Comparison of Renewable Energy Implementation in Geographically and Climatically Diverse Regions

Abstract

This study compares renewable energy sources in Slovakia and Spain, countries with different geographical, climatic and political conditions. It examines both countries’ current state of play and assesses how their laws and policies have contributed to the transition to renewable energy sources. The study focuses on several forms of renewable energy, including solar, wind, hydropower and biomass energy. The comparison considers several variables, including production, consumption and environmental impact. The analysis findings highlight the contrasts and similarities between the two nations and shed light on the best strategies to advance sustainable energy development. The study also compares the leading strategies and policies for renewable energy sources to understand which factors support or hinder the transition to sustainable and clean energy. The results of this study can be helpful for government agencies, businesses, academia and members of the public interested in supporting sustainable energy development.

1. Introduction

Renewable energy has become a key objective in fighting against climate change. Many countries have set ambitious targets to transition to sustainable energy sources to reduce their carbon footprint and promote a cleaner and greener future. However, different countries have achieved various levels of success in promoting the growth of renewable energy sources, so it is essential to examine and compare the strategies used by other nations to determine the best plan for developing sustainable energy. In addition, it is worth noting that renewable energy plays a key role in ensuring energy security and reducing dependence on imported energy sources. This stimulates the country’s economic development by reducing the cost of imported fuels and creating new jobs in the renewable energy sector. In addition, both countries actively attract foreign investment in renewable energy sources, indicating their attractiveness to investors and readiness for international cooperation. This not only helps to attract the necessary financial resources but also provides access to advanced technologies and best practices in the renewable energy sector. The growing interest in renewable energy is not only reflected in the political and economic sphere but is also becoming a cultural phenomenon. Developing new technologies and creating environmentally friendly solutions are becoming part of the modern lifestyle. Consumers are becoming increasingly demanding and consider choosing ecologically friendly energy sources an essential part of their lifestyle. This approach contributes to creating a new cultural environment in which knowledge about renewable energy sources, their benefits and environmental impact is becoming a necessity and a fashion.

The European Union has established a comprehensive set of legislation governing the development and implementation of renewable energy sources. Key legislative acts include the Renewable Energy Directive (2009/28/EC), the Energy Union Governance and Climate Action Regulation (Regulation EU/2018/1999), the Renewable Energy Directive (EU/2018/2001), the 2030 Climate and Energy Frameworks, the Green Deal, the Energy Efficiency Directive (2012/27/EU), the Electricity Market Regulation (2019/943), the Electricity Directive (2019/944) and the EU Strategy for Heating and Cooling. These legislative acts and policy frameworks set out specific objectives, guidelines and mechanisms for EU Member States aiming to promote and develop renewable energy sources within their national contexts [1].

Slovakia and Spain are two such countries that have made significant efforts to implement renewable energy sources. This paper compares the use of renewable energy sources in Slovakia and Spain while examining the extent to which their respective policies and laws support the growth of sustainable energy sources. The report explores many forms of renewable energy, including solar, wind and hydropower, and assesses each country’s investment, production, consumption and environmental impact. The survey findings shed light on the best practices for developing sustainable energy sources while highlighting the contrasts and similarities between the two nations. Significant attention is paid to innovations in the renewable energy sector, such as energy storage, the development of new technologies and increases in efficiency. Spain and Slovakia actively pursue research and development in these areas, contributing to developing the local scientific and technological base and supporting competitiveness in the international market.

Studies show that Slovakia uses more renewable energy per capita than Spain but has a lower share of the total due to the lack of detailed statistics on the consumption of a specific type of energy. This is due to the countries’ geographical location and meteorological conditions. In the more northerly countries (Slovakia), energy consumption for heat production prevails in the energy mix. The heat is produced either from fossil fuels or from biomass. Globally, heat from RESs produced a share of 6.3%. On the other hand, in southern countries, it is possible to talk about the higher consumption of cold air, produced by electricity. The production of electricity from RESs prevails over heat production in most countries. Globally, electricity produced from RESs presents a share of 29%. Therefore, if less heat is produced from RESs in a country where more heat is consumed, the share of RESs in total energy consumption logically decreases [2].

Given the abovementioned information, comparing the development of renewable energy sources in Spain and Slovakia becomes relevant and interesting for studying strategies that can be successful in the context of other countries. Studying these two approaches can help identify the most effective ways to develop renewable energy sources and exploit their potential for both countries and global society. By comparing the strategies of Spain and Slovakia in the context of renewable energy sources, we can analyse the technical aspects and their support through political and legislative means. This will allow us to understand how individual countries respond to energy challenges and which political strategies help them to develop different types of renewable energy sources.

