A Study on the Estimation of Facilities in LNG Bunkering Terminal by Simulation—Busan Port Case
Round 1
Reviewer 1 Report
Small corrections are needed:
verse 165 nbv_day should be with the lower index: nbv_day
verse 173 Ntl_day should be with the lower index: Ntl_day
verses 181-186: For the same types of vessels the same average speed - a reductive assumption but OK.
Equation (32) and next a few: Regression analysis was done with using polynomial function (chosen mathematical estimation) having no influence on real technical situation. In such case it should be given the domain of value x (axis x) - here the range of TEU - from about 5000 up to 30000. For example for equation (32) using other regression (exponential function) like:
Fcontainer = 0.27144 . TEU2/3
the results are good in wider domain.
Assumptive methodology without remarks.
Obtained results (e.g. Table 19) without comments. They depend on assumptive data and methodology.
Conclusions are proper if the assumption about the LNG development and change the marine fuels to LNG is predicted in good direction.
Author Response
Response to Reviewer 1 Comments
Point 1
 verse 165 nbv_day should be with the lower index
Response 1: We corrected it to nbv_day in line 181
Point 2: verse 173 Ntl_day should be with the lower index
Response 2: We corrected it to Ntl_day in line 189
Point 3: Equation (32) and next a few: Regression analysis was done with using polynomial function (chosen mathematical estimation) having no influence on real technical situation. In such case it should be given the domain of value x (axis x) - here the range of TEU - from about 5000 up to 30000.
Assumptive methodology without remarks.
Response 3: We revised it in line 206-208 as” The regression analysis performed in this study was applied on the assumption that 500TEU-8,000TEU is valid for container ships and 6,500GT-190,000GT is valid for bulk carriers, general cargo ships, tankers and cruise ships. Based on these assumptions, equations (32) to (35) were derived.”
In addition, we add a limit of result below equation (32), (33), (34) and (35)
Point 4: Obtained results (e.g. Table 19) without comments. They depend on assumptive data and methodology
Response 4: We revised the sentence on line 420-423. “The results in Table 19 are derived on the assumptions about demand in Table 2, the assumptions about the conversion rate of LNG vessels in Table 3, and the assumptions about the LNG density, the capacity of LNGC, LNGTL, LNGBV, LNG storage tank, STS/ TTS classification criteria, and fuel consumption of LNGFV in Table 4.”
Response 5 : We have received checking the English-style from Professor Ross who is American professor in Kyungsung University.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear authors,
Thank you for your exploration of how we can better estimate the size of LNG infrastructure required with consideration for the operational status of ports according to the estimated amount of bunkering demand. Here are some suggestions that should improve the quality of your paper.
Minor Essential Revisions:
​In Keywords, without (LNGBV) since other two (terminal and facility) are without acronym. LNGBV could also be the last keyword if the authors want it. In keywords shouldn't be explanations of acronyms anyway. In Introduction, line 40, LNGBV is explained again and in line 52 again. All acronyms should be explained only once and after that used only as acronyms, without multiple explanation. In 5.3. Simulation Execution Results, Table 16. and 17., missing a period after the name of the table. In line 189, TEU was mentioned first time, but not explained. In line 248, Figure 8 should be with the reference of the map used. It should say 'modified from (ref.)'. In line 399, dash should be consistently used with a space before and after the dash, pictures B and D need correction. In line 400, a reference of the photos is missing. In Conclusions, line 435, the reference should not be in Conclusions. Floating Offshore LNG Bunkering Terminal with its reference could be explained in previous chapters.
Author Response
Point 1
 In Keywords, without (LNGBV) since other two (terminal and facility) are without acronym. LNGBV could also be the last keyword if the authors want it. In keywords shouldn't be explanations of acronyms anyway
Response 1: We corrected it to LNGBV without explanation in line 22.
Point 2: In Introduction, line 40, LNGBV is explained again and in line 52 again. All acronyms should be explained only once and after that used only as acronyms, without multiple explanation.
Response 2: We corrected it in line 39, and 51
Point 3: . In 5.3. Simulation Execution Results, Table 16. and 17., missing a period after the name of the table.
Response 3: We corrected it in Table 16 and 17 with adding period after the name of the table.
Point 4: line 189, TEU was mentioned first time, but not explained.
Response 4: We corrected it in line 205 with the explanation of TEU.
Point 5: In line 248, Figure 8 should be with the reference of the map used. It should say 'modified from (ref.)'.
Response 5: In line 268, we revised it in Figure 8 with the reference of the map.
Point 6: In line 399, dash should be consistently used with a space before and after the dash, pictures B and D need correction.
Response 6: In line 422, we revised it in Figure 11 with a space before and after the dash, pictures B and D.
Point 7: In line 400, a reference of the photos is missing.
Response 7: In line 422, we revised it in Figure 11 with a reference of the photos
Point 8: In line 400, a reference of the photos is missing.
