Research of a Thermal Management System for Electric Vehicles

1^st Report: System Proposal and Performance Analysis of Defrosting and Heating Mode

Abstract

Current thermal management technology for electric vehicles is investigated and issues identified. One key issue is the consumption of electrical energy due to battery cooling, anti-fogging of the windshield by introducing outside air and cabin heating. Another issue is cabin heating being interrupted during the defrosting operation of heat pump. Solutions are proposed as follows:

Batteries to be cooled using the evaporation latent heat of the condensate water as a by-product of cabin cooling.

A desiccant-coated heat exchanger is adopted to dehumidify the inside air of the cabin. Accordingly, this facilitates anti-fogging of the windshield by recirculating the interior air , allowing less fresh air into the vehicle cabin and less resulting heat loss due to incoming cold fresh air.

Furthermore, to maximize the electrical energy savings, heat generated by motors and invertors is recovered as a supplemental heat source of the heat pump.

The heat generated by batteries is utilized to remove the frost on the evaporator surface of the heat pumps, whereupon the cabin can be heated continuously.

This system can be operated in three modes: cooling mode for the cabin, battery, motor and invertor, heating mode for the cabin and battery, defrosting and cabin-heating mode. A system description of the three modes is given in this paper and the system performance during defrosting and cabin-heating mode is analyzed in detail. According to cycle simulations, based on a weight of 294 kg and heat recovery from the battery stored at 25°C, 162g of defrosting can be achieved within five minutes while heating the cabin. The decrease in battery temperature in this case is approximately 4°C and the compressor's power consumption is below 1 kW.