Since the dawn of time, energy in some form has been a key element in society’s life and development. Current civilization is dependent on energy to a far greater extent than it used to be. Energy shortages are a serious threat to the functioning of individuals as well as to society as a whole. Therefore, access to energy is a safety determinant in this respect. Like all resources, energy is a scarce commodity [8]^[1]. This means that energy resources need to be rationally managed in order to prevent the risks of energy shortages.

What is security in general? It is important to reflect on this issue since this idea is ambiguous; on the theoretical level, its essence is not considered often and is sometimes questioned. According to the Cambridge Dictionary, the term “Security” is associated with the protection of persons, buildings, or a country against threats such as crime or attacks by foreign countries. In people’s consciousness, and generally by scholars, the term “Security” is associated with “no risks” [9]^[2]. An investigation of the concepts of “Security” functioning in different areas of life can be an introduction to creating the concept of “Energy Security”.

In response to the risk of turbulence in the global energy system, both countries and international organizations take into account the challenges of energy security in their activities, currently linking them to economic and environmental issues.

It seems that Cherp and Jewell [10]^[3] explain the rationale for having a closer look at the problem of a conceptual approach to energy security very appropriately by citing their Energy Security Assessment Framework. Drawing up the framework for the concept of energy security is the starting point for further considerations. Identification of vital energy systems as well as identification of their essential features, in particular vulnerabilities of vital energy systems, are the next important steps in the assessment of energy systems. The steps outlined can provide a basis for the assessment of the safety status of energy systems and actions that follow the assessment, such as the implementation of a selected energy policy.

32. The Framework of Energy Security Concepts Outlined by Scholars

3.1. The Energy Security

2.1. The Energy Security

In the first half of the 20th century, and particularly during the second World War, the concept of energy security was strictly related to securing supplies of fuel for the army. In the post-war period, the importance of supplies to the army, especially oil supplies, did not decrease. In addition, oil has become the primary energy carrier in many sectors of the economy in developed countries. Industrialized countries did not produce enough oil to meet their own needs. Hence, oil was imported mainly from developing countries. For that reason, energy security focused on securing oil supplies for a long time. In this regard, energy security was conceptualized by political analysts within a single strategy that merged peaceful diplomacy and war into a complementary whole [12]^[4]. Over time, the security of the oil supply became an important focus of interest for China, India, and other fast-growing economies, leading to increased competition for resources [13]^[5]. Such a perception of energy security in the second half of the 20th century was influenced by the significant dependence of the global economy (especially transport) on oil and its limited resources. In addition, the increase in demand from rapidly developing countries, especially China and India, can lead to increased price volatility and, as a result, long-term price increases. An additional risk factor in oil supplies is the concentration of most of the known resources in a small number of countries, mainly in the Middle East and in the countries of the former Soviet Union. In the 21st century, concerns over energy supply, in addition to oil, have grown for the supply of natural gas. This problem mainly affects the Eurasian market. Concerns about the stability of supplies must be taken into account not only by consumers, but also exporters of energy raw materials. The economies of countries exporting energy raw materials are exposed to price fluctuations which destabilize their export revenues. Since the traditional challenges connected with ensuring a sufficient supply of energy carriers, especially oil and gas, did not change fundamentally, they remained at the heart of energy security programs in an unchanged form for the majority of the 20th century. Energy security is one of the fundamental conditions for economic development. As energy demand is growing much faster at the present stage of society’s development than in the past, energy security has become an indispensable component of national security. Owing to its key significance, energy security is an importance factor in shaping international relations [14]^[6].

