Residential Solar Thermal Performance Considering Self-Shading Incidence between Tubes in Evacuated Tube and Flat Plate Collectors

Round 1

Reviewer 1 Report

This paper studied the thermal performance of evacuated tube solar collectors by considering self-shading incidence between tubes. The research topic is interesting and the structure of the paper is relatively complete. However, I have the following major concerns.

1. The abstract should be well organized, the main novelty, methodology, objective, significance and results of the study should be clearly clarified. The novelty and methodology of this study is not quite clearly described in the abstract.
2. What does the authors mean for the state of “The evacuated tube collectors were more efficient and reduced energy consumption by up to 26.3%”? Is the energy consumption means that consumed by pump? Why less energy is consumed if the flow rate is the same? And also, I didn’t notice the calculation process in the manuscript.
3. There are some errors for the unit in Fig. 6. The authors should double check the whole manuscript.
4. Please double check the solar radiation stated in 3.1, is it 5159W/m2?
5. The unit for solar radiation should be W/m2, what’s the meaning of wh/m2 in the last paragraph of 3.1?

Author Response

Answers to Reviewer 1

This paper studied the thermal performance of evacuated tube solar collectors by considering self-shading incidence between tubes. The research topic is interesting and the structure of the paper is relatively complete. However, I have the following major concerns.

We do appreciate to reviewer revisions and concerns, to improve this manuscript quality.

1. The abstract should be well organized, the main novelty, methodology, objective, significance and results of the study should be clearly clarified. The novelty and methodology of this study is not quite clearly described in the abstract.

 

A rewrite of the abstract has been performed. The main novelty has been described.

1. What does the authors mean for the state of “The evacuated tube collectors were more efficient and reduced energy consumption by up to 26.3%”? Is the energy consumption means that consumed by pump? Why less energy is consumed if the flow rate is the same? And also, I didn’t notice the calculation process in the manuscript.

This aspect has been clarified in the abstract also. Describing that is the backup thermal requirement

 

1. There are some errors for the unit in Fig. 6. The authors should double check the whole manuscript.

We had change the unit “lts” for “L”

 

1. Please double check the solar radiation stated in 3.1, is it 5159W/m2?

 

Thank you for the correction. We had corrected this aspect. We were talking about daily energy irradiated, so the unit has been changed to Wh/m2

1. The unit for solar radiation should be W/m2, what’s the meaning of wh/m2 in the last paragraph of 3.1?

As said before, we were talking about solar energy, so the units have been corrected to wh/m². Thank you for you time and corrections

 

Reviewer 2 Report

The research deals with the comparative performance of solar thermal collectors in equatorial area and in altitude for low temperature operation (<50°C). This is relevant because first it relies on actual experimental set-up and also due to its particular environment (altitude and equatorial location). However, the use of ETCs for the level of temperature desired (~45°C) is really questionable… Why analysing such advance and costly technology for such low level of temperature? It is not clear if the storage is connected to the 4 collectors’ outlet directly. The percentage of increase in terms of temperature is not relevant at all.

Above all, the work is poorly released in this paper both in terms of presentation and analysis. The introduction does is too much detailed on certain aspects while it does not end with the presentation of the next sections. Conclusions and discussion are treated together while they should be split. Conclusion shall be short and summarizing the results of the study. Tables are really cumbersome and disorganised. Units are wrongly defined. The authors shall keep the same number of digits for the decimal parts. Generally if there is no reference to an assertion (such as in l31), it is better not to mention it.

English shall be reviewed and syntax corrected.  

Deep revamp of the paper has to be done in order to be accepted.

If the authors accept here are some suggestions:

