Credit: Harry Whitver
DEVap consists of two distinct stages: a dehumidifier stage and an indirect evaporative cooling stage. Water is added to the tops of both stages, while liquid desiccant is pumped through the first stage. Some outdoor air is mixed with return air from the building to form the supply air stream, which flows from left to right through the two stages. NREL developers believe that a commercial building application of this technology will come to market in about five years, and a residential version may be available in 10.
While some promising new building technologies were discussed at the DOE’s recent Building America Technical Update meeting in Denver, one theme repeated with almost militant frustration was that U.S. heating and air conditioning manufacturers are not supplying equipment sizes commensurate with high-performance housing requirements. James Cummings, of the Florida Solar Energy Center, points out that not only are most air conditioning systems sized for peak demand, resulting in significant oversizing for 90% of operation time, but that this has been exacerbated with high-performance enclosures that typically require smaller equipment than manufacturers offer. “Try to get a 1-ton or smaller air conditioning unit, and you can’t,” says Cummings. Cooling systems also are set to respond to sensible or air temperature controls, when the main burden for most, especially high-performance home air conditioning, comes with latent loads, or humidity.
John Straube, a principal at Building Science Corp. and professor of building science at the Civil Engineering Department of the University of Waterloo, says the age of dual systems has passed, with one system providing household heat and the other hot water. With the low heating requirements resulting from improved enclosures, energy demands have shifted from space to water heating. His preferred solution would come with combining a high-efficiency, gas, tankless hot water system with a small air handler and a micro-duct system.
One of the more exciting developments at DOE involves research on a “super advanced” desiccant enhanced evaporative air conditioning (DEVap) system: a compact, cost-effective cooling unit that uses 90% less electricity and up to 80% less total energy than its traditional counterparts, while also efficiently managing humidity so that it can maintain a comfortable atmosphere for building occupants without the need for overcooling. Another development comes with emerging technology in radiant floor air conditioning that promises a complete heating and cooling system that requires no blowers or ducting when coupled with an energy recovery ventilation system devoted exclusively to indoor air quality.
Go to www.ecohomemagazine.com/vision-2020 for more.