Trendline Assessment of Solar Energy Potential in Hungary and Current Scenario of Renewable Energy in the Visegrád Countries for Future Sustainability

sustainability

Article Trendline Assessment of Solar Energy Potential in Hungary and Current Scenario of Renewable Energy in the Visegrád Countries for Future Sustainability

Baibhaw Kumar 1,* ,Gábor Szepesi 1 , Zsolt Conkaˇ 2,* , Michal Kolcun 2, Zsolt Péter 3,László Berényi 4 and Zoltán Szamosi 1

1 Institute of Energy Engineering and Chemical Machinery, University of Miskolc, 3500 Miskolc, Hungary; [email protected] (G.S.); [email protected] (Z.S.) 2 Department of Electric Power Engineering, Technical University of Košice, 040 01 Košice, Slovakia; [email protected] 3 Institute of World and Regional Economics, University of Miskolc, 3500 Miskolc, Hungary; [email protected] 4 Institute of Management Science, University of Miskolc, 3500 Miskolc, Hungary; [email protected] * Correspondence: [email protected] (B.K.); [email protected] (Z.C.)ˇ

Abstract: This article aims to present some opportunities for improved solar energy utilization by raising the share of renewables in energy generation in the Visegrád Countries (Poland, Czech Citation: Kumar, B.; Szepesi, G.; Republic, Slovakia, and Hungary). The analysis is based on the status of the renewable energy targets ˇ Conka, Z.; Kolcun, M.; Péter, Z.; in the member countries and their future possibilities. This paper derives input through a thorough Berényi, L.; Szamosi, Z. Trendline investigation of independent data, government policies, European Commission reports, and other Assessment of Solar Energy Potential data available online with free access. The analysis is processed by focusing on Hungary, as a country in Hungary and Current Scenario of with various possible facets of solar energy demand and supply in the region. The assessment Renewable Energy in the Visegrád Countries for Future Sustainability. methodology is in the context of a geographical map, technical regression analysis, temperature Sustainability 2021, 13, 5462. distribution proﬁles, and the relative trends of solar potential in Hungary. The country currently https://doi.org/10.3390/su13105462 has ten solar power plants with more than 10 MWp, and ﬁve remarkable plants under 10 MWp capacity spread over Hungary. The analysis on geographical aspects clubbed with technical and Academic Editors: Marc A. Rosen, solar affecting parameters was carried out to harvest the sustainable potential of solar energy in the Inga Zicmane, Gatis Junghans, region. This study attempts to establish a relationship between the current and future prospects of Svetlana Beryozkina solar energy in Hungary as a nation, and as part of the Visegrád countries, based on assessment for a and Sergey Kovalenko sustainable future.

Received: 18 March 2021 Keywords: renewable energy; Visegrád countries; solar potential; Hungary Accepted: 11 May 2021 Published: 13 May 2021

Publisher’s Note: MDPI stays neutral 1. Introduction with regard to jurisdictional claims in published maps and institutional afﬁl- The political instability in the Central European region gave birth to the Visegrád iations. countries in 1991. Later, in the year 1993, the dissolution of Czechoslovakia led to the formation of a quadrangle group of countries, which later came to be known also as the “Visegrád Group”, or the “V4 countries”. In the beginning, this informal association’s main goal was to integrate political and economic cooperation fully [1]. Energy security is a global concern nowadays. All nations around the world have framed energy policies in Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. contrast with sustainable growth. Almost all regions and continents have adopted their This article is an open access article own national policies as well. Similarly, the European Union (EU) framed H2020 targets distributed under the terms and to reduce greenhouse gas emissions in 2007 [2]. The 2030 climate and energy framework conditions of the Creative Commons was recently documented for the EU to reduce greenhouse emissions by at least by 55% Attribution (CC BY) license (https:// compared to 1990 [3]. Reducing carbon emissions and dependence on conventional energy creativecommons.org/licenses/by/ sources is a major challenge for all European nations, especially V4 countries. Settled in the 4.0/). middle of the EU, the V4 countries can signiﬁcantly contribute to curbing energy security

Sustainability 2021, 13, 5462. https://doi.org/10.3390/su13105462 https://www.mdpi.com/journal/sustainability Sustainability 2021, 13, x FOR PEER REVIEW 2 of 18

