Energy consumption of battery cooling in hybrid electric vehicles

摘要

Lithium ion cells are presently the most promising technology for the use in hybrid vehicles. The cells heat up due to internal heat generation. This may lead to premature aging and necessitates an efficient thermal management. The heat sink for the cells is the automotive refrigeration cycle. The cells can be cooled by evaporation of the refrigerant or via a secondary coolant loop. Models for battery cooling systems are added to an existing Modelica library in order to examine the influence of battery cooling on the complete air-conditioning cycle. The lithium ion cells are also modeled with Modelica, making an analysis of the complete system possible. The library can serve as a design tool for the battery cooling system. In this study, the thermal load caused by the battery during the New European Drive Cycle (NEDC) is calculated for a hybrid vehicle. Results are presented for direct evaporative cooling of the cell. The study is carried out for the refrigerants R134a and R1234yf. The impact of the battery cooling on the refrigerant cycle and the resulting additional load on the compressor are determined for two climatic conditions. The energy demand of the compressor is increased by up to 10 % depending on the climatic conditions and the refrigerant. In hot weather conditions, the thermal comfort of the passengers is reduced if the battery cooling is switched on.