Design and Thermal Characterization of Two Construction Solutions with and without Incorporation of Macroencapsulated PCM

Round 1

Reviewer 1 Report

Article “Design and characterization of a construction solution with a 2 thermally active core” is well presented. It has large and easy to read introduction, results of heat transfer from DSC and T-History, there are also results from laboratory stand and conclusions. But there is some questions for all of this work:

1. In introduction there is information about EU energy savings, but there is no calculation about is it better or not and is it going to reduce power. I realize that this is not easy to calculate exactly price but maybe some calculation will show trends, if it isn’t possible to do, then maybe some energy calculation?
2. PCM which was tested, was it properly prepared? Manufacturer says that it has to be in first use cooled to 0 °C because it is very hygroscopic.
3. In DSC method how big was sample which was tested, it’s very important for this solution to get well data.
4. There is information about DSC that heating and cooling rate was 1 °C min-1, why it was like that? Was it tested in other ratio? Is it compatible with manufacturer data? Maybe it used other ratio? This is important because larger probe will behavior different than small one in different ratios.
5. There is no description about T-History method, how was it measured and with what aperture, how big was tested sample. The same with DSC.
6. There is no graphic which shows macrocapsules how is it build, also there is no information about how much PCM is in one plate, what is ratio aluminum to PCM
7. There is no description about measuring system, has it been calibrated, which class is it, how was the sample rate. This is very important if there is comparison data acquired.
8. Charts has to be corrected, some of them has not readable lines, some has to small font.
9. Suggestion: in figure 9 maybe it will be better to join results in one chart

There is some comments in pdf file for the manuscript given. Please also check it.

Comments for author File: Comments.pdf

Author Response

The authors highly appreciate this revision of the submitted manuscript and acknowledge the valuable suggestions and recommendations for improving the quality of the paper. In this sense, the suggestions have been fully addressed in this revised manuscript version and a detailed analysis of the reviewers’ comments is provided below.

Article “Design and characterization of a construction solution with a 2 thermally active core” is well presented. It has large and easy to read introduction, results of heat transfer from DSC and T-History, there are also results from laboratory stand and conclusions. But there is some questions for all of this work:

1. In introduction there is information about EU energy savings, but there is no calculation about is it better or not and is it going to reduce power. I realize that this is not easy to calculate exactly price but maybe some calculation will show trends, if it isn’t possible to do, then maybe some energy calculation?

R: The data of energy savings presented in the introduction section, represent some of the EU goals and therefore only exemplify predictable data. However, the authors recognise that this information may not have been clearly exposed in the introduction and, thus, the manuscript text was adjusted accordingly.

2. PCM which was tested, was it properly prepared? Manufacturer says that it has to be in first use cooled to 0 °C because it is very hygroscopic.

R: The authors considered the manufacturer's recommendations and all the PCM was frozen at 0 °C before testing (DSC, t-history and hot box) and its application.

3. In DSC method how big was sample which was tested, it’s very important for this solution to get well data.

R: The weight of the PCM samples used in the DSC tests was approximately 32.15 mg. This information has been added in the text of the revised manuscript.

4. There is information about DSC that heating and cooling rate was 1 °C min-1, why it was like that? Was it tested in other ratio? Is it compatible with manufacturer data? Maybe it used other ratio? This is important because larger probe will behavior different than small one in different ratios.

R: The authors do not have information regarding the heating and cooling rate used by the manufacturer; thus, the heating and cooling rate adopted was an equivalent rate based on the literature, from the experience of other authors that have been developing similar DSC tests to characterize PCM solutions.

5. There is no description about T-History method, how was it measured and with what aperture, how big was tested sample. The same with DSC.

R: According to the comments 3 and 4 made from the reviewer, additional information was added in the manuscript to complete the missing information regarding DSC tests.

The methodology adopted for the t-history test consisted in heating the samples up to 60 ºC in a water bath until completely melt and then cooled down to 10℃ to find the supercooling degree. The total weight of the samples was approximately 15gr.

The missing information was updated in the manuscript.

6. There is no graphic which shows macrocapsules how is it build, also there is no information about how much PCM is in one plate, what is ratio aluminum to PCM

R: A new figure showing the PCM macrocapsules was added into the manuscript (Figure 1), as well as information regarding the total weight of PCM per container.

7. There is no description about measuring system, has it been calibrated, which class is it, how was the sample rate. This is very important if there is comparison data acquired.

R: Regarding the tiny houses (test cells) monitoring, the authors would like to clarify that this specific task has not yet started neither is objective of the present manuscript. The thermal behaviour of the test cells in free floating conditions was simulated with EnergyPlus software, with the objective of selecting an adequate temperature range for the acquired PCM, that was used into the developed construction solutions. Thus, the simulation was considered in this work, only for comparison purposes, to aid the PCM operating temperature range selection.

The monitoring and observation campaign of the construction solutions in real operation conditions will take place in a near future.

