Solar cooling and refrigeration with high temperature lifts - thermodynamic background and technical solution

The need for air-conditioning in buildings and for industrial process cooling - e.g., in food industry - is growing rapidly all over the world. A new promising approach to meet this increasing demand in an environmentally sound way is the use of solar energy in combination with heat driven cold production. Many technical solutions are possible to use solar heat for air-conditioning. Key issues for system design and selection of components are: - The selection of the room air-conditioning distribution systems: e.g., radiative ceilings and other ""high temperature"" systems need only chilled water temperatures in the range of 15-18°C while chilled water networks supplying fan-coil systems require temperatures at 7-10°C. - The heat rejection technology used: a wet cooling tower allows for lower heat rejection temperatures than dry air-cooling. - The presence and size of a storage to overcome mismatches between solar gains and cooling loads. A very attractive solution in terms of energy density is an ice storage; however this storage requires cold production temperatures below 0°C. The system selection is mainly based on climate and load conditions analysis and on the energy (electricity, back-up fuel) and water costs and availability. In this paper a basic thermodynamic analysis is presented which gives insight into the interaction between the selection of the proper technical solution and the climate and load conditions. In the second part of the paper a special focus is given on a newly designed system which can be applied under extreme climatic conditions, i.e., hot and humid climates.