Partial Recirc/Two Layer Flow HVAC Energy Savings and Defog Performance in Electric Vehicles 2021-01-0212

Vehicle climate control systems are currently being investigated to reduce energy consumption and therefore improve range for Battery Electric Vehicles (BEVs), Plug-in Hybrid Vehicles (PHEVs), and Extended Range Electric Vehicles (EREVs), while they operate in pure electric mode. In particular, vehicle heating systems have been investigated due to their high energy demand in winter time to maintain cabin comfort. On the other hand, heating energy is typically not required with internal combustion engines where the waste heat from the engine is sufficient to heat the vehicle’s cabin.

The energy required to heat traditional vehicle architecture under different ambient is typically well understood in the automotive sector. Scavenging heat (ambient or vehicle) and reducing the thermal vehicle load are two main methodologies to improve warm-up or reduce energy. Both methodologies have their benefits to reduce energy consumption; however they also have their drawbacks, such as potentially impacting other vehicle requirements.

In this paper, two different load reducing technologies are compared utilizing recirculation inlet within the vehicle cabin. The systems are evaluated under different ambient conditions with different number of occupants to compare the energy required to warm-up a BEV vehicle to an acceptable level, as well as the potential for window fogging or frosting, which would be a requirement negatively impacted. The first technology investigated looked at different levels of partial recirculation inlet air to the system and the resulting energy savings and window fogging/frosting. The second technology investigated is two layer flow, which utilizes 100% recirculation air to the floor and 100% fresh air to the front and side windows in the cabin. The feasibility of the technology and its energy reduction were evaluated using the same metrics. The annual energy usages and the range penalties in winter for a BEV with different load reducing systems are then calculated and compared.