Geographical and Temporal Variations in Plug-in Electric Vehicle HVAC Loads

Abstract

Plug in electric vehicles are vehicles that use energy from the electric grid via an onboard battery pack to provide tractive and HVAC power to the vehicle. The nonexistent (electric vehicles) or reduced-sized (plug in hybrid vehicles) engine in these vehicles results in high energy conversion efficiencies and lack of waste heat. More importantly, the net gasoline energy consumption for transportation is reduced resulting in lower GHG emissions and environmental pollution. On the downside, energy demand by HVAC systems for cabin conditioning impedes their ability to travel longer distances on a single charge. The steady increase in demand for these vehicles has resulted in research initiatives to overcome these range limitations. Cabin conditioning is a source of range limitation due to the lower onboard energy storage capacity of lithium ion (720kJ/kg) relative to gasoline (47.2MJ/kg). The factors such as local ambient temperature, local solar radiation, local humidity, length of the trip and thermal soak have been identified to affect the cabin conditioning and to therefore affect vehicle range.The focus of this paper is to outline the development of a detailed systems-level approach by interlinking transient environmental parameters with real world driver behavior, charging behavior, and regional passenger fleet population for HVAC system operation. The resulting engineering toolset can be used to determine geographical distribution of energy consumption by HVAC systems to identify potential high impact zones, establish HVAC component specifications and optimize overall vehicle energy management for long service life. Complexities involved in marginal electricity generation to accommodate vehicle electrification can be understood for better demandresponse by utilities. The study can also be used to estimate the potential of vehicle electrification and alternative accessory technologies as a means to achieve net reduction in gasoline consumption and greenhouse gas generation.