Effective Cooling System for Solar Photovoltaic Cells Using NEPCM Impingement Jets
Round 1
Reviewer 1 Report
The introduction/literature review should be enhanced to include other cooling technologies, and the assessment should be measured against some of these. the authors should show what was not adequately investigated in the previous studies on this subject, i.e. what is the research gap, as far as the parameters tested in this research are concerned.
The comparison should be made with zero nano-encapsulated phase change material (NEPCM) slurry, and all the results should be compared to reference case data.
Has the diameter of the nozzle been already optimized, or on what basis has the diameter of the nozzle been selected, as this would have a considerable impact on the jet quality for a given pressure or flow rate?
The results are very limited and lack discussion. This has impacted the conclusions which are very superficial. This should be expanded to include parametric analysis to result in "an effective cooling system" as indicated in the paper title. What is recommended in the conclusions is actually what this paper should have addressed, refer to the title of the research paper.
Author Response
Response to Reviewer 1 Comments
Point 1: The introduction/literature review should be enhanced to include other cooling technologies, and the assessment should be measured against some of these. the authors should show what was not adequately investigated in the previous studies on this subject, i.e. what is the research gap, as far as the parameters tested in this research are concerned.
Response 1: Thanks for your feedback. The literature review has been updated and the research gap is pointed out in the last paragraph of the introduction.
Point 2: The comparison should be made with zero nano-encapsulated phase change material (NEPCM) slurry, and all the results should be compared to reference case data.
Response 2: It has been added on Page 8 that “According to the obtained results, at the solar irradiation of 1000 W/m2, adding 2% of NEPCM particles into pure water of the JIC system reduces the PV temperature from 43 to 41.7 °C under the same operating conditions.”. However, the simulations of the PV/JIC system in 3D with the VOF model are highly expensive and we could run zero nano-encapsulated phase change material when the solar irradiation is 1000 W/m2.
Point 3: Has the diameter of the nozzle been already optimized, or on what basis has the diameter of the nozzle been selected, as this would have a considerable impact on the jet quality for a given pressure or flow rate?
Response 3: Thanks for pointing it out. We agreed with the reviewer, and the assumed diameter is based on the previous studies on similar geometries [1,2]. The nozzle diameter of 1 mm provided higher efficiency, while it increases the pressure drop and reduces the economic efficiency. A relevant discussion has been added on Page 3.
[1] Mohammadpour, Javad, Fatemeh Salehi, Mohsen Sheikholeslami, and Ann Lee. "A computational study on nanofluid impingement jets in thermal management of photovoltaic panel." Renewable Energy 189 (2022): 970-982.
[2] Javidan, Mohammad, and Ali Jabari Moghadam. "Experimental investigation on thermal management of a photovoltaic module using water-jet impingement cooling." Energy Conversion and Management 228 (2021): 113686.
Point 4: The results are very limited and lack discussion. This has impacted the conclusions which are very superficial. This should be expanded to include parametric analysis to result in "an effective cooling system" as indicated in the paper title. What is recommended in the conclusions is actually what this paper should have addressed, refer to the title of the research paper.
Response 4: This study is the primary research on the combination of the NEPCM slurry with JIC systems for PV panels. Thanks for pointing it out. We updated discussions relevant to each figure and also the conclusions to address your feedback.
Reviewer 2 Report
This paper numerically investigates the cooling system for solar photovoltaic cells using NEPCM impingement jets. The idea behind this study is novel and the contents of the article are explained well. However, there are few points that are needed to be addressed before accepting this in the journal “thermo”.
1. The literature review to illustrate the study gap is not enough. It should be comprehensive and include the thermal management systems based on PCMs and jet impingement I recommend the following papers to be added which are published recently in the prestigious journals.
(i) doi.org/10.1016/j.ijheatmasstransfer.2022.122591
(ii) https://doi.org/10.1016/j.renene.2022.03.069
(iii) https://doi.org/10.1016/j.renene.2022.09.004
(iv) doi.org/10.1007/s10973-019-08961-8
(v) https://doi.org/10.1016/j.ijheatmasstransfer.2019.118852
2. Novelty of this study should be explained further in the light of existing literature.
3. It would be better to add a separate sub-section for validation.
4. Grid independence should be performed and explained.
5. There is a lack of explanation of the physical phenomena behind the results.
6. The conclusion section can be improved further and it is advisable to add bullet points if possible.
7. The symbol of the degree should be corrected in the line 184.
Author Response
Response to Reviewer 2 Comments
This paper numerically investigates the cooling system for solar photovoltaic cells using NEPCM impingement jets. The idea behind this study is novel and the contents of the article are explained well. However, there are few points that are needed to be addressed before accepting this in the journal “thermo”.
Response: We appreciate your overall positive evaluation of the paper. We have tried to apply all helpful comments, meet expectations, and synthesize the gaps.
Point 1: The literature review to illustrate the study gap is not enough. It should be comprehensive and include the thermal management systems based on PCMs and jet impingement I recommend the following papers to be added which are published recently in the prestigious journals.
