Sorption chillers

Sorption chiller technology is rapidly developing, especially that using solar energy. - As highlighted by Jacob and Kohlenbach* during the latest IIR Gustav Lorentzen Conference on Natural Working Fluids in Sydney, in Europe, numerous new sorption chillers with small- and medium-scale cooling capacity - up to 500 kW - are now available on the market: 7 single-effect water/lithium bromide and 2 water-lithium chloride absorption chillers; 7 ammonia/water chillers as well as 2 water/silica gel and 2 water/zeolith adsorption chillers. The market potential for solar and thermal (district heat or waste heat from CHP units, biomass as well as processes) is very large, so various companies have developed complete solar cooling kits for the product business with specific costs between 3000 and 4500 €/kW cooling. Maximum operation time and low-cost driving heat are the key factors influencing the economic efficiency of thermal and solar cooling kits. A solar fraction of minimum 70% should be achieved in Europe to ensure economic operation. Of 400 solar cooling realized in Europe in 2008, about 60% use absorption chillers, 11% adsorption chillers and 29% open systems such as DEC (desiccant evaporative cooling) and liquid sorption systems. - In Japan, Tokyo Gas, Osaka Gas and Toho Gas have developed a solar-assisted absorption chiller-heater. While preferentially utilizing solar heat, it can provide the cooling load required by automatically performing backup with gas combustion when the solar heat falls, thus maintaining the required capacity in a stable manner. It is claimed that a roughly 24% reduction in yearly primary energy consumption used for space cooling/heating can be achieved compared with the previous gas air-conditioning system when installed in a 4000 m2 building. The new product makes it possible to maximize the amount of solar heat to be used since it can use even low-temperature solar heat thanks to a newly installed solar heat condenser and optimized cooling water path. It can also maximize the efficiency of the solar cooling system by computing the region of temperatures in which the solar heat is used which varies with the cooling load, and also by performing system control for using hot water taken out of the heat collector at the lowest possible temperature. It has a rated cooling COP higher than 1.3 (corresponding to the rated cooling COP of higher than 3.5 in the case of an electric system) when the system operates with gas alone. - In China, absorption chillers from LS Mtron won the bid for the Chengdu Huirong international project, which is to be one of the 10 landmark buildings in Chengdu, with a total construction area of 150000 m2. The total cooling capacity of the plant is 15.1 MW, claimed to be the largest absorption chiller project. * U. Jakob, P. Kohlenbach. Recent developments of sorption chillers in Europe.