AC innovation promises 90 pc saving

Researchers at the U.S. National Renewable Energy Laboratory (NREL) in Golden, CO, have come up with a new air-conditioner design that they say will dramatically increase efficiency and eliminate gases that contribute to global warming.

The desiccant-enhanced evaporative, or DEVap, air conditioner combines evaporative cooling with a water-absorbing material to provide cool, dry air while using up to 90 percent less energy.

The U.S. uses about 100 quadrillion British Thermal Units each year, according to the U.S. Energy Information Administration. Up to 40 percent of that is used in buildings, with about 5 percent going to air conditioning. The new system could cut that in half in less-humid areas and by up to 90 percent where humidity is high.

The desiccant used in the system is relatively harmless (calcium chloride is used in road salt), though its corrosiveness requires that metal be eliminated from the hardware. It also replaces the chlorofluorocarbons that are used as the refrigerant in traditional air conditioners. Those CFCs can easily leak, and every kilogram of them provides the same greenhouse gas effect as about 2,000 kilograms of carbon dioxide.

It might take about five years to develop the system to a point where NREL can hand it off to industry for commercialization. The system is designed to replace existing systems without many changes, so it could be phased in as people upgrade their old air conditioners.

The desiccant can be reused simply by heating it up to boil off the water. In an industrial setting, that might be done using waste heat from another industrial process. In the home, natural gas or solar energy would work.

The setup could make solar thermal energy systems, which absorb sunlight to heat a home and its water, more cost effective. During hot summer days, solar energy that might otherwise go to waste could therefore actually help keep a building cool.