Investigation of thermal concentration effect in a modified solar chimney

Abstract

In solar chimney the flow of air in the system plays a dominant role. Solar chimney systems are usually large and have a low efficiency. In this research a redesigned experimental solar chimney power plant with a modified collector layout was evaluated. A tracking mirror reflector was used to enhance the thermal concentration effect underneath the chimney. The emphasis was on increasing the temperature at the transition zone between the collector and the chimney base and creating an improved overall temperature difference. Mathematical analysis of the thermal and flow behavior of the currents, under the influence of the concentration effect from the reflector, led to the development of a simulation algorithm to assist in the evaluation process. A comparative analysis was applied to investigate the effect of thermal concentration on the air flow velocity under the chimney. The indicators were the variation of the overall thermal radiation in the transition zone and the instigated temperature rise with hourly ambient temperature change. The obtained results suggested up to 10.25% increase in the maximum temperature obtained at the chimney base. This induced a maximum air flow velocity improvement of 22.22%. The impeding effect of density reduction at the considered temperature range was checked against the total theoretical output power. At peak output when the power scored 56.867% rise from the average for the day, air flow velocity showed 25.316% increase while the air density was reduced by only 2.069% from the mean values for the day.