Trane has become the second manufacturer to achieve Western Cooling Challenge certification after being spurred on by a University of California, Davis, initiative to build more energy efficient air conditioning.
In response, Trane built a rooftop air conditioner that it claims is 40% more energy efficient than conventional units. The Voyager DC is a hybrid rooftop air conditioner that uses indirect, evaporative cooling to increase cooling capacity and reduce peak electrical demand.

The Voyager DC uses water evaporation to cool outside air for the condenser on an otherwise conventional air conditioner. The air conditioner then uses the water chilled by evaporation to cool the hot outside air used for building ventilation. Such techniques increase the number of hours a system can use 'free cooling' to cool a space, and dramatically reduce the amount of time a system has to operate at full speed. In addition, the Trane Voyager DC incorporates variable speed fans, staged compressors and other measures to maintain high efficiency rates.

For a product to be Western Cooling Challenge certified, it must be at least 40% more efficient than Department of Energy 2010 standards. Entries must also be market-ready. Following laboratory testing, the equipment was verified by the UC Davis Western Cooling Efficiency Center.

Trane is the first major manufacturer to enter the challenge, reflecting an industry interest in marketing air conditioning systems that are designed for specific climates.

Jonathan Woolley, UC Davis Western Cooling Efficiency Center associate engineer, said: 'Trane's Voyager DC met our performance goals on the mark and promises to be one of the most cost effective, climate-appropriate cooling technologies available for commercial buildings.'

Established in 2008, the challenge by the UC Davis Western Cooling Efficiency Center, is the most demanding certification of its kind. It aims to help manufacturers develop more efficient cooling technologies, particularly for hot, arid climates, such as that of California. The scheme also helps building owners to install and use those products.