compared to 1990 [3]. Reducing carbon emissions and dependence on conventional en‐ Sustainability 2021, 13, 5462 2 of 16 ergy sources is a major challenge for all European nations, especially V4 countries. Settled in the middle of the EU, the V4 countries can significantly contribute to curbing energy security problems through cooperation. The V4 countries still have a long path to cover to reduceproblems their dependence through cooperation. on fossil fuels, The and V4 countriesrenewable still energy have could a long be patha possible to cover solu to‐ reduce tion.their The dependence joint policy paper on fossil on energy fuels, andsecurity renewable recommended energy creating could be better a possible regional solution. in‐ The frastructurejoint policy for paperthe regional on energy energy security market recommended [4]. creating better regional infrastructure forToday, the regional the energy energy security market concern [4]. is a global issue and seeks global cooperation to tackle emergingToday, the energy energy scarcity. security The concernconcerns is regarding a global issueenergy and production seeks global are not cooperation only to limitedtackle to emergingdeveloping energy countries. scarcity. However, The concerns there are regarding challenges energy to meet production CO2 emissions, are not only and a sustainable environment cannot be left behind. In such a case, renewable energy limited to developing countries. However, there are challenges to meet CO2 emissions, and sources emerged as a promising solution at the beginning of the 21st century. The emer‐ a sustainable environment cannot be left behind. In such a case, renewable energy sources gence of various non‐conventional energy sources opened the doors of cooperation emerged as a promising solution at the beginning of the 21st century. The emergence of among nations as well. The Visegrád Countries in the Central European region are an various non-conventional energy sources opened the doors of cooperation among nations example of countries with mutual interests that should look beyond boundaries to de‐ as well. The Visegrád Countries in the Central European region are an example of countries velop emerging energy sectors. The renewable sources are not yet as user‐friendly or eco‐ nomicallywith mutual viable interestsas the conventional that should fossil look fuel beyond‐based boundariesenergy market. to develop The mutual emerging agree‐ energy mentssectors. could The accelerate renewable the innovations sources are related not yet to as various user-friendly renewable or economically sources among viable na‐ as the tions.conventional The European fossil Commission’s fuel-based energy National market. energy The and mutual climate agreements plans (NECP) could reports accelerate the highlightinnovations the effectiveness related to variousof V4 nations renewable with sourcessome recommendations, among nations. Thewhich European are high Commis-‐ lightedsion’s in Nationalthis study. energy In this andstudy, climate each country, plans (NECP) namely reports Poland, highlight the Czech the Republic, effectiveness Slo‐ of V4 vakia,nations and withHungary, some is recommendations, discussed regarding which their arecurrent highlighted energy status in this in study. renewable In this study, sourceseach [5,6]. country, namely Poland, the Czech Republic, Slovakia, and Hungary, is discussed regardingThe EU aims their to current increase energy the share status of renewable in renewable energy sources consumption; [5,6]. the target value is 32% [7].The The EU national aims to increaseenergy and the climate share of plans renewable (NECP) energy reflect consumption; the renewable the energy target value percentageis 32% [ share7]. The for national V4 countries energy as Poland and climate (23%), Hungary plans (NECP) (21%), reﬂectCzech Republic the renewable (22%), energy andpercentage Slovakia (19.2%) share forby 2030. V4 countries Thus, according as Poland to (23%),the current Hungary scenario, (21%), V4 nations Czech Republic should (22%), lookand for Slovakia new potentials (19.2%) and by analyze 2030. Thus, their renewable according energy to the currentproduction scenario, strategy. V4 Figure nations 1 should showslook a forcomprehensive new potentials recent and status analyze picture their of renewable the share of energy renewable production sources strategy.in energy Figure 1 consumptionshows a comprehensive of the V4 Countries recent [8]. status picture of the share of renewable sources in energy consumption of the V4 Countries [8].

10 %share 2030 5 2020 0 Hungary Poland Czech Slovakia Republic

2020 2030

Figure 1. Share of energy from renewable sources in final gross consumption of energy in V4 Figure 1. Share of energy from renewable sources in final gross consumption of energy in V4 Countries NECP and future expectations by 2030 [9]. Countries NECP and future expectations by 2030 [9]. Thus, the requirement of investigations on the possible supply of power through Thus, the requirement of investigations on the possible supply of power through re‐ renewable energy sources (RES) becomes inevitable. The study could be briefly framed in newable energy sources (RES) becomes inevitable. The study could be briefly framed in the context of the following research assessments: the context of the following research assessments: • The status of renewable energy consumption share trends in V4 Countries, focusing on Hungary as a case study for solar energy harnessing. • Comparative study for the V4 countries on irradiation observation parameters through regional maps and graph trend analysis. • Recent observation of the performance of grid-connected PV systems for a fixed angle. Profiling of various cities was conducted to observe their potential for the potential study of Hungary. Sustainability 2021, 13, x FOR PEER REVIEW 3 of 18