3.2. An outline of the History of Contemporary Energy Security Studies

2.2. An outline of the History of Contemporary Energy Security Studies

Energy has accompanied humanity throughout the entire history of development—from prehistoric times—and the importance of energy in this process is growing disproportionately with the increasing intensity of development processes. Thus, one can try to trace the concept of energy security on this path, although, in its early stages, it was not conceptualized for obvious reasons [15]^[7]. Studying the evolution of the concept of energy security can identify key aspects of this issue. The observation of evolution can help in assessing the sources of changes in the concept of energy security over time due to the impact of historical factors on the formation of analyzed trends in future periods [16]^[8]. In the early stages of human civilization, energy security was associated with ensuring access to flammable materials, mainly wood, without incurring excessive risks and expenditures exceeding the value of fire for a community. Hence, for thousands of years, the concept of energy security included three basic criteria:

• availability of sufficient supply of energy carriers,
• affordability of fuel sourcing (lower than the perceived value of fire),
• resilience of the energy supply system to external interference.

The indicated criteria (availability, affordability, and resilience), which are the basis for the creation of an energy security system, did not generally change until the middle of the last century. Although the basic paradigm of energy security has not changed, energy security strategies have evolved with the development of technology and economic development. In particular, the availability criterion changed. The main sources of the redefinition of availability were technological changes and technical innovations opening the way for new energy sources in lieu of fossil fuels. Availability was extended by intra-national and international trade. The criterion of affordability evolved, taking on short- and long-term dimensions. The essence of the concept of energy security, unchanged almost throughout the history of human civilization, underwent an accelerated transformation in the middle of the last century. The constantly increasing energy demand, satisfied with fossil fuels, led to environmental disasters, resulting in radical shifts in energy policy regarding primary energy sources [18]^[9].  The hopes of the fossil fuel industry to maintain its position in the structure of energy production and consumption through technological progress were dispelled as a result of policies aimed at reducing the carbon footprint. In this context, concerns about pollution from the burning of fossil fuels gave way to the view that CO₂ emission connected with fossil fuels is the main source of the greenhouse effect and climate change [19,20]^[10][11]. Technologies for reducing pollution from the burning of fossil fuels did not prove sufficient to meet the CO₂ emission reduction targets. There were opinions that the high level of energy consumption put humanity under environmental constraints due to fossil fuels. The concept of energy security in some form has accompanied civilization since its initial stages, but analyses in this area taking into account the principles of scientific research began only around 1975 [23]^[12]. Until 2001, publications on energy security were so rare that they were not even included in later reviews by some authors [11]^[13]. As the traditional concept of energy security did not change in the last century, most of the literature on energy security devoted to this challenge refers to the historical roots and traditional perception of the concept. However, there has been a considerable increase in interest in the concept of energy security in recent decades. This interest is accompanied by an increasing number of publications that show the shifting focus of studies. Following the inclusion of new dimensions to the concept, the definition of energy security constantly expanded. A decade ago, an alternative approach to conceptualization appeared, manifested by simplifying the definition to make it more widely applicable [24]^[14]. Simplification of the definition is justified until it covers all relevant issues. For example, the phrase ‘The freedom from disruption of energy supplies for whatever reason’ proposed by Čehulić et al. is an oversimplification, as it focuses solely on supply [25]^[15]. 

3.3. Research Gaps in the Field

2.3. Research Gaps in the Field

A relatively large number of publications dealing with energy security does not release thise research trend from the problem of research gaps already signaled by various authors. Undoubtedly, such gaps should include scholars’ selective approach to the concept of energy security. Many of the papers to date refer to isolated aspects of energy security, such as technical, environmental, and economic aspects [27]^[16]. This leads to the omission of other important dimensions within a non-comprehensive concept. A considerable number of publications focus exclusively on a selected country [28]^[17], region [29]^[18], economic sector [30]^[19], energy technology [31^[20][21],32], or chosen perspective [33]^[22], thus losing the value of universality. Therefore, voices have been raised for over a decade supporting ideas of conceptualizing energy security based on a systemic approach [34]^[23]. Sovacool and Mukherjee [35]^[24], as well as Sovacool and Brown [36]^[25], also suggested an integrated approach in the search for a formula for assessing energy security using multiple indicators.

