Energy / Climate Change

December 19, 2007


Cooling Effect of Sprinkling Water on Photocatalyst-Coated Glass Demonstrated

Keywords: Climate Change Environmental Technology Local government Manufacturing industry University / Research institute 

On August 29, 2007, the New Energy and Industrial Technology Development Organization (NEDO), a Japanese independent administrative institution, demonstrated the cooling effect of a system that sprinkles water on a glass coated with photocatalysts, and was the world's first demonstration of this system using a real building. The demonstration was part of a project for developing practical applications of photocatalytic technology invented in Japan. Project members include the Waterworks Department of Yokohama City, YKK AP Inc., Nippon Sheet Glass Co., and Sekisui Chemical Co.

The demonstration involved photocatalyst-coated glass curtain walls approximately 130 square meters in area and water sprinkling systems; it revealed that the evaporation of water thinly spread on the surface of the glass helped reduce the temperature of the room by about two degrees Celsius and the temperature of the glass surface by about 10 degrees. The demonstration showed that this system can reduce the amount of heat radiated from the glass and also reduce the air-conditioning load by about 20 percent. Thus, this technology could also potentially be applied as way to deal with the urban heat island effect by curbing rises in outer air temperature.

From 2003 through 2005, NEDO tested the new cooling system, which combines photocatalysts (titanium dioxide) with an efficient water sprinkling system, on college campuses and elsewhere. These tests were part of a project to develop highly functional housing components using photocatalysis. The room temperature lowering effect and a 10 to 30 percent reduction in air conditioning loads have been consistently obtained throughout the project.

The present demonstration using a real building verified the effectiveness of this cooling system, not only for conserving energy but also for mitigating the urban heat island effect. A computer simulation also revealed that application of this system for an entire residential block would result in improvements in environmental problems involving thermal radiation from buildings heating nearby outdoor living spaces; temperatures from thermal radiation were decreased by approximately six degrees Celsius (the maximum average figure for areas in the shade).

Posted: 2007/12/19 02:21:36 PM
Japanese version