Solid Sorption Refrigeration With Calcium Chloride Methanolates on Technical Scale

Thermochemical solid/gas sorption systems are known for their environmental benefits. They can use low-grade temperature sources for supplying cold storage and cooling of buildings. The thermochemical working pair calcium chloride/ methanol is well suited for sorption refrigeration and storage due to low costs, high energy density and good cyclability. The energy storage capacity results from the reversible sorption of methanol by the salt. Heating up the salt (desorption) stores thermal energy. Refrigeration results from the endothermic methanol evaporation which is induced by the salt reabsorbing the methanol and thus lowering the methanol vapor pressure. This study presents results from a 2 kW technical scale demonstrator of a closed thermochemical process with calcium chloride/ methanol. The demonstrator consists of two alternatingly working sorption reactors to enable continuous operation. The operation was done under atmospheric pressure using fans for the mass transport of methanol. Overall functionality is demonstrated by supplying up to 5 kWh of stored cooling energy from a reactor containing 9.7 kg dried calcium chloride. Optimization potentials are identified in desorption temperatures of around 90°C and/or condenser temperatures around 15°C, reduction of pressure and the use of mechanical compression.