Development of a Pilot Plant Solar Liquid Desiccant Air Conditioner

In a pilot plant liquid desiccant air conditioner (LDAC) developed at Materials & Energy Research Centre (MERC), dehumidification of the outside air is achieved through a honeycomb packed-bed heat and mass exchanger, using lithium chloride solution as the desiccant. The dry air thus obtained is evaporative cooled inside a cooling pad and directed into the conditioned space. The dilute solution from the dehumidification process is concentrated in a honeycomb packed-bed scavenger air regenerator using hot water from flat plate solar collectors. Carryover of the desiccant particles has been avoided by using eliminators. In this paper the experimental results obtained from testing the prototype of the liquid desiccant absorber unit have been presented and compared with a previously developed model for the packed-bed. The comparison reveals that good agreement exists between the experiments and model predictions. The inaccuracies are well within the measuring errors of the temperature, humidity and the air and solution flow rates. The above tests further reveal that the unit has a satisfactory performance in controlling the air temperature and humidity when installed on a commercial site of about 250 m2 area. A commercialization study is underway to take the solar LDAC into the market if it can compete with the conventional vapour compression system. The study reveals that the operating cost of an LDAC is significantly lower than its conventional counterpart. The costs would further reduce if a storage system was used to store the concentrated solution of liquid desiccant. A simple payback of five years was determined for the solar components of the liquid desiccant system in this study.

Keywords:

Liquid desiccant , Dehumidification , Packed-bed , Solar regeneration