A Bibliometric Analysis and Disruptive Innovation Evaluation for the Field of Energy Security

Abstract

The field of energy security is an important, complex and evolving field with important implications at the international, national and regional levels. Considering that no scholars have conducted bibliometric studies on the current energy security field, the authors of this study chose to use a bibliometric approach to conduct a search on the Web of Science using “energy security” as the keyword, and they conducted a systematic review of 5236 papers published between 2005 and 2022 to determine the current status and development of research in the field of energy security by addressing the following six questions: (1) What are the characteristics of the types of literature in the field of energy security? (2) What are the annual publication and citation frequency trends in the field of energy security? (3) What is the distribution of source journals, countries/regions, institutions, scholars and topics in the field of energy security? (4) What are the research hotspots in the field of energy security in the recent development history? (5) What are the most influential studies and the most disruptive studies in the field of energy security? (6) What are the characteristics of the different levels of cooperation networks in the field of energy security? Finally, we concluded the following: (1) In terms of publication dynamics, the number of annual publications and the citation frequency in the field of energy security maintain an upward trend, with a large number of source journals and a wide range of topics. The number of countries, institutions and scholars involved in research in the field of energy security keeps increasing, but the cooperation is fragmented and geopolitical. (2) From the perspective of research themes, research in the field of energy security has both strong technical characteristics and is associated with social science research themes. The contradictions between energy security and social, economic, environmental, land and climate issues, the interplay between energy supply systems and complex geopolitical and international relations issues and the important role of renewable energy and related technologies in maintaining national/regional energy security are the main issues of concern to researchers. (3) In terms of research centers, although the UK and the US still retain a first-mover advantage in this field, China has gradually overtaken and has become the country with the largest output of literature in recent years. The center of research in the field has also gradually shifted from Europe and the US to the East and South Asia regions. Overall, the governance of energy security issues still requires a combination of policy, economic and technological aspects. The results will help scholars systematically understand the current status of research, research frontiers and future trends in the field of energy security.

1. Introduction

In recent years, international energy security has faced a complex situation, with climate change, COVID-19, regional crises, unilateral restrictive measures and other factors causing serious impacts on the balance of international energy supply and demand. Since energy access affects the supply of basic human needs and is related to national economic growth, political stability and the overall development and security of other sectors, the issue of energy security has inevitably become an important factor and issue affecting the foreign policies of various countries and the global pattern.

So, what exactly is energy security? Energy security is a complex issue. The United Nations defines energy security as the sustained availability of energy in all its forms, in sufficient quantities and at affordable prices. The International Energy Agency (IEA) believes that there are two main aspects of energy security: long-term energy security and short-term energy security. The former relates to investment in energy supply and how it is linked to economic development and environmental needs, while the latter is primarily concerned with how quickly energy systems can respond to sudden changes in the energy supply-and-demand cycle. In addition, the definition of energy security may vary from country/region to country/region [1], which depends on a variety of factors, including: location, natural resources, economic status, energy access and its vulnerability to energy supply disruptions, political systems and international relations.

To address the global issue of energy security, it is crucial to reach an international consensus. As a global issue, energy security has been an important topic for the United Nations for a long time. The 2030 Agenda for Sustainable Development was adopted at the 70th session of the United Nations General Assembly in 2015 and was officially launched on 1 January 2016. This agenda calls on countries to take action to work towards achieving the 17 Sustainable Development Goals (SDGs) over the next 15 years. Of these 17 goals, the 7th is to ensure access to affordable, reliable and sustainable modern energy for all.

Of course, under the premise of reaching an international consensus, each country must also designate its own energy security policy guidelines according to its own national conditions. The following is an example of energy security policy development in China and the United States.

China has been concerned about energy-related issues at an early age. In 1980, Deng Xiaoping proposed that “energy is the primary issue of the economy”. In 1982, the 12th National Congress of the Communist Party of China identified energy as a strategic priority for socio-economic development. Since 1996, when China became a net importer of crude oil, energy security has faced many supply risks, and the issue of the security of energy use has become increasingly acute. Therefore, since the 8th Five-Year Plan, the central government has paid further attention to the energy security issue and has made appropriate policy adjustments according to the different stages of socio-economic development, continuously promoting the construction of China’s energy security system in terms of various aspects such as promoting scientific and technological innovation, promoting industrial development and strengthening foreign cooperation. On 13 June 2014, in the sixth meeting of the Leading Group on Finance and Economics held by the Party Central Committee, General Secretary Xi Jinping stressed that “Energy security is a global and strategic issue related to national economic and social development and is vital to national prosperity and development, improvement of people’s lives and long-term social stability. In the face of new changes in the pattern of energy supply and demand, new trends in international energy development, to protect national energy security, we must promote energy production and consumption revolution”. At the 20th National Congress of the Communist Party of China, General Secretary Xi Jinping further made it clear: “It is necessary to improve the national security system, the efficient and authoritative national security leadership system, the national security legal system, strategic system, policy system, risk monitoring and early warning system and the national emergency management system and build a global linkage, three-dimensional and efficient national security protection system, enhance the ability to maintain national security and ensure energy security”.

Since the enactment of the Energy Policy and Conservation Act in 1975, the U.S. government has enacted the Energy Conservation and Production Act (1976), the Warner Amendment (1983), the National Energy Efficiency Improvement Act (1990), the Energy Policy Act (1992) to promote the timely and efficient transformation of the national energy system and to ensure U.S. leadership in energy, the National Energy Policy Plan (1995), the National Comprehensive Energy Strategy (1998), the Energy Independence and Security Act (2007), the Clean Energy and Security Act (2009) and other related policies. On 15 November 2021, President Biden signed the Infrastructure Investment and Jobs Act, which provides USD 11 billion for grid infrastructure investments, USD 66 billion for emerging energy technology-related industries and USD 24 billion to enhance the resilience of the U.S. energy supply chain and energy competitive advantage. On 16 August 2022, President Biden also passed the Reducing Inflation Act. As the largest national public investment driven by the U.S. government since Roosevelt’s New Deal in the 1830s, the passage of the bill means that the U.S. government will raise and authorize USD 391 billion for energy and climate change spending. This includes USD 128 billion for renewable energy and grid storage, USD 30 billion for nuclear power, USD 13 billion for electric vehicle incentives, USD 14 billion for home energy efficiency upgrades, USD 22 billion for improving home energy access and USD 37 billion for advanced manufacturing. The history of energy security policy development in China and the United States shows that energy security issues are simultaneously important, complex, evolving and diverse.

Considering the various characteristics of energy security issues, relevant domestic and foreign scholars have conducted a series of energy security studies from different research perspectives. Since the research in this field involves many disciplinary directions and different research granularities, some scholars have also conducted some retrospective summaries of the research results in this field. The existing retrospective studies focus on the evolution and development of concepts related to the field of energy security [2,3,4], the research of the components of energy security [5], the summary of cross-disciplinary research methods [6], the summary of energy security assessment methods [7,8,9,10,11,12] and the multi-perspective analysis of specific types of energy [13,14,15,16,17]. The complexity and diversity of research in the field of energy security make it difficult for early researchers and non-specialists to understand the current status and development of research in the field of energy security, and no scholar has conducted a bibliometric study of the entire field of energy security. The authors of this study decided to introduce a bibliometric analysis to systematically review publications in the field of energy security in order to address the following six questions. (1) What are the characteristics of the types of literature in the field of energy security? (2) What are the annual publication and citation frequency trends in the field of energy security? (3) What is the distribution of source journals, countries/regions, institutions, scholars and topics in the field of energy security? (4) What are the research hotspots in the field of energy security in the recent development history? (5) What are the most influential studies and the most disruptive studies in the field of energy security? (6) What are the characteristics of the different levels of cooperation networks in the field of energy security?

