Examination of the theoretical model for flat-plate solar collectors and integration with solar radiation decomposition/transposition models

Water heating and climatization are important segments of the residential energy consumption. In this regard, solar thermal energy is a great prospect for promoting energy sustainability. An experimental and theoretical examination of the classical model to evaluate the thermal performance of flat-plate solar collector (FPSC) was conducted in this work. The experimental data were obtained between the months of March and May in Porto Alegre city, Brazil. The model was also integrated with a solar radiation model, for which sixteen combinations of decomposition/transposition models were evaluated. The three best combinations of decomposition/transposition models were identified. The experimental data were compared with the classical model, called M1, obtaining a relative error (RE) between 1.98 and 11.48% and a mean relative error (MRE) of 6.38%. Afterward, two correction factors were identified by the theoretical examination of the classical model. These factors were implemented to correct the determined value of the useful energy. Moreover, two new models, which incorporate the correction factors, were tested, namely, models M2 and M3, respectively. These models were compared with experimental data. The results show a MRE of 4.35 and 3.38%, respectively. Therefore, model M3 showed better results than the classical model M1. A case study was carried out implementing the model M3 to study the FPSC performance in Porto Alegre, Brazil.