What’s new, Kozubal says, is a design that manages to merge evaporative cooling and desiccant drying into a cost-effective system. “It makes this type of air conditioning viable for commercial and residential processes for cooling,” he says.
The industry is working on a variety of methods to improve the efficiency of air conditioning, Jacobi says, from the use of heat exchangers to improvements in the compression systems of traditional machines. “It’s an area of great importance to the nation, because about a third of our nation’s energy use is in buildings.”
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. Kozubal says his system could cut that in half in less-humid areas and by up to 90 percent where humidity is high. “When you talk about a technology that can save 2 to 3 percent of the nation’s entire energy supply, that’s quite a lot,” he says.
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. What’s particularly attractive is that it 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.
Kozubal says 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 it’s absorbed. 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. In fact, Kozubal says, 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.
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