TECHNIQUES TO REDUCE THE ENERGY CONSUMPTION IN BUILDING IN HOT ARID REJOIN

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1 TECHNIQUES TO REDUCE THE ENERGY CONSUMPTION IN BUILDING IN HOT ARID REJOIN Prof. Dr. Ghanim Kadhem Abdul Sada Mechanical Engineering Dept. / Al Mustansiriya University Baghdad IRAQ ghanimkadhim@yahoo.com ABSTRAC: The sun is powerful energy source. Early cultures were adapted to using the sun to temper their indoor climates. They chose orientations, design and materials that exploited this powerful energy source. Now days the unnecessary energy consumption by buildings has become a matter of concern and criticism. The researchers and other professionals have begun a search for a more acceptable and responsible design of the buildings. The Iraqi climate is extremely hot and arid zone covers a belt between 29 ºto 36 º N, The energy required for air conditioning the Iraqi buildings is about 60% of the entire energy consumption in buildings. This research deals with the possibility of using different technics for the reducing energy consumption in building by blocking or eliminates the effect of direct solar radiation in summer season. The results show that thermal conductivity of local insulation materials are very low, so that is consider a good insulation materials for Iraq buildings.the energy transmission through the roof surface is about 4%. This system reducing energy consumption in building during summer season which is the cooling is dominated in Iraq. Keywords: passive system, insulation materials, water spray system, 1. INTRODUCTION In hot climates in earlier day man had to protect himself against the temperature rise because there was no possibility to cool his living space by any artificial means, Thus in traditional houses local materials were often combine with suitable house design in order to maintain a good shelter against the hostile environment [1]. There were always foresight solutions that brought the indoor environment to the human comfort level or to acceptable conditions. This need for keeping the indoor condition within the comfortable level by natural means is call passive cooling systems.passive cooling refers to technologies or design features used to cool buildings naturally. The term passive implies that energy-consuming mechanical components like pumps and fans are not used [2]. The problems of maintaining suitable indoor comfort conditions can be solved by studying the effect of design variations on the thermal performance of the building. This can be done by examining both the old methods of construction and design. In hot climate such as Iraq ( lat N) is characterized by a long hot summer season,and short cold season. Therefore the cooling systems is required over the hot summer period. Hence the cooling demand is dominate in Iraq [3]. It is important to protect the building envelope against the direct incident of solar radiation. The buildings in Iraq are built from bricks walls and concrete flat roofs, Which are acts as a solar collectors [4].The exterior surface of the roofs of the buildings are exposed to solar radiation so that most solar radiation absorbed by roofs,therefore emitted heat to the interior living spaces of the buildings. There are techniques for cooling the buildings by using passive systems. Passive cooling refers to technologies or design features used to cool buildings naturally. Passive cooling building design attempts to integrate principles of Physics into the building exterior envelope to slow heat transfer into a building, by using thermal insulation to reduce the heat transfer through the wall and roofs or by using water spray upon the exterior roof surfaces.

