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Peer-Review Record

Designing Hydrogen and Oxygen Flow Rate Control on a Solid Oxide Fuel Cell Simulator Using the Fuzzy Logic Control Method

Processes 2020, 8(2), 154; https://doi.org/10.3390/pr8020154
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Processes 2020, 8(2), 154; https://doi.org/10.3390/pr8020154
Received: 9 December 2019 / Revised: 15 January 2020 / Accepted: 21 January 2020 / Published: 25 January 2020

Round 1

Reviewer 1 Report

Below please find some comments and suggestions for further corrections:

Abstract, line 18: “The test results obtained set point voltage can be achieved that is an average of 334.73 volts with H2-O2 pressure an average of 4428 Pa” – to complex sentence, need to be simplified. Introduction – could be developed and supplemented by more recent literature. A more comprehensive literature review and summary is recommended. Figure 1 – is quite general, although some descriptions repeat themselves such as at yellow background: “variable input” for current and temperature. Line 64 – there is a new paragraph “2.Algorithm System”, while point 2 was already presented in line 44 as “2. Materials and Methods”. The numbering of manuscript chapters must be adjusted. Point 2.2, line 88 – typing error “Hhydrogen” – double “h”, Point 2.2, line 93 – repetitions “errors and errors” –what is a difference between them? What's the point of this repetition? Point 2.2, lines 93 and 94 – the Authors mentioned about a “fuzzy logic method with a predetermined membership function and rule base” - the proposed research method is not presented in the manuscript and needs to be discussed in detail. Line 109 – three times there is point 2.2, in that case as “2.2. SOFC simulator model”. the numbering of manuscript chapters must be adjusted. Line 109 – SOFC simulator model was not presented completely and should be presented in details with explanations, some parameters are missing in Table 1, while they appeared in equations (1) – (8). There is lack of description of the control of SOFC using fuzzy logic control approach. The idea of the fuzzy logic approach was not presented at all in the manuscript and needs additional inputs from the Authors. Line 110 – “…of previous studies.” – there is lack of reference, how can it be check? What kind of previous studies do the Authors mean by this? Line 118 – the Authors gave the cell number without any characteristics of cells – if they were planar or tubular, what kind of materials were used to build them? Types of materials influence significantly into the cell performance, thus it cannot be considered without any assumptions regarding materials type. Line 119 – “molar constant of hydrogen valve” the phrase is unlikely to be appropriate and should be replaced by a generally applicable phrase such as: “valve molar constant for hydrogen”. Similar for water and oxygen in lines 120 and 121. Lines 119 – 121 – please check the correctness of the unit for the valve molar constant for H2, O2, H2 In my opinion there should be [-]. Line 123 – hydrogen – oxygen flow ration was given as 1.145, while below it seems that different ratio was assumed. Please explain this discrepancy. Line 126 – please check the correctness of the unit for current density. In my opinion it should be [A/cm2], instead of [A]. Line 129 – “… of the SOFC emulator” – probably it should be “simulator” instead of “emulator”. Line 132 – in the equation (1) there is a parameter qH2O , which was not presented in the manuscript and the reader does not know how to establish it. Moreover, many parameters such as: I, qO2 and others were not described in the paper and should be presented directly. Line 138 – lack of definition and unit for Vact and Vconc, R Line 145 – lack of reference for the equations (7) and (8). Line 150 – “…Oxygen”. Why oxygen is written by capital letter? Please unify the description through the manuscript, because currently sometimes is written by capital letter and sometimes no. Line 162 – “The average SOFC output voltage has not reached the set point value of 333 volts” - What does it mean? Please add comments. Line 163 – “The difference in pressure (∆pressure) of Hydrogen- Oxygen exceeds above 4000 Pa” - What kind of consequences does that entail? Line 164 – “While the flow rate of Hydrogen and Oxygen is 0.79 and 0.67 mol/s” - it means that the hydrogen to oxygen ratio was equal to 1,179 instead assumed 1,145 as it was mentioned in table 1? What does it mean? How can this be commented upon? Line 165 – results obtained and presented in table 2 should be not only shown but also discussed. Figure 8 - what was the reason for a sudden drop in voltage at 20100 ms (orange curve)? Lack of the explanation in the text. Figure 9 - the maximum value of the flow rate axis should be assumed the same as in Figure 5 and it should be 1,0 volt. The adoption of the same scope in the graph will make it easier for the reader to analyse. Figure 10 - how can the Authors comment a sinusoidal curve for hydrogen pressure in Figure 10 (orange curve)? Did the Authors notice that that curve had a completely different shape in the corresponding Figure 6? How it can be explained? Figures 7 – 11 – lack of maximum values at the X-axis. Line 189 – “The value of HidHydrogen-Oxygen Pressure is in the range of 4000 Pa far below ∆the pressure without a…” – firstly, a typing error “HidHydrogen”, secondly what was the main reason of a deltaP drop? In the paper there is lack of physical explanations of the system behaviour, which need to be delivered.”…. ∆the…” – typing error to be removed. Table 3 – sometimes the Authors used "," and sometimes "." as decimal. Please standardise the decimal system. Figures 13 - 17 - how can the Authors explain different shape curves presented in Figures 13 and 17 before introducing negative or positive disturbance at 30000 ms? Should not the curves in Figure 13 and Figure 17 be similar before the disturbances occurred? Where do the large fluctuations before the occurrences of a positive disturbance result from as it can be seen in Figure 17? Figure 18 - what results in a hydrogen pressure at 10100 ms shown in Figure 18? What is the result of such a curve course in that specific area? Table 6, rows 2 and 3 – The Authors use two different systems to denote decimal values, which causes a mess. Line 237 – “SOFC simulators and Hydrogen and Oxygen flow rate controllers have been designed quite well…” - why the components names are written in capital letters? Line 238 – “…333 volts, ie from the…” – what is that “ie”? Line 243 – “The system in general is still able to improve when the external current is enlarged and reduced from its normal value” - the Authors did not explain the reasons for such behaviour of the system. The Authors stated on the basis of the results, but did not discuss or attempt to justify it. Why did not the Authors carry out any discussion with the help of obtained results and based on literature date? There are similar research studies in the literature in this area, which could also be referred to and compared to the obtained results. Please extend discussion and comparison to other studies. References – limited number of references. Some of them are quite old such as [6] – 1990 or [9] – 2000. It is recommended to update the literature review and to extend it.

