Overall statement:

The researchers presented a comprehensive numerical study on impact of solar irradiance and fluid inlet temperature on PV/T with nanofluid (Al2O3-water) and without (pure water). The findings display minimal change in efficiency variation (as per fig. 7) when using water, or nanofluid (2% weight). The authors found a maximum temperature difference between the two fluids of 3 kelvin.

Strengths:

The strength is that the study carries out a CFD to simulate the behavior of PV/T whereas many other papers only focus on energy-balance. The authors did well in justifying the assumptions made in the numerical study and supported their claims with quality references. Moreover, the MAPE of study is 7.46% which is acceptable (less than 10% [1] ).

1. The authors claim the environmental parameters studied are solar radiation and inlet fluid temperature. However, I would not consider the inlet fluid temperature to be environmental but more of an operational parameter which can be altered using heat exchangers or having different designs [2].

2. It would’ve been much appreciated to include a photo of the mesh or dimensions of geometry; even though design is similar to ref. 55. The same point applies to the lack of temperature distribution figures in the article.

3. Considering only one pipe has its disadvantages. The accuracy could be improved by considering the entire design shape of absorber with consideration for pressure drop which occurs throughout the process. This point could be utilized for future complimentary research to have a more sophisticated understanding of the performance.

4. To provide context when discussing electrical efficiency, it is recommended to calculate the electrical efficiency of PV module only and compare to effect of cooling by water or nanofluid. However, I understand it is not necessarily the scope of the research.

Minor points: 1. The photovoltaic (PV) used is a module not a panel. 2. The nomenclature assigns two different descriptions to two identical symbols (P), this could be confusing for the readers. 3. th (for thermal) and Elec (for electrical) should be added to subscripts. Also, it is recommended to edit nomenclature in alphabetical order.

. 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.

References:

[1] C.D. Lewis. Industrial and Business Forecasting Methods. Butterworths. 2,194-196, (1982). [2] Elbreki, A. M., Alghoul, M. A., Al-Shamani, A. N., Ammar, A. A., Yegani, B., Aboghrara, A. M., ... & Sopian, K. (2016). The role of climatic-design-operational parameters on combined PV/T collector performance: a critical review. Renewable and Sustainable Energy Reviews, 57, 602-647.