Reverse Osmosis Desalination Plants Energy Consumption Management and Optimization for Improving Power Systems Voltage Stability with PV Generation Resources

Round 1

Reviewer 1 Report

The paper titled “Reverse Osmosis Desalination Plants Energy Consumption Management and Optimization for Improving Power Systems Voltage Stability under PV Generation Resources” and written by Zeyad A. Haidar et al. studied the use of Reverse osmosis desalination plants as additional load to improve the voltage stability of a power system with photovoltaic generation resources. The studies that involve renewable energy and desalination are of great relevance to human life. I recommend a moderate revision based on the following comments:

1. First, the authors should be specific about the desalination plant, they should mention that this study is about a seawater reverse osmosis desalination plant, which require more energy than brackish water reverse osmosis desalination plants.
2. The number of publications regarding reverse osmosis and renewable energy is important. I found the number of references a little reduced considering this fact. In page 2, lines 64-74, the authors mentioned the dynamic energy consumption of RO desalination plants. Put an RO system under variable operating conditions is very challenging, it affects the performance of the system in terms of water production and water quality (important requirement for drinking water), establishing safe operating windows is key in this kind of systems. I recommend the authors to include and comment the following papers in the introduction:
   1. Optimal design of energy sources and reverse osmosis desalination plant with demand side management for cost-effective freshwater production
   2. Performance evaluation and boron rejection in a SWRO system under variable operating conditions
   3. Optimal technical and economic configuration of photovoltaic powered reverse osmosis desalination systems operating in autonomous mode
   4. Simulations of BWRO systems under different feedwater characteristics. Analysis of operation windows and optimal operating points
   5. Integration of hybrid power (wind-photovoltaic-diesel-battery) and seawater reverse osmosis systems for small-scale desalination applications
   6. Reverse osmosis desalination process optimized for maximum permeate production with renewable energy
3. Page 4, line 151, please better write Figure 1 shows instead of demonstrate. Regarding this paragraph, the authors mention the way to operate the RO desalination plant under ON/OFF strategy. Operating under intermittent regime could be problematic with this sort of plants. Beside this, one of the main problems of the RO desalination plants is fouling of RO membranes, which decrease the performance of the membrane in terms of water production. This should be at least mentioned by the authors. I suggest the following papers regarding intermittent operation of RO systems:
   1. Long-term intermittent operation of a full-scale BWRO desalination plant
   2. Impact of intermittent operation on reverse osmosis membrane fouling for brackish groundwater desalination systems
   3. Effects of wind intermittence and fluctuation on reverse osmosis desalination process and solution strategies
4. Page 4, line 184, write Figure instead of figure.
5. There is a typo in the title of section 2.4
6. Please, write the variables in italics, check the entire document.
7. Please, include a nomenclature.
8. IF thousand separator is used, please use it in the entire document.
9. Could the authors provide the permeability coefficient of the membranes?.
10. Pressure drop on membrane surface depends on flow and feed spacer geometry as well as polarization concentration phenomena. I understand the RO system modeling is not the main goal of this paper but it should be mentioned in the section of RO modeling. Feed spacer geometry can play an important role on RO membrane performance. Please, check published papers.
11. Table 2 include the words flow and pressure but, those terms were already abbreviated. Please, check the entire document and use the abbreviations.
12. TDS is a variable, please, write it in italics, as well as SEC.
13. Page 16, line 637, write Figure instead of figure. Check the entire document.
14. Page 17, lines 654-656. Please, write 3 as superscript. Revise the entire document.
15. The authors compare CRRC and VRRC operations. Does CRRC require more equipments? More feedwater pumps, high pressure pumps, filters? Did the authors consider this? IT would be relevant when study the investment costs and the economic viability of the system.
16. Why the authors study a desalination plant to control the voltage stability? Is it possible other technology (hydro pump storage)?
17. Following studies are very close to this paper and it should be included in the literature:
    1. Optimal Management of the Desalination System Demand in Non-Interconnected Islands
    2. Mapping RO-Water Desalination System Powered by Standalone PV System for the Optimum Pressure and Energy Saving
    3. On-Off Control Strategy in a BWRO System under Variable Power and Feedwater Concentration Conditions

Author Response

Please check the attached file. Our reply is in red.

Author Response File: Author Response.docx

Reviewer 2 Report

In this manuscript, the authors coupled the operation of a water desalination plant with that of a solar farm. The idea was to investigate whether the plant could be used as a variable load to stabilize the electrical grid however without affecting freshwater production. The work was proposed as a simulation exercise using some dimensions from the city of Riyadh. Three scenarios were proposed: no control, ON/OFF control of the desalination plant pumps, and variable control. It was shown that the latest outperformed the others both in terms of electrical stability and in terms of freshwater production.

 

The manuscript is well written and clear.

 

Detailed comments

 

1. The authors should make sure that all acronyms are displayed for long at least once also beyond the abstract.

2. The authors should decrease the use of acronyms. They make the text cumbersome to read.

3. The authors should give the names of the countries together with the locations for all the examples reported in the introduction.

4. Please report the version and vendors of the programs used.

5. Why was the 30-bus IEEE system used?

6. Specification on the voltage and frequency of the power grid should be given.

7. Please see the attached file for some minor spelling/grammar mistakes.

 

Comments for author File: Comments.pdf

Author Response

Please check the attached file. Our reply is in red.

Author Response File: Author Response.docx

Reviewer 3 Report

The paper is generally accepted and is knowledgeable for readers but some comment should be mentioned:

• There are some grammatical mistake should be corrected in revise version.
• Use newer references in the literature review and compare proposed approach with them
• The quality of some figures are not enough readable and they should be more clarified.
• Highlights the innovative result in more detail in the conclusion part.

Author Response

Please check the attached file. Our reply is in red.

Author Response File: Author Response.docx