Spray Cooling in
In 1996 a WhiteCap™ roofing
system, which enables the downsizing of conventional cooling equipment, was
installed on a General Services Administration (GSA) Port of Entry station
In dry western and south-western US climates, where hot days are followed by cool nights with minimum temperatures below 65°F (18°C) typical capacities are 25 ton-hours per 1,000 square feet (93 square meters) of roof surface in peak conditions. Typical capacities tend to be higher in medium weather. For well-designed buildings with moderate loads, this typical capacity is sufficient to provide all cooling. For buildings with peak loads exceeding 25 ton-hours per 1,000 square feet, WhiteCap™ capacity allows significant downsizing of conventional cooling equipment.
Water usage is approximately 1.7 to 2.6 litres/kWh (0.15 to 0.20 gallons/kBtu) cooling. The installation saves about 1020 kWh/week in cooling energy.
Cost for design and construction of the system was approximately USD 28,500 (Note that the cost was relatively high because of the small scale of the project.) The system saves cooling energy worth USD 56 /week. Therefore in this case the WhiteCap™ system has a pay-off period of about 9.8 years.
Davis Energy Group
US GSA Tucson Field Office/9PMM-28
See also: Nightsky System Cools Roof Tops