• L31 ‘since the late 19^th century’, give a reference to this assessment
• L40: Ref [6] it is not contextualised, which country, which climates? ‘shorter’ to which extend?
• L41: Ref [7] this responds to the point above, as it depends on the climate and the location, but be more precise. Where?  
• L47: ‘the overall price difference is reduced’. To which extend? Any reference?
• L53: [12] space missing before and after the brackets.
• L56: ref [14]: Where and when the study was led? Use ‘et al.’
• L61: [5] typing mistake
• L94: masl, not sure if this is an acceptable unit for the paper. 2000 m and 3000 m above the sea level sounds more correct.
• L95 – l101: precise the countries of the 6 cities. Reference the year of the study
• L101: Not clear at all. ‘on roofs’? What this means?
• L102-l110: this paragraph is inconsistent with the study. How to compare PV with thermal collectors? I suggest to remove this paragraph. It is quite odd in the development of the introduction
• L122-l156: this is already part of the development. Why not including it in subsection of the Materials and Methods?
• Figure 2: top right: remove the red rectangle, the text in the titles are much too small
• Figure 3.a: Resolution is too poor
• ‘Although ETC and FPC technologies have been compared in the past [2], [27], [28], the performance characteristics and effects of collector orientations and the effects of the solar incidence angle have not been studied in a real installation: this is a really strong statement. It hard to believe that the orientation of the collectors (Incidence Angle Modifiers) have not been studies, as IAMs are given the manufacturer.
• Introduction shall end by an introduction of the following sections
• L172: ‘lts’ use International Units
• L180-190: What is the reasoning behind the use of different orientations for 2 types of collectors? How can they be compared? Why not using only one type of collector on 4 different orientations? This shall be clearly explained here, not in the introduction.
• Thermocouples types have to be more detailed especially in terms of error? +/- 1°C like for K-types? This is important as the inlet/outlet temperatures are very close for this experiment
• Figure 4: (The authors) this shall be removed as well as in the other figures.
• Figure 5.a It seems that shading may occur between ETCs and FPCs, please specify if yes, develop how this impacts the measurements.
• Figure 5.a The shading effects from the built environment shall be explained if any. Are there any buidligns around shading the set-up?
• L204: ‘litres’
• L206-209: reader may not understand the sentence.
• Table 1: ETC.wes etc. have not been defined in the text prior to the reference (l206) of the table.
• wes is cumbersome, suggestion ETCw etc.
• Table 1: lts -> L
• L231: rephrase ‘the day on the day’
• L233: 5195 W/m2 cannot be reached on Earth without concentration.
• L235: Comparing increase of temperature level makes no sense at all. In thermodynamics, first the unit shall be K, so the percentages will be even lower. Second why not comparing the gain of power with a simple equation dm/dt.cp.dt, where dm/dt, can assumed to the same all the time.
• L254: 38.8°C vs 33.18°C. It makes no sense to go to the second digit. Also keep hamony between the number of digits.
• Figure 6 shall be split into 2 figures as they are the core of the study and they are very ard to read
• L266: w shall be replaced by W. It seems that you refer to the cumulate irradiance. Energy not power. This is quite confusing.
• Table 2: tite on the same page
• Table 2 is simply unreadable. Words are split in several line. Percentages compared on the temperatures up to the second digit.
• Figure 7: titles are on different page. ‘Figure 6b’?
• Figure 7: Was the storage linked to only one type of collector for each day of experiment
• ETCs, with ‘s’ in red
• Table 3 is unreadable and split on 2 pages. Similar remarks to table 2. Units (m^2). The colours are expanding up to the text section.
• L385: [23][23][23]…
• Include a discussion section: why not doing such a study for a storage system of >70°C for instance. ETCs would make more sense.

Good luck!

Author Response

Answers to Reviewer 2

 

The research deals with the comparative performance of solar thermal collectors in equatorial area and in altitude for low temperature operation (<50°C). This is relevant because first it relies on actual experimental set-up and also due to its particular environment (altitude and equatorial location). However, the use of ETCs for the level of temperature desired (~45°C) is really questionable… Why analysing such advance and costly technology for such low level of temperature? It is not clear if the storage is connected to the 4 collectors’ outlet directly. The percentage of increase in terms of temperature is not relevant at all.

Thank you, very much dear reviewer, for your time and corrections. The use of evacuated collectors are adequate for locations where there is high level of cloudiness. So even if evacuated tube collectors are recommended to high temperature applications, this technology capability helps to obtain thermal energy when there is diffuse irradiation.  A high level of cloudiness is recurrent in the location of this research. We had decided to consider a higher level of temperature as “temperature requirement” accordingly to several regulations for residential hat water heating. ETC are the main technology for residential hot water in several countries where there is important amount of cloudiness, as Ecuador.

Above all, the work is poorly released in this paper both in terms of presentation and analysis. The introduction does is too much detailed on certain aspects while it does not end with the presentation of the next sections. Conclusions and discussion are treated together while they should be split. Conclusion shall be short and summarizing the results of the study. Tables are really cumbersome and disorganized. Units are wrongly defined. The authors shall keep the same number of digits for the decimal parts. Generally, if there is no reference to an assertion (such as in l31), it is better not to mention it.

First, we had described at the end of the introduction a presentation of the research contents following, between Lines 198 to 205, for a better release of the work in the next sections.

English shall be reviewed and syntax corrected.  

