Implementation of natural down-draft evaporative cooling devices in commercial buildings: the international experience.

Conventional evaporative coolers are high-pressure high-volume devices that deliver cool air by water evaporation wetted pads. Natural down-draft evaporative coolers, or "Cool Towers", are devices developed at The University of Arizona's Environmental Research Laboratory. Similar to conventional coolers, these devices are equipped with wetted pads and sprays at the top which provide cool air by evaporation but the air is moved by gravity flow saving the energy required by the blower. In arid regions, cool towers are useful for cooling buildings and outdoor private and public areas. This paper focuses on recent implementation of cool towers in two international projects in arid regions. It also demonstrates CoolT, a software developed by the author, which was used for sizing and designing the cool towers used in these projects. The two demonstrated projects are: 1) The Botswana Technology Center (BTC}, a Headquarters office building in Botswana, South Africa. The building energy loads were first optimized through energy conservation measures where the heating load, as predicted by computer simulation, was reduced by 89.9% and the cooling load by 24%. The cooling load was further addressed by the use of a series of integrated cool towers. 2) The Ministry of Municipal and Rural Affairs (MOMRA) ''Environmental Rowdah" project in Riyadh, Saudi Arabia is the second, recently built, project which demonstrates the use of cool towers in outdoor spaces. Tue Rowdah is equipped with a 76 feet high cool tower, the biggest in the world, which provides cool air to the surrounding outdoor space. The tower performance, as predicted by the CoolT program, demonstrated that on a typical June day in Riyadh, at 3:00 p.m. the ambient air temperature of 107.1°F {41.7°C) will be cooled down to 73.9°F (23.2°C) i.e. 33.2°F (18.4°C) lower, but the 13% relative humidity of air is increased to 75% at the tower discharge.