Energy and environmental protection aspects of dessicant cooling.

Ventilation and air conditioning systems mainly use fossile primary energies as gas, oil and coal for the heating and cooling processes. Air conditioning means heating and humidifying the supply air during the winter season and cooling and dehumidifying the supply air in the summer season. For these summer operations the supply air in general is cooled down lower than the dew point in order to dehumidify the air by condensation. Afterwords the supply air is reheated again to reach the required temperature level for room inlet. For this air treatment process cooling and heating energy are used simultaneously, The cooling energy thereby is generated in general in a conventional cooling compressor unit based on CFC-refrigerants. Due to the threat of an atmospheric ozone depletion leading to a "Greenhouse effect" mainly caused by CO2 from burning fossile primary energies and the CFC-based refrigerants (1) used as cooling vapour in compressor chillers new developments of cooling equipment have a realistic chance to enter the HVAC market. Today it is necessary to operate air conditioning systems with a minimum of primary energy consumption and low pollutant emissions. At the same time the requirements for the indoor air quality are increasing. Therefore alternative and new air conditioning systems are now introduced using "Desiccative and Evaporative cooling" (DEC) air treatment processes (2). These units can be operated all over the year and have to be compared under energy and environmental operation aspects with traditional air conditioning systems.