The spelling has been sent to AJE, the editorial that has review the English grammar

Deep revamp of the paper has to be done in order to be accepted.

 

If the authors accept here are some suggestions:

• L31 ‘since the late 19^th century’, give a reference to this assessment.

The reference about this assessment has been described

• L40: Ref [6] it is not contextualized, which country, which climates? ‘shorter’ to which extend?

Reference has been contextualized

• L41: Ref [7] this responds to the point above, as it depends on the climate and the location, but be more precise. Where?  

Also has been contextualized

• L47: ‘the overall price difference is reduced’. To which extend? Any reference?

In this aspect, we had to withdraw

In this regard, we prefer to withdraw the assertion, since despite knowing that there has been a reduction in costs, since there have been several companies with the capacity to carry out this type of installation, but we have not detected any firm studies

• L53: [12] space missing before and after the brackets.

It has been solved

• L56: ref [14]: Where and when the study was led? Use ‘et al.’

It has been described the context and it was corrected the citation problem

• L61: [5] typing mistake

It also has been corrected

• L94: masl, not sure if this is an acceptable unit for the paper. 2000 m and 3000 m above the sea level sounds more correct.

It has been corrected

• L95 – l101: precise the countries of the 6 cities. Reference the year of the study

It has been corrected

 

• L101: Not clear at all. ‘on roofs’? What this means?

The expression has been changed to: “on sloping roofs of buildings”

 

• L102-l110: this paragraph is inconsistent with the study. How to compare PV with thermal collectors? I suggest to remove this paragraph. It is quite odd in the development of the introduction

Even it is a different technology, the electrical performance is also dependent on irradiation incidence and its angle of incidence. So we ask to the reviewer considering that this previous study is quit necessary to explain to the readers another technology output whit a similar geometry solar capture as FPCs like PV is. So we had explained in the paragraph that it is a study performed on the same city and reflects also a performance in concordance of orientation and solar capture.

 

• L122-l156: this is already part of the development. Why not including it in subsection of the Materials and Methods?

The reviewer is right. This part fits much better on the section “Material and Methods”, and it has been changed.

• Figure 2: top right: remove the red rectangle, the text in the titles are much too small

These two aspects had been corrected also

• Figure 3.a: Resolution is too poor

It has been corrected, we had enlarged the grapgh

• ‘Although ETC and FPC technologies have been compared in the past [2], [27], [28], the performance characteristics and effects of collector orientations and the effects of the solar incidence angle have not been studied in a real installation: this is a really strong statement. It hard to believe that the orientation of the collectors (Incidence Angle Modifiers) have not been studies, as IAMs are given the manufacturer.

Dear reviewer. we had tried to find out similar research but with this methological process of real installations working, we couldn find until now, a similar process of analysis and comparison. We have clarified this point as “we analysed as far we can review in literature.

 

• Introduction shall end by an introduction of the following sections

We had stated the introduction, to next section.

 

• L172: ‘lts’ use International Units

We had changed al the units marked as “lts” by “L”

 

• L180-190: What is the reasoning behind the use of different orientations for 2 types of collectors? How can they be compared? Why not using only one type of collector on 4 different orientations? This shall be clearly explained here, not in the introduction.

We had stated on L 234 : “We had set four systems in order to obtain the performance comparatively under exact irradiation condition: one FPC arranged facing parallel to sun path and facing perpendicular to sun path, and a set of two ETCs as the same criteria, one facing parallel to sun path versus the other facing perpendicular to the sun path.”

 

• Thermocouples types have to be more detailed especially in terms of error? +/- 1°C like for K-types? This is important as the inlet/outlet temperatures are very close for this experiment

It has been found in the  the thermocouples has +/- 0,5 º C precision

• Figure 4: (The authors) this shall be removed as well as in the other figures.

It has been removed

• Figure 5.a It seems that shading may occur between ETCs and FPCs, please specify if yes, develop how this impacts the measurements.
• Figure 5.a The shading effects from the built environment shall be explained if any. Are there any buidligns around shading the set-up?

We had explained accordingly with both aspects described before that: The solar arrangement of the collectors, as consequence of the low slope, and high altitude solar path in the region, interfere minimally and for a few minutes only very early in the morning and very late in the afternoon with shadowing between collectors, with negligible performance losses due to this effect. The built environment also does not affect the solar incidence in this place.

 

• L204: ‘litres’

We had changed all “litres” by “L” as unit symbol

• L206-209: reader may not understand the sentence.

