Turning on your air conditioner during the summer is now part of our daily reflexes, along with opening the doors and turning on the lights. When bills come, though, it’s also a habitual, often compulsive reflex to pay hundreds of dollars to electricity utilities – you couldn’t live in our own sweat, after all, when the temperature outside is 100 degrees, could you?
DOE’s National Renewable Energy Laboratory (NREL) has combined three classic methods of cooling down the air into one invention that could save 50 to 90 percent of your monthly electricity bill (on air conditioning). The invention is called “DEVap” (Desiccant-Enhanced eVaporative air conditioner). Eric Kozubal, one of the inventors, said “The idea is to revolutionize cooling, while removing millions of metric tons of carbon from the air.”
Kozubal also said that their DEVap device uses three methods to extract heat from the air: membranes, evaporative coolers and dessicants. Each of these had been used separately since ages, but nobody thought combining them in such a fashion could save energy in such amounts.
DEVap uses water and liquid dessicant (like those silicagel balls found in new shoes, only liquid) to draw in the outside air, exhaust some of it and return cool, dry air to the area being cooled. These two methods improve the dehumidification part, which is the most energy-consuming. An example of a simple evaporative cooler would be a water-soaked bed sheet put in your window, or having a fan blow air on it. The evaporation of water would cause the sheet to lose temperature and cool the air that hits it. The same happens when you shiver if you get out of the sea, even though it’s hot outside.
Still, only the use of dessicants and evaporative coolers isn’t enough in areas with high air moisture. For these areas, membranes kick in. The membranes in the DEVap are hydrophobic, which means water tends to bead up rather than soak through the membranes, just like it happens when water is falling on a freshly waxed car. This allows the membranes to control the liquid flows within the cooling core. “It’s that property that keeps the water and the desiccant separated from the air stream,” Kozubal said.
All these three methods cool the air and dehumidify it in one step, without needing refrigerants. Classic A/C machines may use CFC of HCFC as the heat exchanging liquid, which is most of the times bad for the environment, because the pipes containing them ultimately break down and release these potent greenhouse gases into the atmosphere. A pound of CFC or HCFC in refrigerant-based A/Cs contributes as much to global warming as 2,000 pounds of carbon dioxide. The DEVap replaces the refrigeration cycle from classic A/Cs with an absorption cycle that is thermally activated and that uses far less energy.
NREL wants to license the technology to various industry manufacturers, so that in a few years it should be able to change things radically in how much energy we use to cool our homes and offices.