2. Materials and Data Processing

2.1. Research Object

Bibliometrics is an interdisciplinary discipline that uses mathematical and statistical methods to provide a comprehensive analysis of the research landscape and development history of a given field. Considering the global nature of energy security issues, the Web of Science database was selected as the literature source for this study. As an important database for global access to academic information, the Web of Science includes multidisciplinary content from nearly 9000 of the most prestigious and high-impact research journals and more than 12,000 academic conferences worldwide. In this study, we searched the Web of Science core collection (SCIE, SSCI) for the subject term “Energy Security”, obtained 5236 documents (published from 2005 to 2022) for the study (as of 3 December 2022) and exported the full literature records in plain text format and Excel file format for further analysis.

2.2. Research Methods

This study used bibliometric and visualization methods to analyze the data. Excel was used to statistically analyze the acquired papers, highly cited papers, authors, countries, institutions, keywords, etc. and to produce line graphs of relevant change trends. VOSviewer was used to produce a collaborative network of authors, institutions and countries with a co-occurrence network of subject terms. CiteSpace was used for the keyword burst detection analysis. Navicat, Python and Sqlite were used for the disruptive innovation evaluation of research papers.

2.3. Data Acquisition and Processing

The data required for this study mainly include literature data and citation relationship data. Among them, literature information data can be obtained more easily using the Web of Science. However, due to the commercial property of the Web of Science database, it does not allow researchers to obtain a large amount of citation relationship data without purchasing the relevant APIs, nor does it allow researchers to utilize the data in depth and distribute it twice without any obstacles. This poses great difficulties for scholars concerned with relevant research in conducting results validation, multi-perspective studies and baseline comparisons.

To guarantee the reproducibility, rigor, transparency and independent validation of the study [18], the authors of this study chose to use COCI [19], the main database of OpenCitations, as the source of citation relationship data for the disruptive innovation measurement in this study. As of October 2022, this database already contains over 76 million bibliographic resources and 1.392 billion citation links. According to a recent independent analysis by Martín [20], the coverage of COCI is now close to the coverage of Web of Science and Scopus. Therefore, the citation relationship data obtained from COCI can largely reflect the real field dynamics. OpenCitations provides COCI dump data in CSV, N-Triples and Scholix formats on Figshare. In this study, we chose to use the CSV format for the dumped dataset. After downloading the data locally, we jointly used the Navicat database management tool 15, Python 3.9 and SQLite3.lib 3.35.5 to complete the transformation of the dataset from multiple fragmented files to a single database. After the database conversion was completed, the entire database was sliced and indexed by citation creation time to further optimize the measurement process.

2.4. Indicator for Disruptive Innovation Evaluation

In 1912, the Austrian economist Schumpeter [21] was the first to put forward the basic connotation of innovation in his classic book “The Theory of Economic Development: An Inquiry into Profit, Capital, Credit, Interest and the Business Cycle”, that is, innovation is the establishment of a production function, a new combination of production factors and production conditions in the production system. This pioneered the study of innovation theory. Later, Henderson [22] classified innovation into four categories—incremental innovation, structural innovation, modular innovation and radical innovation—from the perspective of knowledge management. In 1996, Christensen [23] of Harvard Business School pioneered the “disruptive innovation theory”, classified innovation into continuous innovation and disruptive innovation based on the values on which the innovation relies in his book “The Innovator’s Dilemma” [24] and built a basic framework of disruptive innovation theory. Disruptive innovation has thus become an important paradigm in the field of innovation research.

Based on the idea of disruptive innovation, Huang [25] proposed the Disruption Score, which argues that the emergence of disruptive research disrupts existing citation paths and creates new research paradigms. Wu [26] further extended this idea to the paper level by publishing “Large teams develop and small teams disrupt science and technology” in Nature and proposed the Disruption Index (referred to as D-index, as in formula (1)), which measures disruption by calculating the citation substitutability of focus papers in the citation network. Based on this index, Bornmann [27] studied disruptive papers published in Scientometrics. Horen [28], Sullivan [29] and Meyer [30] mined the disruptive papers in craniofacial surgery, pediatric surgery and synthetic biology, respectively.

As a brand-new bibliometric index, the D-index brings us a new evaluation idea, but the index itself still has certain shortcomings. In response, Bornmann [31] explored the convergent validity of the index and possible variants that might enhance the effectiveness of its measurement. Ruan [32] reflected on the limitations of the application of the disruption index as an indicator of scientific and technological progress. Liu [33,34] empirically investigated the stability time windows of the disruption index within different subject areas and addressed the mathematical inconsistency of the traditional D index [35] by proposing the $D_Z$ index (as in Formula (2)). This series of studies made it possible to evaluate the disruptive innovation of research papers and gradually matured.

$$\mathrm{D}=\frac{N_F-N_B}{N_F+N_B+N_R}$$

(1)

$$D_Z=\frac{2*N_F{}^2}{2*N_F+2*N_B+N_R}$$

(2)

In Formulas (1) and (2), $N_F$ refers to the literature that only cites the focus paper (FP), $N_B$ refers to the literature that cites both the focus paper and the references of the focus paper and $N_R$ refers to the reference that only cites the focus paper and does not cite the references of the focus paper.

3. Result and Discussion

3.1. Publishing Trend

3.1.1. Domain Level

As of 4 December 2022, there were a total of 5236 articles related to energy security in the Web of Science core set (SCIE, SSCI), and the distribution of their document types is shown in

Table 1. Type and quantity distribution of papers in the field of energy security.

Document Type	Quantity	Proportion/%
Article	4289	81.914
Review	701	13.388
Conference Paper	137	2.617
Book Review	123	2.349
Editorial	94	1.795
Online Publication	83	1.585
Book Chapter	14	0.267
News	12	0.229
Conference Abstract	7	0.134
Letter	7	0.134
Revise	3	0.057
Data Paper	1	0.019

. Among them, the article is the document type with the highest percentage, accounting for 81.914% of the total literature in the field of energy security, followed by the review, accounting for 13.388% of the total literature in the field of energy security. In addition to the two types that accounted for the largest share, the types that accounted for more than 1% were conference papers (2.617%), book reviews (2.349%), editorials (1.795%) and online publications (1.585%). The quantity of each of these types is much lower than the quantity of articles and review papers. This is due to the fact that some original studies are classified as both Article and Conference paper, resulting in a sum of the percentile of each type that is greater than 100%.

In the past decade or so, the numbers of citations and publications in the field of energy security have shown a continuous increase year by year (as shown in Figure 1). In 2005, only 26 papers were published on the topic of energy security. Among them, scholars from the United States published 11 articles, scholars from Japan published 3 articles, scholars from Australia, Canada and the United Kingdom published 2 articles each and scholars from Brazil, Egypt, France, India, China and Spain published 1 article each. However, by 2021, 633 papers covering the topic were published, with 93 countries participating in the study, proving the increasing importance of energy security globally.

3.1.2. Journal Level

The field of energy security has undergone 18 years of development since the first paper was published in 2005. In this study, a total of 32 journals (as shown in

Table 2. Journals with an average annual publication of more than one article.

Publication	Quantity	Proportion/%
Energy Policy	520	9.931
Renewable Sustainable Energy Reviews	325	6.207
Energies	239	4.565
Energy	210	4.011
Applied Energy	161	3.075
Sustainability	141	2.693
Journal of Cleaner Production	130	2.483
Renewable Energy	90	1.719
Energy Research Social Science	76	1.451
International Journal of Hydrogen Energy	68	1.299
Energy Economics	59	1.127
Energy Strategy Reviews	58	1.108
Energy Reports	45	0.859
Energy Sources Part B Economics Planning and Policy	44	0.84
Environmental Science and Pollution Research	42	0.802
Biomass Bioenergy	37	0.707
Fuel	33	0.63
Resources Policy	29	0.554
Science of the Total Environment	29	0.554
Oil Gas Journal	28	0.535
Energy for Sustainable Development	27	0.516
Environmental Research Letters	26	0.497
Journal of World Energy Law Business	25	0.477
Energy Environment	23	0.439
Water	23	0.439
Energy Sources Part A Recovery Utilization and Environmental Effects	21	0.401
Environment Development and Sustainability	21	0.401
Environmental Science Technology	21	0.401
International Affairs	21	0.401
Global Change Biology Bioenergy	20	0.382
Biofuels Bioproducts Biorefining-Biofpr	19	0.363

) with an average annual number of more than one article were screened from the source publications of 5236 publications on related topics, accounting for 3% of the total number of publications (1065) that have published literature on the topic of energy security. The journal with the highest number of publications is Energy Policy, with 520 publications, accounting for 9.931% of the total number of publications in the field of energy security. Renewable Sustainable Energy Reviews (325), Energies (239), Energy (210), Applied Energy (161), Sustainability (141), Journal of Cleaner Production (130), Renewable Energy (90), Energy Research Social Science (76), International Journal of Hydrogen Energy (68), Energy Economics (59) and Energy Strategy Reviews (58) published more than 1% of the total publications in the field, accounting for 6.207%, 4.565%, 4.011%, 3.075%, 2.693%, 2.483%, 1.719%, 1.451%, 1.299%, 1.127% and 1.108%, respectively. From the distribution of the main source publications in the field of energy security, we can see that strategy and policy, international relations, renewable energy, clean energy, bioenergy, traditional oil and gas energy, resource recovery and environmental protection are the mainstream concerns in this field.