We had clarified this sentence explaining that the local solar path in the equator is close to east-west in the whole year

 

• Table 1: ETC.wes etc. have not been defined in the text prior to the reference (l206) of the table.

We had moved the abbreviation table to the beginning of tha manuscript, in order to indicate to the readers all the short terms that will use in the manuscript at the start.

• wes is cumbersome, suggestion ETCw etc.

We had changed ETCwes for ETCw, and others the same along all the manuscript. Extrally it improve Tables and Images with this short nomenclature

• Table 1: lts -> L

It has been changed.

• L231: rephrase ‘the day on the day’

It has been corrected

• L233: 5195 Wh/m2 cannot be reached on Earth without concentration.

It has been corrected. We are dealing with energy, so it is not irradiation. Sorry about the mistake

• L235: Comparing increase of temperature level makes no sense at all. In thermodynamics, first the unit shall be K, so the percentages will be even lower. Second why not comparing the gain of power with a simple equation dm/dt.cp.dt, where dm/dt, can assumed to the same all the time.

The reviewer is right. To take % comparison iof ºC temperature is not appropriate. So we decided to compare only on º C.

• L254: 38.8°C vs 33.18°C. It makes no sense to go to the second digit. Also keep hamony between the number of digits.

This aspect has been corrected. We changed to two significant digits the whole manuscript

• Figure 6 shall be split into 2 figures as they are the core of the study and they are very ard to read

The reviewer is right in the appreciation. But we consider important to compare how close or far are temperatures between technologies. So, we maintain in the graph integrated the curves temperatures. But we had increased the size of this grphics in order to permit to reader a better visualization

• L266: w shall be replaced by W. It seems that you refer to the cumulate irradiance. Energy not power. This is quite confusing.

We had corrected the units, we are dealing with energy, so corresponds wh

• Table 2: tite on the same page

We had corrected this error

• Table 2 is simply unreadable. Words are split in several line. Percentages compared on the temperatures up to the second digit.

We had made the corrections. Also we do not keep comparison in %, only in temperature, accordingly to previous review.

• Figure 7: titles are on different page. ‘Figure 6b’?

We had corrected this mistake also

• Figure 7: Was the storage linked to only one type of collector for each day of experiment

It has been solved

• ETCs, with ‘s’ in red

Sorry dear reviewer, we could not find this error

• Table 3 is unreadable and split on 2 pages. Similar remarks to table 2. Units (m^2). The colours are expanding up to the text section.

We had improved it, we had reduced the texts of the abbreviations.

• L385: [23][23][23]…

It has been corrected also

• Include a discussion section: why not doing such a study for a storage system of >70°C for instance. ETCs would make more sense.

We consider in this research the energy requirement for DHW. So a required higher temperature is not required, but we had changed from 45 º C to 50 º, accordingly to several norms

Good luck!

Thankyou

Reviewer 3 Report

A good article related to solar thermal collectors and their related technologies. Discussing the effect of orientation and system configuration, including other factors on the output of solar thermal collectors was interested to read and understand the practical/physical aspect of this technology.     

(Line 102-110) Need further elaboration of discussion of PV panel orientation and its energy generation with reference to [23]. Does this also apply to solar thermal collector orientation and its performance?

Storage capacity in terms of time?? How much time the storage can keep the water warm as solar energy will be available for a limited time? What about the capacity of the storage?

Tables 2 and 3 need formatting for clear understanding.

Reference formatting (line 385)

suggestion: If possible, include a minor comparison with the PV technology with the above-mentioned technology.

Author Response

Answer Reviewer 3

 

A good article related to solar thermal collectors and their related technologies. Discussing the effect of orientation and system configuration, including other factors on the output of solar thermal collectors was interested to read and understand the practical/physical aspect of this technology.     

Thankyou dear reviewer for your time and good recommendations. 

 

(Line 102-110) Need further elaboration of discussion of PV panel orientation and its energy generation with reference to [23]. Does this also apply to solar thermal collector orientation and its performance?

We had done in line L144 a deeper explanation on PV and ST technologies, to understand how solar irradiation inside in the performance of both technologies

Storage capacity in terms of time?? How much time the storage can keep the water warm as solar energy will be available for a limited time? What about the capacity of the storage?

Dear reviewer, it is dependent on the level of isolation and temperature level. We cannot stae how long the heat is maintained in the storage time , but the heat is reduced a along time as you can see in figures 7a and 7b in this case. 200 L storage has been used for this research as explained on L 181

Tables 2 and 3 need formatting for clear understanding.

