Building a Better Air Conditioner

Right now we’re all well aware that air conditioning makes up the biggest part of our energy bills during the summer. If you’re gasping at the bills and thinking there must be a better way, take heart. The U.S. National Renewable Energy Laboratory has found a way to make air conditioners 90 percent more efficient than traditional air conditioners, which operate using technology that’s almost a century old.

Eric Kozubal co-inventor of the DEVap air conditioner
Eric Kozubal, co-inventor of the DEVap air conditioner, examines a prototype air flow channel for his new, energy-efficient air conditioner. Photo By Pat Corkery/Courtesy National Renewable Energy Laboratory. 

Indirect evaporative cooling divides air into two streams separated by a membrane. Water passes through one stream, making it cool and moist and cooling down the membrane which then cools the second stream without making it moist. The new, efficient design, called DEVap (desiccant-enhanced evaporative), adds another element—a liquid desiccant, or drying agent--to this process. As hot, humid air enters the AC, the desiccant (in this case, calcium chloride, a common ingredient in road salt), pulls moisture out of the air, leaving it warm and dry. The air is then put through the indirect evaporative cooling process, which can function more efficiently once moisturize has been removed. Once the calcium chloride is saturated, it can be heated to boil off the water.

DEVap cooling core
This illustration shows how the DEVap cooling core uses water and liquid desiccant to draw in outside air, exhaust some of that air and return cool, dry air to the area being cooled. Photo Courtesy National Renewable Energy Laboratory. 

Not only is the new design more efficient, but the desiccant it calls for will replace the chlorofluorocarbons (CFCs) traditionally used in air conditioners. CFCs can easily leak out of air conditioning units and devastate the environment. Every kilogram of CFC has the same effect as 2,000 kilograms of carbon dioxide on the atmosphere.

The design is expected to take another five years to develop before it can be sold to the public.