Selection of a favorable zeolite for solar adsorption cooling: How straightforward is it?

A theoretical investigation was carried out for determining the performances of NaX, LiX, NaA, NaY, SAPO-34 and FAPO-5 zeolites used as coatings in solar adsorption cooling systems. The regeneration temperatures of the zeolites varied in a broad range. The daily temperature variation of the zeolite adsorbent and the power of the solar adsorption cooling system were calculated for each zeolite by using different coating mass and wind speed values. It was determined that for the summer weather conditions investigated, the regeneration temperature of the zeolite had strong impact on the performance of the solar adsorption cooling system. The aluminophosphates, often considered as very suitable for adsorption heat pump and cooling systems due to their quite low regeneration temperatures, generally had lower performances while the aluminosilicates with higher regeneration temperatures performed much better. This was related to the relatively high minimum adsorbent temperature in the system using solar energy, resulting in quite lower amount of water circulation for the adsorbents with relatively low regeneration temperatures. It was also determined that using different amounts and types of zeolite affected the operating period of the solar cooling system, as well as the power along the daily cycle.