The Application of Downdraught Evaporative Cooling Systems in Non-domestic Buildings. A case study: the Green Office, Tehran

The use of cooling in buildings is continuing to increase in the World. This is raising concern that it will undermine the Kyoto Protocol’s objectives towards reducing mankind’s contribution to global warming. To counter this trend, there is increasing interest in hybrid and passive downdraught evaporative cooling (PDEC) in particular.The JOULE research project into Passive Downdraught Evaporative Cooling (PDEC 1996-1999) concluded that in architectural and engineering terms 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. This system provides improved performance and other advantages over directly wetted cellulose pads, but it still has a number of disadvantages: high quality water required, risk of nozzles blocking up, risk of dripping (carry-over), risk of microbiological contamination (Legionella). It was clearly desirable to design an evaporative cooling system which avoids these problems. A new direct evaporative cooling system based on porous ceramic evaporators was the subject of a research project funded by the European Commission (Evapcool 2001-2003).The Evapcool porous ceramic system represents a low cost and very simple means to provide comfort in buildings in hot–dry regions of the world. The research has resulted in prototype components which have been performance tested. The integration of these components into the building fabric was firstly illustrated in relation to a generic office building. The studies showed that these components can be integrated within walls or roofs in a variety of ways to deliver cooling to perimeter areas of both existing and new buildings