Solar Desalination by Humidification–Dehumidification: A Review
, Alaa A. El-Bary 3, Gasser E. Hassan 4, Nidhal Becheikh 1, Abdulhakim Bawadekji 5 and Mahmoud M. Elewa 3,*
Round 1
Reviewer 1 Report
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The review is good. Here are some recommendations.
The English level is good. However, authors are still requested to check the English carefully for grammar, spelling, and syntax throughout the entire manuscript. The language should be revised and proofread to ensure that review is communicated clearly.
The structure of the review needs to be revised. The review contains so many sections and subsections. Some sections should be condensed to form a section.
In the abstract, lines 29 and 30, authors should explain what they mean by “thermal energy systems have the lowest GOR”
In abstract, line 29, GOR is written as “gain” output ratio and in line 35, it is written as ‘gained’ output ratio. Authors are advised to be consistent with either gained or gain throughout the manuscript.
Introduction, page 1, line 45, never begin a sentence with a numeral. Kindly rephrase “30%”
Page 3, line 109, “MSF is the most often utilised method”. RO is the most widely used method. Thus, I think it is better to rephrase it to “MSF is the most often thermal based utilised method”.
The demerit column for the “Solar thermal powered RO” in Table 1 page 7 is blank. Do you mean “Solar thermal powered RO system” has no demerit?
Page 8, line 317, “is simply a pair of vertical ducts joined at the top to circulate the air”. The vertical duct is wrong. Some horizontal duct HD are also available. Example (Performance assessment of a cross-low packed-bed humidification–dehumidification (HDH) desalination system – the effect of mass extraction). Please rephrase the statement.
Page 10, line 345, “specific water production (RR)” and in page 11, line 363 “3.1.3. Recovery ratio (RR)”. Revise the abbreviation.
Recovery ratio is also missing under “3.1. Parameters impacting the HD system’s performance”.
Page 13, lines 457 - 463, the introduction on bubble column humidifier is not sufficient. A lot of work has been done on bubble column humidifier. Therefore, authors are advised to provide more discussion on the bubble column humidifier.
Page 13, lines 469 - 471, the introduction on dehumidifier is not sufficient. Authors need to provide discussion on various types of heat exchangers, bubble columns, and desiccant used as dehumidifier, just like they did to the various type of packing materials used in the humidifier.
Check page 15, line 530
In Figure 6 and section 4.1, I do not understand why authors added solar still to classification of HD system. Solar still is a method different from HD method. In solar still, both vapor evaporation and condensation take place in one component, while in HD system, evaporation and condensation takes place in humidifier and dehumidifier, respectively. Authors are advised to provide an explanation on why solar still is added to the HD classifications.
Similarly, solar pond section 4.6 should not be a class of HD system.
Solar still and solar pond integrated with HD system can be discussed under hybrid systems (section 4.7)
Section number in 1143 and 1117 are the same.
Authors are also requested to update Table 5 to accommodate some of the following published articles in the field of HD process IF FOUND APPROPRIATE.
· Humidification-dehumidification desalination system operated by a heat pump, https://doi.org/10.1016/j.enconman.2018.01.067
· Experimental investigation of heat pump driven humidification-dehumidification desalination system for water desalination and space conditioning, https://doi.org/10.1016/j.desal.2019.114199
· Experimental and theoretical study on a heat pump driven open-air humidification dehumidification desalination system, https://doi.org/10.1016/j.energy.2020.118252
· Heat pump operated humidification-dehumidification desalination system with option of energy recovery; Separation Science and Technology, https://doi.org/10.1080/01496395.2019.1706576
· Investigation of heat pump-driven humidification–dehumidification desalination system with energy recovery option, https://doi.org/10.1007/s10973-020-09794-6
Provide additional columns to each table providing GOR, cost and productivity
Author should provide summary section at the end of each major section.
Provide discussion and analysis on the most recent innovations introduced in the field of HDH system
A final paragraph with the main research and development topics to be addressed in the future to make these technologies more attractive and commercially available needs to be included.
Similarity report is quite high (36%). Please revise the entire manuscript to reduce the similarity index below 30%.
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Comments for author File: 
Comments.pdf
Author Response
The review is good. Here are some recommendations.
Thanks a lot for reviewing our manuscript and for your valuable comment.
- The English level is good. However, authors are still requested to check the English carefully for grammar, spelling, and syntax throughout the entire manuscript. The language should be revised and proofread to ensure that review is communicated clearly.