2 The usage of passive cooling techniques in modern buildings however, can often eliminate the need for mechanical cooling or at least significantly reduce the size and cost of the equipment. This study deal with different insulation materials were added to the south face of walls surface, as well as water spray system upon the exterior roof surface to minimize the effect of incident solar radiation upon the roofs and wall surfaces. The results show that thermal conductivity of local insulation materials are very low, so that is consider a good insulation materials for Iraq buildings.the energy transmission through the roof surface is about 4%. This system reducing energy consumption in building during summer season which is the cooling is dominated in Iraq. 2.THERMAL INSULATION MATERIAL Many experiments are done to measure the thermal conductivity of different local materials at different conditions; such as papyrus, and palm leaves. The thermal conductivity of papyrus material was (0.059 W/ m. k). Therefor the thermal conductivity of papyrus is low,so that these materials consider a good thermal insulation as well as low cost. The villages in the south of Iraq are build the walls and roofs from papyrus. The confortable conduction inside door of these houses are accepted conditions without using air conditions units. 3.WATER SPRAY ROOF SYSTEM Water spray roof system (WSRS) is an integrated roof surface, provides a means to cool the roof surface and eliminate the effect of solar radiation which is incident upon external roof surface causing increase the heat gain transfer to inside living space. WSRS is suitable for hot and dry climates such as Iraq and other hot arid reigns. WSRS consisting of a piping grid and conventional water spray nozzles is installed on the roof surface as shown in figure (1), and connected to water pumping, to sprayer water, over the external roof surface and kept it wet. Experimental work has been done in Baghdad Iraq (Lat 33 N) for two hot days (7 & 8) July. The roof of the building is divided in to two zones one zone is wet surface and the other zone is dry surface. 4. RESULTS AND DISCUSSIONS - The results show that the papyrus insulation material is used upon the roofs and south walls surface of houses building reduces the heat flow inside the living space from 98 W / m 2 for un insulated roof to 17 W / m 2, insulated roof by papyrus,25 mm thickness. The results of this experimental work of water spray system are shown in the following figures. Fig (1) show the incident solar radiation on a horizontal surface on Baghdad (lat.33 N ) for two days 7 & 8 July.These days are choose because the maximum amount of solar radiation in this month which measured in Baghdad. Figures. (2) & (3) shown the three curves, these are dry surface temperature, ambient temperature and wet surface temperature. Note from the figures that when using water spray the roof surface temperature decreases, from 51 C to 23.5 C The decrease in wet surface temperature due to present of water upon the roof, which are reduce the intensity of solar radiation incident on the roof as well as the evaporation of water absorbed heat from roof surface. The temperature of water spray is 23 C. Fig (4) shown the amount of heat transfer through the roof to indoor living space. The heat transfer is reduced about 96%, when using water spray roof system. 5. CONCLUSIONS Many conclusions can be drawn from this study which can be summarized as follows. 1-The local thermal insulation materials are available in Iraq such as papyrus palm leaves, good insulation with low cost. 2- The roofs in Iraq's building working as solar collectors. 3- Minimized the effect of solar radiation upon the roofs surfaces by using water spray roof system. 4- Hence the heat transfer from outdoor to indoor through the roofs is small. Hence large moment of energy will be saved with using water spray roof system. 5- This method WSRS gives good indication to use it in building in hot arid rejoins.

3 6.REFERENCES :- (1)Inaam Amen Al bazaz The use of solar energy in buildings M.Sc thesis Baghdad university (2) Muthana l. Abdullah The effect of local insulation in building M.Sc thesis Mustansiriya university (3) Abdulsada G. K Appropriate techniques model to minimize environments impacts of building (paper summated to ISES solar world congress 2006.Florence Italy ). (4) Abdulsada G.K. Minimizing effect the impact of enlivenment upon residencebuilding in hot arid regions (Iraq) " 8 UTEG10, Clean Energy congress 2010 Turkish (5) Iraq Meteorological Organization Climatic ATLS of Iraq.1993

4 Fig. 1: Water spray system

5 Solar radiation (W/m²) rariation on 7 july incident on 8 july Gx on 7 july Gx on 8 july Local Time ( hr ) Fig. 1 : show the incident solar radiation on a horizontal surface measured In Baghdad lat. 33 N ref. [5]. Temperature, ( C ) Data on 7 July 2004 Ambient temperature Wet surface (measure) Dry surface (measure) Wet surface (theoretical) Local Time, ( hr ) Fig. 2 : show the effect of using water spray roof system on the temperature of roof surface in Baghdad on 7 July

6 Temperature ( C ) Data on 8 july 2004 Ambient Wet surface measure Dry surface measure wet surface thioretical Local time ( hr ) Fig. 3 : show the effect of using water spray roof system on the temperature of roof surface in Baghdad on 8 July. 48 Heat gain through roof per unit area, W/m² Effect of using WSRS on 8 July 2004 With using WSRS Witout using WSRS Local Time ( hr ) Fig. 4 : show heat gain through the roof with and without water spray roof system.