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
4.3.1. 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].
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]. 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].
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]. 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]. 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]. There are not many studies in the literature assessing empirically the effects of climate policies [
123].
Technology is inextricably linked to the production and use of energy [
125]. 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].
With increasing CO
2 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]. 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]. 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].
Energy determines all kinds of economic activity. However, its resources are limited, and, in addition, energy creates external effects [
144]. Alongside energy security and economic stability, environmental sustainability is seen as one of the dimensions of the energy sector [
143]. 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]. 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].
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]. 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]. 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].
4.3.2. 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].
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.