A new approach to the cooling of buildings across the developing world that needs nothing but wind and sun to operate has been devised by engineers in India. Writing in the International Journal of Sustainable Design, the team explains the concept of a combined solar chimney and wind tower system that can reduce the temperature of incoming appear by 5 degrees Celsius.

Jyotirmay Mathur of the Mechanical Engineering Department, at the Malaviya National Institute of Technology, in Jaipur, together with architect and urban designer Rajeev Kathpalia of Vastu Shilpa Consultants, in Ahmedabad, point out that the development of energy-efficient, and even passive, cooling systems for buildings is essential in the light of environmental pressures and costs. In the past, they point out, building designers had to rely on natural ways and means for maximising comfort inside buildings.

The team has now reasoned that two distinct technologies - the so-called solar chimney for roof-based based ventilation and a wind tower that provides a draft of air could be combined simply and effectively into a passive cooling system.

They have designed a building that incorporates a multi-storey wind tower clad with heavy stone panels which produces an upward draft of air drawn into the building passively and cooled by the massive tonnage of the stone classing. The air flows through the rooms and corridors and accumulates heat as it does so. This is then carried to the top of the building and vented with large black, thermally conducting, panels providing a way to shed the heat quickly from the top of the building.

The result is a reduction in internal temperature of several degrees. The resulting temperature drop would be sufficient to improve the comfort of people in the building without the need for powered air conditioning that is both expensive to install, maintain and operate.

"The combination of solar chimney and wind tower is found to be a good design option for urban buildings," the researchers conclude, "We have demonstrated how natural resources can be utilised to design sustainable buildings in an urban area where design of truly sustainable buildings is extremely difficult."

"Design of passive cooling system for a building in composite climatic conditions in India", by Jyotirmay Mathur and Rajeev Kathpalia in Int. J. Sustainable Design, 2008, vol 1, pp 110-126