3.1.3. Country Level

In 2005, only 11 countries published research in the field of energy security, but by the end of 2021, 93 countries/regions had conducted relevant research (among which the top 30 countries in terms of published papers are shown in

Table 3. Top 30 countries in terms of number of published papers.

Country/Area	Output	Proportion/%
USA	997	19.041
People’s Republic of China	899	17.17
England	604	11.536
India	376	7.181
Australia	289	5.519
Germany	240	4.584
Japan	221	4.221
Canada	215	4.106
Poland	174	3.323
Italy	158	3.018
Netherlands	156	2.979
Malaysia	151	2.884
Turkey	136	2.597
Sweden	126	2.406
Pakistan	124	2.368
South Korea	122	2.33
Spain	119	2.273
Brazil	112	2.139
Denmark	105	2.005
Austria	103	1.967
Singapore	99	1.891
South Africa	95	1.814
France	92	1.757
Iran	86	1.642
Scotland	85	1.623
Finland	80	1.528
Switzerland	76	1.451
Norway	75	1.432
Thailand	75	1.432
Russia	74	1.413

). This indicates that relevant research in this area has received wide attention from the international academic community. Among all participating countries, the 10 countries with the highest number of publications are USA (997), China (899), England (604), India (376), Australia (289), Germany (240), Japan (221), Canada (215), Poland (174) and Italy (158), accounting for 19.041%, 17.17%, 11.536%, 7.181%, 5.519%, 4.584%, 4.221%, 4.106%, 3.323% and 3.018% of the total number of publications in the field of energy security, respectively. Among them, the USA, China and England have more obvious output advantages. The quantity of publications reflects, to some extent, the research strength of these countries in the field of energy security and the importance they attach to energy security.

To further understand the dynamic development process of each country/region in the field of energy security, this study counted the distribution of the 10 countries with the highest quantity of published papers in terms of publication years (as shown in Figure 2). Overall, the 10 countries with the highest number of published papers are not all the first to join the field. The United States maintained its research dominance within the field until 2019, before being surpassed by China. China has maintained its absolute lead in the field of energy security internationally for the last three years, accounting for 30% of the total publications from the top 10 countries in terms of published papers. Energy security research in most countries has maintained a stable trend.

3.1.4. Institute Level

As shown in

Table 4. Institutions in the top 5000th of published papers.

Institute	Country	Output	Proportion/%
United States Department of Energy (DOE)	US	125	2.387
Chinese Academy of Sciences	PRC	124	2.368
University of California System	US	87	1.662
Indian Institute of Technology System (IIT)	India	78	1.49
University of London	UK	75	1.432
National University of Singapore	Singapore	67	1.28
International Institute for Applied Systems Analysis (IIASA)	Austria	66	1.261
Tsinghua University	PRC	54	1.031
Imperial College London	UK	53	1.012
University of Chinese Academy of Sciences (CAS)	PRC	48	0.917
University of Cambridge	UK	46	0.879
Aarhus University	Denmark	45	0.859
University of Oxford	US	45	0.859
National Institute of Technology (NIT) System	India	43	0.821
University of California Berkeley	US	43	0.821
University of Sussex	UK	43	0.821
Swiss Federal Institutes of Technology Domain	Switzerland	42	0.802
Universiti Malaya	Malaysia	42	0.802
University of Tokyo	Japan	42	0.802
Beijing Institute of Technology	PRC	37	0.707
China University of Petroleum	PRC	37	0.707
Beijing Normal University	PRC	35	0.668
University System of Georgia	US	35	0.668
Oak Ridge National Laboratory	US	34	0.649
Udice French Research Universities	France	33	0.63
Australian National University	Australia	32	0.611
China University of Mining Technology	PRC	32	0.611
Lund University	Sweden	32	0.611
Utrecht University	Netherlands	32	0.611
North China Electric Power University	PRC	31	0.592
University of Leeds	UK	31	0.592
Stanford University	US	30	0.573
Xiamen University	PRC	30	0.573
European Commission Joint Research Center	European Commission	29	0.554
Eth Zurich	Switzerland	27	0.516
Universiti Teknologi Malaysia	Malaysia	27	0.516
University College London	UK	27	0.516
University of Manchester	UK	27	0.516
Harvard University	US	26	0.497
Kyoto University	Japan	26	0.497

, among the institutions that publish papers in the field of energy security, the top 0.5% of institutions are selected according to the number of published papers. The institution with the highest number of publications is the United States Department of Energy (DOE) (125), accounting for 2.387% of the total number of publications in the field of energy security, followed by the Chinese Academy of Sciences (124), University of California System (87), Indian Institute of Technology System (IIT) (78) and University of London (75), accounting for 2.368%, 1.662%, 1.49% and 1.432% of the total number of publications in the field of energy security. Among the countries where the high-producing institutions are located, China tops the list with nine, followed by the United States (8), the United Kingdom (7), India (2), Japan (2) and Malaysia (2). Research institutions in China, the U.S. and the U.K. occupy absolute dominance in this field.

3.1.5. Scholar Level

Among the scholars who have published in the field of energy security, the scholars who have participated in more than 10 publications are listed in

Table 5. Scholars with publications greater than or equal to 10.

Author	Output	Nation	Citation
Sovacool, Benjamin	63	US	2311
Lin, Boqiang	19	PRC	647
Ren, Jingzheng	18	PRC	615
Huang, Guohe	15	PRC	574
Jewell, Jessica	14	US	686
Riahi, Keywan	12	Austria	853
Hughes, Larry	12	Canada	342
Shukla, Priyadarshi	11	India	474
Limmeechokchai, Bundit	11	Thailand	174
Krikštolaitis, Ričardas	11	Lithuania	164
Bazilian, Morgan D.	11	USA	368
Cai, Yanpeng	11	PRC	535
Taghizadeh-Hesary, Farhad	11	Japan	303
Mondal, Alam Hossain	10	Bangladesh	243
Komendantova, Nadejda	10	Austria	164
O Gallachoir, Brian O.	10	Ireland	447
Goldthau, Andreas	10	Germany	490
Masjuki, H.H.	10	Malaysia	1096

, among which the most published scholar is Sovacool Benjamin, who has participated in 63 publications with 2311 cumulative citations and is a highly cited scholar in interdisciplinary research, as selected by Clarivate. The top five scholars also include Lin Boqiang (19), Ren Jingzheng (18) and Huang Guohe (15) from China and Jewell Jessica (14) from the United States, with 647, 615, 574 and 686 cumulative citations, respectively. Among the 18 selected countries with high-output authors, China (4), the United States (2) and Austria (2) have more than one author.

3.2. Research Situation and Evolution

3.2.1. Research Topic Distribution

The 5236 retrieved papers in the field of energy security were classified into 90 research directions by the Web of Science, and the specific distribution is shown in

Table 6. Distribution of research topics in the literature in the field of energy security.