8. Charts has to be corrected, some of them has not readable lines, some has to small font.

R: The authors agree with the suggestion, and thus, Figures 2, 3 and 4 were improved and updated in this revised version of the manuscript.

9. Suggestion: in figure 9 maybe it will be better to join results in one chart

R: The authors agree, and Figures 9a) and b) were improved and merged into a joint chart.

Reviewer 2 Report

The subject matter discussed in the article is very interesting and may be of interest to Infrastructures readers. However, I feel the lack of translation of the research carried out into the issues suggested in the title of the article.

1. Chart (Fig. 4.) It is important in the context of the thesis of the article, therefore it deserves an improvement enabling the interpretation of the presented dependencies. For example, I suggest a clearer color differentiation in order to separate the reference values ​​from the values ​​resulting from the use of PCM.
2. I have doubts as to the interpretation of the results presented in Figure 10. The 4 degrees decrease in temperature found by the authors concerns the first of the three presented simulations (10 to 25 hour range). The others indicate a worsening of the temperature lowering effect. Does the observation in the range of 60 hour to 75 hours indicate that the time to release the accumulated latent heat is too short?
3. Do value of temperature changes programmed in this test (Acive chamber)  are correlate with temperature  changes in real conditions? 
4. In my opinion, the conclusions are superficial and require redrafting. The research results mainly concern the characteristics of the discussed solution and the properties of PCM. Research interpretation does not translate into project conclusions (see article title). They ignore the limitations related to the effectiveness of PCM in the situation observed, for example, in Figure 10. I suggest extending the conclusions to include aspects related to the proper selection of the phase transition temperature and the ability to accumulate heat under certain conditions.
What is the impact of the results of research on the phase change heat and the heat conductivity coefficient performed by the authors on the design recommendations? 

Author Response

The authors highly appreciate this revision of the submitted manuscript and acknowledge the valuable suggestions and recommendations for improving the quality of the paper. In this sense, the suggestions have been fully addressed in this revised manuscript version and a detailed analysis of the reviewers’ comments is provided below.

The subject matter discussed in the article is very interesting and may be of interest to Infrastructures readers. However, I feel the lack of translation of the research carried out into the issues suggested in the title of the article.

 

1. Chart (Fig. 4.) It is important in the context of the thesis of the article, therefore it deserves an improvement enabling the interpretation of the presented dependencies. For example, I suggest a clearer color differentiation in order to separate the reference values ​​from the values ​​resulting from the use of PCM.

R: The colours of the temperature curves were updated and contrast highlighted (in the plot of the Figure 4 – updated manuscript Figure 6), and in this revised version of the manuscript the temperature behaviour for the test cell without PCM is presented with the curve in grey scale and continuous dash, while the curves referring to the temperature behaviour for the test cell containing PCM are presented coloured and with discontinuous dash.

 

2. I have doubts as to the interpretation of the results presented in Figure 10. The 4 degrees decrease in temperature found by the authors concerns the first of the three presented simulations (10 to 25 hour range). The others indicate a worsening of the temperature lowering effect. Does the observation in the range of 60 hour to 75 hours indicate that the time to release the accumulated latent heat is too short?

R: The authors agree with the observation made by the reviewer. In this sense, a new sentence commenting the obtained results was added in this revised version of the manuscript, indicating that the latent heat of the PCM would not be fully discharged considering a daily cycle.

 

3. Do value of temperature changes programmed in this test (Acive chamber)  are correlate with temperature  changes in real conditions? 

R: Preliminary tests were made in the south orientated surface using a thermographic camera. During the most severe weather conditions, similar values were attained. Thus, and acknowledging the hot box test limitations (e.g. programming temperature curves), to fully charge and discharge the PCM this temperature range was adopted.

4. In my opinion, the conclusions are superficial and require redrafting. The research results mainly concern the characteristics of the discussed solution and the properties of PCM. Research interpretation does not translate into project conclusions (see article title). They ignore the limitations related to the effectiveness of PCM in the situation observed, for example, in Figure 10. I suggest extending the conclusions to include aspects related to the proper selection of the phase transition temperature and the ability to accumulate heat under certain conditions. What is the impact of the results of research on the phase change heat and the heat conductivity coefficient performed by the authors on the design recommendations? 

R: The authors agree that the selected title does not characterize the performed work. Thus, in this revised version of the manuscript, the title has been improved as well as the conclusions section to better represent the developed research.

Reviewer 3 Report

The title of this paper is misleading.  The term "thermally active core " is not explained in the text. 

The methodology doesn't provide a clear explanation of why specific PCM material was selected. 

Another critical point is the absence of real measurement of indoor air temperature stability in the Tiny Houses case study. So how theoretical simulations (Figure 3) were validated. 

conclusions are were generic and the presented data is pretty predictable. 

Also, data presented on tiny houses and it's construction is now used in this research. 