3.4. Fundamentals of Conceptualization of “Energy Security”

2.4. Fundamentals of Conceptualization of “Energy Security”

In order to accurately communicate their ideas to the recipients, scientists need to show the presented issues properly. Definitions and explanations of the terminology are usually an introduction to a discussion. Irrevocably, understanding a given concept implies knowing its definition. Definitions and explanations of key concepts enable the content audience to synthesize knowledge on a given topic [38]^[26]. The use of conceptual definitions is intended to properly clarify and delineate the subject and scope of considerations [39]^[27]. Defining a given concept can be done by describing its characteristics and establishing the relationship between its components. The conceptual framework positions research within the methodological approach used and in a potentially broader context. Neuman [5]^[28] states that a scientific definition should be unambiguous and have a clear and specific meaning. Baldwin [9]^[2] adds that defining the problem should establish relations with theoretically important aspects of the research subject. In addition, the conceptual approach should be operationalizable and enable empirical research. Ravitch and Mittenfelner [40]^[29] note that the conceptual framework established by the definition of a research problem can serve as a guide to identifying and selecting, and then integrating research theories. A precise definition of the research subject is also necessary for determining research questions, determining the position of the scholar, and drawing conclusions from the research material. Despite the increasingly widely accepted, up to the point of universal recognition, the importance of the issue of “energy security” remains an ambiguous concept and thus probably still widely contested. So far, there is no consensus among energy policy scientists on the form of conceptualization of energy security. Currently, authors dealing with this issue in reviews cite several dozen definitions referring to various aspects of energy security [11]^[13]. If one were to collect all the definitions appearing in literature, their number would reach several hundred. In the literature, one can notice a trend of growing interest in the operationalization of energy security, which translates into the search for effective ways to quantify this abstract problem. These interests are reflected in numerous publications discussing how energy security can be measured through the use of a wide range of indicators relating to various aspects of this phenomenon. The hitherto efforts of a wide range of scholars have not led to forming a universal and widely accepted concept of energy security. Scholars point to the lack of a clear and coherent definition of energy security [41]^[30]. Definitions are conceptualized from different perspectives. Individual concepts are usually created in response to arbitrarily identified threats to energy security to analyze selected research problems. Individual concepts can also be based on contradictory assumptions. Early concepts of energy security focused on the security of the supply of energy raw materials. From today’s perspective, they are difficult to consider as definitions or concepts because the security of supply is only a selected element of energy security. However, studies made in this convention are also still being published today. Works addressing the problem of energy security quantification constitute a particularly broad class. They mostly focus on indicators signaling threats to energy security and the resilience capacity of the energy system [1]^[31]. Such works combine several indicators or develop a comprehensive indicator to support integrated energy policy-making, prioritization, thinking about risk factors, tracking energy security challenges over time, and facilitating the overview of the overall dependence. However, quantification should not be equated with an explanation, conceptualization or definition of the issue. The idea manifested in the classification of energy security dimensions and their comprehensive perception is the basis for the conceptualization of modern works in this area. Such an approach refers to the essence of the conceptualization of energy security proposed by Cherp and Jewell [34]^[23]. The presented work is a search for threads contained in the proposals submitted by individual authors. Their (subjective) classification may be a recommendation for future works on the development of the concept of energy security. The article focuses on theoretical aspects of the concept of energy security presented in the literature on the subject. In view of the search for a general formula on this issue, which would be applicable in any country and in relation to the entire energy sector, the authors decided not to direct their work by referring a priori to any theory.

