**1. Introduction**

The energy policy is one of the key pillars of the functioning of individual countries, as the energy sector is a driving force behind the economic development. The energy demand has been growing worldwide for many years, in line with the dynamic development of the economy on a global scale. This trend also continues in projections for the next decades [1]. Numerous actions have been taken around the world to accelerate the energy transition towards low-carbon economies using renewable energy sources (RESs). This is because, among other things, such an intensive use of energy products has negative effects on the environment, such as excessive exploitation of non-renewable energy sources and high emissions of harmful substances, including CO2, SO2, or nitrogen oxides. These problems are highlighted and discussed in References [2–7], among others. Such actions on a global scale include the United Nations Framework Convention on Climate Change (UNFCCC) [8] signed in Rio de Janeiro in 1992, and the Kyoto Protocol [9], which came into force to supplement the UNFCCC. However, the greatest intensification of energy transition activities has been observed in Europe.

The policy related to the use of renewable sources is a key element of the energy policy implemented in the European Union (EU). In a broader context, it is a pillar of activities

**Citation:** Matuszewska-Janica, A.; Zebrowska-Suchodolska, D.; ˙ Ala-Karvia, U.; Hozer-Ko´cmiel, M. Changes in Electricity Production from Renewable Energy Sources in the European Union Countries in 2005–2019. *Energies* **2021**, *14*, 6276. https://doi.org/10.3390/en14196276

Academic Editors: Bartlomiej Iglinski and Michał Bernard Pietrzak

Received: 9 August 2021 Accepted: 24 September 2021 Published: 2 October 2021

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undertaken in the implementation of the sustainable development goals. In the document "Next steps for a sustainable European future European action for sustainability" [10], the European Commission (EC) has outlined goals to be achieved by 2030. Among the 17 goals, there are two that relate directly to the energy sector. The first one concerns ensuring access to energy sources that are, above all, affordable, reliable, and sustainable. The second of these goals concerns acting to mitigate climate change and its impacts. In another document, "Clean energy for all Europeans" [11], the EC has set a target of 50% of electricity in total EU energy consumption in 2050. Furthermore, 80% of the electricity is to be obtained from renewable sources or nuclear energy. This means that electricity will gain importance, and ultimately, it will be the key source of energy in the EU. The policy of moving towards low-carbon economies also means that the main burden of electricity production will be on renewable sources.

Eurostat's statistics clearly show that while electricity consumption has not increased significantly in recent years, the changes that have taken place in electricity production are significant. Firstly, the share of renewable sources in electricity production has increased significantly, from 16.3% in 2005 to 34.6% in 2019. Secondly, the diversification of renewable sources used has increased across the EU countries. Currently, wind energy has the largest share among renewable energy sources. In line with "EU Strategy to harness the potential of offshore renewable energy for a climate neutral future" [12], further intensive development of wind energy technology is planned in particular in marine areas. Solar energy is also gaining importance. From the perspective of the consumer, internal business processes, the development and financial aspects, solar and wind energy are considered the most competitive renewable sources in electricity production [13].

Therefore, the question arise what changes have occurred in the use of renewable sources in the production of electricity in the EU countries. In particular, the period of interest is 2005–2019. The beginning of this period was selected for two reasons. First, 2005 was the first full year in the EU after its largest enlargement. Second, when analyzing the statistics, since 2005, the greatest progress in the use of renewable sources in the EU can be observed. The end of the study period is related to the availability of data at the time of the analysis. Due to the fact that the composition of the EU underwent changes, in the presented analysis, it is assumed that the research sample includes countries from the composition from 2020 (EU-27) and the UK as the EU member until 2019. It should also be noted that the aggregate statistics for the EU area provided in the presented analysis concern the composition of the EU-27. These statistics are also used as a benchmark for national statistics. However, in more detailed analyses, considering individual countries, the UK is also added.

The aim of the conducted analysis is to assess changes in the use of renewable sources for electricity production in the EU countries in 2005–2019. This goal is carried out in two steps. In the first step, changes in the concentration of renewable sources are assessed in the production of electricity from renewable sources, using the Gini coefficient. In the second step, we apply k-means algorithm for clustering of EU countries (EU-27 + UK). The conducted study allows us to verify the following hypotheses:


The literature presents numerous studies on the use of renewable sources, which are presented in international cross-sections. However, they mostly refer to several issues. The first is the analysis of the use of RES (or types of RES) in energy consumption or production (without dividing this energy into its types). The second is the analysis of share of total RES in different types of energy consumption or production. The third is the analysis of only one type of RES. In contrast, there is a lack of studies that present an analysis of the use of different types of renewable sources in the production of renewable electricity and examine their concentration. The approach presented in this paper is fulfilling the research gap. It should also be noted that we aimed to show changes in the composition of the energy portfolio composed only of RES used for electricity generation in the presented study. Therefore, this analysis refers to "renewable electricity".

