Solar energy, liquid desiccant, solar collector cum regenerator, sorption technology, open cycle
A solar liquid desiccant cooling system uses renewable energy and natural refrigerant (water) which makes it attractive. Its main components are air dehumidifier, solar liquid desiccant regenerator and direct/indirect evaporative cooler. In this cooling system, strong liquid desiccant absorbs water from air in the dehumidifier that must be rejected in the solar regenerator. This makes regeneration of a liquid desiccant one of the key processes in the cooling system that requires thermal energy. The energy needed for regeneration can be obtained from sun with the help of an open type solar collector cum regenerator. It also enables storage of energy in the form of regenerated desiccant for use during non-sunshine hours. Detailed analysis of the performance of this device has prime importance in integrating it with a liquid desiccant air cooling system. This entails the development and experimental performance testing of a liquid desiccant solar regenerator under actual weather conditions over the sunshine hours. A solar collector cum regenerator of effective solar area of 4 m2 was fabricated using corrugated sheet metals, layers of thermocol insulation, insulation wood box, glass supporting frames and glasses. The solar collector cum regenerator was mounted on a metal supporting structure inclined at 14o. The corrugated absorber was coated with iron oxide, before black paint, to minimize corrosion. This paper presents transient regeneration performance of the solar collector cum regenerator in terms of increase in concentration, mass of water evaporated and solar collector cum regenerator efficiency. Desiccant concentration increase, total mass of water evaporated and mean daily solar collector cum regenerator efficiency during regeneration of LiCl and CaCl2 solutions were found to be 0.33-0.46 & 0.31-0.47; 13 & 17 kg and 36 & 43%, respectively. These typical results were obtained from experiments carried out on separate days between 9 am and 4 pm in the month of May. The mass of water evaporated was estimated using an equation derived by applying conservation of solution mass. The experimental procedure and the performance analysis technique used are useful in designing solar components of open cycle liquid desiccant cooling systems.