2. Literature Review

Renewable energy sources still face challenges, such as intermittency, storage and grid integration, all of which play a crucial role in shaping national and regional energy policies. To address intermittency, governments are incentivising a mix of renewable energy sources, including wind and solar, to reduce the overall variability. Energy storage is a key focus of energy policy, as storing excess renewable energy could smooth out intermittency. In addition, to address grid integration, many governments focus on modernising their energy grids to facilitate the integration of renewable energy. However, it plays a crucial role in the global energy mix. Therefore, it is necessary to have continued investment and innovation [3,4]. The research in the RES area demands further attention. Puksec et al. have already studied papers orientated towards RES use in the framework of conferences, reflecting topics such as sustainable energy systems, RES potential, etc. Wind energy has proven to be the most promising solution for rapidly expanding the electricity generation from RESs [5]. In contrast, solar energy’s importance has increased over the years, and will reach a 43% share of electricity generation from RESs by 2050 [6]. Innovative technologies can transform abandoned coal mines into sustainable energy centres [7]. Using AHP, abandoned underground mines can be selected for CAES technology [8].

RESs are still relatively financially demanding compared with conventional energy sources [9], and progress in RES use demands support from economic mechanisms, as mentioned by Gavurova et al. [10]. The analysis results declare that financial support mechanisms from the country and the EU are significant determinants in the development of RES use (mainly in the area of biogas) in Slovakia, with a positive impact on important economic indicators of effectiveness. RESs would then have acceptable effectiveness regarding the living environment. State support from political leaders at the local, national and EU levels can increase the acceptance of RES use. Azarova et al. illustrated that the EU opinion influences some countries, while the opinion of national or local politicians influences other countries [11]. The economic and political view must be supported by an environmental point of view regarding the triple bottom line (people, profit, planet), as mentioned by Baris and Kucukali [12]. This will influence the most appropriate renewable energy alternative with the highest social, economic and environmental benefits.

The use of RESs is different across countries, and there are various types of RESs [11]. Comparing countries from other regions provides the key element for international competitiveness assessment in the RES market [13]. The RES area has concerns for the global community, mainly due to the effect of fossil fuel dependence on the rate of RES adoption in developing countries [14]. The local population’s resistance to new energy infrastructure supports the interest and concern. It can hinder the EU’s goal of increasing the RES use rate [11]. Moreover, variable renewables will attain a very high penetration level into energy systems, particularly in regions well endowed with solar and wind potential, and are well suited mainly in rural populations [15]. In European conditions, there is a trend to evaluate the effect of renewable energy use on the living standard of inhabitants [16], forming a cluster of nations depending on the identified patterns of relation. However, this is closely connected with trust in governments, which strongly predicts political efficacy [17]. In this area, there is some cross-national variation in Europe. Moreover, countries must cooperate and contribute to cost-effectively achieving the 2020 EU RES target, to provide Member States (MS) with the flexibility to meet national RES objectives. Caldés et al. studied whether MS have met or are having difficulties meeting the RES target [18,19].

Such variation must be studied, providing a space for this paper’s subject. We choose to deal with RESs in Slovakia since Slovakia, as a post-communist country, still faces the consequences of economic transformation and struggles with the optimal management of natural resources. It has been proved by Broźyna et al., showing the increase in the share of RESs, that the improvement of energy efficiency goes hand in hand with mining and the exploitation of energy sources notorious for transition economies such as Slovakia [20]. RES use in Slovakia is studied in comparison with other post-communist countries, such as in the study of Broźyna et al. [20], comparing Slovakia and Czech Republic; the study of Mikušová et al. [21], comparing Slovakia with Hungary; the study of Kut et al., comparing Slovakia with Poland [4]; and the study Pavolová et al., comparing Slovakia with neighbouring countries, which found possibilities for increasing RES use [22]. The results show that post-communist countries have a growing interest in RES use.

The scholarly research about these organisations that promote renewable energy has been scattered and limited, especially in the case of countries that do not have a tradition of disseminating green energy, e.g., countries from Southern Europe, such as Spain [23]. As for the situation in Spain, Montoya et al. showed that wind energy continues to experience a reasonable growth rate and does not seem affected by regulations, making it the most sustainable RES in Spain [24]. Marques et al. proved a similar result, revealing that feed-in tariffs and premiums contribute negatively to wind electricity production [25]. Capacity payments encourage fuel and natural gas producers to bid low and increase electricity production from renewable resources. The current economic and political context presents the main barrier to RES development in Spain, and Spanish RES cooperatives, unlike in other European countries, are few in number [26]. Ciarreta et al. showed that, despite the progress achieved in various RES technologies, the level of development reached is still unable to compete with that of conventional energy sources that use fossil fuels [27]. If technological progress continues and market imperfections are corrected, the two types of technology could compete in the medium term in the electricity production network.