43. The Main Conceptual Frameworks of Energy Security

4.1. Traditional Approaches

3.1. Traditional Approaches

Energy security is a very broadly defined concept, which takes on a special meaning from the social, economic and political perspective, with increasing consumption of energy, regardless of its form, which is characteristic of developed and developing communities. During periods of increased fluctuations in international energy markets, with different scales of impact covering selected energy carriers and groups of energy carriers, the concept of safety is of particular interest to many scientists. In the sphere of such a wide issue as energy security, it is obvious that many trends/directions of its consideration can be indicated. Energy security in the traditional sense can be seen as a national or transnational security problem because securing steady supplies of fossil fuels, in particular, is crucial for the functioning of the economy and defense of the country or organization. At the same time, there are also concerns about the impact of fossil fuel exploitation on the environment and human health, which requires a more balanced approach to ensuring energy security in general. Many definitions of energy security provided by national or transnational agencies [IEA, OPEC, EC, APERC, and IAEA] are embedded in the traditional approach often referred to in the literature as the 4As [1^{[13][24][30][31][32][33][34][35][36][37][38]},11,35,41,44,52,55,57,58,59,60], aggregated into four areas. In the 4As, i.e., the approach proposed by the International Energy Agency (IEA), energy security is defined by the following key attributes:

• Availability—the ability to provide steady and sufficient access to energy, both in quantity and adequate quality. It is physical access to resources of energy that can already be used in various forms in the energy system.
• Affordability—ensuring that energy costs are at a level that makes it accessible to all social and economic groups. This is connected also with the costs of the energy system and whether it is affordable for its users. The price of energy is the most common indicator of the affordability of specific system energy carriers. In this respect, there are many indicators, including the magnitude of investments made to improve energy security and the ability to bear costs.
• Acceptability—the ability to satisfy social needs and expectations in the field of energy security. This refers to the subject of public perception and support for various energy sources, which often involves social elements such as social assistance and environmental issues. In this context, attention should be paid to the social acceptability of various types of burdensome emissions into the environment, e.g., CO₂ emission from the energy system and investments to move away from fossil fuels.
• Accountability—ensuring the accountability of countries and other entities in the energy sector for their actions and decisions in order to ensure security. This means having sufficient access and the possibility to use energy sources to ensure equality within society (without exclusion). The quantitative diversity, as well as the diversity of energy sources and supply directions, provide the basis for minimizing the risk associated with supplies and ensuring access to this energy.

In the 4As approach, energy security is considered a comprehensive issue, which should not be reduced only to selected attributes, e.g., to the issue of energy availability. This definition requires consideration of many social, economic, environmental, geopolitical, etc. aspects. However, the completeness of the traditional definition of energy security is not a necessary condition for its applicability. In the literature on the subject, there are also scientific studies taking into account a different set of attributes, e.g., the 3As [1,45,46,48]^{[31][39][40][41]} or even the 2As [50]^[42]. Cox points out that accessibility and affordability are paramount for energy security. In contrast, Štreimikienė [49]^[43] provides a definition based on selected specific energy security indicators. In this paradigm, Štreimikienė is not isolated [54,61,62,63]^{[44][45][46][47]}. The various concepts of definitions presented, with a different range of attributes or characteristics, prove that the traditional approach to the energy security of 4As is no longer sufficient nowadays. Hence the rhetorical question: is it possible to define energy security, and can the definition itself close the framework of energy security? In a study on the evolution of energy security, Ang et al. [11]^[13] decompose the attributes of the traditional approach and put their own complete definition based on seven attributes, thus inspiring a discussion in the scientific community in the field. This way, energy security has become ubiquitous in discussions about energy management and climate change. Political documents, reports and scientific research equate this concept to uninterrupted access to energy sources, diversification of these sources, direction and volume of supply, resistance to external threats and energy self-sufficiency. However, the participants of this discourse also draw attention to the polysemicity of the term, or abstractness or indefinability [50,52,56,64]^{[33][42][48][49]}.

