Performance Loss Rates of a 1 MWp PV Plant with Various Tilt Angle, Orientation and Installed Environment in the Capital of Cyprus

Round 1

Reviewer 1 Report

In this paper, the authors have introduced an on-line diagnosis method using PV plant electrical output. I have some comments regarding this paper.

1.      Introduction should be revised. More recent related literature should be included.

2.      Some of the experimental papers related to PV degradation should be included, i.e.,

https://www.mdpi.com/1996-1944/13/2/470,

https://www.mdpi.com/1996-1944/12/24/4047

3.      The methods for PLR, i.e., STL, CSD, and YoY methods should be clearly defined.

4.      A detailed explanation for each model should be provided.

5.      The result obtained by this method should be compared with the other reported method.

6.      It should be explained, why degradation rates differ for each reason?

7.      The size of the texts of each Figure should be enlarged.

Author Response

"Please see the attachment."

Author Response File: Author Response.docx

Reviewer 2 Report

The paper describes the determination of the performance loss rates. Overall, the paper is well done and presented. Here are some minor comments:

The two systems with pronounced soiling traces, Arena & Stonite, are also the ones with a low tilt explaining the higher soiling. It would be good to mention, there is a little bit of discussion on soiling further on, but it could be mentioned around Fig. 7.

Stonite appears to have a much higher loss than the other 2 systems, no matter the analysis. Can you speculate on why that might be? The downward traces that appear to be soiling in Fig. 7 are dramatic, in the 30-40% range. Perhaps more than just soiling? Stonite also happens to be the last system installed.

Line 155: diffuse irradiation

Figure labeling in the text seems to be off by one.

Line 371: should be Fig. 4.

Line 386: Fig. 5

Line 398: Fig. 6

Line 418: Fig. 7

Minor: In the graphs PLR (performance loss rate ) already contains the word “rate”, no need to have another rate “PLR rate”.

Author Response

"Please see the attachment."

Author Response File: Author Response.docx

Reviewer 3 Report

In the paper, the authors proposed a comprehensive method for calculating the performance loss rates of PV plant in different venues. Considering various tilt angles, orientations and installation environment, this method combined statistical methods with performance metrics. The feasibility and accuracy of the proposed method is validated on four-year power data measured by inverters.

In the current version, the novelty of the proposed method is not clear. The following comments are suggested.

 Q1. The statistical methods and performance metrics have been well studied and applied in Table 1. Besides, the in-plane irradiation model and temperature model in section 3 are just adding a contrast step to the existing models. Please highlight the contributions of this work with bullet points in section 1.

 Q2. Although the authors claim to analyze a 1 MWp PV plant, the performance loss rate of the PV plant is still divided into three PV systems in section 4.2. How to measure the relationship between the whole PV plant and the local PV systems?

 Q3. Formula symbols in the paper need to be italicized and uniform format. For example, Eq. 2, Eq. 3, R2, T_{cell_type_avg}, etc.

 Q4. Some symbols are malformed in the text. For example, Idt, Id in line 166 and 167.

 Q5. The left of the Eq. 5 should be I_bt.

 Q6. The meaning of the symbols in Eq. 16-18 needs to be explained.

 Q7. What's the meaning of the last term of Eq. 19?

 Q8. Repeat the text of performance ratio in line 269.

 Q9. Improve the quality of all figures. Besides, the font in the figure and table should not be larger than the main text.

 Q10. Figure 3-6 do not match the reference position in the main text. For example, Figure 5 has no subgraphs in line 398.

 Q11. Figure 10 - add description.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Well done. Accepted.

Author Response

Dear Reviewr 

We would like to further thank you for the valuable feedback and comments once more.

Kind regards,

Authors

Reviewer 3 Report

Comments:

The comments have been addressed. However, some advices are listed below:

 1. Improve the quality of all figures. The resolution looks low.

 2. Uniform the table format. The content should not be italicized.

 3. PR-TC (line 588) and TCPR (line 604) in the paper need to uniform.

 4. R² (table 5) and R2 (table 6) in the paper need to uniform.

 5. Fix ‘Tabelle 5 MBE RMSE and R2 of the models’ >> ‘Table 5: MBE RMSE and R² of the models’ (line 420).

 6. Fix ‘T_{celltype_avg}’ >> ‘T_{cell_type_avg}’ (line 351).

Author Response

"Please see the attachment."

Author Response File: Author Response.docx