Through this in-depth investigation, this paper seeks to contribute to the ongoing debate on the transition to more sustainable energy systems by offering insightful information on developing alternative energy sources in Slovakia and Spain. For example, Jefferson found the burden of RES use in industrialised countries and limitations for investors in RESs due to the different national schemes for RES technologies [28]. At the same time, Aykut and Yurtcan pointed to RES technologies as promising due to their economical and environmentally friendly nature, highlighting that they bring added value due to their commercial applications [29,30]. It would require years of evaluation to result in a sizeable global contribution from renewables. Geographical differences in RES use are connected to climatic inequalities resulting from climate change and increased energy availability [31]. On the other hand, Potrc et al. discussed energy availability in the context of individual sectors, mainly the transport and power sector, where it is providing new job opportunities, including social aspects of RES sustainability and the geographical and climatic view [6]. Spain is representative of the other countries in the Mediterranean region. In this region, Raji et al. (2024) found that Morocco has made industry a new driving force for its national economy, with sectors like the automotive and aeronautics sectors achieving remarkable results. However, this progress has not yet been mirrored in the PV energy sector, where projects often depend on the physical connection to the national electricity grid [32]. Nassar et al. (2018) pointed to the wind energy potential in the Gaza Strip [33].

Due to the abovementioned information, the presented contribution aims to highlight the elements essential to supporting the growth and development of the renewable energy sector while also making a significant contribution to our understanding of the development of RESs in Slovakia and Spain in the area of the chosen sectors. The results of this study will be helpful for policymakers, industry experts, stakeholders and anyone interested in renewable energy.

3. Materials and Methods

This paper’s main objective is to present a thorough and comparative study of the growth of renewable energy sources in Slovakia and Spain. In the countries studied, using renewable energy sources is becoming an increasingly important part of the global energy mix, and their expansion and development significantly affect energy, the environment and the economy.

Comparing these two countries is particularly insightful due to their differing geographical and climatic conditions, which influence their renewable energy strategies. Spain benefits from abundant sunshine and favourable wind conditions, making it a leader in solar and wind energy. On the other hand, Slovakia has significant potential for hydro and biomass energy due to its natural resources. These differences provide a comprehensive view of how various renewable energy sources can be optimised in different environments.

A comparison of renewable energy sources (RESs) in Slovakia and Spain can be helpful for several reasons, first due to their geographical differences and different approaches to RES policies and support. Slovakia has more potential for hydro and biomass energy but fewer sunny days for solar energy. Thanks to its warm and dry climate, Spain has a vast potential for solar energy and suitable conditions for wind energy. Spain is among the leaders supporting RESs in Europe. It has a strong emphasis on solar and wind power plants. Spain’s technological investment in wind and solar power has propelled it to become a European leader in renewable energy. Policies such as the Climate Change and Energy Transition Act of 2021 and projects such as Iberdrola’s extensive network of solar and wind farms demonstrate Spain’s commitment to renewable energy [34]. Slovakia still has the potential to increase the share of RESs but faces other challenges, such as investment barriers and legislative restrictions. The comparison can inspire improving policies in Slovakia using the Spanish experience. Both countries are committed to EU targets for reducing emissions and transitioning to green energy. Slovakia can adapt quickly to these targets using Spain as a model.

Technological and economic comparisons, as well as energetic independence and security, are essential. Thanks to longer-term investments, Spain uses advanced technologies for energy production from RESs, while some areas in Slovakia are less developed. The comparison can help identify technologies that Slovakia could implement to use RESs more effectively. Dependence on fossil fuels is a problem in both countries, but RESs offer the opportunity to increase energy independence.

To achieve the goal, this research began with an analysis of the current energy mix in Slovakia and Spain and the energy laws and regulations in force in both countries. Subsequently, the study addressed the specifics of the renewable energy sectors in each country, emphasising the types of RES used, their capacity and their share in the overall energy mix. The study also examined the programmes and policies implemented in both countries to promote renewable energy sources and how they have achieved the desired results. The paper also includes comparisons of the two countries to uncover similarities, contrasts and variables that helped or hindered the development of RESs.

The steps that made up the workflow were as follows:

• Research to gain more information about the laws and programmes in place to support the use of RESs and the current state of the renewable energy sector in Slovakia and Spain.
• Reviewing statistical data on the availability and share of RESs in the overall energy mix of Slovakia and Spain. The research used both primary and secondary sources. Interviews with industry experts were used as primary sources to gain more information about the potential challenges faced by the renewable energy sector in both countries and the effectiveness of policies and initiatives. Published reports and data were used as secondary sources to learn more about the laws and programmes in place to support the use of RESs and the current state of the renewable energy sector in Slovakia and Spain. The study also compares the two countries to identify parallels, differences and elements that have helped or hindered the growth of the renewable energy sector.
• Comparative analysis of the two countries to find out what they have in common, what they do not and what factors have helped or hindered the growth of the renewable energy sector.

