**1. Introduction**

Solar chimney with passive cooling tower design (SCPC) is a system that uses solar energy that strikes the aluminum and glass in a chimney to generate a buoyancy force in the chimney. This force drives outside hot air to pass through the evaporative pad (expanded paper) and causes reduction of indoor temperature, high humidity and constant enthalpy [1]. The thermal

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

performance of solar chimneys using different configurations has been experimentally investigated by different researchers. The concept of metallic solar wall (MSW) on a full-scale model was studied for a single-room house under tropical climatic conditions in Thailand. It was shown that a MSW with 2 m height and 0.145 m air gap (cavity between glass and aluminum) can produce a mass flow rate up to 0.02 kg/s for a house with a base area of 11.55 m<sup>2</sup> and a height of 2.68 m and optimum natural ventilation. Such low-cost solar chimney construction can significantly reduce heat gain in the house by creating adequate flow rate to improve thermal comfort [2]. The thermal performance of a solar chimney was investigated on a full-scale model under Mediterranean daylight and night-time conditions for natural ventilation. A 4.5 m high, 1.0 m wide and 0.15 m thick reinforced concrete wall was used as a solar absorber, whose southern surface was painted matte black with insulation on the side and back surfaces. The absorber wall was covered by glass of 0.1 m thickness to reduce the convection heat. With this configuration, a maximum flow rate of 374 m<sup>3</sup> /h was reported at a solar intensity of 604 W/ m2 occurring at around 13:00 h. Discharge coefficient was experimentally determined to carry out volumetric flow rate calculation. It was concluded that the airflow rate through a solar chimney system is greatly affected by the pressure difference between openings caused by thermal gradients and by wind velocity [3]. An experiment of solar-induced ventilation strategy was conducted. The experiment consisted of two parts, namely, a roof solar collector and a vertical stack. The purpose of the roof solar collector was to capture as much solar radiation as possible, thus maximizing the air temperature inside the channel of the roof solar collector. The heated air inside the channel rose and flowed into the vertical stack due to the pressure difference between the two zones. Meanwhile, the vertical stack was important in providing significant height for sufficient stack pressure. The walls of vertical stack were insulated to minimize the heat loss to the environment. The findings indicated that the proposed strategy was able to enhance the stack ventilation, both in semi-clear sky and overcast sky conditions. The highest air temperature difference between the air inside the stack and the ambient air was achieved in the semi-clear sky condition, which was about 9.9°C (45.8–35.9°C). Besides, in the overcast sky condition, the highest air temperature difference was 6.2°C (39.3–33.1°C) [4]. Also, an experimental study of a vertical channel simulating a solar chimney and a Trombe wall was conducted. The vertical channel had a transparent cover and an absorber plate, painted matte black. The vertical channel was open at both ends, and its dimensions were 1.025 m high, 0.925 m wide and 0.02 m–0.11 m variable depth. Heat input to the absorber plate was supplied by electrical means (200–1000 W) in steps of 200 W. Air temperature and velocity measurements inside the channel were obtained. The results showed that air temperature was increased continuously along the channel height, while the cover and the absorber plate temperatures were not. The cover temperature, as well as the absorber plate temperature, increased continuously to the middle height and then began to decrease. The authors concluded that the mass flow rate is a function of the heat input as well as on the channel depth, while the efficiency of the system is a function of the heat input only [5].

for mechanical cooling systems [10]. This traditional technique was based on natural environmental conditions such as wind, water and vegetation to achieve significant indoor thermal comfort [11]. It was concluded that if passive solar solutions are integrated in existing buildings, building energy demand can be reduced [12]. Many researches have been conducted to examine passive cooling strategies in the buildings. Maerefat and Haghighi studied solar chimney integrated with evaporative cooling cavity. This integrated system was capable of providing good indoor conditions during daytime in the living room [10]. Alemu et al. developed a model using passive cooling technique in earth air tunnel. This model investigated the integration of passive techniques [13]. Developing solar chimney with direct evaporative cooling tower using numerical simulation was done using COMIS-TRNSYS software to provide indoor thermal comfort under the climatic conditions of Assiut, Egypt. The results show

[7, 8]. Macias et al. developed a passive cooling system for a residential building. Natural ventilation was enhanced with the aid of a solar chimney, and fresh air was cooled down by circulation within the duct area of the building. It was found that the passive cooling system allowed for ensuring thermal comfort through low conventional energy consumption based