We had corrected this issue

Reference formatting (line 385)

We had corrected it

suggestion: If possible, include a minor comparison with the PV technology with the above-mentioned technology.

We had performed this comparison

Round 2

Reviewer 1 Report

The manuscript has been revised based on the comments.

Author Response

Thank you for your time

Reviewer 2 Report

The authors have furnished consistent effort in amending the document considering the remarks. The draft has been improved and is more consistent. However it requires further improvements to be scientifically relevant. Fundamental precisions have been added.

First the results are exposed with 2 digits for the decimal parts in table 2 and table 3. However, the precision of the thermocouple is reportedly 0.5°C. The 2 digits make no sense. 1 digit is more than sufficient. This tolerance shall be clearly stated when it goes to conclusion. Also a reference to the model of thermocouples has to be given

Although details are given on the orientation of the collectors, the inclination is different in the 4 cardinal positions. It would have been interesting to have a comparison between the 2 technologies with the same inclination (FPC.n vs ETC.n for instance). Indeed the solar spectrum is not the same at the beginning and at the end of the day so the collectors will not have symmetric output, especially if the climate is cloudy generally more during a moment of the day rather than another (cloudy cover in the morning for instance).  

The need to stay at 45°C is proper to the region where the study is been led. In northern hemisphere for instance, the thermal collectors are used to heat up water up to temperatures 70°C, so efficiency matters, leading sometimes to the choice of ETCs.

Some remaks:

L109-124: this seems to be more a self-citation which is not relevant with thermal energy.

Figure 4: ETC.sou is at 7:00 Am and ETC.wes is 7:30 AM. ETC.sou, harmonise the ‘label’.

Figure 4: This figure should in an annex file. Maybe it would be relevant to do it for FPC in the annex

Figure 6: no title.

Line 273 ‘wh/m2’

Table 2: unreadable. It would be better to split in 3 tables (same remarks for table 3).

Author Response

 

The authors have furnished consistent effort in amending the document considering the remarks. The draft has been improved and is more consistent. However it requires further improvements to be scientifically relevant. Fundamental precisions have been added.

We do appreciate very much you time for your precise corrections, it helped a lot to increase the manuscript quality

First the results are exposed with 2 digits for the decimal parts in table 2 and table 3. However, the precision of the thermocouple is reportedly 0.5°C. The 2 digits make no sense. 1 digit is more than sufficient. This tolerance shall be clearly stated when it goes to conclusion. Also a reference to the model of thermocouples has to be given

We had changed to 1 digit in all temperature parameters as suggested

Although details are given on the orientation of the collectors, the inclination is different in the 4 cardinal positions. It would have been interesting to have a comparison between the 2 technologies with the same inclination (FPC.n vs ETC.n for instance). Indeed the solar spectrum is not the same at the beginning and at the end of the day so the collectors will not have symmetric output, especially if the climate is cloudy generally more during a moment of the day rather than another (cloudy cover in the morning for instance).  

Yes, this aspect is important and we now are ending with another study with thi comparison. But we had to change the orientation of the collectors. We had now some comparisons about technologies in the same orientation, We had included this picture, you can observe comparing with Figure 2. But this is another study that goes beyond this actual research, that we are focused on different overall performance and shadowing effect between tubes.

 

The need to stay at 45°C is proper to the region where the study is been led. In northern hemisphere for instance, the thermal collectors are used to heat up water up to temperatures 70°C, so efficiency matters, leading sometimes to the choice of ETCs.

Yes, when the maximum demands stands principally in winter, the ETCs prevail better that FTCs. But in our research we had to figure out the better output of ETCs in high altitude equatorial region.

Some remaks:

L109-124: this seems to be more a self-citation which is not relevant with thermal energy.

Probably it is on L106? We think that it is important to show a research that tabulates a comparison between different equatorial cities climate conditions. Probably the reader can do his own research, but we think that it is possible to show to the reader an analysis that we performed, that shows the similarity of different cities climate that we think that this research could be extrapolated

I think probably is L 119? This reference we think is important, because as far we can see, this is the only research that exposes the different irradiation condition in Cuenca, accordingly to if it is morning or afternoon hours.

Figure 4: ETC.sou is at 7:00 Am and ETC.wes is 7:30 AM. ETC.sou, harmonise the ‘label’.

Yes. The reviewer is right. There was a mistake, and in this only graphic was marked as 7:00 am when the sun level is to a very low altitude. So it was corrected to 7:30 that is the right data.