Research Topic	Quantity	Proportion/%
Energy Fuels	2429	46.39
Environmental Sciences Ecology	1701	32.487
Science Technology Other Topics	1022	19.519
Engineering	946	18.067
Business Economics	841	16.062
Thermodynamics	315	6.016
Government Law	250	4.775
Chemistry	230	4.393
International Relations	226	4.316
Biotechnology Applied Microbiology	155	2.96
Agriculture	144	2.75
Area Studies	142	2.712
Materials Science	106	2.024
Public Administration	93	1.776
Geography	92	1.757
Computer Science	90	1.719
Electrochemistry	85	1.623
Meteorology Atmospheric Sciences	82	1.566
Nuclear Science Technology	82	1.566
Water Resources	82	1.566
Mechanics	58	1.108
Geology	53	1.012

. Among them, 22 directions accounted for more than 1% and 5 directions accounted for more than 10%, namely, Energy Fuels, Environmental Sciences Ecology, Science Technology Other Topics, Engineering and Business Economics, accounting for 46.39%, 32.487%, 19.519%, 18.067% and 16.062%, respectively. The sum of the percentile of each type is greater than 100% due to the fact that some original works are attributed to multiple categories in the Web of Science. Among the research directions involved in the field of energy security, it involves environmental science, thermodynamics, chemistry, biotechnology, agriculture, materials science, geography, computer technology, electrochemistry and nuclear science and technology, which have strong technical characteristics, and is also related to politics, law, international relations, regional governance and other social sciences, which is a typical interdisciplinary field.

3.2.2. Keywords Distribution

The analysis of high-frequency keywords, their frequency of occurrence and their total link intensity can be used to reveal research trends and research hotspots in the field. The analysis of the papers in the field of energy security revealed that this field currently contains a total of 16,485 keywords. Among them, 1683 keywords appeared at least 4 times, 1310 keywords appeared at least 5 times and 637 keywords appeared at least 10 times, accounting for 9.99%, 7.95% and 3.86% of the total, respectively. The keywords were ranked according to TLS, and the top 30 keywords were selected, as shown in

Table 7. Top 30 keywords by TLS in the field of energy security.

Keyword	TLS	Occurrences	Average Publication Year
energy security	6720	1273	2016.787
renewable energy	4613	632	2017.837
energy	2965	497	2015.938
policy	2528	355	2017.144
China	2294	350	2017.095
sustainability	1997	266	2017.761
consumption	1949	260	2018.406
biomass	1698	235	2015.688
emissions	1698	238	2016.816
performance	1665	251	2017.629
power	1659	252	2017.012
biofuels	1517	224	2014.277
security	1509	229	2017.261
climate change	1491	209	2017.254
impact	1459	205	2018.647
model	1404	232	2017.731
energy policy	1337	224	2016.536
electricity	1330	190	2017.118
optimization	1319	185	2018.082
sustainable development	1302	185	2017.611
systems	1283	193	2017.516
climate change	1253	218	2015.13
oil	1249	201	2016.01
bioenergy	1188	169	2015.687
generation	1159	161	2018
biodiesel	1156	176	2015.253
system	1137	168	2017.488
CO2 emissions	1123	143	2018.86
life-cycle assessment	1122	150	2017.336
management	1114	158	2017.671

. The keyword with the largest TLS value is energy security, with a TLS value of 6720 and a total of 1273 occurrences, followed by renewable energy, with a TLS value of 4613 and a total of 632 occurrences. From the table, we can also find that the keywords with a higher TLS generally appear after 2015, which reflects that the energy security field is a booming field with a high potential for innovation.

3.2.3. Keywords Co-Occurrences

The co-occurrence analysis of keywords in the field of security energy was performed, and the results are shown in Figure 3. From the figure, we can find that the keywords in this domain are mainly divided into five clusters. By analyzing the clustering patterns shared by keywords and the keyword composition characteristics within the clusters, researchers can gain further insight into the scope and interrelationship of different sub-research areas in the field of energy security. Combining the relevant literature and the keyword co-occurrence pattern map, we found some very interesting conclusions.

In the yellow cluster, the keywords “China”, “carbon emissions” and “economic growth” have a strong influence. This cluster represents the contradictory situation of developing countries in terms of energy security and climate protection. A number of scholars have conducted studies on this issue. Wu [36] argued that the successful implementation of energy conservation and emission reduction policies in China proves that climate change protection and energy security in China can be a win–win situation. Lin [37] estimated 11 energy security indicators for long-term energy supply by applying the MARKAL framework to Pakistan and found that energy security and energy supply systems are equally optimal in cost reduction, carbon dioxide and energy supply reduction scenarios. La Rovere [38] showed that the decoupling of economic growth and greenhouse gas emissions is possible with the use of appropriate policy instruments and will not harm the economic and social development of Brazil. Pode [39] used India as a sample to confirm that the introduction of a renewable energy portfolio would enhance energy security and reduce carbon emissions, preventing energy shortages from impeding the country’s industrial growth and economic development. The abovementioned four representative developing country study cases can exemplify the important value of energy security research in resolving the conflict between energy security and climate protection.

In the green cluster, the keywords “energy policy”, “geopolitics”, “Russia”, “Germany” and “crisis” have a strong influence. This cluster reflects the interplay and intensification between the single energy supply system represented by Russia–EU and complex geopolitical and international relations issues. In response, Hadfield [40] found, through an analysis of EU and Russian strategic cultures and bilateral energy security policies, that despite the trend towards convergence between EU and Russian energy security policies, there will be persistent intransigence in the bilateral energy dialogue due to their different subject visions. Ostrowski [41] pointed out that the European Community has played a crucial role in providing a collective voice for Central and Eastern Europe and supports its regional energy integration to reduce its vulnerability to external pressure from Russia, but geopolitical concerns and the constraints of the Cold War legacy that surface in a cyclical manner make European energy security problematic in the absence of a more general political solution between Russia and the West.

In the blue cluster, the keywords “renewable energy”, “wind” and “solar” have a strong influence. This cluster reflects the important role of renewable energy in maintaining national/regional energy security and that of wind and solar energy in expanding the share of renewable energy. Zong [42] analyzed the composition of renewable energy in the G7 countries and found that the share of different types of renewable energy varies from country to country, with hydroelectric energy accounting for a high share of the total renewable energy capacity in the G7 countries, but the use of wind and solar energy is rapidly increasing. Cergibozan [43] analyzed the impact of renewable energy on energy security risks in 23 OECD countries over the period 1985–2016, demonstrating that the total renewable energy reduces energy security risks in OECD countries. However, due to the differences in the characteristics of each country, such as the level of industrial production, the total energy, the level of economic development and urbanization, each country should implement policies aimed at reducing its energy security risks that are specific to the unique characteristics of each country according to local conditions. Trifonov [44] selected EECCA countries for his study, confirmed the positive impact of increasing the share of renewable energy on the level of energy security and pointed out that the rational adjustment of the energy mix would further enhance this positive effect. The above study reflects that the vigorous development of renewable energy will be an important tool in maintaining energy security, and the integrated formulation of a renewable energy development strategy according to the internal development and external environment of the country will be a strong driver enhancing the effectiveness of this tool.

In the red cluster, the keywords “bioenergy”, “alternative fuels” and “global warming” have a certain influence. In the purple cluster, the keywords “climate”, “food security” and “supply chain” have a strong influence. These two clusters reflect the relationship between researchers’ perceptions of the environmental problems associated with the heavy use of traditional energy sources, the role of bioenergy in reversing environmental problems and whether the heavy use of bioenergy poses other problems. In response, Danish [45] investigated the biomass energy consumption and environmental pollution in BRIGS countries from 1992 to 2013 using a generalized system moment method model empirical estimation, and the results showed that bioenergy has a role in reducing environmental pollution. However, Spangenberg [46] pointed out that bioenergy can be a valuable component of the new energy mix, but without significant reductions in energy consumption, its contribution will remain negligible. Without structural changes in the energy system, the blind development of bioenergy will pose the same risks to environmental security, biodiversity and food security. Therefore, the use of indigenous biomass (especially residues and waste [47]) to replace a portion of imported fossil fuels is a viable strategy for maintaining energy security using bioenergy [48]. At the same time, the establishment of a policy system consisting of legislation, development plans and incentives to maintain the consistency and continuity of relevant policies [49] in order to avoid the supply chain problems caused by free-market blindness may be an important guarantee for the rational construction of bioenergy systems.

