The performance and the thermal behavior of the solar chimney were investigated experimentally. The experimental data were collected from small pilot solar chimney which was designed and constructed at Sabratha Faculty of Engineering-Libya. Solar chimneys need solar radiation in order to work, thus, to have more stable condition, solar energy should be stored during the day and released back during the night. In order to investigate the temperature field during daylight and hours of darkness, the data were collected for a period of 24 hours for several days of months, May and June 2014. The investigation also include the effect of thermal storage on the temperature field. The solar chimney system contains two main components; the solar collector and the solar chimney. The solar collector roof has a circular area of 126 m2. A PVC pipe 0.2 m in diameter and 9 m in height was used as a chimney. Water containers were put as thermal blocks to study the effect of thermal storage on the performance of solar chimney. The measurements included the intensity of solar radiation inside/outside the collector, temperature and velocity of heated air at the entrance of the chimney, temperature and speed of wind outside the collector, temperature of the ground inside the collector and temperature measurements of air at particular points at different levels throughout the collector. Solar irradiance was found to affect the chimney temperature and subsequently chimney air velocity. The temperature difference between the hot air at chimney entrance and the ambient reached about 45 °C, which generates the driving force of airflow in the chimney. The hot air velocity in the chimney can reach 3.6 m/s (≈ 0.118 kg/sec). Wind speed was found to have a small influence on the performance of the solar chimney. The results indicate that the solar chimney system can operate in northwestern Libya. If this type of system is used on a large scale it can trap solar radiation and store a sufficient amount of heat through the use of additional heat storage such as water, which raises the air temperature in the collector after sunset to a sufficient value capable of generating air flow for a long time to run turbines to produce electricity during the day and after sunset especially during the summer time.
Solar chimney; buoyancy effect; thermal storage; renewable energy