Design and optimization of an air heating solar collector with integrated phase change material energy storage for use in humidification–dehumidification desalination

Abstract

Compared to solar water heaters, high-temperature solar air heaters have received relatively little investigation and have resulted in few commercial products. However, in the context of a humidification–dehumidification (HD) desalination cycle, air heating offers significant performance gains for the cycle. Heating at a constant temperature and constant heat output is also important for HD cycle performance. The use of built in phase change material (PCM) storage is found to produce consistent air outlet temperatures throughout the day or night. In this study, the PCM has been implemented directly below the absorber plate. Using a two dimensional transient finite element model, it is found that a PCM layer of 8cm below the absorber plate is sufficient to produce a consistent output temperature close to the PCM melting temperature with a time-averaged collector thermal efficiency of 35%. An experimental energy storage collector with an 8cm thick PCM layer was built and tested in a variety of weather and operating conditions. Experimental results show strong agreement with model in all cases.