Overall, the five clusters are highly intertwined with each other, reflecting that the energy security issue is an interdisciplinary, multidimensional and complex problem. The governance of energy security issues needs to be carried out jointly from policy, economic and technological perspectives. Among the five clusters, the overall influence of the purple cluster is small, indicating that this research direction has not received the focused attention of current scholars in the field of energy security yet. We believe that the reasons why this area has not become a mainstream hotspot in the field of energy security may include: a. Only some of the research contents in interdisciplinary research areas such as food security and biodiversity overlap with the field of energy security; b. Under the premise that the two core research tasks of energy supply meeting the current socio-economic development needs and energy sustainability have not yet been realized, most research scholars in the field of energy security have probably not shifted their research focus to this subfield.

3.2.4. Burst Keywords Analysis

Burst words are keywords with a high word frequency occurrence within a specific statistical interval, reflecting the research hotspots and evolutionary trends in the field of energy security at different times. In this study, we used CiteSpace software to count the emergent words of research in the field of energy security from 2005 to the present and filtered the top 30 keywords by mutation intensity (as shown in

Table 8. Burst keywords in the field of energy security.

Keywords	Topic	Year	Strength	Begin	End	2005–2022
energy	Complex	2006	12.35	2006	2013	▂▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂
climate change	Environment	2006	11.82	2006	2012	▂▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂
energy security	Complex	2005	6.97	2007	2008	▂▂▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂
biofuel	Energy	2007	14.68	2007	2014	▂▂▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂
ethanol	Energy	2007	13.17	2007	2014	▂▂▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂
vegetable oil	Energy	2007	8.63	2007	2012	▂▂▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂
biomass	Energy	2007	7.98	2007	2012	▂▂▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂
fuel	Energy	2007	5.86	2007	2010	▂▂▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂
biodiesel	Energy	2007	5.63	2007	2011	▂▂▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂
energy policy	Policy	2007	5.48	2007	2013	▂▂▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂
United States	Policy	2008	6.59	2008	2016	▂▂▂▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂
greenhouse gas	Environment	2009	8.46	2009	2012	▂▂▂▂▃▃▃▃▂▂▂▂▂▂▂▂▂▂
security of supply	Infrastructure	2009	8.13	2009	2014	▂▂▂▂▃▃▃▃▃▃▂▂▂▂▂▂▂▂
fuel cell	Energy	2009	4.88	2009	2012	▂▂▂▂▃▃▃▃▂▂▂▂▂▂▂▂▂▂
nuclear power	Energy	2010	9.17	2010	2015	▂▂▂▂▂▃▃▃▃▃▃▂▂▂▂▂▂▂
science	Complex	2010	5.41	2010	2016	▂▂▂▂▂▃▃▃▃▃▃▃▂▂▂▂▂▂
agriculture	Agriculture	2010	4.96	2010	2015	▂▂▂▂▂▃▃▃▃▃▃▂▂▂▂▂▂▂
economics	Economics	2010	4.69	2010	2015	▂▂▂▂▂▃▃▃▃▃▃▂▂▂▂▂▂▂
energy security indicator	Complex	2013	4.84	2013	2015	▂▂▂▂▂▂▂▂▃▃▃▂▂▂▂▂▂▂
air pollution	Environment	2007	4.89	2014	2017	▂▂▂▂▂▂▂▂▂▃▃▃▃▂▂▂▂▂
environmental impact	Environment	2011	4.52	2018	2019	▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂
diversification	Complex	2013	4.88	2019	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃
operation	Infrastructure	2016	4.88	2019	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂
index	Complex	2017	4.93	2019	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃
power plant	Infrastructure	2019	4.54	2019	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂
renewable energy source	Energy	2008	6.52	2020	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃
hydrogen production	Energy	2009	5.43	2020	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃
power system	Infrastructure	2014	5.14	2020	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃
circular economy	Economics	2020	5.42	2020	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃
composite indicator	Complex	2020	4.9	2020	2022	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃

). In this study, the selected keywords were classified into the seven categories of Agriculture, Complex, Economics, Energy, Environment, Infrastructure and Policy according to the research topics they belonged to.

In terms of temporal distribution, each year has burst words in the top 30 except for 2012 and 2015, indicating that the field of energy security is under continuous development and expanding into new research subfields. In terms of category distribution, the Energy category has the most emergent words, accounting for 1/3 of all emergent words (10). This is followed by the Complex category (7), Environment category (4), Infrastructure category (4), Economics category (2), Policy category (2) and Agriculture category (1). In terms of content, the keywords in the Energy category include “biofuel”, “ethanol”, “vegetable oil”, “biomass”, “fuel”, “biodiesel”, “fuel cell”, “nuclear power”, “renewable energy source” and “hydrogen production”. These keywords represent technological research in the field of energy security. The keywords in the Complex category include “energy”, “energy security”, “science”, “energy security indicator”, “diversification”, “index” and “composite indicator”. These keywords represent macro studies and energy/technology evaluation in the field of energy security research. Keywords in the Environment category include “climate change”, “greenhouse gas”, “air pollution” and “environmental impact”, which represent research related to environmental impact in the field of energy security. The keywords in the category of Infrastructure include “security of supply”, “operation”, “power plant” and “power system”, which represent the research related to infrastructure and the supply chain in the field of energy security. The keywords of the Economics category include “economics” and “circular economy”, which represent the research related to energy economy in the field of energy security. These keywords represent research on topics related to “energy policy”, “international relations”, “geopolitics”, “international trade”, etc. The last category is Agriculture, which represents research related to land, agriculture, ecology and food in the field of energy security. In terms of time distribution and content distribution (Figure 4), the energy security field focused on macro studies, policy studies and energy technology studies in the early years and then gradually began to focus on environmental studies, economic studies and infrastructure studies on related topics. The latter is likely to become a new research focus in the field of energy security in the future.

3.3. Research Evaluation

3.3.1. Academic Influence

From the 5236 papers in the field of energy security, the top 1% of papers were filtered by the cumulative frequency of citations since publication, as shown in

Table 9. Top 1% of papers in the field of energy security with cumulative citations.