The answer: Thanks a lot for reviewing our manuscript and for your valuable comment. We have done language editing throughout the manuscript.
- The structure of the review needs to be revised. The review contains so many sections and subsections. Some sections should be condensed to form a section.
The answer: Thanks for the comment, done according to your suggestions in the preceding comments.
- In the abstract, lines 29 and 30, authors should explain what they mean by “thermal energy systems have the lowest GOR”
The answer: Thanks for the valuable comment, the sentence was deleted because it is not very true.
- In abstract, line 29, GOR is written as “gain” output ratio and in line 35, it is written as ‘gained’ output ratio. Authors are advised to be consistent with either gained or gain throughout the manuscript.
The answer: Thanks for the comment. Changed to “gain” output ratio throughout the manuscript.
- Introduction, page 1, line 45, never begin a sentence with a numeral. Kindly rephrase “30%”
The answer: Thanks for the comment. The sentence was rephrased.
- Page 3, line 109, “MSF is the most often utilised method”. RO is the most widely used method. Thus, I think it is better to rephrase it to “MSF is the most often thermal based utilised method”.
The answer: Thanks for the comment. Changed as your valuable suggestion.
- The demerit column for the “Solar thermal powered RO” in Table 1 page 7 is blank. Do you mean “Solar thermal powered RO system” has no demerit?
The answer: Thanks for the comment. “Solar thermal powered RO” system has no potential demerits. Written and highlighted
- Page 8, line 317, “is simply a pair of vertical ducts joined at the top to circulate the air”. The vertical duct is wrong. Some horizontal duct HD are also available. Example (Performance assessment of a cross-low packed-bed humidification–dehumidification (HDH) desalination system – the effect of mass extraction). Please rephrase the statement.
The answer: Thanks for the comment. Done and highlighted.
- Page 10, line 345, “specific water production (RR)” and in page 11, line 363 “3.1.3. Recovery ratio (RR)”. Revise the abbreviation.
The answer: Thanks for the comment. Revised and corrected.
- Recovery ratio is also missing under “3.1. Parameters impacting the HD system’s performance”.
The answer: Thanks for the comment. The recovery ratio is present under section 3.1.3.
- Page 13, lines 457 - 463, the introduction on bubble column humidifier is not sufficient. A lot of work has been done on bubble column humidifier. Therefore, authors are advised to provide more discussion on the bubble column humidifier.
The answer: Thanks for the comment. More discussion on the bubble column humidifier was added and highlighted.
- Page 13, lines 469 - 471, the introduction on dehumidifier is not sufficient. Authors need to provide discussion on various types of heat exchangers, bubble columns, and desiccant used as dehumidifier, just like they did to the various type of packing materials used in the humidifier.
The answer: Thanks for the comment. More discussion on dehumidifier types were added.
- Check page 15, line 530
The answer: Thanks for the comment.
- In Figure 6 and section 4.1, I do not understand why authors added solar still to classification of HD system. Solar still is a method different from HD method. In solar still, both vapor evaporation and condensation take place in one component, while in HD system, evaporation and condensation takes place in humidifier and dehumidifier, respectively. Authors are advised to provide an explanation on why solar still is added to the HD classifications.
- Similarly, solar pond section 4.6 should not be a class of HD system.
The answer: Thanks for the comment. Solar still and solar pond can be integrated with HD for solar seawater greenhouse which is the main objective of this review paper
- Solar still and solar pond integrated with HD system can be discussed under hybrid systems (section 4.7)
The answer: Thanks for the comment. Solar still and solar pond integrated with HD were moved to hybrid systems (section 4.6)
- Section number in 1143 and 1117 are the same.
The answer: Thanks for the comment. Section numbers were corrected.
Authors are also requested to update Table 5 to accommodate some of the following published articles in the field of HD process IF FOUND APPROPRIATE.
- Humidification-dehumidification desalination system operated by a heat pump, https://doi.org/10.1016/j.enconman.2018.01.067
- Experimental investigation of heat pump driven humidification-dehumidification desalination system for water desalination and space conditioning, https://doi.org/10.1016/j.desal.2019.114199
- Experimental and theoretical study on a heat pump driven open-air humidification dehumidification desalination system, https://doi.org/10.1016/j.energy.2020.118252
- Heat pump operated humidification-dehumidification desalination system with option of energy recovery; Separation Science and Technology, https://doi.org/10.1080/01496395.2019.1706576
- Investigation of heat pump-driven humidification–dehumidification desalination system with energy recovery option, https://doi.org/10.1007/s10973-020-09794-6
The answer: Thanks for the comment. All citations were added to Table 5.
