Investigation of Solar Chimney System and the Effct of Thrmal Storage Capacity on the System Performance Part I: Experimental Investigation

Abstract

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 fild 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. Th investigation also include the effct
of thermal storage on the temperature fild. Th solar chimney system contains two main components; the solar collector and the solar chimney. Th 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 effct 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 diffrent levels throughout the collector. Solar irradiance was found to affct the chimney temperature and subsequently chimney air velocity. The temperature diffrence between the hot air at chimney entrance and the ambient reached about 45 °C, which generates the driving force of airflw in the chimney. Th hot air velocity in the chimney can reach 3.6 m/s (≈ 0.118 kg/sec). Wind speed was found to have a small inflence 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 suffient amount of heat through the use of additional heat storage such as water, which raises the air temperature in the collector aftr sunset to a suffient value capable of generating air flw for a long time to run turbines to produce electricity during the day and aftr sunset especially during the summer time.