A new operating model for improving thermal efficiency of double-glazed solar air-phase change material collector: An experimental study

The heat storage type solar air collectors that only release heat at night have a low thermal efficiency. In this study, an experiment is conducted on a double-glazed solar air-phase change material (PCM) collector. An effective new operating model that performing air heating simultaneously in the energy storage stage is proposed to improve the overall efficiency of the heat storage type solar air collector. During the experiment, air heating is started at different times each day according to the degree of heat storage of the PCM. It is found the nighttime air heating is affected by the degree of heat storage of the PCM, the airflow velocity of air channel, and the inlet air temperature. The thermal efficiency of the solar air collector depends on the air heating start time during the day and airflow velocity of air channel. Under different weather conditions and operating conditions, the solar thermal efficiencies ranged from 34.51 % to 44.49 %. The results show that under the premise of ensuring the complete melting of the PCM, properly performing the air heating in the daytime can not only ensure nighttime air heating, but also improve the overall thermal efficiency.