No experimental studies were found for the integration of solar chimney with cooling strategies in residential buildings in Egypt except for the ventilated Trombe wall as a solar heating and cooling for building retrofitting in semiarid climate (Saint Katherine, Egypt) [15]. The purpose of using solar chimney is to generate natural air movement and improve stack-

ings in Egypt. The main aim of this study is to investigate the performance of an (SCPC) integrated within a room as a passive cooling technique to provide sufficient fresh cooled air, indoor comfort, and reduce room cooling loads. This stage is the second phase of a project for developing an integration of solar chimneys with passive cooling technique (SCPC) to reduce

A single room was built in Assiut University (El-Gorib site) in Assiut, Egypt. Room dimensions are 3.8 x 3.8 x 2.8 m (L × W × H) based on the previous numerical model of solar chimneys integrated with passive cooling [7, 8]. It is located at a latitude of 27°3'N and a longitude of 31°15′ E. In terms of climatic characteristics, Assiut is located in southern Upper Egypt zone. It is characterized by hot dry summers with a maximum outdoor temperature that ranges from 41–46°C and a minimum temperature that ranges from 16–21°C in the summer

at 2-minute time interval to analyze 1-year data (2015). **Figure 1** shows the temperature and humidity patterns of 2015. Selecting 2 months for monitoring (August and September) was done to test indoor environment using passive air conditions. These periods were selected to

in the winter. Outdoor climate analysis was done based on field measurements

/h with indoor thermal comfort of 80% acceptable range

New Passive Cooling as a Technique for Hot Arid Climate

http://dx.doi.org/10.5772/intechopen.74081

85

concentration and indoor comfort for low-energy build-

in the summer and 650

that the system generates 130.5 m<sup>3</sup>

on a 2-year monitoring period [14] .

induced ventilation with low CO<sup>2</sup>

to 800 W/m<sup>2</sup>

energy used in buildings in Assiut, Egypt.

**2. Test room and SCPC system description**

months. This zone has a global radiation range of 1000 to 1125 W/m<sup>2</sup>

It was concluded that a serious problem of discomfort exists inside houses in projects of new Assiut city based on natural ventilation strategy only [6–9]. Traditional passive techniques were used in ancient architectures to achieve the desired summer comfort without the need for mechanical cooling systems [10]. This traditional technique was based on natural environmental conditions such as wind, water and vegetation to achieve significant indoor thermal comfort [11]. It was concluded that if passive solar solutions are integrated in existing buildings, building energy demand can be reduced [12]. Many researches have been conducted to examine passive cooling strategies in the buildings. Maerefat and Haghighi studied solar chimney integrated with evaporative cooling cavity. This integrated system was capable of providing good indoor conditions during daytime in the living room [10]. Alemu et al. developed a model using passive cooling technique in earth air tunnel. This model investigated the integration of passive techniques [13]. Developing solar chimney with direct evaporative cooling tower using numerical simulation was done using COMIS-TRNSYS software to provide indoor thermal comfort under the climatic conditions of Assiut, Egypt. The results show that the system generates 130.5 m<sup>3</sup> /h with indoor thermal comfort of 80% acceptable range [7, 8]. Macias et al. developed a passive cooling system for a residential building. Natural ventilation was enhanced with the aid of a solar chimney, and fresh air was cooled down by circulation within the duct area of the building. It was found that the passive cooling system allowed for ensuring thermal comfort through low conventional energy consumption based on a 2-year monitoring period [14] .

No experimental studies were found for the integration of solar chimney with cooling strategies in residential buildings in Egypt except for the ventilated Trombe wall as a solar heating and cooling for building retrofitting in semiarid climate (Saint Katherine, Egypt) [15]. The purpose of using solar chimney is to generate natural air movement and improve stackinduced ventilation with low CO<sup>2</sup> concentration and indoor comfort for low-energy buildings in Egypt. The main aim of this study is to investigate the performance of an (SCPC) integrated within a room as a passive cooling technique to provide sufficient fresh cooled air, indoor comfort, and reduce room cooling loads. This stage is the second phase of a project for developing an integration of solar chimneys with passive cooling technique (SCPC) to reduce energy used in buildings in Assiut, Egypt.