### **2. Renewable Energy Sources in Literature and EU Directives**

Renewable energy sources (RESs) are in line with the concept of the "Sustainable Development Strategy of the European Union" adopted in June 2001. The very notion of sustainable development was defined in the Brundtland Report (WCED, 1987) as development meeting the needs of the present generations without limiting the same possibilities for the future ones [14]. Such development is then to be applied at both the social and environmental levels. The verification of the 2001 strategy that took place in 2006 allowed to pursue a long-term concept of sustainable development. Article 3 of the Treaty on the Functioning of the European Union (TFEU) urges the EU to disseminate the principles of sustainable development and to guard climate change and a low-carbon economy, inter alia, by lobbying multilevel actions improving the quality of the environment [15]. It is being implemented on multiple levels, both in the long and short terms [16]. In the case of energy policy, this takes place on the basis of various directives or strategies of the European Energy Union.

Moreover, the TFEU, and in particular, its Article 194, can be indicated as a point of reference for formulating strategies related to the EU energy policy in general. The first point of Article 194 presents the objectives of the EU energy policy by calling all EU countries, among others, to promote energy efficiency, to save energy, to develop new and renewable forms of energy and to ensure security of energy supply in the EU. The first milestone indicated in the process of formalizing the EU's energy strategy is said to be the White Paper on renewable energy, adopted in 1997 [17]. The White Paper included goals that the production of electricity from renewable sources was to increase to 23.5% by 2010 (from 14.3% at that time). The next step was, the already mentioned, issuance of Directive 2001/77/EC of the European Parliament and of the Council of 27 September 2001 on supporting the production of electricity produced from renewable sources on the internal market [18]. This Directive indicated country-specific targets to be met by the year 2010 with regard to the use of RES in the production of electricity. For the entire EU, this indicator was 22%, and for individual countries it ranged from 5.7% for Luxembourg to 78.1% for Austria. The biggest increase was expected for Denmark—by 20.3%, from 8.7% in 1997 to 29% in 2010. On 10 January 2007, the European Commission issued a communication entitled "Renewable energy road map—Renewable energies in the 21st century: building a more sustainable future" [19]. In that document, the Commission indicated that the greatest progress with regard to the use of renewable sources has been made in the production of electricity. In addition, there were suggestions that in 2020, electricity production from renewable sources could increase up to 34% (from 15% at the time of the release). "Directive 2009/28/EC of the European Parliament and of the Council on the promotion of the use of energy from renewable sources" was issued in 2009, amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC [20]. The Directive 2009/28/EC set a target that by 2020 the share of total energy consumption from renewable sources should amount to 20%. This goal was mentioned in the Europe 2020 strategy [21] as one of the five main priorities determining the development of the EU. Furthermore, the directive 2009/28/EC also contained guidelines related to the electricity production, in detail it stressed that energy produced from renewable sources should be prioritized and use of support schemes for electricity production from RES. In 2018, the Renewable Energy Directive was amended again [22] and showed that support schemes for renewable electricity have proved to be useful tools. In addition, a target was set to increase the share of renewable energy consumption in the total energy consumption up to 32% by 2030. In March 2019, the EC published the "Clean energy for all Europeans package" [11] presenting numerous strategic proposals in the field of energy. According to

this document, electricity will gain strategic importance in the EU. Additionally, estimates are given that electricity will be responsible for more than half of the EU's energy needs by 2050, with RES and nuclear energy expected to account for 80% of the electricity generated in the EU. A discussion of the factors affecting electricity is given in Reference [23].

Due to the fact that one of the priorities of the EU's energy policy is to increase energy efficiency and increase the share of renewable energy, there is a strong synergy of renewable energy concept with some of the goals of sustainable development [24]. Research on various renewable energy sources in terms of sustainable development indicators (e.g., price of generated electricity, availability of renewable sources, gas emissions, land requirements, efficiency of energy conversion, water consumption, and social impacts) rank individual energy sources. Assuming that all factors are of equal importance, wind, hydro, solar and geothermal energy are in the first place. Wind energy has the lowest greenhouse gas emissions but requires a large land area and high investments [25].

