Hybrid air conditioner cuts energy use by 50 to 90%

Eric Kozubal, an NREL senior engineer and coinventor of the EVap air conditioner examines a prototype air flow channel of the new device. DEVap, which stands for desiccantenhanced evaporative air conditioner, uses membranes to combine the efficiency of evaporative cooling and the drying potential of a liquid desiccant. The graph superimposed on the photo shows how hot humid air, in red, changes to cool dry air, in blue, as air passes through the DeVap core.

Photo: Pat Corkery

Engineers at the National Renewable Energy Laboratory, Golden, Colo., have combined evaporative cooling with desiccants or drying agents into a more efficient air conditioner, one that uses 50 to 90% less energy than conventional units. The new air conditioner can also be powered by natural gas or solar power. While evaporative cooling reduces the temperature of air flowing through the device, desiccants -- in this case, a flowing liquid -- removes the humidity. The result: cold-dry air.

Select figure to enlarge.

In the device, incoming air is dried as water is pulled from it and passes through a membrane separating the air flow from the desiccant. The membrane only lets water vapor pass through. The desiccant is a highly concentrated and viscous salt solution of lithium chloride or calcium chloride. Incoming air also cools as heat from it is drawn through the membrane and a barrier separating the desiccant and into a flow of coolant, most likely water. The coolant, in turn, gives its heat up to a stream of exhaust air -- actually cooled, dry air diverted from the unit's output.

Information

National Renewable Energy Laboratory, www.nrel.gov