Title	Type	First Author	Source Publication	Year	Citation
Renewable energy resources: Current status, future prospects and their enabling technology	Review	Ellabban, Omar	Renewable & Sustainable Energy Reviews	2014	1286
Progress and recent trends in biofuels	Review	Demirbas, Ayhan	Progress In Energy and Combustion Science	2007	1145
Review of solutions to global warming, air pollution, and energy security	Review	Jacobson, Mark Z.	Energy & Environmental Science	2009	964
Hydrogen energy, economy and storage: Review and recommendation	Review	Abe, J.O.	International Journal of Hydrogen Energy	2019	907
Review of electrical energy storage technologies, materials and systems: challenges and prospects for large-scale grid storage	Review	Gur, Turgut M.	Energy & Environmental Science	2018	901
Dimethyl ether (DME) as an alternative fuel	Article	Semelsberger, Troy A.	Journal Of Power Sources	2006	830
Assessment of the Impact of Plug-in Electric Vehicles on Distribution Networks	Article	Pieltain Fernandez, Luis	IEEE Transactions on Power Systems	2011	751
Biofuels sources, biofuel policy, biofuel economy and global biofuel projections	Article	Demirbas, Ayhan	Energy Conversion and Management	2008	733
Surface and Interface Engineering of Noble-Metal-Free Electrocatalysts for Efficient Energy Conversion Processes	Review	Zhu, Yun Pei	Accounts of Chemical Research	2017	675
Recovery and recycling of lithium: A review	Review	Swain, Basudev	Separation and Purification Technology	2017	658
Hydrogen and fuel cells: Towards a sustainable energy future	Article	Edwards, P.P.	Energy Policy	2008	636
Energy supply, its demand and security issues for developed and emerging economies	Review	Asif, M.	Renewable & Sustainable Energy Reviews	2007	634
Challenges and opportunities towards fast-charging battery materials	Review	Liu, Yayuan	Nature Energy	2019	634
Microalgae biofuels: A critical review of issues, problems and the way forward	Review	Lam, Man Kee	Biotechnology Advances	2012	604
Energy justice: A conceptual review	Review	Jenkins, Kirsten	Energy Research & Social Science	2016	594
A review of wind energy technologies	Review	Herbert, G.M. Joselin	Renewable & Sustainable Energy Reviews	2007	590
Urban energy use and carbon emissions from cities in China and policy implications	Article	Dhakal, Shobhakar	Energy Policy	2009	557
A review of recent literature to search for an efficient catalytic process for the conversion of syngas to ethanol	Review	Subramani, Velu	Energy & Fuels	2008	548
Energy systems modeling for twenty-first century energy challenges	Review	Pfenninger, Stefan	Renewable & Sustainable Energy Reviews	2014	521
Indicators for energy security	Article	Kruyt, Bert	Energy Policy	2009	486
The effect of bioenergy expansion: Food, energy, and environment	Review	Popp, J.	Renewable & Sustainable Energy Reviews	2014	474
Hydrogen membrane separation techniques	Review	Adhikari, S.	Industrial & Engineering Chemistry Research	2006	463
Opportunities and challenges for biodiesel fuel	Review	Lin Lin	Applied Energy	2011	445
Renewable energy consumption, CO(2) emissions and oil prices in the G7 countries	Article	Sadorsky, Perry	Energy Economics	2009	434
Nanostructured electrodes for lithium-ion and lithium-air batteries: the latest developments, challenges, and perspectives	Review	Song, Min-Kyu	Materials Science & Engineering R-Reports	2011	425
Ensuring energy security	Article	Yergin, D.	Foreign Affairs	2006	422
Materials for the Recovery of Uranium from Seawater	Review	Abney, Carter W.	Chemical Reviews	2017	408
The interdisciplinary nature of SOIL	Article	Brevik, E.C.	Soil	2015	407
The promise and challenges of microalgal-derived biofuels	Article	Pienkos, Philip T.	Biofuels Bioproducts & Biorefining-Biofpr	2009	402
Assessment of utility energy storage options for increased renewable energy penetration	Review	Evans, Annette	Renewable & Sustainable Energy Reviews	2012	394
Biotechnological processes for conversion of corn into ethanol	Review	Bothast, RJ	Applied Microbiology and Biotechnology	2005	386
Crop residues as raw materials for biorefinery systems—A LCA case study	Article	Cherubini, Francesco	Applied Energy	2010	381
Zeolitic imidazolate framework ZIF-7 based molecular sieve membrane for hydrogen separation	Article	Li, Yanshuo	Journal of Membrane Science	2010	377
A Survey on Cyber Security for Smart Grid Communications	Article	Yan, Ye	IEEE Communications Surveys and Tutorials	2012	372
Fuel cell and battery electric vehicles compared	Article	Thomas, C.E.	International Journal of Hydrogen Energy	2009	371
Oil prices and the stock prices of alternative energy companies	Article	Henriques, Irene	Energy Economics	2008	362
Application of quantitative P-31 NMR in biomass lignin and biofuel precursors characterization	Review	Pu, Yunqiao	Energy & Environmental Science	2011	357
Bioenergy from plants and the sustainable yield challenge	Review	Karp, Angela	New Phytologist	2008	357
Recent progress in the development of anode and cathode catalysts for direct methanol fuel cells	Review	Tiwari, Jitendra N.	Nano Energy	2013	356
The impact of renewable energy consumption to economic growth: A panel data application	Article	Inglesi-Lotz, Roula	Energy Economics	2016	345
Bioethanol production from renewable sources: Current perspectives and technological progress	Review	Zabed, H.	Renewable & Sustainable Energy Reviews	2017	344
The international political economy of the global land rush: A critical appraisal of trends, scale, geography and drivers	Article	Cotula, Lorenzo	Journal of Peasant Studies	2012	344
Energy security: Definitions, dimensions and indexes	Review	Ang, B.W.	Renewable & Sustainable Energy Reviews	2015	340
State of the art of thermal storage for demand-side management	Article	Arteconi, A.	Applied Energy	2012	340
Novel hydrogen storage materials: A review of lightweight complex hydrides	Review	Jain, I.P.	Journal of Alloys and Compounds	2010	335
Effects of US Maize Ethanol on Global Land Use and Greenhouse Gas Emissions: Estimating Market-mediated Responses	Article	Hertel, Thomas W.	Bioscience	2010	334
Do urbanization and industrialization affect energy intensity in developing countries?	Article	Sadorsky, Perry	Energy Economics	2013	333
Economic impacts from the promotion of renewable energy technologies: The German experience	Article	Frondel, Manuel	Energy Policy	2010	331
Lessons for effective renewable electricity policy from Denmark, Germany and the United Kingdom	Article	Lipp, Judith	Energy Policy	2007	331
Vulnerability of US and European electricity supply to climate change	Article	van Vliet, Michelle T.H.	Nature Climate Change	2012	328
Current status of hybrid, battery and fuel cell electric vehicles: From electrochemistry to market prospects	Review	Pollet, Bruno G.	Electrochimica Acta	2012	325
A review of renewable energy technologies integrated with desalination systems	Review	Eltawil, Mohamed A.	Renewable & Sustainable Energy Reviews	2009	320

. Among the 52 selected highly cited articles, 30 (57.69%) were of the Review type and 22 (42.31%) were of the Article type. The journal with the highest number of highly cited papers published was Renewable & Sustainable Energy Reviews (9), followed by Energy Policy (5), Energy Economics (4), Applied Energy (3), Energy & Environmental Science (3) and Industrial & Engineering Chemistry Research (2). From the source journals of highly cited papers, we can find that renewable energy is an important research hotspot in the field of energy security. In addition, political, funding, environmental, regulatory and technical issues in energy use and development related to energy security are also important subfields of energy security research. From the perspective of annual distribution, papers were selected in the top 1% of the total cited frequency every year in this field from 2005 to 2019, reflecting the continuous concern of relevant researchers in this field.

Among the 52 highly cited papers, most of the studies explored technological issues related to securing energy security. Bothast [13] discussed the biotechnological process and future prospects of converting corn to ethanol. Semelsberger [50] introduced the advantages and implications of DME as an alternative fuel over conventional petroleum energy sources. Adhikari [51] reported on different types of membranes used for hydrogen separation from hydrogen-rich mixtures and their performance in terms of hydrogen selectivity and permeability. Asif [52] quantified the current depletion period of major energy sources (coal, oil, natural gas and nuclear fissile materials) and discussed the feasibility of switching to renewable energy sources. Subramani [53] summarized the conversion of syngas to higher alcohols by various catalytic pathways. Karp [54] reviewed the yields of a range of key bioenergy crops and suggested targets that could be improved. Edwards [55] and Song [56] presented the current status, technical challenges and development forecasts for hydrogen cells, fuel cells and other advanced batteries. Pienkos [57] gave a brief overview of algae research sponsored by the U.S. Department of Energy and analyzed the potential of microalgae biofuels and the technical and economic hurdles that need to be overcome before the production of microalgae-derived diesel fuel alternatives becomes a large-scale commercial reality. Li [58] tested the hydrogen separation performance of ZIF-7 molecular sieve membranes and summarized the key scientific challenges for advanced battery development. Pu [59] reviewed the application of 31P NMR in the quantitative analysis of the biomass lignin structure. Lam [60] summarized the practical problems faced by the microalgae biofuel industry and proposed several solutions. Evans [61] summarized the development of energy storage technology and compared the performance parameters of major energy storage solutions. Tiwari [62] presented the latest progress in the development of DMFC catalysts. Ellabban [63] described how renewable energy is currently being used and its future prospects. Zhu [64] discussed recent advances in the design and fabrication of efficient electrocatalysts based on carbon materials, graphitic carbon nitride and transition metal oxides or hydroxides. Zabed [65] provided an overview of first- and second-generation bioethanol production models, discussing in detail the potential of various biomass sources, technical approaches, the role of microorganisms and factors affecting the ethanol production process. Abney [66] provided a comprehensive review of recent developments of materials developed to recover uranium from seawater from 2000 to 2016 and discussed the challenges of conducting reliable and reproducible uranium adsorption studies. Swain [67] summarized the lithium recovery technology. Gur [68] provided a comprehensive review of the technologies, materials and systems portfolio related to electrical energy storage and presented recent advances with challenges that have yet to be overcome. Liu [69] discussed the challenges and future research directions of fast charging from the battery material level. Jain [70] presented a fundamental understanding of the physical, chemical and structural properties of lightweight hydride materials.