- Provide additional columns to each table providing GOR, cost and productivity
- Author should provide summary section at the end of each major section.
The answer: Thanks for the comment. Most major sections were summarized.
- Provide discussion and analysis on the most recent innovations introduced in the field of HDH system
- A final paragraph with the main research and development topics to be addressed in the future to make these technologies more attractive and commercially available needs to be included.
The answer: Thanks for the comment. Discussions were provided in separate sections named “Recent advancements in HD desalination systems” (section 7) and “Suggestions for further work” (section 8).
- Similarity report is quite high (36%). Please revise the entire manuscript to reduce the similarity index below 30%
The answer: Thanks for the comment. The authors tried hard to dampen the plagiarism.
Reviewer 2 Report
The paper gives a through review of the HD desalination process using renewable energy sources. The paper is well-written but needs some changes to improve its quality.
The title is not relevant to the content of the review paper "Greenhouse Desalination by Solar Humidification-Dehumidification: A review". In the paper the authors reviewed many types of desalination systems that uses renewable energy sources with a focus on the HDH technology. So I suggest that the title should be adjusted. For example "Desalination by the Humidification-Dehumidification process: A review"
Include a table of content so it will be easy to go to each section quickly.
Many of the figures need citations and permission from the publishers. Be sure to get these permissions and cite the source of the figure (e.g. Fig 3, 7, and others).
The paragraphs in lines 115 - 149 and 150 - 175 are not relevant.
The paragraph in lines 176 - 189 need citations.
Line 323: it should be called humidifier and not evaporator.
In section 3.1.5. The Energy reuse factor (F) is not clearly explained. While it is defined in the text as the ratio of the energy retrieved from the heated working fluid to the energy supplied by it, the given equation (Eq. 4) is a mass ratio. Please clarify this performance parameter. In addition, the denominator of this equation is almost zero. Since the humidity ratios of the air enters the dehumidifier and leaving the humidifier are almost the same.
Section 4.1.2. Air preheated solar still systems needs citation
The authors ignored the commercial application of the HD process by a company (Gradiant Inc.). The HD process commercialized under the carrier gas desalination.
Author Response
The paper gives a thorough review of the HD desalination process using renewable energy sources. The paper is well-written but needs some changes to improve its quality.
Thanks a lot for reviewing our manuscript and for your valuable comment.
The title is not relevant to the content of the review paper "Greenhouse Desalination by Solar Humidification-Dehumidification: A review". In the paper the authors reviewed many types of desalination systems that uses renewable energy sources with a focus on the HDH technology. So I suggest that the title should be adjusted. For example "Desalination by the Humidification-Dehumidification process: A review"
The answer: Thanks for the comment. The title changed to "Solar Desalination by the Humidification-Dehumidification process: A review"
Include a table of content so it will be easy to go to each section quickly.
The answer: Thanks for the comment. Table of contents inserted in the manuscript
Many of the figures need citations and permission from the publishers. Be sure to get these permissions and cite the source of the figure (e.g. Fig 3, 7, and others).
The answer: Thanks for the comment. All non-open access figures already took permission from their publisher.
The paragraphs in lines 115 - 149 and 150 - 175 are not relevant.
The answer: Thanks for the comment.
The paragraph in lines 176 - 189 need citations.
The answer: Thanks for the comment. Already cited.
Line 323: it should be called humidifier and not evaporator.
The answer: Thanks for the comment. Done, changed
In section 3.1.5. The Energy reuse factor (F) is not clearly explained. While it is defined in the text as the ratio of the energy retrieved from the heated working fluid to the energy supplied by it, the given equation (Eq. 4) is a mass ratio. Please clarify this performance parameter. In addition, the denominator of this equation is almost zero. Since the humidity ratios of the air enters the dehumidifier and leaving the humidifier are almost the same.
The answer: Thanks for the comment. Most references use this dimensionless indicator.
Section 4.1.2. Air preheated solar still systems needs citation
The answer: Thanks for the comment. Done, already cited.
The authors ignored the commercial application of the HD process by a company (Gradiant Inc.). The HD process commercialized under the carrier gas desalination.
The answer: Thanks for the comment. Added to section 2.
