Analysis of a sorption energy storage system for cabin air heating and dehumidification in electric vehicles

This work investigates the integration of a Sorption Thermal Energy Storage (TES) into the Air Conditioning (AC) system of electric vehicles. The proposed device reduces the energy demand for cabin heating under winter conditions, leading to a driving range increase. The TES dehumidifies the cabin air through a desiccant bed (zeolite 4A), preventing window fogging, enabling higher air recirculation rates, and consequently reducing the required heating power. An experimentally validated numerical model was used to analyze the adsorption and regeneration processes and to identify suitable operating conditions. Regeneration was found to be effective at moderate temperatures (around 120°C), with a counter-current airflow configuration providing faster and more efficient desorption compared to parallel-flow operation. A simplified model integrating TES, AC unit and cabin was developed and used to compare different configurations. Heating energy consumption with and without TES under different ambient conditions, passenger loads, airflow rates, and regeneration states were evaluated. Heating energy savings ranged from 17% to 70%, increasing with higher ambient humidity. Considering the desiccant bed volume, electric energy savings up to 1.3 kWh L⁻¹ for heat pump systems and 3.3 kWh L⁻¹ for PTC heaters were estimated, corresponding to a potential driving range increase of 13.4 km L⁻¹ and 33.5 km L⁻¹, respectively. Preliminary TES tests on a mock-up vehicle confirmed the effective dehumidification capacity of the proposed technology.