Thermodynamic investigation and optimization of a low-concentrating photovoltaic thermal collector
摘要
The primary objective of this study is to advance the thermodynamic understanding and operational efficiency of flat-plate solar collectors by conducting an exergy-based optimization using real collected experimental data. To achieve this, the research explicitly avoids simplifying assumptions frequently adopted in previous works—including constant overall heat loss coefficient and equalization of inlet fluid temperature to ambient—and instead incorporates actual measured variations from a closed-loop experimental setup. Key scientific contributions include: (i) systematic evaluation of upper, lower, and side reflectors alone and in conjunction with focusing lenses, (ii) quantification of the dynamic behavior of the overall loss coefficient, and (iii) derivation of scenario-specific optimum operational parameters for exergy efficiency based on measured flow rates, solar flux, and inlet temperature. The study reveals that the use of reflectors alone resulted in the highest daily energy efficiency at 55.6% and exergy efficiency of 4.62% at solar noon, improving over the reference case by 3.4 percentage points. Parameter optimization showed the ideal flow rate to be around 0.01 kg s−1 and optimal inlet temperature near 70 °C, with exergy efficiency benefiting from increased solar flux (up to 1200 W m−2) but reduced by higher ambient temperature. These results demonstrate that advanced optical augmentation and real-time data-driven optimization can enhance collector exergy efficiency by over 20%, providing practical recommendations for next-generation solar thermal system design and deployment.