Adsorption cooling system for cold storage using methanol/silicagel

Abstract For the cold storage of agricultural products at temperatures of 2–4°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°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 T0=−2°C, a heating water temperature of Th=85°C and a condenser temperature of Tc=30°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.