Browse Publications Technical Papers 2018-37-0026
2018-05-30

Total Thermal Management of Battery Electric Vehicles (BEVs) 2018-37-0026

Battery Electric Vehicles (BEVs) are encountering weather-dependent drive range, higher cost and limited battery life as the key hurdles to achieving wide consumer acceptance. This translates into a strong need to reduce a significant energy drain and resultant drive range loss due to auxiliary electrical loads of which the cabin thermal management load is predominant. Studies have shown that thermal sub-system loads can reduce the drive range by as much as 45% under ambient temperatures below -10oC. Often, cabin heating relies purely on resistive energy extraction (PTC heater) contributing to the significant range loss. Regaining a significant part of this range loss may significantly improve the attractiveness of electric vehicles among consumers. The authors present a unified thermal management system (UTEMPRA) that satisfies diverse thermal and design needs of the auxiliary loads in electric vehicles. The UTEMPRA system integrates a semi-hermetic refrigeration loop with a coolant network and as such can be used for heating and/or cooling vehicle components and the cabin as well as for waste energy harvesting. The modes of operation allow a heat pump and A/C to function without reversing the refrigeration cycle to improve thermal efficiency. The refrigeration loop consists of an electric compressor, a TXV, a liquid-cooled Condenser (LCC) and a chiller, the latter two components replacing the condenser and the evaporator by exchanging heat with coolant instead of air as in a traditional system. The LCC and chiller also act as sources of hot and cold coolant streams that may be directed to various components of the thermal system. The coolant-based heat distribution is adaptable and saves significant refrigerant quantity per vehicle. Also, coolant based system reduces refrigerant emissions by requiring fewer piping joints. The authors present bench-level test data and simulation analysis and also will describe a preliminary control scheme for this system.

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