The NREL process, called DEVap (Desiccant-Enhanced eVaporative), is based on the principles of evaporative cooling, which has been around for awhile. In evaporative cooling, water flows over mesh, and a fan blows air through the wet mesh to cool the air. The problem with evaporative cooling is that the cooler air is very humid, which is about the last thing you want when the climate is already humid. Also, when its already humid, the air blowing over the mesh can’t absorb enough moisture to become really cold. NREL combines evaporative cooling with a second type of cooling process – one that uses desiccants to pull moisture out of the air. Desiccant cooling solutions have also been around for awhile, but they are very complex units that are primarily used in industrial drying processes. The DEVap unit uses hydrophobic membranes (water beads up on the membranes instead of soaking into the material) along with a salt based desiccant solution to remove the moisture from the cool air. The result is am A/C unit that creates both cold and dry air. It’s an extremely efficient process compared to current refrigeration based air conditioners, since most current air conditioners use a lot of electricity to run the refrigeration cycle. The DEVap evaporative cooling technique uses far less electricity than the compressors used in today’s air conditioners.
NREL has just patented the DEVap concept – they plan on taking a couple of years to make the technology smaller and simpler and even more efficient. Then NREL plans to license the DEVap to industry. “We’re never going to be in the air conditioner manufacturing business”, said Ron Judkoff, Principle Program Manager for Building Energy Research at NREL. “But we’d like to work with manufacturers to bring DEVap to market and create a more efficient and environmentally benign air conditioning product.”