The EU put grea<sup>t</sup> emphasis on various types of activities and promotion of renewable energy [26–28]. However, due to its high cost, generating energy from renewable sources on a large scale is not possible without support [29]. These support strategies differ from one Member State to another [30]. There are many ways to promote ecological solutions, as well as their various combinations. Some of the EU countries decide to promote one support system, others promote hybrid solutions [31]. However, as it turns out, one of the most beneficial actions is financial support [32,33]. Next to it, there are also tax incentives, feed-in tariffs and tenders [34]. Important aspects related to the promotion of renewable energy are social pressure, environmental impact, and the level of development of the country. The concern for the environment and the pressure of subjective norms have also an indirect influence [35].

The increased focus on sustainability in the energy field is a response to dwindling natural resources and high CO2 emissions. Required technological changes supporting sustainable development strategies include replacing fossil fuels with renewable energy, saving energy, or improving the efficiency of its production [36]. The EU is taking a number of actions to reduce CO2 emissions such as supporting the development of the renewable energy sector and supporting research on innovations within this sector. Restrictive measures are also taken, for examples introduction of the "European Union Emission Trading" [37,38]. RES are considered a solution to an environmental degradation [39], depletion of non-renewable resources, destruction of the ozone layer or increasing energy consumption [40]. Another reason for using renewable energy and striving to increase its share in energy consumption by the EU is the awareness of high dependence on energy imports [41] and the shortage of energy reserves [42]. The higher variety of energy sources ensures higher energy security that should take into account the security of energy supply and demand for it, as well as the existing energy shortages and its surplus [43]. The EU countries apply equal strategies in this field. In the case of coal-based countries, the coal is converted into a growing share of gas and a slow increase in the share of renewable energy [44]. Renewable energy can also be a factor in supporting economic growth. Environmentally friendly companies and institutions also receive a positive perception [45]. In the long run, there is a two-way relationship between economic growth and renewable energy consumption [46,47]. Renewable energy production also expands spatially to neighboring countries. This is due to the spread of knowledge and the similar potential of renewable energy [48].

It is also worth noting, in the context of considering electricity generation, that this aspect (getting electricity) is considered when evaluating regions in terms of attractiveness to investors [49]. In turn, given the strong focus on creating socially responsible businesses, sourcing electricity from renewable sources gains an additional dimension.

According to Eurostat, RES include hydro (RA100), wind (RA300), Solar (including RA410—Solar thermal and RA420—Solar photovoltaic), biofuels (R5110-5150\_W6000RI— primary solid biofuels, R5220P—pure biodiesels, and R5290—other liquid biofuels), biogases (R5300), renewable municipal waste (W6210), other (RA200—geothermal and RA500tide, wave, ocean). In the literature, individual sources are mentioned in different level of detail. For example, Reference [50] mentions sun, wind, waves, tides, or biomass fuels. Meanwhile, the main sources are solar, wind, and biomass energy [51].

RES are used directly to heat or light homes, as well as to produce fuel and electricity [52]. The importance of the transport sector is increasing, the increase in renewable energy consumption reduces CO2 emissions in this sector by around 12% [53]. This occurs through, inter alia, use of biofuels [54] that are combined with other technologies [55].

The EU promotes the direct use of renewable energy for both heating and cooling [56]. Research on transforming the heating sector into solutions using renewable energy is focused, for example, on smart grid or smart energy systems [57]. In urban environments, district heating and cooling systems (5GDHC) are proposed, among others concepts [58]. However, in the case of cooling, the RES Directive does not contain a definition of renewable cooling, and therefore it may be difficult to directly include cooling from renewable sources [59]. Nevertheless, the future lies in various types of integrated energy systems that will ensure high energy efficiency. In the case of cooling, these include, for example, district cooling systems (DSC) used in the construction sector for drying and cooling rooms. The most suitable RESs for such systems are biomass, solar, geothermal, surface water, solar, and waste heat energy [60]. The adaptive energy supply systems under development try to also consider the changeable availability of renewable energy. Finally, thanks to new technological solutions, renewable energy has a chance to be cheaper [61].

