Residential air conditioners (RACs) are one among many unavoidable commodities used today by large number of households. While RACs do provide immediate relief from the hot and humid weather, the long term ill effects of using RACs is rather huge. The powered required for running the RACs is generated using fossil fuels that emits significant amount of green house gases besides increasing also particulate matter in air. An ever increasing demand of RACs from 1.2 billion in today’s date to over 4.5 billion by 2050 can add about 132 GT of CO2-equivalent (CO2) emissions, which can be extrapolated to a temperature rise of 0.5 0C by 2100. Calculations show that power input to a compressor of a 2-ton AC (using R410A as refrigerant) is ~2.15 kW; if this AC is operated for the whole day, would consume 186 thousand kJ of energy. All these factors would sum up to an unaffordable world to live in, with potentially dangerous heat condition in near future. Clearly, it is high time to think of an efficient and sustainable alternate cooling system ensuring significantly decreased consumption with zero or miniscule emission.
It is to mitigate this need that we have come up with a novel cool-roof technology which consists of a light, cooling insulation cover for placing on the roof and wall of a building. The cooling effect is accrued via three different mechanisms: (a) Reflection of solar radiation, (b) Radiative cooling and (c) Thermal insulation. By using this cooling cover, it is possible to decrease the inner wall temperature of the room by 8 – 10 oC. The cover consists of a superhydrophobic and self-cleaning surface which allows easy drainage of water and prevention of accumulation of dust. The cooling material is flexible, is long lasting yet degradable over 5-10 years. It is easily deployable, washable, removable and re-deployable. It can be placed on the roof or hung on a wall.