Apparent delay analysis for a flat-plate solar field model designed for control purposes

• Published in: Solar energy 2019-01, Vol.177, p.241-254
• Main Authors: Ampuño, Gary, Roca, Lidia, Gil, Juan D., Berenguel, Manuel, Normey-Rico, Julio E.
• Format: Article
• Language: English
• Subjects: Bilinear model; Delay; Dynamic models; Dynamic simulation; Energy balance; Error analysis; Error reduction; Heat transfer; Pipelines; Solar energy; Step response; Temperature; Test procedures; Thermal energy
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2018.11.014

•A temperature delay is observed in solar fields based on flat-plate collectors.•The effect of the apparent delay can be demonstrated with first-order models.•Dynamic model validation is improved through the inclusion of the apparent delay in a bilinear model. This study presents an analysis of the effect of the transport delay which occurs in solar flat-plate collector fields and how to include its behavior in dynamic models suitable for control purposes. This investigation has been carried out using simplified models based on dynamic energy balances and models based on step response methods and experimental tests. The solar flat-plate collector field encompasses parallel absorber pipes intertwined with pipelines which act as several first-order plus dead time systems in parallel. The effect is an apparent delay observed at the outlet temperature that must be included in the dynamic model in order to reduce the error between the real measurement and the model prediction. The main contribution of this paper is the procedure to evaluate the apparent delay to obtain adequate dynamic models aimed to be used for control purposes.