(i) doi.org/10.1016/j.ijheatmasstransfer.2022.122591
(ii) https://doi.org/10.1016/j.renene.2022.03.069
(iii) https://doi.org/10.1016/j.renene.2022.09.004
(iv) doi.org/10.1007/s10973-019-08961-8
(v) https://doi.org/10.1016/j.ijheatmasstransfer.2019.118852
Response 1: Thanks for suggesting the relevant references. They have been added to the literature review. The introduction has been accordingly updated.
Point 2: Novelty of this study should be explained further in the light of existing literature.
Response 2: The last paragraph of the introduction has been updated to address the reviewer’s feedback.
Point 3: It would be better to add a separate sub-section for validation.
Response 3: It has been noted.
Point 4: Grid independence should be performed and explained.
Response 4: Thanks for pointing it out. Further explanations have been added on Page 7 about the mesh study. However, since the grid independence study has been carried out in our previous study on the same geometry [1], we show the mesh study results.
[1] Mohammadpour, Javad, Fatemeh Salehi, Mohsen Sheikholeslami, and Ann Lee. "A computational study on nanofluid impingement jets in thermal management of photovoltaic panel." Renewable Energy 189 (2022): 970-982.
Point 5: There is a lack of explanation of the physical phenomena behind the results.
Response 5: The relevant discussion has been updated for each figure in the updated version of the manuscript.
Point 6: The conclusion section can be improved further and it is advisable to add bullet points if possible.
Response 6: Thanks for your feedback. It has been updated based on your comment.
Point 7: The symbol of the degree should be corrected in the line 184.
Response 7: Noted.
Reviewer 3 Report
Please see attached file.
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 3 Comments
In this manuscript, the authors present a numerical study regarding improving the efficiency of the photovoltaic system using jet impingement cooling. The effect of the solar irradiation, latent neat, mass flow rate, number of nozzles, and the jet-to-surface distance have been investigated. It has been shown that the efficiency of the photovoltaic system can be improved by optimizing the above parameters, though the improvement is not very significant. I would like to pass the following comments to the authors, the manuscript may be considered acceptance given these comments have been addressed.
Point 1: It would be helpful to explain how Eq. (11) is derived. Is this an empirical expression? If so, is there any limitation of using this expression?
Response 1: Thanks for your comment. All limitations to using this empirical expression Relevant explanation has been explained on Page 7
Evans’s empirical correlation (Equation 11) to calculate the efficiency of the flat silicon PV module (η_PV) is dependent on the NOCT, wind speed, and ambient temperature.
Point 2: For Fig. 3, information such as the number of nozzles, the mass flow rate, and the jet-to-surface spacing should be properly mentioned in the main text. Additionally, what would be the PV efficiency if jet-impingement cooling is not included under the same condition as used in Fig. 3? It would be helpful to include these data for comparison to show the effectiveness of the cooling in increasing the PV efficiency.
Response 2: Thanks for your helpful feedback. The number of nozzles, the mass flow rate, and the jet-to-surface spacing have been added to the relevant discussion in Figure 3.
In regard to the second part, the PV efficiency without the cooling system has been added to compare the obtained results in Figure 3 on Page 8.
The maximum power increment percentage () also was adopted to compare the results obtained at the different mass flow rates with the conventional PV panels.
Point 3: In Equation (12), please clarify the definition of subscript “i”.
Response 3: It represents the number of elements or facets. It has been noted under Equation 12.
Point 4: For Fig. 4, it would be helpful to mention the solar irradiation of 1000 W/m^2 in the main text . Fig. 3 shows that the solar irradiation of 600 W/m^2 has the highest efficiency, it is a little confusing why 600 W/m^2 is used after Fig. 4. How the results in Fig. 4 would change if 600 W/m^2 is used instead of 1000 W/m^2?
Response 4: Thanks for pointing it out. Although the maximum efficiency is obtained at the lowest solar irradiation, the rest results are shown and discussed for the solar irradiation of 1000 W/m2 as the severe condition to reveal the efficiency of the JIC on the PV efficiency. It has been added to the manuscript on Page 9 as follows:
“Although the maximum efficiency is obtained at the lowest solar irradiation, the rest of the results are shown under the intensive solar irradiation of 1000 W/m2 to evaluate the JIC performance.”
Point 5: Similar to Comment 5, in the Conclusions, the authors mention that the PV efficiency is maximized at the solar irradiation of 600 W/m^2, however, Figs. 4-6 used 1000 W/m^2, this should be clearly pointed out and explained.
Response 5: It has been addressed in response to the previous comment.
Point 6: As shown in Table 6, including the jet-impingement cooling in the PV system improves the PV efficiency from 15.56 to 15.81, which doesn't seem to be significant. Are there ways to further improve the efficiency by further optimizing the jet-impingement cooling system?
Response 6: Typically, the efficiency of PV cells is 15-20%, and the improvements of proposed cooling techniques for electrical efficiency are not that much in previous studies. According to Table 6, using the current JIC with 8 jets increases the PV efficiency to 15.56%, while the efficiency of the conventional PV panel is 13.3%. We agreed with the reviewer, increasing the number of nozzles from 8 to 24 has a slight effect on the cooling performance, but it can provide more uniform temperature distribution resulting in a longer life span.
Round 2
Reviewer 3 Report
I appreciate the responses from the authors. All my comments have been fully addressed and the revised manuscript has been improved. Therefore, I would like to recommend the acceptance for publication.