Response 8: In line 422, we revised it in Figure 11 with a reference of the photos
Point 9: In Conclusions, line 435, the reference should not be in Conclusions.
Response 9: In Conclusions, we deleted the reference.
Point 10: Floating Offshore LNG Bunkering Terminal with its reference could be explained in previous chapters.
Response 10: “Floating Offshore LNG Bunkering Terminal with its reference..” is repositioned to line 119-121 of Chapter 2.3.
Response 11 : We have received checking the English-style from Professor Ross who is American professor in Kyungsung University.
Author Response File: Author Response.pdf
Reviewer 3 Report
1. line 54, why use STS and TSS to bunkering system, Suggested explanation Complete.
2. line 226,Regression analysis with 17 observations does not meet the basic assumptions of regression analysis.
3.There are a number of literature discussed emission have been published in international journals. The authors should read and cite more journal papers about emission calculation.
Author Response
Point 1
 Line 54, why use STS and TSS to bunkering system, Suggested explanation Complete.
Response 1: In line 54-59, we revised the sentence with “ In addition, STS and TTS are the most commonly used bunkering method, which enables bunkering during the unloading operation of the ship, no need to move to another place for bunkering, and no separate construction is required in the harbor for bunkering.
On the other hand, the PTS bunkering method requires piping work to install the LNG pipeline in the port, and the installed LNG pipe is likely to be exposed to the port unloading process and cause an accident. “
Point 2: 2. Line 226,Regression analysis with 17 observations does not meet the basic assumptions of regression analysis.
In Introduction, line 40, LNGBV is explained again and in line 52 again. All acronyms should be explained only once and after that used only as acronyms, without multiple explanation.
Response 2: Yes, the number of data is not enough for Regression analysis. However, we meet the difficulty to increase the number of data because a data presents a year. The accuracy of future trend made us to select the recent 17 years data reflecting pre-reviewers’ opinion. In addition, we would explain that 17 data show the representative of 27,000 ships per year. 27,000x17 data are included in the 17 data. In the paper, we will try to show that the average number of calling ships is not changing and the average GT of ships is increasing as a case study. For your understanding I uploaded actual data with the revised version.
Point 3: . There are a number of literature discussed emission have been published in international journals. The authors should read and cite more journal papers about emission calculation.
Response 3: We added Reference 16, 18, 19, 20 in line 111-128.
Response 4 : We have received checking the English-style from Professor Ross who is American professor in Kyungsung University.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Na.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The appraisal presented in Fig. 2 & 3 depends strongly on accepted time period (will be different for last 15 years) - the 25 years period is more reasonable.
There is no comments why the location of LNG infrastructure should be Busan New Port - the required time for LNG transport among ports is lenghtened (needed place?).
There is no risk estimation for TTS and STS (not important?).
Table 12 etc. LNG density accepted as 500 kg/m3. It knows that pure LNG at -162oC has density of 442 kg/m3 and a little more if contents a small quantity of higher hydrocarbons. It makes the difference about 10%.
Fig. 10 is illegible.
Table 16 - the result of verification depends on the earlier estimated data, so simulation must be correlated to prediction.
There is no more information about the LNG bunkering infrastructure - will be prepared only for vessel bunkering?
There is no information (estimation) about expenses for re-liquefaction of LNG vapors in LNG storage tanks and LNGBVs. What about the possibility of methane slip to atmosphere during LNG storage, bunkering etc.
Author Response
Review 1
Point 1: The appraisal presented in Fig. 2 & 3 depends strongly on accepted time period (will be different for last 15 years) - the 25 years period is more reasonable.
Response 1: I agree with the reviewer 's opinion that the accuracy of the prediction will increase as the forecast period is shorter in the future. However, since the goal of this study is to determine the LNG bunkering station facility requirements, it takes at least five years for construction. Therefore, the facilities required for 2025 and 2030 should be at least predicted. => Modified
Point 2: There is no comments why the location of LNG infrastructure should be Busan New Port - the required time for LNG transport among ports is lenghtened (needed place?).
Response 2:. In Korea, the Ministry of Maritime Affairs and Fisheries selected five ports like Busan Port, Incheon Port, Gwangyang Port, Ulsan Port, and Pyeongtaek Port as the ports for constructing LNG bunkering terminals. This study was conducted on Busan port, which has the largest number of inbound and outbound vessels among the five ports. Yeondo in Busan New Port was selected as bunkering station considering the moving distance between bunkering station and the calling ship’s location, natural conditions, fishing rights, vessel traffic, facility safety, operational safety, site expansion, etc.
Point 3: There is no risk estimation for TTS and STS (not important?).
Response 3:
The reason for choosing the two methods STS and TTS is that shipping company considers that it is a proper way to reduce travel time and waiting time for bunkering. PTS is not considered in the study because the terminal operators claim to be excluded due to operational risk and technical safety issues.
.
