A Historical Analysis of Hydrogen Economy Research, Development, and Expectations, 1972 to 2020

Round 1

Reviewer 1 Report

The authors present a review on the progression of the hydrogen economy since its conceptualization in 1972 until 2020, in respect to academic literature, media articles and industrial progress. The article is well written and interesting. There are a few points that need addressing:

1.  The abstract needs revision. The authors state in the abstract ‘Progress towards an operating hydrogen economy is discouragingly slow despite global efforts to accelerate it. There are major mismatches between the present situation surrounding the hydrogen economy and previous proposed milestones that are far from being reached.’ Someone who is an expert in the hydrogen economy will know that these claims are true, but for someone who is not, these are just claims made by the authors that may or may not reflect reality. These claims are not backed up with evidence in the main section of the article. Therefore, the authors either need to revise their abstract to reflect the story of their main article or leave the abstract as is and provide a section in the introduction outlining the evidence that shows the regression of the hydrogen roadmaps among various countries or continents.   

2.  The authors haven’t mentioned what these projects from the IEA are about. Are these research project that focus on the development of electrolysers, fuel cells, hydrogen storage devices etc? Or other government projects? Details on these need to be added.

3.  Figures 2-6 need to be revised and a bigger fond to be used since none of the keywords can be read.

4.  Why Figure 6 contains keywords from 2010 to 2019 and not 2020 as outlined in the article’s title?  

5.  In Figure 8, the (a) and (b) are missing from the figure.

6.   The definition of green hydrogen provided by the authors in line 520-521 ‘In contrast, green hydrogen is hydrogen produced by renewables such as solar and wind.’ Needs to be revised by the correct definition, stating that water is used during the process to produce hydrogen. The way it is currently worded it implies that the difference between blue and green is that the later is produced by renewable energy to produce the hydrogen, implying that fossil fuels are the source of hydrogen for either blue or green. This is incorrect.

7.   The grammar in this sentence is incorrect ‘  The efficiency of both fuel cell and electrolyzer is getting higher while the cost is lower.’ Line 588-589

8.  The references throughout the manuscript need to be updated, the message ‘in Error! Reference source not found’ is present in line 83, 154, 188, 249, 272, 274, 277, 288, 345, 354, 365, 366, 368, 393, 472, 571.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript by Yap and McLellan “ A historical analysis of hydrogen economy research, development, and expectations, 1972 to 2020” presents a bibliometric analysis of the history of the hydrogen economy from 1972 to 2020.

The paper is interesting as it is. Although lacking details (inherent to the type of analysis presented), it is interesting to see how certain events influenced the interests in hydrogen. It presents a high level overview in terms of the growth phase, links to events and influences, roles and actors and expectations of the hydrogen economy.

The paper can be accepted for publication if the authors consider the following minor comments:

1.     Please compress citations: [1][2][3] should be [1-3]. Please check the whole manuscript.

2.     Please correct reference errors. There are quite some reference errors throughout the manuscript.

3.     For all figures, please mention what is plotted on the axes.

4.     A useful addition to the paper would be a market analysis of hydrogen. For example, how the scale/cost of hydrogen (green, blue, gray etc) changed in time and which event was responsible for this. Also, the number of startups/companies in the field of hydrogen would be interesting. Unfortunately, academic interest does not always translate into applications in practice, but this might be different for hydrogen?.

5.     An Outlook at the end of the paper would be useful.

Author Response

Please see the attachment.

Author Response File: Author Response.docx