Improving Performance of Heating, Ventilation, and Air-Conditioning System of Electric Vehicle Using Evaporative Cooling: A Model-Based Analysis

<div>Modern day electric vehicles (EVs) use conventional heating, ventilation, and air-conditioning (HVAC) systems from engine-based vehicles. This brings forward new challenges in the name of range anxiety and thermal comfort of passengers that need to be achieved through a single charge of the battery unlike through high energy density fossil fuels. The present work deals with developing a high-fidelity physics-based model of HVAC components from core fundamentals that use location and time parameters to compute heat load so that performance can be analyzed in various climates. It is validated with real data from tests on a practical HVAC system of a running transit electric bus. Using this model as base, a cooling methodology based on direct evaporative cooling (DEC) is introduced, and the benefits of such a technique are illustrated by the comparison between the conventional and newly proposed system. It is observed that the DEC-assisted vehicle HVAC system achieves significantly greater cooling than the conventional system, using lesser energy (via compressor run by an electric motor) than before. The effect on tractive power consumption, total energy drawn from the battery, and thermal comfort of passengers has been studied to see where the new system stands as a general proposal. The model-based analysis performed in this article gives insight into the real-time behavior of conventional and DEC-assisted HVAC and builds the foundation for developing hybrid HVAC techniques like DEC-assisted HVAC for improving energy efficiency of the HVAC system.</div>