Flat plate thermal solar collector efficiency: Transient behavior under working conditions part II: Model application and design contributions

• Published in: Applied thermal engineering Vol. 31; no. 14; pp. 2385 - 2393
• Main Authors: Rodríguez-Hidalgo, M.C., Rodríguez-Aumente, P.A., Lecuona, A., Gutiérrez-Urueta, G.L., Ventas, R.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-10-2011; Elsevier
• Subjects: Accumulators; Applied sciences; Collector performance; Collector thermal efficiency; Collectors; Energy; Energy. Thermal use of fuels; Engineering Sciences; Exact sciences and technology; Flat plate collector; Flat plates; Heat transfer; Inertia; Mathematical models; Mechanics; Natural energy; Physics; Solar collectors; Solar Domestic Hot Water; Solar energy; Solar thermal conversion; Theoretical studies. Data and constants. Metering; Thermics; Transient model; Wind velocity; Collector thermal efficiency; Transient model; Collector performance; Flat plate collector; Solar Domestic Hot Water; Solar energy; Solar collector; Ageing; Unsteady state; Wind velocity; Modeling; Steady state; Standards; Operating conditions; Accident; Hot water production; Thermal efficiency; Working condition; Performance
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2011.04.002

An experimental research was performed on a solar facility with a nine-year-old, on-campus field with 50 m
2 area of flat plate solar collectors. A transient model was developed, adapted to the characteristics of this facility and experimentally validated as described in Part I of this paper.
The efficiency normalization curve (ENC) operating conditions for the steady-state test are different from the working conditions. Significant differences between the ENC and the model based predictions were found and quantified.
The significance of the transient behavior is compared with the thermal inertia proposed in the EN-12975:2006 standard for the quasi-dynamic test.
Using the model capabilities to predict the collector performance under transient working conditions, the influence of the operating conditions on the collector efficiency and on the useful heat produced is studied individually. The relevance of those conditions is ranked as follows: the wind (velocity magnitude and direction) was the most influential, followed by the aging of the collector surfaces, convective heat losses, thermal inertia and the incident angle of irradiance.
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► The model predicts the solar field efficiency under real operating conditions. ► Results evaluate the influence of working conditions on the efficiency. ► Collector normalizing curve is recovered for the corresponding operating conditions.