Point 4: Table 12 etc. LNG density accepted as 500 kg/m3. It knows that pure LNG at -162oC has density of 442 kg/m3 and a little more if contents a small quantity of higher hydrocarbons. It makes the difference about 10%.
Response 4: Modified Table 13.
Point 5: Fig. 10 is illegible.
Response 5: Figure 10 is deleted.
Point 6: Table 16 - the result of verification depends on the earlier estimated data, so simulation must be correlated to prediction.
Response 6: Modified Table 17 and Table 18.
Point 7: There is no more information about the LNG bunkering infrastructure - will be prepared only for vessel bunkering?
Response 1: We added section 5.8. Main Facility Specification
Point 8: There is no information (estimation) about expenses for re-liquefaction of LNG vapors in LNG storage tanks and LNGBVs. What about the possibility of methane slip to atmosphere during LNG storage, bunkering etc.
Response 1: The scope of this study is limited to estimating the size of bunkering infrastructure. Liquefaction and cost-related aspects of LNG storage tanks and LNGBVs have been excluded from the scope of this study since they are related to terminal operations after the LNG bunkering terminal has been constructed.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The subject of the paper is relevant and the findings interesting
However, the way the paper is composed does not qualify for a scientific journal. It has the character of an engineering assessment for the port of Busan. In order to give the paper a more scientific basis it is recommended to:
- present the system of bunker supply in a more generic way, including the relevant formulae (but without going into Busan-related calculations).
- give a more general introduction of the simulation model. It is not clear in the present paper how the simulation model is applied. It looks more like a spread-sheet exercise, where the deterministic result is multiplied by the peak factor, obtained from Busan records. I would expect application of random selection from interarrival distributions for the different ship types and regions, which leads to more realistic results of bunker-LNG requirement, LNGBV's etc. taking into account a certain service level.
- then present the results for the Busan case, with all calculations in an Appendix
- finally the conclusions shall start with more general ones, instead of focussing entirely on Busan.
Two specific comments at this stage:
(i) the estimation of ship numbers is questionable. It is a worldwide trend that ship sizes increase, but ship numbers do not increase. This is also apparent in Fig.3 for Busan Port, where the number of ships over the past 15 years only fluctuates. The regression analysis leads to overestimation.
(ii) the cost figures presented are excessive. If one considers bunkering as a business, an investment of this magnitude will never be justified. One element that has not been addressed is that with the change from bunker-oil to LNG existing facilities come available and should be used as good as possible. It would be an interesting aspect of the paper to consider the extent to which this is feasible, ao from a safety point of view (LNG-safety criteria). Also it seems justified to consider the use of Floating Storage vessels instead of building new LNG storage tanks.
Author Response
Reviewer2
The subject of the paper is relevant and the findings interesting
However, the way the paper is composed does not qualify for a scientific journal. It has the character of an engineering assessment for the port of Busan. In order to give the paper a more scientific basis it is recommended to:
Point 1: We present the system of bunker supply in a more generic way, including the relevant formulae (but without going into Busan-related calculations).
Respond 1: We restructured the paper following your comment with the view of scientific method in section 2.4.
Point 2: give a more general introduction of the simulation model. It is not clear in the present paper how the simulation model is applied. It looks more like a spread-sheet exercise, where the deterministic result is multiplied by the peak factor, obtained from Busan records. I would expect application of random selection from interarrival distributions for the different ship types and regions, which leads to more realistic results of bunker-LNG requirement, LNGBV's etc. taking into account a certain service level.
Respond 2: We tried to show random distribution in Table14 and Table 15.
Point 3: - then present the results for the Busan case, with all calculations in an Appendix
Respond 3: We revised it to Appendix Table 4-Table13.
Point 4: finally the conclusions shall start with more general ones, instead of focussing entirely on Busan.
Response: We revised it and deleted Busan port in conclusion
Point 2:
(i) the estimation of ship numbers is questionable. It is a worldwide trend that ship sizes increase, but ship numbers do not increase. This is also apparent in Fig.3 for Busan Port, where the number of ships over the past 15 years only fluctuates. The regression analysis leads to overestimation.
Response(i): We revised it following your comment in section 3.1.
As of 2018, the number of vessels entering Busan Port has increased steadily from 27,400 to 27,800 in the past 17 years.
(ii) the cost figures presented are excessive. If one considers bunkering as a business, an investment of this magnitude will never be justified. One element that has not been addressed is that with the change from bunker-oil to LNG existing facilities come available and should be used as good as possible. It would be an interesting aspect of the paper to consider the extent to which this is feasible, ao from a safety point of view (LNG-safety criteria). Also it seems justified to consider the use of Floating Storage vessels instead of building new LNG storage tanks.
Response(ii):
We added following sentence in conclusion section
In particular, as the construction cost of the LNG storage tank on the land is about 200-250 million USD per unit, it is worth considering the construction of Floating Offshore LNG Bunkering Terminal (FLBT).
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
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