Steady state operation exergy‐based optimization for solar thermal collectors

Abstract

AbstractIn this investigation, exergy‐based optimization was carried out on two configurations of solar thermal collectors. A set of control sensors were utilized to control the performance of the system and monitor the design variables, that is, inlet and outlet temperature of the solar fluid, ambient temperature, incident solar flux, and required mechanical and electrical work in the system. The fluid temperature was considered to vary in the range of 120–180°C with respect to technical and economic considerations. The collector surface area was considered 606 m2 in both configurations, and a medium solar incident was considered about 520 W/m2. The maximum acceptable temperature difference is obtained as function of the input temperature. The technical limitation is plotted for both configurations of solar collectors. It was noticed that the exergy flow of simple evacuated tubes can reach the maximum value when the input temperature is greater than 115°C for an incident solar flow, from 250 W/m2 up to the limit of 950 W/m2. Exergy analysis demonstrated that more control is required on the temperature control to obtain the optimum performance of the solar collector. Thus, applying exergy optimization approach can be very useful to guide control system, the maximum outlet temperature being a key variable on the performance of the collectors.