4.2. Analysis of Energy Security Threats—Index Approach

3.2. Analysis of Energy Security Threats—Index Approach

An analysis of energy security threats using an index approach involves the creation of a composite index that quantifies the various factors that contribute to energy security. The index can be used to assess the level of energy security in a country or region and to identify the specific threats that need to be addressed. Many studies show that the nature of energy security has a multidimensional interpretation. Measuring energy security is a complex problem that can be conveniently tackled through the use of an indicator set [55]^[34]. It needs to account for the important physical, social, and economic characteristics. As energy security is difficult to measure using one simple measure, the various indicators are meant to accurately represent the different dimensions under study. Narula and Reddy [65]^[50] stated that individual indicators of energy security are insufficient to give a complete picture. It is often analyzed using a set of indicators (or metrics) that represent the various dimensions it encompasses based on a specific framework. Researchers have studied the dimensions, indicators, and values of energy security in their respective countries because of the context-dependent nature of energy security [35,66,67]^[24][51][52]. The use of quantitative methods has become mainstream in energy security studies, especially in cross-country comparisons and long-term research [69]^[53]. The analysis covers not only energy supply but also comprehensive risks, including energy transportation and energy use [70]^[54].  Energy security research can broadly be divided into two areas: studies that look at the issue from a spatial perspective and studies that examine it from a temporal perspective. Among many methodological approaches presented in the literature, two main types of energy security indicators are identified: vulnerability-based indicators and outcome-based indicators. Vulnerability-based indicators of energy security are used to identify potential weaknesses in a country’s or region’s energy system that could lead to supply disruptions or price fluctuations. These indicators include energy import dependency, geographic concentration of energy imports, energy storage capacity, energy diversification, infrastructure redundancy, and energy price volatility. Outcome-based indicators of energy security are used to measure the actual performance of a country’s or region’s energy system in terms of its ability to deliver reliable and affordable energy to its users. They include mostly energy access, affordability, reliability, efficiency and sustainability. These indicators are important for assessing the overall performance of a country’s or region’s energy system and for identifying areas where improvements can be made to improve energy security.