The study used statistical techniques to examine information obtained from primary and secondary sources. These techniques use descriptive statistics to provide a summary of the data. Statistical analysis was used to evaluate the success of initiatives and policies, analyse the current state of the renewable energy sector in Slovakia and Spain and identify any opportunities and challenges the industry faced in both countries. Based on the study’s findings, conclusions and recommendations were drawn to support the expansion and development of renewable energy sectors and remove all obstacles.

4.

Concluding and presenting proposals for stakeholders, industry experts and policymakers in both countries to improve RES legislation in the EU.

We compared these two countries’ renewable energy use based on the data analysed in the next chapter. However, since these two countries have different sizes and populations, we compared all the data analysed in percentages and kWh per capita.

4. Results

4.1. Development of RES Energy in Slovakia

Based on statistics from [SEAS] from 2022, we can describe the current situation in the field of renewable energy in Slovakia [35]. SEAS states that Slovakia is also making progress in creating renewable energy. To increase energy production and reduce its carbon footprint, the country invests in various sustainable energy sources, including hydropower, biogas and biomass. Nearly all regions in Slovakia have exceeded the 20% threshold for RESs in electricity generation (Figure 1). Slovakia’s determination to reduce its carbon footprint and achieve a cleaner future has motivated its efforts to develop alternative energy sources. According to the Ministry of Economy, Slovakia has met the target of generating at least 14% of electricity from renewable sources by 2020. In 2022, Slovakia obtained 23% of its electricity from renewable sources, a significant increase compared to previous years. The Vajnory Solar Park near Bratislava is one of Slovakia’s most important renewable energy initiatives. One of the largest solar parks in Slovakia, it has a capacity of 7.5 megawatts and an area of 22 hectares.

The renewable energy market in Slovakia consists of various categories, including hydropower, solar power, biofuels and others. This paper deals with the market size and forecasts for this area. Based on the installed capacity, market estimates and projections were prepared for the given segment (GW). According to our study, the primary key trends affecting the Slovak renewable energy market are the following:

The solar energy market in Slovakia is expected to grow significantly.

Slovakia intends to promote renewable energy sources that replace fossil fuels to ensure cost-effective electricity and heat generation. Experts expect that, by replacing solid fossil fuels with renewable energy sources, Slovakia will be among the European Union’s cleanest countries by the end of 2025 [36]. The installed capacity of solar energy in 2021 was 535 MW, and the amount of solar energy produced was 663 GWh, a 12.56% increase compared to 2020. In the upcoming years, Slovakia’s solar energy capacity is expected to grow due to multiple factors. In 2024, Slovakia increased its solar capacity by 274 MW, surpassing a total installed capacity of 1 GW. The country aims to add around 300 MW of new solar capacity annually. Furthermore, Slovakia is enhancing its solar module manufacturing capabilities [37]. Many domestic companies, including Agora Solar, plan to open a 150 MW module manufacturing plant. Such production lines will increase the country’s installed capacity for solar power. During the forecast period, new and ongoing solar power projects could boost the solar power market in the country.

The growing potential of bioenergy can drive the market.

In Slovakia, wood biomass provides material for heat, although biogas plants that produce heat from by-products of plant and animal production are more environmentally friendly. Slovakia had −225 megawatts of installed bioenergy capacity in 2021, and, in 2020, total production was 1673 GWh. The ministry is trying to accelerate the use of second-generation biofuels from biomass crops such as wood, organic waste, food crop waste, some biomass crops and non-food crops. These modern biofuels also guarantee a significant reduction in greenhouse gas emissions. Several methods can be used to utilise biomass. Similar research in biomass utilisation is partially completed, focusing on some of the above areas [38]. Even without subsidies, the Slovak market for biogas, used for combined heat and power generation, and biofuels in transport is becoming increasingly competitive. All of these technologies are available in Slovakia. Businesses are also contributing to the national bioenergy effort. For example, Evonik invested significantly in constructing a new rhamnolipids production plant in January 2022. The company hopes to meet the growing demand for bioproducts in Central Europe. Slovakia has the highest technological potential for bioenergy production, as it is one of the most scientific and forested nations in the European Union.

Future implementation of geothermal energy.