The development of new renewable energy technologies could be reflected in a decrease in electricity production costs [62]. This, in turn, could translate into lower electricity prices. Lower electricity prices can be equated with achieving the EU's affordable and clean energy goal (Sustainable Development Goal (SDG) 7). The prices of energy carriers have a wider dimension. They affect the general price level in the economy and thus have an impact on economic growth (see, e.g., References [63,64]).

The production of electricity by using renewable energy is confirmed by green certificates. They are used by energy companies, which are obliged to include renewable energy in the overall energy balance. They are therefore traded, which can help to meet the renewable energy target [65]. Green certificates also support producers of renewable energy. Apart from green certificates, feed-in tariffs are another form of support [66].

In connection with the new proposals for the EU on increasing the share of renewable energy in general energy consumption, considerations of 100% of renewable energy share arise in the literature. Multistage analysis, considering the impact in terms of energy, environment and economy indicates that such system is achievable by combining heating, electricity, cooling, and transport sectors [67,68]. Such considerations can also be found in relation to specific countries. A Danish study showed that the pursuit towards 100% of the share of renewable energy from local sources is possible. A decision on the participation of biomass and wind energy is said to be crucial [69]. According to [70] a total transition to renewable energy and closure of nuclear energy is also possible in Germany by 2050. An overview of other literature on different energy systems in terms of 100% renewable energy can be found in Reference [71]. The literature also points out the need for electricity storage in the case of transition to renewable energy and including it in intelligent energy systems [72]. The renewable energy defects include the lack of continuity of its production, which is often associated with the climate. There are different solutions in the field of optimization methods [73].

Due to the subsequent objectives placed by the EU, renewable energy will play more and more importance. It is anticipated that the share of renewable energy in gross final energy consumption in the EU in 2050 will amount to 55–75% [74]. Furthermore, the achievement of climate neutrality is associated with an increase in renewable energy by 2050 by over 80% [75]. Therefore, the national and local level implementation of these goals, as well as the similarity among EU countries in terms of achieving the targets of sustainable development, concentration of renewable sources or their shares are crucial. Recent research on a relationship between RES and sustainable EU development carried

out on the basis of a hierarchical method of cluster (Ward's method) gave division of countries into five clusters. Countries that best deal with the use of renewable energy and make progress in sustainable development are Denmark, Finland, Latvia, and Sweden. Meanwhile, at the other end, there are Belgium, Cyprus, Lithuania, Luxembourg, and Malta [76].

Pacesila, Burcea and Colesca [77] examined the similarity in terms of the share of renewable energy in total consumption for EU countries, however the share of renewable energy considered was treated jointly for all sources. The research, carried out by using the k-means method for data from 2013, resulted in three clusters: the first cluster included countries with energy dependence of up to 30% (Denmark, Sweden, Estonia, Romania, and Czech Republic), the second one consisted of countries with energy dependence between 30% and 70% (Latvia, Austria, Slovenia, Finland, Germany, France, Bulgaria, Croatia, Greece, Slovakia, Hungary, Poland, Netherlands, and United Kingdom), and the last cluster (Lithuania, Portugal, Spain, Italy, Belgium, Cyprus, Ireland, Malta, and Luxembourg) with energy dependence higher than 70%. Additionally, a ranking was created in terms of the characteristics of renewable energy. The results showed that RES can help reduce energy dependency.

On the other hand, Reference [78] determined the concentration of consumption of RES in 28 EU countries in 2016. The concentration factor was 0.59. The high value of the coefficient was due to the fact that there were several countries that have high consumption of renewable energy, while all the rest have low consumption. Countries with high consumption of clean energy were Germany, Italy, and France.

The share of renewable energy in total energy consumption in 2004–2016 and the concentration of total energy consumption and renewable energy were examined in Reference [79]. The Gini coefficient was calculated for 2004 and 2016 and a high concentration of renewable energy consumption was found in several countries. For the energy in total, the concentration factor was 0.62 in 2004 and 2016. In the case of renewable energy, 0.58 (2004) and 0.59 (2016). The highest total energy consumption was in Germany, France, the UK, Italy, and Spain. The structure of renewable energy consumption was very similar; however, Sweden took the place of the UK. The concentration factor was also determined in Reference [80], but it only referred to the level of primary production, export, import, and total energy supply in the EU.

Due to the fact that the existing research focuses only on the share of renewable energy in total energy production, there is a need for extended research in terms of the use of renewable energy in electricity production. This paper will fill the research gap in this area.
