"The idea behind this effort was to have industry and individuals with good ideas work with ORNL to stimulate research and development to integrate desiccant systems with conventional vapor compression technology," said Jim Sand, a researcher in ORNL's Engineering Science & Technology Division.

According to ORNL, while conventional vapor compression air conditioning systems do a great job of cooling, they are not designed to handle temperature and humidity loads separately. As a result, people tend to set thermostats to lower settings to offset relatively high humidity. Compounding the problem is that oversized compressors are frequently installed to dehumidify the incoming air. Furthermore, to meet humidity requirements, vapor-compression systems are often operated for long cycles at low temperatures, which reduce their efficiency and may require reheating the very cold dehumidified air to achieve some degree of comfort.

"Obviously, when you have this going on in thousands of buildings across the country, it wastes a lot of energy and puts an unnecessarily high burden on the electric grid," Sand said. "So part of DOE's interest in desiccant air conditioning systems is in reducing that load while allowing people to be more comfortable in healthier environments."

One of the partners in the program, SEMCO, has already introduced an active desiccant-vapor compression hybrid rooftop unit. And a partnership with Trane and Charles Cromer of the University of Central Florida has resulted in the Trane Active Cromer Cycle system, which is expected to be on the market by the end of the year or in early 2005.

A third partner, the team of Kathabar and AIL Research, is also developing a system, Sand said. Field demonstrations are scheduled for this summer, and commercial production could begin within 18 months.

Publication date: 07/19/2004