Thermal Performance of Parabolic Trough Solar Collectors under the Condition of Dramatically Varying DNI

Frequently interrupted by dense clouds during the operational period, the thermal performance of parabolic trough solar collectors will experience considerable variations. Therefore, both theoretical and experiment studies were developed to analyze the dynamic thermal performance under the condition of dramatically varying direct normal solar irradiance (DNI) based on energy balance equations and a thermodynamics analysis. Particularly for a closed system, this unfavorable weather condition leads to the variation in the outlet temperature of parabolic trough solar collectors. Consequently, both of main factors which impact on the running status of the whole system are coupled to make heat transfer processes complex. In order to eliminate important errors due to fluctuations of the outlet temperature and DNI, the differential control volume methodology was used to model the solar irradiance in each volume based on the time intervals of the data acquisition system.