While the development of the modern air conditioner spurred a great deal of city growth, it is hardly the first example of an air-cooling system. Indeed man has been using one method or another to change the air around us for hundreds of years, if not thousands. Now researchers at the National Renewable Energy Laboratory have combined two of these old techniques into a new technology with some interesting benefits.
One of the old ways to cool the air was to pull the heat out of it by using that energy to evaporate water. Unfortunately this method can only be applied where the air is dry and will readily absorb the water. To overcome this, the researchers added a desiccant to the setup, which dries the air before cooling it. When air first enters the Desiccant-Enhanced Evaporative (DEVAP) system it passes through channels submerged in a liquid desiccant. The channels are made out of a special membrane that will only let water permeate it, and not the desiccant or the air. The cooling part of the system then bleeds off some of the dry air to evaporate water and cool the rest of the air.
This new design is considerably simpler than the traditional air conditioner, and benefits because of it by a reduced energy requirement and safer materials involved. With 15% of the energy we generate going to air conditioning, with that amount reaching 70% on the hottest days, any increase in efficiency would be appreciated, which is why commercial and eventually residential units are already in development.