Figure 4: This figure should in an annex file. Maybe it would be relevant to do it for FPC in the annex

The idea of Figure 4 is to show the irradiation permeability between tubes when this are arranged parallel to the solar path vs when these are oriented perpendicular to the solar path. Then, in FPCs, this effect do not is relevant, since the irradiation does not goes between the tubes. WE do not find a real contribution to extend this table with sun incidence to the FPC. So we took this Table to as an annex at the end of the manuscript as the reviewer proposes.

Figure 6: no title.

It had been corrected

Line 273 ‘wh/m2’

It had been corrected

Table 2: unreadable. It would be better to split in 3 tables (same remarks for table 3).

We think that for more easy reading, it is important to maintain in integrated tables table 2 and table 3. But considering that we had reduced significant digits and we have increase the size of the charts, we Think now it is easier to understand these.

 

Thank you for your time again in correcting and recomendidns so valuable comments to our work.

Reviewer 3 Report

No more queries. All the queries are responded satisfactorily. 

Author Response

Thank you for you time

Round 3

Reviewer 2 Report

The authors have responded to the comments. Some formatting can be improved for a better interpretation of the results by the reader.

It is clearly understood that for technical availability at the moment of set-up or any other contextual insights, the choice of the orientation has been determined. However it would be an asset to explain in the draft the expected impacts of such orientation in terms of comparison purpose. Because it would have been better to have same orientation for both set of collectors. The solar spectrum might not be indeed the same throughout the day.

Regarding the self-citation, it is not a major issue if well put into context in a more succinct manner (1-2 sentences). “Regarding solar PV, it has been found that etc.”

If Figure 4 is to show the shading between the tubes, it would be better to have a fixed view orthogonally to the collector. The Figure is misleading as so far, this shading is not well rendered and seems to more focus on the shade on the collector by the ground itself.  

In the tables, wh instead of Wh is still used.

The daily energy is with 2 decimal numbers, it would be better to remove them

You may gain space even more in the tables by removing the “FCP.n-FPC.e” lines of comparison on both the average and the max. They are somehow cumbersome and can be easily explained in the text directly. Also put ‘avg’ and ‘max’ in an extra column in the left without having to repeat it in each header. Put directly the ‘daily irradiation value’ in the Title of the column directly (Medium Daily irradiation, 3177 Wh.m^-2). You save 3 columns.  

Author Response

The authors have responded to the comments. Some formatting can be improved for a better interpretation of the results by the reader.

 

Thankyou for you time again dear reviewer to improve our work. We did the following aspects accordingly to you suggestions:

It is clearly understood that for technical availability at the moment of set-up or any other contextual insights, the choice of the orientation has been determined. However it would be an asset to explain in the draft the expected impacts of such orientation in terms of comparison purpose. Because it would have been better to have same orientation for both set of collectors. The solar spectrum might not be indeed the same throughout the day.

To clarify this we had stated on L272 this statement: "So, in this purpose an analysis of comparing to systems of ETC displayed one of them perpendicular to sun path versus one deployed parallel to solar path is required and comparing these to FPC also, so the incidence of orientation in this latitude is figured out"

 

Regarding the self-citation, it is not a major issue if well put into context in a more succinct manner (1-2 sentences). “Regarding solar PV, it has been found that etc.”

We have stated in L164: Regarding solar PV, it has been found that there is not a significant incidence to orientation in this latitude, especially when the solar plates are arranged in a low inclination, with a flat surface as FPC tecnology

If Figure 4 is to show the shading between the tubes, it would be better to have a fixed view orthogonally to the collector. The Figure is misleading as so far, this shading is not well rendered and seems to more focus on the shade on the collector by the ground itself.  

In this aspect, considering that these simulation renders where in order to demonstrate the hours where the shading effect do appear, and these are now as annex in the end, we decided to extend in Figure 4 a view when the sun is at 13:30, and there is no shading between tubes, to be better understood

In the tables, wh instead of Wh is still used.

It has been fixed

The daily energy is with 2 decimal numbers, it would be better to remove them

It has been taked all the decimals out of the daily energy descriptions

You may gain space even more in the tables by removing the “FCP.n-FPC.e” lines of comparison on both the average and the max. They are somehow cumbersome and can be easily explained in the text directly. Also put ‘avg’ and ‘max’ in an extra column in the left without having to repeat it in each header. Put directly the ‘daily irradiation value’ in the Title of the column directly (Medium Daily irradiation, 3177 Wh.m^-2). You save 3 columns.  

We have made these suggetions in order to get an easier chart for readers.

 

Thank you for your time again

Author Response File: Author Response.pdf