Environmentally Sustainable Recycling of Photovoltaic Panels Laminated with Soft Polysiloxane Gels: Promoting the Circular Economy and Reducing the Carbon Footprint

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This article successfully describes the advantage of PDMS applying to a protection film on PV devices in terms of more effective recycling means. The recycling effectiveness is clearly investigated and provided clear comparison with conventional films. I this point of view, this investigation suggests worth results. On the other hand, this investigation focuses on just recycling efficiency, and no description of potential influence of the initial performance of the PDMS laminated PV panels. It is highly recommended to discuss any influence of the initial PV performance related to the PDMS lamination.

Here are some itemized comments.

1. Current conventional protection film's refractive index is ca. 1.48 which is very close to the grass substrate. On the other hand, typical refractive index of PMDS is ca. 1.40. Due to refractive index mismatching, some relatively shallow angle of incident Sun light will not penetrate in the PV panel. This may significantly reduces PV efficiency. It is highly recommended to describe the initial PV conversion efficiency by the PMDS film in comparison to current conventional films.
2. In general, PMDS film surface shows "soft". Although it is beneficial for removing the film. On the other hand, soft surface may have some mechanical scratching, which may reduce PV conversion efficiency. Please discuss any potential influence of the surface softness.
3. Figures 5 and 6: The photos are not clear to have the figure captions' description.
4. Conclusion: It would be highly suggested that not only just recycling efficiency, total performance comparison would be required to clarify the advantage of the PDMS film. Even recycling efficiency is significantly superior to the conventional one, if the PDMS protection film degrades PV conversion efficiency due to lower refractive index, practical point of view, it may not be clear which is superior. Therefore, it is required to discuss any influence of the PDMS film to clarify the total superiority of the PDMS film.

Author Response

Dear reviewer,

Thank you for useful comments.

The article was improved as follows:

• The MDPI English editor was used
• References were numbered according to MDPI standards
• Concerning the low refraction index 1,4 of PMDS yes it can reduce PV panel power but on the other hand high transmittance of PDMS will increase the PV panel power by +0.5% and up to 1.5 %. It is confirmed by measurements. see Ref. [8] in our article by b. Ketola. Following paragraph was included to the revised article:

 

“On the other hand, the refractive index of PDMS does not match the index of the PV panel front glass as closely as the EVA does. Therefore, because of the refractive index mismatch, the output power of the laminated PDMS panels could be reduced by approximately -0.1% and up to -0.3% compared with that of the laminated EVA panels. However, the transmittance of the PDMS is very high. Using equal solar cells, the output power of PDMS laminated PV panels is approximately +0.5% and up to +1.5% higher [8] than that of EVA laminated panels. Therefore, the positive effect of high PDMS transmittance substantially outperforms the negative effect of refractive index mismatch”

 

• The PDMS soft gel is not used as protective film but as an encapsulant in our PV panel design. The layer of PDMS soft gel 1.3mm thick is placed between 2 tempered/hardened glass sheets 3.2mm thick. These glass sheets protect the PDMS gel against mechanical and chemical influences

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer comments for authors

 

Environmentally sustainable recycling of photovoltaic panels laminated with soft polysiloxane gels: Promoting the circular economy and reducing the carbon footprint.  

• Summary

The manuscript is based on the use of polydimethylsiloxane (PDMS) lamination in photovoltaic panels to increase the reuse efficiency of solar modules. A comparison of recycling capacities between PDMS and commonly used materials, such as ethylene vinyl acetate (EVA), is provided. The authors show the process of recycling PDMS laminated panels. According to the study, more than 80% of the total panel weight can be reused without the high energy requirements of EVA laminated cells, which could potentially reduce the carbon footprint. The work aligns with the principles of the circular economy, emphasizing the reuse and recycling of resources.       

 

• General concept comments

The study on improving the recycling process of solar cells is important, as demand for these renewable energy devices has been increasing in recent years. The introduction highlights the various materials used to laminate photovoltaic panels, including EVA, POE, and PDMS, and emphasizes the advantages of PDMS in terms of efficiency, reliability, and recyclability. In general, the methodology is clear and shows a step-by-step recycling process through a series of pictures. The study also quantifies the energy required for delaminating EVA/POE and PDMS panels, showing a significant energy reduction in the latter material. However, there are some questions related to the context, reproducibility, and results that require clarification (see specific comments).