In addition to the research on energy technologies, some scholars have also studied the energy economic issues related to energy security. Demirbas [14,15] analyzed the progress of research on different types of biofuels themselves and the related socio-economic issues. Henriques [71] analyzed the impact of oil prices on the value of alternative energy companies. Sadorsky [72] proposed an empirical model of renewable energy consumption in G7 countries. Eltawil [73] combined technical and economic perspectives to review the progress in the field of renewable energy desalination. Pollet [74] summarized the technological developments, advantages and disadvantages of hybrid, pure electric and fuel cell electric vehicles and the impact of these technologies on consumers from an electrochemical and market perspective. Jenkins [75] proposed that energy justice provides a new incentive framework for bridging existing and future research on energy production and consumption. Cotula [76] explored the factors influencing the price of land in the context of energy security. Abe [77] reviewed recent studies addressing the storage of hydrogen energy to improve its economics. Inglesi-Lotz [78] adopted a panel data analysis to estimate the impact of renewable energy consumption on economic welfare, confirming that the impact of renewable energy consumption or its share in the total energy structure on economic growth is positive.

Environmental issues related to energy security have also received the attention of some scholars. Jacobson [79] reviewed energy solutions related to global warming and air pollution. Dhakal [80] studied alternative energy sources used by large Chinese cities to reduce CO₂ emissions. Cherubini [81] proposed the use of crop residues as feedstock for biorefinery systems. Thomas [82] constructed a model for comparing the social benefits of partially electrified vehicles replacing conventional gasoline vehicles and found that the combination of fully electric vehicles with hybrids and plug-in hybrids is the best combination model today. Lin [83] provided an overview of the technological development of biodiesel and the possible environmental and social impacts associated with biodiesel production. Hertel [84] studied the negative environmental impacts and land use issues associated with the production of corn ethanol in the United States. van Vliet [85] explored the impact of the climate change-induced reduction of cooling water sources on thermoelectric-based energy systems. Brevik [86] summarized the relationship between soil studies and energy security studies.

Second, a number of scholars have also examined the interplay between energy policy, international relations and national development. Lipp [87] summarized the lessons learned from renewable electricity policies in Denmark, Germany and the UK. Frondel [88] critically reviewed the relevant impacts of the Renewable Energy Act on job creation and climate protection. Sadorsky [89] examined the impact of income, urbanization and industrialization on energy security in 76 developing countries. Pfenninger [90] classified national and international energy policy-related models and noted their important value as a source of information for policy formulation.

In addition, as the practice of securing energy continues, a number of scholars have conducted a series of studies addressing related supply chains and infrastructures. Herbert [91] provided a review of studies on the technical and economic aspects of wind energy resource evaluation, wind energy conversion systems and control systems. Pieltain Fernandez [92] proposed an evaluation methodology for identifying and quantifying the impact of different levels of plug-in electric vehicles on distribution grid investments and energy losses. Yan [93] summarized the cybersecurity needs and possible vulnerabilities of smart grids and surveyed current cybersecurity solutions for smart grids. Arteconi [94] demonstrated the current status of the application of thermal storage technology in supply chain management.

Finally, conceptual and methodological research on energy security is also essential. Kruyt [2] distinguished four dimensions of energy security (availability, accessibility, affordability and acceptability) and classified energy security research according to this taxonomy. Yergin [95] summarized the multifaceted factors that influence energy security. Ang [4] provides an overview of energy security definitions, definition variations of themes, the energy security index, areas and methods of index focus and energy security in the context of national energy policies.

3.3.2. Disruptive Innovation

Innovation is the essential requirement for academic papers and is the core feature reflecting the academic level of the papers. As an important carrier of academic results, it is important to conducting the reasonable and efficient innovative evaluation of papers. Therefore, facing the important issue of energy security, introducing the evaluation perspective of disruptive innovation will be an important step in exploring the key research in this field. In this study, we chose to use the absolute disruptiveness index to measure the innovativeness of Article-type papers in this field with more than 10 references from 2005 to 2019 [31,32]. The top 20 of these papers are shown in

Table 10. Top 20 research papers with disruptive innovation in the field of energy security.

Title	First Author	Journal	Year	Dz
Urban energy use and carbon emissions from cities in China and policy implications	Shobhakar Dhakal	Energy Policy	2009	14.158
North-East Asian Super Grid for 100% renewable energy supply: Optimal mix of energy technologies for electricity, gas and heat supply options	Dmitrii Bogdanov	Energy Conversion and Management	2016	8.766
Vehicle Electrification: Status and Issues	A.G. Boulanger	Proceedings of the IEEE	2011	7.758
Assessment of the Impact of Plug-in Electric Vehicles on Distribution Networks	Luis Pieltain Fernandez	IEEE Transactions on Power Systems	2011	7.377
Assessing oil supply security of South Asia	M. Mohsin	Energy	2018	5.938
The international political economy of the global land rush: A critical appraisal of trends, scale, geography and drivers	Lorenzo Cotula	The Journal of Peasant Studies	2012	5.716
Impact of uncoordinated plug-in electric vehicle charging on residential power demand	Matteo Muratori	Nature Energy	2018	5.606
A comparative analysis of electricity generation costs from renewable, fossil fuel and nuclear sources in G20 countries for the period 2015–2030	Manish Ram	Journal of Cleaner Production	2018	5.477
Transportation in a 100% renewable energy system	Antonio García-Olivares	Energy Conversion and Management	2018	5.337
European renewable energy policy at crossroads—Focus on electricity support mechanisms	Doerte Fouquet	Energy Policy	2008	5.204
Geopolitics of European natural gas demand: Supplies from Russia, Caspian and the Middle East	Mert Bilgin	Energy Policy	2009	4.983
Indicators for energy security	Bert Kruyt	Energy Policy	2009	4.766
Japan’s energy security predicament post-Fukushima	Vlado Vivoda	Energy Policy	2012	4.588
Development of biofuels for the UK automotive market	G.P. Hammond	Applied Energy	2008	3.461
Long-term energy strategy scenarios for South Korea: Transition to a sustainable energy system	Jong Ho Hong	Energy Policy	2019	3.384
Methodologies and applications for critical infrastructure protection: State-of-the-art	Jose M. Yusta	Energy Policy	2011	3.346
The potential of methanol as a fuel for flex-fuel and dedicated spark-ignition engines	J. Vancoillie	Applied Energy	2013	3.241
Ethanol and the Local Economy: Industry Trends, Location Factors, Economic Impacts, and Risks	Sarah A. Low	Economic Development Quarterly	2009	3.193
Re-envisioning the role of hydrogen in a sustainable energy economy	John Andrews	International Journal of Hydrogen Energy	2012	3.181
Advantages of converting Diesel engines to run as dual fuel ethanol–Diesel	Alberto Boretti	Applied Thermal Engineering	2012	3.097

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First, the annual distribution shows that eight years of research papers were selected in the top 20 for the level of disruptive innovation in the field, and the annual distribution ranges from early in the field (2008) to the end of the selected time window (2019). This phenomenon indicates that the field of energy security is still in a process of continuous innovation and disruption. Second, from the source of journals, seven papers were selected from Energy Policy, two papers were selected from Applied Energy and one paper was selected from every other journal. This phenomenon indicates that major innovations in energy policy will have a significant impact on securing energy security. Finally, in terms of article topics, the topics covered by the top 20 research papers in this field in terms of disruptive innovation level include: energy policy, renewable energy, carbon emissions, energy evaluation, energy economics, power facility construction and evaluation, energy conversion, traditional energy, land use and energy transportation. These topics will be the focus of subsequent research.

