35. Passive Strategies for Natural Air-Conditioning of Building for Different Climate of India

Solar passive architecture which essentially consist of collection, storage, distribution, and control of thermal energy flow, offers an exceptional opportunity for energy conservation through the harnessing of solar energy and can save atleast 35% of the energy required for heating and cooling of building. Internationally it has been recognised that this ‘near to natural’ technology can play a significant role in building industry now and in near future. Various available opportunity of passive architectural are shape and orientation of buildings, shading devices, etc., and more developed concepts like Trombe-Michel wall, solar absorption cooling and solar dehumidification and evaporation cooling, wind tower coupled with evaporative cooling, roof pond, size, shape/location and glazing of window, construction and insulating material of wall and roof, external finishes of the building enclosure, employment of trees, shrubs, pool of water and foundation, etc. Broadly climate zones of India can be classified into 6 zones, viz., hot and dry, warm and humid, moderate, cold and cloudy, cold and sunny, and composite. Evaporative cooling of the house using roof ponds, moist internal surface or indirectly through the heat exchangers is the most effective way of cooling and does work well in hot and dry and composite climate. It can be further augmented by heat transfer to the night sky for cooling in the following day, where the temperature difference between the air and sky is of the order of 9–15 ^OC. A method of natural air-conditioning in hot and humid regions are very limited as the diurnal temperature fluctuation are low and sky temperatures are high. Use of wind effects/improve ventilation and dehumidification of air are the two effective means that improves achieving comfort conditions. Dehumidification of air may be achieved by the use of a variety of desiccants, which can be regenerated using solar heat for reuse. While dehumidification itself improves comfort conditions. It can be further augmented by evaporative cooling through partial dehumidification. Underground shelters provides the advantage of thermal capacitance effect and moisture retention effect of the earth. It has been universally realised that no single method will be sufficient to provide satisfactory comfort conditions for the complete year for any climate. Hence, it is advisable to adopt a combination of various techniques. In India considerable work has been carried out in the area of natural air-conditioning.