Credit: Courtesy DOE's National Renewable Energy Laboratory
Chilling Out A DEVap system would use up to 80 percent less energy than a conventional air conditioner.
How many times have you been in a building whose temperature was uncomfortably cold? Air conditioning accounts for 15 percent of annual energy consumption in the U.S., and it’s safe to say a portion of that cold air is being wasted.
Getting some people to turn up the thermostat might be futile. But researchers at the DOE’s National Renewable Energy Laboratory (NREL) in Golden, Colo., have come up with a system that can cool buildings and use 40 percent to 80 percent less energy than conventional A/C units. While this system is being developed initially for commercial buildings, its co-inventor, Eric Kozubal, a senior mechanical engineer at NREL, envisions a scaled-down version for residential installation. “Air conditioning is air conditioning,” Kozubal says about his concept.
The system he and his team devised is a souped-up version of an evaporative cooler—more commonly called a swamp cooler—that for decades has ventilated homes and other buildings in drier, moderate climates such as Denver. In fact, vapor compression cooling dates back to the early 1900s, says Kozubal.
Evaporative coolers are far less efficient in hotter or humid climates. Kozubal thinks he’s solved that problem with a DEVap (for Desiccant Enhanced Evaporative) air conditioning system that dehumidifies incoming air through a hydrophobic membrane that contains liquid desiccants: concentrated salt solutions of lithium chloride or calcium chloride. That air then passes into a second stage of thermal contact with a moistened, water-impermeable surface that evaporates the water into a separate cooler air stream. No carbon-emitting refrigerants necessary.
The NREL developed energy simulations to model DEVap’s performance in hot and dry Phoenix and hot and humid Houston. It achieved energy savings of 81 percent and 25 percent, respectively, demonstrating that the concept could work in most climates. Kozubal tells Builder that the next step is to build a “proof of market” prototype, and get the design to where the machine can be replicated. The laboratory already has applied for international patent protection for the DEVap concept, and Kozubal thinks commoditization is about two years away.
The NREL is working with several private companies, including Woburn, Mass.-based startup 7AC Technologies, which licenses the system. 7AC’s CEO, Peter Vandermeulen, is optimistic that DEVap will be ready for sale sooner than later, and that its total costs will be comparable to air conditioners/humidifiers connected to many homes’ HVAC systems. “The price of copper isn’t going down, and refrigerants are becoming more problematic,” he says. Vandermeulen and Kozubal also note that DEVap’s cost premium would be defrayed by energy cost savings within three years of usage.