 

Please check some articles on thermally activated PCM panels which can be useful for literature analyses on the further development of research topic:

DOI: 10.3390/en13215715  Cooling panel with integrated PCM layer: A verified simulation study

DOI: 10.1051/e3sconf/201911101080 Thermally activated concrete slabs with integrated PCM materials

Author Response

The authors highly appreciate this revision of the submitted manuscript and acknowledge the valuable suggestions and recommendations for improving the quality of the paper. In this sense, the suggestions have been fully addressed in this revised manuscript version and a detailed analysis of the reviewers’ comments is provided below.

1. The title of this paper is misleading.  The term "thermally active core " is not explained in the text. 

R: The authors acknowledge that the manuscript title is not completely representative of the performed research, and therefore it was improved and rewritten.

 

2. The methodology doesn't provide a clear explanation of why specific PCM material was selected. 

R: The authors acknowledge that the selection of PCM has not been deeply explained.

In 2012, this research team, initiated work on the PCM incorporation into construction solutions. Several research works were developed using PCM paraffin-based solution. Due to the fact that the paraffinic PCMs had relatively low ignition resistance, the project team decided to focus, at that time, its research on salt hydrated based PCMs. Compared to paraffinic PCMs, salt hydrated based PCMs are not flammable and thus highly adequate for construction solutions incorporation.

The methodology was improved in this revised manuscript version, explaining the PCM selection.

3. Another critical point is the absence of real measurement of indoor air temperature stability in the Tiny Houses case study. So how theoretical simulations (Figure 3) were validated. 

R: Regarding the tiny houses monitoring, the authors would like to clarify that this work has not yet started. The thermal behaviour of the test cells in free floating conditions was simulated with EnergyPlus software with the objective of selecting an adequate melting temperature range for the PCM to be acquired, and therefore to be used in the developed construction solutions. Thus, the simulation was considered in this work, only for comparison purposes, to aid in the PCM melting temperature selection.

4. conclusions are were generic and the presented data is pretty predictable. 

R: The authors recognise that the conclusions are presented in a generic form, and do not cover possible applications of the solutions developed, therefore this section was improved in this revised version of the manuscript.

5. Also, data presented on tiny houses and it's construction is now used in this research. 

R: The work of monitoring and verifying the operation of the construction solutions in real environment will be incorporated in a future work and has not been considered in this research.

6. Please check some articles on thermally activated PCM panels which can be useful for literature analyses on the further development of research topic:

DOI: 10.3390/en13215715  Cooling panel with integrated PCM layer: A verified simulation study

DOI: 10.1051/e3sconf/201911101080 Thermally activated concrete slabs with integrated PCM materials

R: The authors would like to thank the reviewer for sharing additional research works on the topic, which has helped to enrich the present research in this revised version.

 

 

Reviewer 4 Report

The manuscript presents an interesting read using case studies experiments on the design and characterization of a construction solution with a 2 thermally active cores. The introduction and research design are very good. However, the areas requiring improvement are:

1) An extensive literature review covering the key concepts identified as part of the study. The literature review must justify the choice of the topic. As it stands, the introduction is not enough to justify the significance of the study.

2) The results are well presented but were not discussed for the implications and applications. This must be produced for a comprehensive research article. 

Author Response

The authors highly appreciate this revision of the submitted manuscript and acknowledge the valuable suggestions and recommendations for improving the quality of the paper. In this sense, the suggestions have been fully addressed in this revised manuscript version and a detailed analysis of the reviewers’ comments is provided below.

The manuscript presents an interesting read using case studies experiments on the design and characterization of a construction solution with a 2 thermally active cores. The introduction and research design are very good. However, the areas requiring improvement are:

1. An extensive literature review covering the key concepts identified as part of the study. The literature review must justify the choice of the topic. As it stands, the introduction is not enough to justify the significance of the study.

R: The literature review section was thoroughly improved by adding new research works on the topic. However, authors would like to highlight the lack of similar construction solutions in the literature in comparison with the presented solutions at this work.

 

2. The results are well presented but were not discussed for the implications and applications. This must be produced for a comprehensive research article.

R: The authors recognise that the results and conclusions do not cover possible applications of the solutions developed, therefore these points are improved in this revised version of the manuscript.

Round 2

Reviewer 2 Report

The article is an interesting contribution to issues related to the improvement of thermal conditions in the building thanks to the use of PCM. The authors have significantly improved the article in the current version. The literature review is representative. The readability of the charts has been improved. Most importantly, the conclusions and discussion correspond with the presented research results. The use of PCM in building partitions is an issue with great potential. Unfortunately, the importance of PCM is often overestimated. The condition for improving the thermal insulation of the building thanks to the use of PCM requires the proper selection of its properties, melting temperature, phase change heat value or location in the building partition. The authors correctly interpreted the problem, reliably and adequately addressed the above-mentioned issues. 
The presented conclusions are adequate to the presented research results. 

Reviewer 3 Report

The authors were able to address all comments and to make a sufficient review of the initial study.