3.4. Collaborative Relationships

International cooperation is indispensable for both energy security research and energy security assurance. Therefore, this study constructs a network diagram of national cooperation in the field of energy security (see Figure 5). From the clustering results, all the countries included in the cooperation analysis are divided into 17 clusters, reflecting the fragmentation of research cooperation in the field of energy security. The distribution of clusters shows that the cooperating countries in the same cluster have more obvious geopolitical relations, which confirms the significant influence of geopolitics and international relations on energy security. In the case of the EU, for example, despite the establishment of the EU Energy Platform to coordinate measures to secure energy supplies, the gap between the EU’s overall objectives and the national energy security interests of each allied country has grown wider over time. National energy security policies are also increasingly focused on safeguarding their own interests. Compared with the research dispersion of the European Union, the research collaboration of the United States in the Americas, China along the Belt and Road, Southeast Asia and Australia reflects that the two countries have greater academic influence and policy influence in energy security research in their own region. When we further refine the temporal cooperation network of institutions and scholars in the field of energy security (Figure 6 and Figure 7), we can see that the early cooperation in the field of energy security was largely established by British and American academic institutions and related scholars, and as the field received more and more attention from academic institutions and scholars, the research center gradually shifted to the East and South Asian academic institutions and groups of scholars led by China.

4. Prospect

In this paper, we review relevant papers in the field of energy security from 2005 to 2022 and hope to provide suggestions to practitioners and scholars in related fields about further research. In this section, we present future research topics in the field of energy security, clustered by current research topics separately to fill the current research gaps.

Among the yellow clusters, most of the current studies focus on whether the change in energy structure has a positive impact on regional economies and the contradictory relationship between energy security and climate protection. In this regard, considering the differences in the national conditions and the development status of different countries, research on energy structure improvement strategies under different industrial structures and sustainable synergistic development strategies from a multi-system perspective would be beneficial to reducing energy structure risks for various countries around the world. For developed countries and large developing countries, how to clarify the energy responsibilities of enterprises under the policy perspective and reduce the interference of stakeholders in the assessment of energy policies is a direction worthy of research. For other developing countries, how to establish a policy system that protects the local energy technology industry and reduces dependence on imported energy technologies and products will be the focus of research to synergistically safeguard national economic security and energy security.

In the green cluster, most current studies focus on political, economic, diplomatic and military-related conflict issues in the field of energy security. In this regard, we believe that exploring diplomatic solutions, economic cooperation models and legal system construction in the context of political mutual trust and the de-weaponization of energy and analyzing the potential and impact of regional energy cooperation in building a theoretical basis for building interconnected regional energy relations and a common, safe and efficient joint guarantee mechanism so as to deepen the international energy multilateral cooperation mechanism may be the main points of research to strongly mitigate energy conflicts.

In the blue clustering, most of the studies focus on renewable energy production technologies. In this regard, the authors believe that there are three areas that deserve the attention of researchers in related fields in the follow-up research process. First, technologies related to geophysical exploration, extraction, assembly, sealing, automated mechanical processing, energy quality enhancement, potential energy utilization, large-scale energy storage materials and high-end energy transmission equipment will remain the focus of subsequent research, and research on scenario-specific energy extraction and utilization and specific types of resources, such as shale oil and gas, tight oil, natural gas hydrates, oil and gas development in low-temperature environments and LNG development technologies, also needs to be strengthened. Second, issues related to energy resilience should also be the focus of attention in the next phase, such as the construction of demand-oriented energy transmission and storage infrastructure, multi-energy complementary technologies and energy resilience assessment under hybrid network scenarios. Finally, issues related to emergency prediction and security protection measures during energy production, information security technologies and privacy protection systems related to securing energy security and immediate regulatory methods for energy security have not received wide attention and need to be further studied.

In the red clustering and purple clustering, research on technologies related to bioenergy and clean energy has received a great deal of attention, and some researchers have begun to focus on the differences in the environmental benefits of different bioenergy sources themselves. However, only a relatively small number of scholars have gradually started to think about and explore energy security issues from other fields in reverse. In this regard, the authors believe that analyzing the impact of current natural ecological elements on energy security from the perspective of ecological conservation and establishing an integrated utilization/storage/transmission system of bio/clean energy with integrated economic and ecological benefits will be a powerful supplement to the existing research. In addition, research on the intelligent management of the green energy transmission chain, the recycling mechanism of clean energy production facilities, the reusability and harmlessness of waste generated in the process of energy production and supply, the construction of waste utilization technology and the comprehensive utilization framework in the non-energy production supply chain, the eco-inclusiveness of renewable energy infrastructure, urban transformation and infrastructure upgrading in the perspective of energy security will greatly reduce the negative effects generated in the process of energy structure change. In contrast, in the face of current ecological problems that already exist, a strong promotion of research on bioremediation technologies could effectively reduce their continuing negative effects. In addition, from a humanistic perspective, the analysis of the energy vulnerability of specific groups, water safety and food security issues due to energy problems and the impact of the existing energy structure on work, education and values is still underappreciated. To address this issue, it is particularly important to establish a multi-perspective energy efficiency evaluation system and to conduct integrated causal reasoning studies on multiple types of security issues.

Finally, from the perspective of the energy security field as a whole, the construction of an interdisciplinary and holistic research framework and assessment system for energy security as well as a collaborative governance approach may be a milestone exploration in this field in the near future. To achieve these goals, both at the research level and at the national level, there is an urgent need for supporting digital infrastructure and security protection measures, legal policies and public education systems for the reasonable disclosure of energy security information and interdisciplinary, cross-disciplinary, collaborative and efficient scientific and technological R&D systems and collaborative innovation support platforms.

5. Conclusions

In this study, we conducted a bibliometric analysis of the energy security field based on 5236 papers retrieved from the Web of Science Core Collection database from 2005 to 2022 to explore the characteristics of the type of documents, the annual trends of publication and citation frequency and the distribution of source journals, countries/regions, institutions, scholars and topics in the energy security field. This study also mines recent research hotspots, selects the most influential and disruptive papers and analyzes the characteristics of collaborative networks at different levels. Through a series of studies, we obtained the following conclusions: (1) The quantity of annual publications and the frequency of citations in this field maintain an increasing trend; (2) The quantity of source journals for research in this field is large and covers a wide range of topics, and it has strong technical characteristics and is associated with social science research topics too; (3) The quantity of countries, institutions and scholars involved in research in this field is increasing, and international cooperation has a fragmented and geopolitical character; (4) Although the United Kingdom and the United States still retain a first-mover advantage in this field, China has gradually overtaken and has become the country with the largest output in recent years. Research centers in the field have also gradually shifted from Europe and the United States to the East and South Asia regions; (5) The contradictions between energy security and social, economic, environmental, land and climate issues, the interplay between energy supply systems and complex geopolitical and international relations issues and the important role of renewable energy and related technologies in maintaining national/regional energy security are the main issues of interest to researchers; (6) The governance of energy security issues still requires a combination of policy, economic and technological aspects. Our findings provide the first relatively objective and comprehensive bibliometric analysis of the field of energy security research and are believed to provide important information for the academic community, especially for early-career researchers in the field of energy security and for researchers in non-energy-security fields.

Like other bibliometric analysis studies, due to the limitations of the selected databases and the fact that commercial databases are governed by their own rules and external political factors, it is possible that some important articles written in non-English languages were missed in this study. Articles without energy security in any of the searched fields may also have conducted research in the energy field, and this part of the article is also missing in this study. In addition, in this study, open citation data were used in the process of evaluating the study for disruptive innovations, avoiding the need to retrieve citation data directly from databases, effectively reducing the difficulty of obtaining large-scale citation data [96] and ensuring the reproducibility of the study. Due to the special nature of the energy security field, the papers in this field include a large number of citations of relevant legal documents, government reports and official policy documents, and this part of citations is missing in the process of disruptive innovation evaluation in this study, which affects the accuracy of the disruptive innovation evaluation results to a certain extent. In the future study, more accurate measurement results will be obtained by jointly using multiple data sources.