Author Response

Dear Reviewer

We have tried to improve all suggestions and enter from reviewers from beginning to end.
Starting from the abstract, adding the introduction, methods, pictures, discussions and conclusions.
For the improvement of English in this paper, we will include all of them in the journal processes

Thank you for your input and advice

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Summary:

The authors present a fuzzy logic approach to control the flow and overall pressure of oxygen and hydrogen gas, thus controlling the output voltage.

Broad comments:

The introduction does not say anything about the significance of the current work. How novel or different This than other approaches. It does not mention anything about the current industrial standard employed for such controls. The authors described what is SOFC but failed to say anything about current output voltage controlling approaches — no clear hypothesis presented in the introduction — no mention of what kind of valve used in controlling H2 and O2 gas in SOFC. It is not mentioned that how managing the output voltage would impact the SOFC performance. The authors provided no background and significance of these equations included in the text. Equations are disturbing the continuity of the flow. Authors need to explain a bit about the theory behind proposing those equations in the context of SOFC. The conclusion should be rewritten. The graphs presented in the text looks like a lab report presentation.

Specific Comments:

Abstract:

Line 11-12: Complex sentence. Split into two parts.

Line 14: What is the name of the previous model. Mention it. Article abstract should provide a more precise explanation regarding what is done in the specific research. Avoid vague sentences.

 

Line 15-16: “ fuzzy logic control method which has a firm value in determining the angle of rotation.” Is it fuzzy logic providing a firm valuation of the proposed method of determining the angle of rotation? It is not clear.

 

Line 17: The result shows that the output voltage can reach the set point with the average value is 334,73 volt. What is the purpose of this sentence? The authors should mention that setpoints achieved by varying angles of rotation in what order.

 

Line 17 and 18: The average voltage values are different? Is it 334,73 or 334.73V? Both are different. The average output voltage mentioned in the abstract not mentioned anywhere in the text.

 

What is Vact, Vohmic, Vconc? Also, partial pressure symbols were not defined. Table 1 A lot of variables used not explained in the text. What “I” representing? Is it  similar to Ir

 What is Ecell, Ncell?

Authors need to have a better color choice and use clear X and Y-axis.  It looks like authors used Excel for preparing graphs. Many high-quality figures can be arranged via Excel. Also, for charts, line thickness should be the same. Omit using grid lines.

Some graphs are presented with 100 per moving average; some of the charts are having 50 per mov. Avg. Please make it the same and present.

Author Response

Dear Reviewer 2

We have tried to improve all suggestions and enter from reviewers from beginning to end.
Starting from the abstract, adding the introduction, methods, pictures, discussions and conclusions.
For the improvement of English in this paper, we will include all of them in the journal processes

Thank you for your input and advice

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Much better. Try to add some lines to the conclusion. It is too short.

Author Response

Dear Reviewer

Thank you for the advice and guidance
We have tried to fix it.
With this letter we send a response to what needs to be improved
Thank you

Author Response File: Author Response.pdf

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