Adsorption cooling system for cold storage using methanol/silicagel

For the cold storage of agricultural products at temperatures of 2-4 degrees C in India, a solar-hybrid cooling system has been developed, using solar energy from flat plate collectors and the waste heat of a genset, operated with producer gas. A commercially available low temperature (80-90 degrees C) adsorption cooling system for air-conditioning application had to be modified for operation at cooling temperatures below the freezing point of water. Methanol instead of water was investigated as a refrigerant. Because of the inferior thermodynamic properties of methanol and the lower operation temperature, the efficiency is reduced. Calculations showed that the COP for a commercial adsorption cooling system is about 30% when operating the system with methanol/silicagel at a chilled water temperature of T-0 = - 2 degrees C, a heating water temperature of T-h = 85 degrees C and a condenser temperature of T-c = 30 degrees C. A laboratory test facility with heating and cooling capacities of about 2 kW was set up. By comparative experiments with water and methanol, the calculations could be validated, though the specific power density is only 1/10 of the commercial system. (C) 1998 Elsevier Science Ltd. All rights reserved.