GMZ-led project tracking to deliver vehicular thermoelectric generators for Bradley Fighting Vehicle, Honda Accord
|The assembled 200W TEG tested in June delivered 270W of output. Click to enlarge.|
GMZ Energy and its partners are on track to deliver a 1 kW thermoelectric generator (TEG) for the Bradley Fighting Vehicle as well as to design and to integrate a light-duty vehicle TEG into a Honda Accord as part of a DOE-funded project. Thermoelectric materials convert temperature differences into electric voltage; a TEG in a vehicle is designed to convert waste heat to power. GMZ Energy, a provider of advanced nano-structured thermoelectric generation technology, was co-founded by MIT’s Professor Gang Chen and collaborator Zhifeng Ren of the University of Houston.
The project is using Half-Heusler (HH) thermoelectric materials (earlier post) in designing the vehicular TEG systems. Although these materials (ferromagnetic intermetallic alloys with a strong crystal structure that allows great stability at high temperatures) have a ZT (dimensionless figure of merit) lower than some other TE materials such as Skutterudites, the mechanical strength and the reliability of HH compensates for this deficit, according to GMZ.
In June, GMZ successfully generated 270 watts from a TEG as part of $1.5-million program vehicle efficiency research program sponsored by the US Army Tank Automotive Research, Development and Engineering Center (TARDEC) and administered by the Department of Energy (DOE). (Earlier post.)
Combining a modular approach with a scalable thermoelectric heat exchanger design, GMZ Energy will eventually integrate multiple 200W blocks into a single 1,000 W diesel engine waste heat recovery solution. The TARDEC TEG incorporates GMZ Energy’s current TG8-1.0 thermoelectric modules, which are the first commercially available, off-the-shelf modules capable of operating with continuous hot-side temperatures up to 600 °C while at power densities greater than one Watt/cm².
As part of the project work, GMZ has also reduced the cost of its HH material compared to the current production material from from $180/kg to $75/kg and has improved the power density from 5.5 W/cm2 to 6.0 W/cm2.
|An automotive TEG is intended to improve fuel economy by power from waste heat to reduce the electric generator load on the engine. GMZ is targeting a fuel economy improvement of 5%. Click to enlarge.|
The company has completed the design of an advanced TEG for the Honda Accord; Oak Ridge National Laboratory is using its AUTONOMIE vehicle systems modeling platform to investigate effect of TEG size for a given vehicle/engine pairing. In the model, the electric power generation and backpressure of the TEG will feedback to the alternator duty cycle and engine load.
Once complete, the model will allow for parametric investigations of TEG/vehicle configurations including size of the TEG, the impact of other vehicle configurations (e.g., down-speeding, downsized engine, etc.), and the effects of using higher efficiency combustion strategies such as dilute combustion with EGR—which would decrease the exhaust temperature.
Ultimately, GMZ will test the final TEG on the dyno, and integrate it into the vehicle.
For the projects, GMZ Energy is partnering with Oak Ridge National Laboratory; University of Houston; Boise State University; Honda Automotive; Eberspaecher North America; and AVL North America.
Martin Cleary (2014) “Nanostructured High Temperature Bulk Thermoelectric Energy Conversion for Efficient Waste Heat Recovery,” DOE 2014 Annual Merit Review ACE082