Electric vehicles (EVs) need highly optimized thermal management systems to improve range. Climate control can reduce vehicle efficiency and range by more than 50%. Due to the relative shortage of waste heat, heating the passenger cabin in EVs is difficult. Cabin cooling can take a high portion of the energy available in the battery. Compared to internal combustion engine-driven vehicles, different heating methods and more efficient cooling methods are needed, which can make EV thermal management systems more complex. More complex systems typically allow various alternative modes of operation that can be selected based on driving and ambient conditions. A good system simulation tool can greatly reduce the time and expense for developing these complex systems. A simulation model should also be able to efficiently co-simulate with vehicle simulation programs, and should be applicable for evaluating various control algorithms. The MATLAB/Simulink dynamic system simulation environment, widely used in the automotive industry, effectively meets these criteria.
To model the full EV thermal management system, the National Renewable Energy Laboratory's air-conditioning model now incorporates liquid-coolant system components. In the full system model, lookup tables were used to characterize the components' performance. Predicted data obtained with the system simulation model were compared against experimental data. An agreement within 5% for most of the system parameters was achieved. The validated system model was then used to determine which of two possible locations for the power electronics and electric motor in the system is better for quick cabin heating starting from cold soak.