The plan states that geothermal energy production could start as early as 2024, with an installed capacity of 4 MW per year until 2030, when Slovakia could have 28 MW of installed geothermal energy capacity according to the plan. Renewable energy production has focused so far on electricity generation, or, at most, on combined generation, the NECP states. Future financial assistance should also concentrate on heat generation, as geothermal energy has great potential in this area. An aid is a green bonus or surcharge. The recovery plan also includes support for using geothermal energy in the power and heating sectors [3].

In 2022, hydropower accounted for 66.50% of Slovakia’s total renewable energy sources (RESs) used for electricity production. This makes hydropower the dominant renewable energy source in the country, reflecting its significant contribution to the overall energy mix. While not as predominant, solar energy still played a crucial role, contributing 10.15% to the total RESs. This positions solar energy as Slovakia’s third most significant renewable energy source. Biofuel energy also made a notable contribution, constituting 16.38% of the total RESs. This highlights the importance of biofuels in Slovakia’s renewable energy landscape. Although less prominent, other renewable energy sources still contributed 6.89% to the total RESs, showing the diversity of renewable energy sources utilised in the country (Figure 2).

The structure of renewable energy production in Slovakia in 2022 was dominated by hydropower and solid biofuels, reflecting global trends and innovations in the renewable energy sector. Hydropower held a dominant position in the country, with an increase of 796.7 GWh from 2018 to 2022, considering both large and small hydroelectric power plants. Wind energy also demonstrated an increase in production, particularly since 2020. Energy production from biomass increased by 228.8 GWh in 2022 compared to 2018, remaining stable throughout the period. Solar photovoltaics showed a significant increase of 72 GWh in 2022 compared to 2018, especially since 2021 (Figure 3).

The energy mix of Slovakia in 2022 was characterised by a significant reliance on three primary energy sources: thermal power plants, natural gas and nuclear energy. Nuclear energy accounted for 53.59% of the total energy mix, indicating a high dependency on this source. Natural gas contributed 12.56%, while electricity from small hydropower plants comprised 11.93%. Other energy sources comprised a smaller portion of the energy mix, including coal, biomass, solar photovoltaics and hydropower. This composition of the energy mix has implications for environmental and public health given the potential risks associated with nuclear power plants (

Table 1. Energetic mix of Slovakia, 2022. Source: own processing according to [35].

Energy Type	% in the Energetic Mix
Wind energy	0.02%
Biomass	6.31%
Solar photovoltaic	2.22%
Water power plants	3.84%
Small hydroelectric power plants	11.93%
Nuclear energy	53.59%
Coal	5.63%
Natural gas	12.56%
Diesel	1.69%
Other fossil energy	2.21%

and Figure 4).

4.2. RES Use Development in Spain

In 2022, Spain demonstrated its dedication to reducing its carbon footprint and moving towards a cleaner future through significant efforts in renewable energy. According to the Ministry of Energy, regions like Castilla y Leon, Aragon and Galicia have made remarkable progress, with Castilla y Leon leading with 89.6% of its electricity being generated from renewable sources. This showcases the region’s substantial investment in sustainable energy. Spain’s broader strategy aims to transition to a more sustainable energy system, reducing reliance on fossil fuels and minimising environmental impact, reflecting the country’s commitment to a greener future.

In 2022, the electricity production from renewable energy sources in various regions of Spain showed significant variation. Castilla y Leon led, with 89.6% of its electricity coming from renewable sources, followed by Aragon with 75%. Galicia also had a considerable share, generating 64.9% from renewables, and Castilla-La Mancha produced 61.9%. Andalusia generated 45.9% of its electricity from solar photovoltaic sources, and Extremadura contributed 38.7% (Figure 5).

The energy mix for electricity generation based solely on renewable energy sources (RESs) in 2022 was dominated by wind energy and solar photovoltaics. Wind energy accounted for 47% of the total RESs, making it the most significant contributor. Solar energy represented 26%, positioning it as the second most important source. Hydropower contributed 22%, while biogas energy accounted for 3%. Other renewable energy sources made up 2% of the total RESs. This distribution reflects global trends and innovations in the renewable energy sector (Figure 6).

Nuclear energy accounted for more than 20% of the total energy production. Other significant sources included wind energy at 22.1% and mixed cycle at 24.7%. Hydropower and photovoltaics contributed 10.1% and 6.5%, respectively. Other sources derived smaller shares (Figure 7 and

Table 2. Energetic mix in 2022 in Spain. Source: own processing according to Red Electrica [40].

Energy Type	% in the Energetic Mix
Hydraulics	6.5
Turbine pumping	1.4
Nuclear energy	20.3
Coal	2.8
Fuel and gas	0
Diesel engines	0.9
Gas turbine	0.2
Steam turbine	0.4
Combined cycle	24.7
Hydrodynamics	0
Wind energy	22.1
Solar photovoltaic	10.1
Solar heat energy	1.5
Other RES	1.7
Cogeneration	6.4
Non-renewable waste	0.7
Renewable waste	0.3

).