4.3. The Contemporary Approaches to Energy Security Conceptualization

3.3. The Contemporary Approaches to Energy Security Conceptualization

43.3.1. The System Approach to Energy Security

The bridge between traditional forms of conceptualization of energy security and its contemporary approaches is a trend linking energy security with the deregulation of the energy supply. The liberation of energy markets, intended by its supporters, was supposed to separate energy supplies from political motivations and any distortion associated with political motivations. The authors of this trend argued that markets are capable of supplying energy more efficiently and that the diversity of market participants can be a guarantee of security of supply. In place of the public good, treating energy as a market commodity led to questioning the idea of energy independence as potentially dangerous [110]^[55]. However, creating the foundation for a systemic approach to energy systems should rather be attributed to Stirling, who, in his studies, relied on complex systems theories in relation to the management of risks associated with their utilization [111]^[56]. The author suggested diversification and systematic analysis of risks associated with the structure of the energy mix and systems in order to increase energy security. A selective methodological perspective characteristic of individual scientific disciplines leads to a differentiation of the concept of energy security. At the turn of the 20th and 21st centuries, although securing access to primary energy sources remained the focus, energy security ceased to be a purely geopolitical issue. Over time, the issue of energy security became so complex and interdisciplinary that it should not be considered from any single perspective. The links between the components of energy systems mean that considerations on energy security should refer to the entirety of the energy system instead of focusing on its selected aspects. It suggests the need to combine tools representing different methodological perspectives and to rely on different theoretical approaches to energy security issues in response to the interpenetration of particular aspects of the issue at different levels. In addition to the need for comprehensive problem-solving, the urgency to respond to energy security challenges is a factor that leaves a significant mark on energy policy. However, attempts to conceptualize the issue in an excessively broad manner led to the interpenetration of problems of economic efficiency, sustainable development, and energy security policy objectives, which made it difficult to quantify the issue [112]^[57].  The traditionally understood conceptualization of energy security was essentially two-dimensional (availability/affordability). Modern concepts are generally much broader and take into account additional dimensions, such as the environmental dimension [116]^[58]. Debates on energy security reflect the calls for decisive and rapid actions to decarbonize energy systems while ensuring universal access to modern forms of energy for the general public [121]^[59]. At this point, it is worth noting that the energy policy objectives declared a decade ago have changed fundamentally due to climate challenges. Almost all over the world, the profile of electricity generation has been evolving in recent years. The share of electricity produced from coal is decreasing, but in some countries, the declines in natural gas prices in previous years led to considerable increases in the share of this fuel in electricity generation [151]^[60]. There are not many studies in the literature assessing empirically the effects of climate policies [123]^[61].  Technology is inextricably linked to the production and use of energy [125]^[62]. Therefore, directly and indirectly, energy security is strongly conditioned by technological progress. Technological advances make it possible to use new energy sources. For instance, advances in electrolysis have expanded the energy system to include an alternative energy carrier, hydrogen. New technological solutions in the field of production, processing, storage and distribution have the potential to increase energy security. Electric cars are becoming an important complement to the modern energy system, enabling its stabilization [133]^[63]. With increasing CO₂ emissions combined with climate change, there is increasing pressure on political decision-makers to implement clean and renewable energy technologies. The energy transition can not only reduce greenhouse gas emissions but also potentially increase energy security and boost economic growth [153]^[64]. The problem of the role of non-traditional energy sources in the concept of energy security is not perceived unambiguously in the literature. A broad transition to renewable energy is still a matter of the future. The full benefits of this transformation will only be felt within several decades [150,154]^[65][66]. Technological progress in the field of RES increases supply and results in easier access to energy. Supporting the idea of a positive impact of renewable energy on energy security seems obvious in countries with lower levels of development, with poorer infrastructure, and without access to energy resources, where renewable sources can fill the gap created by their backwardness. In addition, renewable sources have the potential to support such societies in their energy transition and reduction of their carbon footprint [127,142]^[67][68]. Energy determines all kinds of economic activity. However, its resources are limited, and, in addition, energy creates external effects [144]^[69]. Alongside energy security and economic stability, environmental sustainability is seen as one of the dimensions of the energy sector [143]^[70]. An increasing number of studies are highlighting that the condition for creating solid bases for prosperity and competitiveness is the balancing of the three aspects of energy: affordability, energy security and environmental sustainability [138]^[71]. Sustainable development in the energy sector determines the ability to meet the growing demand for energy and reduce the global carbon footprint. The energy system can focus on environmental objectives to accelerate decarbonization [143]^[70]. The evolution of energy systems has led scholars to treat energy security issues in an integrated manner and to link them to issues such as universal access to energy and climate issues. Therefore, there have been threads substantiating the creation of mechanisms of energy management at the level of the country, then of international organizations and groups, and in the next step at the global level [147]^[72]. The term global energy governance (GEG) emerged in about the same period as the G8 picked up the theme. One of the first uses of the term GEG took place in the context of the G8’s work on energy [146]^[73]. Increasing concerns about energy security stemmed from the trend of rising oil prices, geopolitical turmoil, and motivation to fight climate change. These original motivations for shaping the global energy order quickly gave way to concerns about energy security on the way to the transition of energy and its coordination on a global scale [148]^[74].

43.3.2. Concluding Remarks

Contemporary literature on energy security is moving away from investigating isolated problems such as the issue of ensuring oil supplies, the issue of securing electricity supplies, the problem of security of transmission networks, and the issue of energy transformation in favor of an integrated approach. This implies the need to look for forms of comprehensive solutions of safety issues for integrated energy mixes based on various energy sources. Conceptual frameworks generally articulate ‘dimensions’ or ‘aspects’ of energy security [117]^[75]. The number of publications attempting to conceptualize and define energy security is impressive. The plethora of definitions reflects the lack of unanimity in the scientific community regarding the essence of the concept. From a historical perspective, definitions were initially relatively general and simple but adequate to “their times”. Over time, a trend has been emerging to include other dimensions in the definition, which causes complexity and excessive expansion of the created concepts. The scholars’ answers to this fact are attempts to simplify the concept of energy security and specify the terms used.