Impact of faults on the efficiency curve of flat plate solar collectors: a numerical analysis

Abstract Thermal solar energy is one of the promising cleaner ways to produce heat. In particular, large scale solar thermal systems (LSTS) can produce low-cost heat for use in district heating networks or industrial processes. However, return on investment is based to long-term reliable operation, and automatically detecting dysfunctions is desirable in these systems. Existing fault detection and diagnosis methods are applicable on many components in such a system, but the impact of faults on solar collectors received little attention. In this paper, the impact of three different faults on solar collectors is analyzed: the « transparent cover failure » fault, the «opacification » fault and the « insulation degradation » fault. To perform this analysis, a numerical model covering both normal and faulty operation is proposed. The model can be tailored to a given solar collector based only on datasheet parameters, and the experimental validation shows a good accuracy, without any calibration, both in normal and faulty operation. This model is used to study in detail the impact of the three studied faults on the solar collector efficiency curve. The results show that some assumptions made in previous work can be challenged, while other are validated for a wider range of conditions thanks to the model presented in this paper.