Nuclear and combined-cycle power plants accounted for approximately half of the total energy production, making them the primary contributors to the energy mix. Wind and solar photovoltaics contributed over a third of the total output and significantly generated energy from renewable sources (Figure 7).

4.3. Comparison of RES Use in Slovakia and Spain

A comparative analysis of Spain (ES) and Slovakia (SR) regarding renewable energy use in different sectors from 2004 to 2022 reveals significant trends. Spain’s share of renewable energy sources (RESs) in the electricity sector increased from 19.02% in 2004 to 50.90% in 2022, while Slovakia’s share rose from 15.40% to 22.90% over the same period. Spain made substantial progress in the transport sector, increasing its RES share from 1.03% in 2004 to 9.68% in 2022. Slovakia also saw an increase, though less pronounced, from 1.50% to 8.93%. In the heating and cooling sector, Spain’s use of RESs grew from 9.55% to 20.04%, while Slovakia’s share increased from 5.06% to 19.92%. Spain has a higher share of RESs in all three sectors than Slovakia, particularly in electricity. This disparity may be attributed to Spain’s abundant sunny days, which favour the development of solar energy, and its favourable geographical conditions for wind energy. Despite having a lower overall share of RESs, Slovakia is demonstrating strong growth, especially in the heating and cooling sector (Figure 8).

A comparative analysis of the development of different types of renewable energy sources (RESs) in Spain (ES) and Slovakia (SR) from 2004 to 2022 highlights the evolution of their contributions to total electricity production. The percentages represent the share of electricity produced by RESs in both countries’ energy supply. This analysis provides insights into the growth and integration of renewable energy in Spain and Slovakia over the specified period (Figure 9).

Spain:

• Wind energy showed a significant increase from 5.92% in 2004 to 23.89% in 2022.
• Solar energy increased from a negligible 0.01% in 2004 to 13.32% in 2022.
• The share of hydropower increased from 11.87% in 2004 to 11.24% in 2022.
• Biomass increased from 0.81% to 1.72% in the same period.
• Other renewable energy sources increased from 0.41% in 2004 to 0.73% in 2022.

Slovakia:

• The share of hydropower increased from 15.31% in 2004 to 15.23% in 2022.
• Biomass increased from 0.01% in 2004 to 3.75% in 2022.
• The share of solar energy increased from 0% in 2004 to 2.32% in 2022.
• Other renewable energy sources increased their share from 0.06% to 1.58%.
• Wind energy remains low and stable at 0.02%.

Spain’s total share of renewable energy sources increased significantly, rising from 19.02% in 2004 to 50.90% in 2022. In contrast, Slovakia’s share of renewable energy sources grew from 15.40% to 22.90% over the same period. These figures indicate a more active RES implementation and development in Spain than in Slovakia, particularly in the wind and solar energy sectors. The development of renewable energy sources is characterised by a significant increase in their percentage share in the total energy balance and the broader introduction of these technologies across various economic sectors. The share of RESs in the electricity sector is a crucial indicator given that electricity is a fundamental driver of economic development and daily consumption. When comparing the two countries, Spain demonstrates more decisive progress in developing RESs. The rapid growth of the share of renewables in the electricity sector can be attributed to substantial investments in solar and wind energy. Conversely, while trailing behind Spain in the overall share of RESs, Slovakia has experienced a notable rise in the utilisation of RESs in the heating and cooling sector. This trend suggests the successful implementation of heat pumps and other thermal solutions (Figure 9).

The comparative analysis of the share of renewable energy sources (RESs) in total electricity production and the distribution of different types of RES in 2022 between Spain and Slovakia reveals significant differences. Spain’s share of renewable energy sources in electricity production is 50.90%, substantially higher than Slovakia’s share of 22.90% (Figure 10 and

Table 3. Share of total energy produced from various RESs in 2022 in the analysed countries. Source: own processing according to Eurostat [41,42,43,44].

Spain	Slovakia
Wind energy 23.89%	Water energy 15.23%
Solar energy 13.32%	Others 6.89%
Water energy 11.24%	Biogas 3.75%
Biogas 1.72%	Solar energy 2.32%
Others 1.43%	Wind energy 0.02%

).

The structure of renewable energy production in Spain and Slovakia exhibits significant differences, with Spain relying more heavily on wind and solar energy. In contrast, Slovakia has a more substantial share of hydropower and biofuels in its energy mix (Figure 10).

