a far smaller engine in a larger vehicle to close out a three-year, $7.8 million project.
AH2PS is the U.S. Department of Energy's Advanced Heavy Hybrid Propulsion System program. It's run by NREL, the National Renewable Energy Laboratory in Colorado. Eaton was awarded a three-year contract in
September 2002 to develop a Class 6 hybrid with the AH2PS goal of improving fuel efficiency by as much as 100 percent.
The first vehicle in the program was a conventional 1652 SC by International Truck & Engine, with a standard engine: a 6.0-liter, dieselfueled VT365 V-8, also by International. The truck was converted to parallel hybrid operation using a motor and inverter, and lithium ion batteries, all from Hitachi, says Eaton program manager Scott Davis.
Second Truck's Engine is Half the Size
United Parcel Service, potentially a major customer tested the hybridized 1652 SC and provided valuable operational input, Davis says. The second truck in the program is a somewhat larger International
4200, but has been fitted with a 3.0-liter, 4-cylinder I-4 engine (an engine product that's new to International, as it is fruit of an acquisition in Brazil). Eaton's parallel hybrid version of the 4200 has a motor and inverter from UQM Technologies, and nickel metal hydride batteries.
"The funding from the Department of Energy allows Eaton and International to explore these farther-ranging concepts," Davis says. He notes too that the partners have gone with electric air conditioning,
power steering and brakes in their second AH2PS vehicle, allowing the truck to save fuel by shutting down the engine when stopped in traffic. "Overall, AH2PS-developed technologies are projected to save approximately
20 million barrels of oil in 2010 and 250 million barrels of oil in 2020," NREL says.
"This is huge," comments Jim Williams, who is sales and distribution director for new products at International. He notes, however, that commercialization will be no sooner than 2007, and possibly as late as 2010.
Also participating in the Eaton AH2PS project is Ricardo in Chicago.
Eaton, Scott Davis, 269-342-3344; International, VK Sharma, 260-461-1237; NREL, Bob Rehn, 303-275-4418; UPS, Robert Hall, 404-828-6556; fax 404-828-8150; UQM, president Bill Rankin, 303-278-2002".
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