The development of passive downdraught evaporative cooling systems using porous ceramic evaporators and their application in residential buildings
Passive Evaporative Cooling is a method that uses the evaporation of water to cool the air. It is traditionally used and is most suitable in hot and dry climates. Its application is based on the availability of water resources and the creation of air movement through the building. The use of clay and porous ceramic in passive downdraught evaporative cooling has a track record in the vernacular architecture of hot and dry climatic regions. As part of this project, an improved design for porous ceramic evaporators has been developed for integration into a perimeter cavity wall system, as an alternative form of passive evaporative cooling.
This research demonstrates that passive evaporative cooling using porous ceramic can provide thermal comfort conditions inside residential buildings in hot dry climates. Porous ceramic components can be integrated simply and effectively within existing housing of 1940s to 1970s which are due for refurbishment. Performance simulations on a case study building in Seville demonstrated that the system can provide comfort conditions after a series of energy saving strategies were applied to reduce cooling loads. An applicability study focusing on the residential stock of Seville assessed that the proposed system can avoid the need for mechanical cooling in 70% of the existing buildings. This could result in substantial energy and CO2 savings, contributing to Spain’s commitment to reduce greenhouse gas emissions by 2010. An outline specification of a typical wall-integrated Porous Ceramic System (PCS) was set out and costed. A Life Cycle Cost analysis over 25 years compared the proposed PCS with a conventional room air-conditioning unit, demonstrating that its cost is half of the conventional option.
The application of the proposed passive cooling system to apartment buildings in Southern European cities could considerably improve comfort and living conditions of the occupants, as well as reduce the use of room air-conditioning. If applied on a large scale, this could produce substantial energy savings and reduce greenhouse gas emissions in the atmosphere.