The analysis highlights Spain and Slovakia’s distinct strategies and energy profiles regarding renewable energy utilisation. Spain’s high share of renewable energy can be attributed to the extensive implementation of green energy policies that encourage investment in solar and wind projects, particularly in regions with high solar and wind potential (Table 3). When comparing renewable energy sources (RESs) between countries, it is essential to consider the percentage of total energy generated and per capita usage. This provides a more comprehensive understanding of each country’s progress in adopting renewable energy.

From 2013 to 2022, Spain and Slovakia showed different trends in RES usage per capita. In Spain, the use of RESs for heating and cooling generally decreased, from 7365.92 kWh/person in 2013 to 6579.92 kWh/person in 2022. Conversely, electricity production from RESs increased, reaching 2838.45 kWh/person in 2022. Although Spain has a higher percentage of RESs in electricity generation, Slovakia’s per capita usage of RESs is higher, particularly in the heating and cooling sector. Slovakia has seen fluctuations in RES usage for heating and cooling, with it peaking at 14,520.62 kWh/person in 2021 before dropping to 13,163.89 kWh/person in 2022. Electricity production from RESs in Slovakia has remained relatively stable, with a slight decrease from 1257.10 kWh/person in 2021 to 1179.71 kWh/person in 2022. Overall, Slovakia’s total RES usage per capita has consistently been higher than Spain’s, reflecting the different energy strategies and resource availability in the two countries (Figure 11 and Figure 12).

Although Slovakia has a lower overall share of renewable energy sources, it strongly focuses on hydropower and biofuels, which may reflect the country’s geographical and natural characteristics and its likely historically developed energy infrastructure.

Differences in the share of other renewable energy sources may reflect differences in available technologies and approaches to integrating less traditional forms of renewable energy, such as geothermal energy, ocean energy or other innovative solutions.

It should be noted that the significant share of renewable energy sources in Spain’s energy mix is in line with the European Union’s commitments to reducing greenhouse gas emissions and increasing the share of renewable energy sources in energy production by 2030. Conversely, although Slovakia has a smaller share of renewable sources, it is also developing its resources in this direction, reflecting the general trend in EU countries to increase the use of sustainable energy sources.

5. Discussion

Several important conclusions result from the preceding analyses concerning the development and use of renewable energy sources (RESs) in Spain and Slovakia:

Dynamics of RES development:

Spain is making significant progress in using renewable energy sources, especially for electricity. The growing share of wind and solar energy reflects active investments in these technologies and the efficient use of natural conditions, such as many sunny days and strong wind flows.

Although Slovakia has a lower overall share of renewable energy sources, it is showing stable growth, especially in biofuels and hydropower, which reflects a focus on its energy sources and potential. It is connected with the results of Gurgul and Ulbrich, who showed that Slovakia, in the context of the V4 economies, records an average rating in the implementation of the energy and climate framework. However, together with Hungary, the situation is better than in Poland and Czech Republic [46].

Diversity of renewable energy sources:

Spain has a high diversity of renewable energy sources, which allows the country to reduce its dependence on traditional energy sources and increase energy independence.

In Slovakia, hydropower remains the key renewable energy source, but the growing share of biofuels indicates an effort to use a broader range of renewable energy technologies.

This paper’s results support the research of Dyduch and Skorek, who investigated whether Slovakia, included in the V4 states’ energy security, can be improved by deepening energy cooperation with partners from southern regions, particularly the Middle East and North Africa [47]. In addition, sustainable economic growth can increase RES use, reforming renewable energy policies and green industries [48].

A study of the legislative, economic and environmental aspects of renewable energy deployment in Spain and Slovakia showed significant progress in their transition to sustainable energy. With an impressive 50.90% share of renewable energy sources, Spain is at the forefront of using wind and solar energy, which has the positive impacts of reducing the carbon footprint and maintaining the ecological balance. In contrast, with 22.90%, Slovakia focuses on hydropower and biofuels, which also contribute to the fight against climate change, but can potentially expand the use of other types of renewable energy. Considering the analysis of the legislative framework, investment attractiveness and environmental aspects of renewable energy sources in Spain and Slovakia, it is worth noting that both countries are taking intensive steps towards energy independence and sustainable development. Spain is using its natural advantages to expand wind and solar energy, while Slovakia, with its strong hydropower sector, has the potential to diversify its energy matrix. The balanced development of renewable energy sources will contribute to environmental sustainability, economic growth, job creation and energy security.

Spain has ambitious targets for renewable energy and sees it as a key element of decarbonisation and the transition to a sustainable economy. Significant investments in renewable energy in Spain, particularly solar and wind power, demonstrate active government and private sector support. Feed-in tariffs and tax incentive policies help attract investors and stimulate the sector’s rapid development.