 

• Specific comments
  1. In lines 95 and 96, it is commented that, in the case of EVA/POE laminated, only 15 % of the panel is recycled. Can the authors provide at least one reference?
  2. Besides the advantages of PDMS in terms of annual degradation and UV resistance, are there any drawbacks or considerations that can be commented on (cost, mechanical properties, others)?
  3. It is suggested to add a general scheme for the recycling process with some representative pictures.
  4. In the results section, delamination times from 4 minutes to 16 minutes are reported. Why are these times so different? How do these times compare to EVA/POE delamination?
  5. In Table 3, in the last row, there is an annual degradation value of -022%, but in line 64, the maximum value is -0.22%. Which is correct?
  6. There are other works related to recycling photovoltaic cells with PDMS or other polymers, for example: https://doi.org/10.1016/j.jallcom.2025.181445,  https://doi.org/10.1016/j.orgel.2013.12.018. It is suggested that a discussion section compare the results of your work with similar studies.
  7. References should be cited in the corresponding format (square brackets and number). Authors' names and abstract should also be edited.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

Thank you for useful comments.

The article was improved as follows:

• The MDPI English editor was used
• References were numbered according to MDPI standards
• Following paragraph was included to the revised article:

 

“On the other hand, the refractive index of PDMS does not match the index of the PV panel front glass as closely as the EVA does. Therefore, because of the refractive index mismatch, the output power of the laminated PDMS panels could be reduced by approximately -0.1% and up to -0.3% compared with that of the laminated EVA panels. However, the transmittance of the PDMS is very high. Using equal solar cells, the output power of PDMS laminated PV panels is approximately +0.5% and up to +1.5% higher [8] than that of EVA laminated panels. Therefore, the positive effect of high PDMS transmittance substantially outperforms the negative effect of refractive index mismatch”

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents an innovative and environmentally sustainable approach to recycling PV panels laminated with soft PDMS gels. The method leverages mechanical delamination at room temperature using polyethylene wedges, avoiding high-energy or hazardous chemical processes typical of EVA/POE-laminated panel recycling.  The authors demonstrate high recycling efficiency and low panel degradation rates, both of which support circular economy principles and carbon footprint reduction. I would like to suggest the publication after addressing following concerns.

1. The manuscript emphasizes environmental benefits and energy savings but lacks a thorough techno-economic assessment. A lifecycle cost comparison between EVA/POE and PDMS-based recycling (including equipment, labor, and handling costs) would enhance the practical relevance of the proposed method.
2. Several grammatical errors and awkward phrasings (e.g., “NO crushing-NO emissions”) reduce the professionalism of the text. Consider thorough proofreading and technical editing for clarity and consistency.
3. The reuse of PDMS clusters is briefly mentioned. Additional detail on purity requirements, polymer reprocessing pathways, or quality control measures would clarify the downstream circular economy claims.

Author Response

Dear reviewer,

Thank you for useful comments.

The article was improved as follows:

• The MDPI English editor was used
• References were numbered according to MDPI standards
• Following paragraph was included to the revised article:

 

“On the other hand, the refractive index of PDMS does not match the index of the PV panel front glass as closely as the EVA does. Therefore, because of the refractive index mismatch, the output power of the laminated PDMS panels could be reduced by approximately -0.1% and up to -0.3% compared with that of the laminated EVA panels. However, the transmittance of the PDMS is very high. Using equal solar cells, the output power of PDMS laminated PV panels is approximately +0.5% and up to +1.5% higher [8] than that of EVA laminated panels. Therefore, the positive effect of high PDMS transmittance substantially outperforms the negative effect of refractive index mismatch”

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript was improved, and the comments regarding the context and methodology were addressed. The work demonstrated a method to increase the recycling efficiency in solar cells, which could have a significant impact on the circular economy and sustainability. In my opinion, the paper should be accepted with two minor recommendations. In line 562 in the conclusion section, it says that waste production could be reduced 114 times. It is suggested that the results and discussion section provide support for how this factor was calculated or estimated. The second minor revision is to follow the corresponding format of authors and affiliations from the Journal.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

                                                                                                                              August 15^th, 2025

                                                                                                               

Thanks for suggestions to improve the manuscript. 

 

The way how the final waste quantity ratio 114 was calculated is explained in separate paragraph in the text (yellow background) “As shown in Table 4, the estimated  waste quantity for the “repowering” scenario involving conventional EVA-laminated panels is approximately 40.0 megatonnes. With 90% recycling efficiency (final waste quantity is 10% only of the initial quantity) the final waste quantity is 4.0 megatonnes.  Whereas estimated  waste quantity for the “regular-loss” scenario using PDMS-laminated panels is 1.75 megatonnes with recycling efficiency 98% (final waste quantity is 2% only of the initial quantity), it is only 0.035 megatonnes . This corresponds to a waste quantity ratio of approximately 114 to 1. The substantial reduction is due to the unique synergistic combination of a low degradation rate (which limits the number of end-of-life panels) and high recycling efficiency. If low-degrading PDMS laminated PV panels are widely adopted, the amount of hazardous PV waste could be significantly reduced after 2035.

 

The authors emails and affections were improved as well

 

Kind Regards

Prof. (Dr) V. Poulek

Author Response File: Author Response.pdf