Evapcool

By Brian Ford, Rosa Schiano-Phan - 11 January 2010

The JOULE Research Project into Passive Downdraught Evaporative Cooling (PDEC) concluded that a mixed mode approach (PDEC + back-up system) is technically and economically viable, and is competitive against conventional air-conditioning for office buildings in southern Europe. This research was based on a specification using misting nozzles under high pressures (20-50bar) to generate a high rate of evaporation and to minimise moisture carry-over, but it still had a number of disadvantages: high quality water required, risk of nozzles blocking up, risk of dripping (carry-over), risk of microbiological contamination, increase in moisture content of the air.
Direct evaporative cooling using porous ceramic evaporators avoids the need for high pressure water supply, drip trays and the maintenance implications of spray nozzle systems. Such a system also reduces the risk of microbiological contamination of the supply air, but requires a large surface area to achieve significant cooling. This approach has been the subject of a European funded research project (Evapcool) which is due for completion in September 2003.
The evaporation of water through porous ceramic pots located within a ‘wind-catcher’ (‘Malqaf’ in Egypt,‘Baud-Geer’ in Iran), has been used traditionally throughout the southern Mediterranean, North Africa and the middle East for centuries to induce cooling and air movement through buildings.
The porous ceramic components investigated as part of the Evapcool project are slim containers through which evaporation is encouraged, while avoiding running water and the need for collection. The integration of these panels within a generic building has been an important element of the investigation. A preliminary sizing of the components was related to building geometry, volume and envelope characteristics and specific cooling demand. In the direct evaporative system, the cooling achieved by direct evaporation from a wet ceramic surface is proportional...