Optimization of latent heat storage in solar air heating system with vacuum tube air solar collector

This paper presents the design and modelling of the heat transfer of a solar air heating system, which consists of a vacuum tube air solar collector (SC) and latent heat thermal energy storage (LHTES), and a parametric analysis of the performance of this system. LHTES is a form of short-term daily storage that stores the SC heat during the day and releases it into the building during the night. Especially in low energy buildings with a high share of passive heating, this can significantly improve the utilization of solar energy for heating. The design of concentric-tube LHTES was optimized regarding the air temperature at the exit of LHTES during the day and the peak shift of heat supply. The results showed that optimal mass of PCM in LHTES is 150-200 kg/m2 and the optimal air flow-rate is 40 m3/h per m2 of the SC aperture area. The analysis of the system performance at different levels of daily solar irradiation has shown that 54-67% of the heat produced by solar air heating system in daytime can be delivered during the night time for building heating.