Reducing the Cooling Load by Evaporative Cooling of the Roof
Dr Sahar Najib Kharrufa, University of Ajman, UAE
Yahya Adil, University of Technology, Iraq
ABSTRACT
Air conditioners consume large amounts of power to cool a building. The purpose of this paper is to test a method using evaporative cooling to reduce this load. An evaporative air cooler is used to cool the roof of a building. This should result in a lower temperature inside which would consequently lead to a drop in the cooling load as well. The tests were conducted in the hot dry weather of Baghdad, Iraq.
Evaporative cooling is cheap and only uses a fraction of the power that compressor units do. Furthermore its cooling effect increases with the rise in temperature and drop in humidity, conditions that prevail in large parts of Iraq.
The test included setting up a thermally insulated compartment above an isolated room. The compartment was cooled by a small evaporative cooler. The walls of the room itself were insulated by adding a 2cm layer of Styrofoam as well as a 10cm air cavity.
The results showed that the combination of roof cooling and wall insulation resulted in an average 5.5oC drop in interior temperature, compared to an ordinary room. A computer simulation showed that this would reduce the cooling load on a compressor air conditioner utilized to further cool the interior by around 38%. These figures are based on the assumption that the temperature inside the room is cooled to acceptable comfort levels.
Keywords
Roof pond; sustainable design; energy conservation; evaporative cooling; cooling load; roof cooling.
Published in: "Energy and Buildings: Efficiency, Air Quality, and Conservation", Nova Publishers, Editor: Joseph B. Utrick, 2009.