Overall statement:

The researchers presented a mathematical model of a static miniature solar concentrating PV/T system to indicate its performance. Numerical simulations were made using CFD and compared to results of experiments conducted outdoors. The authors concluded that the proposed, or studied, system exhibits lower heat loss coefficient; hence supporting their hypothesis.

The strengths

The study offers a comprehensive mathematical model, followed by excellent CFD simulation. Moreover, the methodology is sound, and justifications are offered throughout the manuscript (e.g. manuscript). The authors justified the use of the proposed system of CPVT stating

“the common CPV or CPV/T systems always need the tracking systems and many operation components, which are difficult to integrate with buildings.”

All references employed are relevant to the research.

Weaknesses

1. The software used for CFD was not mentioned. Although professionals can guess the software from the meshing, it is important to declare the type of software used in the study. Moreover, the size of mesh was not indicated as well. Mesh size is declared in others numerical studies [1-3]
2. The error analysis does not consider the uncertainty analysis. It is appreciated to include uncertainty analysis for the experiments in future work [4-6].
3. Although the calculation of PV efficiency is presented, it is recommended to include the specifications of PV used. This will offer the readers better understanding of the experimental setup, and behaviour of PV/T in outdoor conditions.

Minor points: 1. Solar radiation is better referred to as Solar Irradiance (W/m2) [7]

Future work can be done by comparing the proposed system with conventional CPVT, experimentally in outdoor conditions. Moreover, to test the electrical characteristics of the PV in detail.

References: [1] Karanth, K. V., Manjunath, M. S., & Sharma, N. Y. (2011). Numerical simulation of a solar flat plate collector using discrete transfer radiation model (DTRM)–a CFD approach. In Proceedings of the world congress on engineering (Vol. 3, pp. 6-8). [2] Zogou, O., & Stapountzis, H. (2012). Flow and heat transfer inside a PV/T collector for building application. Applied energy, 91(1), 103-115. [3] Getu, H., Yang, T., Athienitis, A. K., & Fung, A. (2014). Computational Fluid Dynamics (CFD) Analysis of Air Based Building Integrated Photovoltaic Thermal (BIPV/T) Systems for Efficient Performance. In eSIM 2014 Conference Proceedings. [4] Taylor, J. (1997). Introduction to error analysis, the study of uncertainties in physical measurements. [5] Ghadiri, M., Sardarabadi, M., Pasandideh-fard, M., & Moghadam, A. J. (2015). Experimental investigation of a PVT system performance using nano ferrofluids. Energy Conversion and Management, 103, 468-476. [6] Al-Waeli, A. H., Sopian, K., Chaichan, M. T., Kazem, H. A., Ibrahim, A., Mat, S., & Ruslan, M. H. (2017). Evaluation of the nanofluid and nano-PCM based photovoltaic thermal (PVT) system: an experimental study. Energy Conversion and Management, 151, 693-708. [7] Duffie, J. A., Beckman, W. A., & Worek, W. M. (1994). Solar engineering of thermal processes.

• This is a post-publication review. The adherence to journal guidelines is not considered as the paper has already been processed by editorial team of the journal