With the help of organic working medium absorbing the solar energy for steam electric power generation, green energy can be provided to automotive accessories so as to improve the vehicle energy efficiency. In the hot summer, the exhausted heat resulting from cars’ directly exposing to the sun can be used to cool and ventilate the passenger compartment. Considering the space occupied by the system in the combination of both practical features for solar heat source--low power and poor stability-- a compact evaporation structure was designed to enhance the solar utilization efficiency. In the research, the heat source of power and temperature variation range was determined by the available solar roof with photo-thermal conversion model. Then started from the ratio of exhausted heat utilization corresponding to evaporator’s characteristic parameter, the performance analysis was made in the different working conditions. What’s more, according to the input energy change characteristic, the control method of the circular flow rate was determined, which ensured the turbine to run stably. The result indicated that the ratio of exhausted heat utilization in the mid and low latitude region was about 6.5%, as well as the volume of this system was suitable for vehicles. Therefore the system showed a good prospect in practices.