Although Slovakia has a smaller share of renewable energy in the overall energy mix, it continues to develop the sector, focusing on hydropower and biomass. Government and EU subsidies and investment incentives aim to increase energy efficiency and expand renewable energy sources. This demonstrates a strategic approach to optimising national resources while meeting climate targets.

Spain generally has a more diversified and mature renewable energy market, with significant investments in infrastructure and technology, giving it an advantage in using renewables to generate electricity. Spain’s strategy, which focuses on increasing installed renewable energy capacity and developing green hydrogen, indicates its commitment to becoming a clean energy leader. Discussing the intentions of strategies and visions or predicting their impact is very difficult. Visions of green hydrogen as the leader of the energy self-sufficiency of states are coming up against scientific evidence of the technical difficulty of fulfilling them every day. However, countries with a robust infrastructure for distributing and storing energy from RESs will have a clear advantage over others.

On the other hand, Slovakia seems to be taking a more conservative approach, focusing on optimising and modernising existing capacities such as hydroelectric power plants. Still, it is also attempting to invest in photovoltaics and wind power.

Slovakia’s results are similar to those in the V4 region since all four countries in the V4 group have identical conditions and historical development [49]. It can also be supported by the study of Sulich and Soloducho-Pelc, which shows a common direction for developing RES technologies [50]. Čeryová et al. found that Slovakia has the highest dependence on energy import compared with the other V4 countries [51].

The results in Spain are similar to those in other Mediterranean countries. For example, Zrelli and Belaida et al. found a relationship between RES use and GDP development, primarily in long-term periods [52,53]. Renewable electricity consumption is the most critical factor in explaining economic growth. Therefore, results from Spain can be used for countries such as France, Slovenia, Greece, Turkey, Lebanon and Israel. Along with geographical conditions, the ecological formation of the Mediterranean countries should be studied [54].

The results are limited to the areas of transport and energy generation. However, the building sector is the second biggest energy consumer, demanding attention regarding such factors as the development of renewable energy systems, sector coupling, thoughtful grid system planning and storage technologies [55]. However, each country needs to study its current energy situation, revising its policies [56]. Alola et al. also studied the building sector and found that, in Mediterranean countries, housing construction policy is not a driver of renewables in Israel [54]. Čeryová et al. studied RESs in the context of individual sectors of the national economy and found that agriculture and forestry are less critical in economic development, especially in Slovakia [51]. They underline the disputation because they present the sectors with great RES potential from the view of biomass production. In addition to the factors influencing RES development, foreign direct investment in RES technologies, the political situation of the country and the influence on the pollution of the living environment also present future research subjects. For example, in some countries, the political situation did not influence RES use and, in this way, pollution (Poland and Hungary), while, in Slovakia and the Czech Republic, RES use was influenced by the country’s political stability [57].

6. Conclusions

When assessing the dynamics of renewable energy development in Spain and Slovakia, it is essential to note that renewable energy sources are a key element in the energy strategy and the policy of strengthening environmental sustainability. The analysis of the distribution of different types of renewable energy shows the strategic direction of each country and identifies potential opportunities for further integration and optimisation. Investments in renewable energy technologies and support for innovation in this area can strengthen energy independence and increase the share of renewable energy in the overall energy mix while protecting the environment and achieving global sustainable development goals. Both countries show growth in the RES sector, aligning with their economic and environmental strategies and commitments to the EU. The study’s results highlight the need for a further integrated approach to developing RESs, particularly in terms of ecological impacts and stimulating investment in this sector.

The research and discussion might interest policymakers and have an application value for energy security and climate policy institutions in the analysed countries. The results can also be used to rank other EU members according to the level of the studied indicators. However, the study is limited to the RES use in transport and electricity generation, even though energy policy in the area of RESs is also challenged by many other factors, dependence on the import of energy resources, increasing environmental pressure and the insufficient and disappointing process of energy policy Europeanisation, which, as mentioned, can be a framework for further searching [47]. Future research will also be oriented toward comparing the analysed area with northern countries. The limitation of the aforementioned study is that it focuses only on the energy and transport sectors. The significant untapped potential of renewable energy could be revealed if extended to the construction or industrial sectors. In the construction sector, integrating renewable energy technologies such as solar panels, wind turbines and geothermal systems could significantly reduce carbon emissions and increase the energy efficiency of buildings [58]. Moreover, the paper shows the share of RESs in selected sectors since 2004. This means a share in the overall energy mix. Every percentage increase in the share of RESs reduces the share of fossil fuels in the energy mix. An in-depth analysis of the energy mix each year could be the subject of future research, which would require unique research precisely in connection with the formation of the energy landscape of each nation.