Innovative Dehumidification Systems for Passenger Compartment of Electric Vehicle

Examensarbete för masterexamen
Master Thesis
Sustainable energy systems (MPSES), MSc
Zhang, Rui
As amethod to mitigate greenhouse gas emissions, electric vehicles (EVs) are regarded as an alternative to conventional cars. TheHVAC system is the most energy-consuming auxiliary systems in EVs. The HVAC system is made up of three functions, heating, cooling, and dehumidification, providing a comfortable driving environment. To be more specific, the AC system aims for cooling and dehumidifying the airflow to the passenger compartment. The heating system takes care of the heating demand in car by circulating hot coolant. In winter time, the cold outside air is heated up to high supply temperature, which consumes large amounts of energy and accelerates batteries depleting. Cabin air can be recirculated to increase the driving range, but the high moisture in it is the main issue. Therefore, alternative dehumidification methods having good performance at lower ambient temperatures are required. Meanwhile, energy consumption in AC system should also be as small as possible to extend driving range. For fully recirculating cabin air, an alternative dehumidification should have a capability of removing the moisture from human respiration and other internal moisture loads. In literature review, several methods of dehumidification have been introduced based on their mechanisms and characteristics. Due to the high requirements of compact and compatibility of automotive HVAC system, the scope of study narrows down to two technologies, AC system with head pressure regulating valve and desiccant wheel system. The AC system can usually be operated above 0 ±C. With a head pressure regulating valve implemented, the modified AC system can also work in winter time as a dehumidifier. When the ambient temperature goes down to -20 ±C, the new system can reduce heating power by 34.5%. The additional cooling power depends on the different level of moisture load. High moisture load can increase the energy consumption in the AC system. Recirculated air can mix with cold outside air with variable recirculation ratio, to cut down energy consumption further. A desiccant wheel gives better performance in term of reducing energy consumption than mechanical dehumidification. The heating power is reduced by 50% after implementing a desiccant wheel, when the ambient temperature is -20 ±C. Instead ofmechanical dehumidification gaining benefit only under an extreme cold weather, a desiccant wheel reduces power consumption in HVAC system on a wider scale.
Samhällsbyggnadsteknik , Building Futures , Hållbar utveckling , Energi , Civil Engineering , Building Futures , Sustainable Development , Energy
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