Air-Conditioning (AC) has become an essential part of modern society as it enables a productive and comfortable life style in hot and humid climates. The amount of installed AC systems is expected to dramatically increase in the coming decades, largely driven by economic growth in developing countries. Since many of these countries, such as China, India, Indonesia and Brazil are in hot climates their AC use will be larger than in most Western countries [1] . Out of the 30 metropolitan areas with the highest demand for AC, all but two are in developing countries [2] . Air-conditioning is a very energy intensive activity. In the USA 5% of the electricity produced is used for AC, and up to 40% of the electricity demand for households in warm climates is due to AC. The rise of air-conditioning will cause a significant increase of fossil fuels. It is difficult for […]