Snyder, K. and Ku, J., "Optimization for Plug-In Vehicles - Waste Heat Recovery from the Electric Traction Motor," SAE Technical Paper 2014-01-1921, 2014, doi:10.4271/2014-01-1921.
The Wayne State University (WSU) EcoCAR2 student team is investigating powertrain optimizations as a part of their participation in the EcoCAR2 design competition for the conversion of a 2013 Chevrolet Malibu into a plug-in hybrid. EcoCAR2 is the current three-year Department of Energy (DoE) Advanced Vehicle Technical Competition (AVTC) for 15 select university student teams competing on designing, building, and then optimizing their Plug-In Hybrid conversions of GM donated vehicles.WSU's powertrain design provides for approximately 56-64 km (35-40 miles) of electric driving before the Internal Combustion Engine (ICE) powertrain is needed. When the ICE is started, the ICE traditionally goes through a cold start with the engine, transmission, and final drive all at ambient temperature. The ICE powertrain components are most efficient when warmed up to their normal operating temperature, typically around 90-100 °C.There are now some conventional vehicles currently available that employ active warm-up to recover waste heat from hot engine coolant to more quickly heat up the transmission fluid for reduced parasitic losses to improve fuel economy by approximately 2%.  The WSU student team is investigating the improvements to fuel consumption (FC) of the ICE powertrain operation in the team's plug-in hybrid through pre-heating the ICE powertrain components before the engine is started. The ICE powertrain component pre-heating would be by recovering waste heat from the electric traction motor during the initial pure electric driving period.Waste heat recovery could be performed by utilizing the motor's liquid cooling loop hot side to route the hot liquid coolant through new heat exchangers added to the ICE powertrain components as the hot liquid flows to dedicated cooling radiator for the motor, at the front of the engine compartment.The WSU team does not yet have any experimental results for these possible optimizations, so this paper looks at quantifying various potentials for fuel consumption improvement.A plug-in hybrid could improve its ICE powertrain's fuel consumption by a calculated 2-3%, due to just pre-heating its ICE powertrain from waste motor heat, based on experimental results from a conventional ICE powertrain on fuel consumption improvements during its warm-up period.