 The status of renewable energy consumption share trends in V4 Countries, focusing on Hungary as a case study for solar energy harnessing.  Comparative study for the V4 countries on irradiation observation parameters Sustainability 2021, 13, 5462 through regional maps and graph trend analysis. 3 of 16  Recent observation of the performance of grid‐connected PV systems for a fixed an‐ gle. Profiling of various cities was conducted to observe their potential for the poten‐ tial study of Hungary. The rise of renewable energy shares by percentage in the Visegrád Countries and the The rise of renewable energy shares by percentage in the Visegrád Countries and the speciﬁc country shares can be observed in Figure2. Short-term dynamic studies reveal specific country shares can be observed in Figure 2. Short‐term dynamic studies reveal unidirectional casualties in the regional group in contrast with energy consumption, carbon unidirectional casualties in the regional group in contrast with energy consumption, car‐ bonemissions, emissions, and and economic economic growth growth [ 10[10].]. The The decompositiondecomposition analysis analysis also also suggests suggests en energy‐ ergyintensity, intensity, and and carbon carbon emissions emissions were were thethe driving force force for for gross gross development development prod product‐ uct(GDP) (GDP) per per capita capita in in the the Visegr Visegrádád Countries [11]. [11]. There There could could be be possible possible heterogeneity heterogeneity in inthe the approaches approaches ofof thethe V4 Countries Countries [12]. [12]. Thus, Thus, further further country country-based‐based distinguished distinguished sta‐ status tusis discussedis discussed in in the the next next chapter. chapter.

FigureFigure 2. 2. RenewableRenewable energy energy share share growth growth by percentage by percentage in V4 in Countries V4 Countries [9]. [9].

2.2. Overview Overview of of the the Member Member State State Positions Positions 2.1. Poland 2.1. Poland Nowadays,Nowadays, solar solar photovoltaic photovoltaic (PV) (PV) technologies technologies are are at atan an all all-time‐time high high in inhigh high lati latitude‐ tudecountries, countries, including including Poland Poland [13 [13].]. Poland’s Poland’s energy energy consumption consumption has has increasedincreased signif significantly‐ icantlyin the in last the decade, last decade, with with 175 TWh 175 TWh recorded recorded in 2019. in 2019. Though Though the the share share of of renewable renewable energy energyin power in power production production reached reached a breakthrough a breakthrough with with 25 TWh 25 TWh in 2019, in 2019, the the significant significant share of sharearound of around 73% is 73% still beingis still producedbeing produced in coal in and coal lignite and lignite plants. plants. The countryThe country also also struggles struggleswith reducing with reducing CO2 emissions, CO2 emissions, as emissions as emissions have been have stagnantbeen stagnant since since 2018 2018 without with further‐ outreduction. further reduction. According According to the European to the European Union Union NECP, NECP, these these numbers numbers predict predict a possible a possibleoutgrowing outgrowing potential potential for the for renewable the renewable sources sources industry industry to foster to foster in the in region. the region. As per the As“INSTITUTE per the “INSTITUTE FOR RENEWABLE FOR RENEWABLE ENERGY” ENERGY” reports, Polandreports, ranksPoland fifth ranks among fifth EUamong countries EUfor countries growing for solar growing photovoltaics solar photovoltaics technology technology capacity capacity for the yearfor the 2020. year With 2020. theWith highest theincrease highest in increase micro installations, in micro installations, the total installedthe total installed power capacity power capacity reached reached 1950 MW 1950 by May MW2020. by The May prime 2020. reasonThe prime behind reason this behind is the developmentthis is the development of solar parks of solar in renewableparks in re‐ energy newableauctions energy with lessauctions than with one MWless than capacity. one MW Due capacity. to the pandemic, Due to the manypandemic, installations many are installationshalted, and are thus halted, 2021–2022 and thus could 2021–2022 be considered could be aconsidered boom in Poland’s a boom in solar Poland’s PV market solar [14]. PVAccording market [14]. to the According energy policyto the energy of Poland policy for of 2040, Poland the countryfor 2040, estimatesthe country 21% estimates RES in gross 21%energy RES consumptionin gross energy by consumption 2030 [15]. by 2030 [15].

2.2. The Czech Republic The Czech goal to reach 22% electricity production by 2030 could be a tough call because it demands an investment of EUR 12.6 billion in the market sector. If only focused on solar energy, the PV plants need to expand from the current capacity of 2.25 GW to 3.8 GW, including closing older solar photovoltaic power plants [16]. An exciting observation revealed that mayors of different regions could play a signiﬁcant role in bridging the gap between renewable energy projects in the Czech areas [17]. According to NECP, Czech Republic has set a lower target for itself with an RES proportion of 22% by 2030. This not only restricts the self-energy producers, but the entrepreneurs and innovators who could play a signiﬁcant role in this transition. Too much focus and dependence on biomass-based energy sources are not recommended for long-term sustainability as Sustainability 2021, 13, 5462 4 of 16

recommended by NECP. Thus, Czechia can uphold its commitment to producing more RES based on solar photovoltaics by following the recommendations of the NECP.

2.3. Slovakia Slovakia has the target of a 19.2% share in renewable energy source consumption by 2030. This percentage of allocation is relatively less than other Visegrád Countries. The greater tilt towards nuclear energy facilities and gasiﬁcation plants reduces the possibility to achieve the given targets by NECP. Slovakia can raise 1–5 MW capacity solar plants and self-sustainable models in photovoltaics utilization facilities. The Slovak Association for the photovoltaic and renewable energy industry recommends enhancing the renewable energy share by approximately 31%, which could be very helpful. The Slovak region also needs to look beyond biomass facilities and tap the available solar potential with better policies [18]. Spatial distribution of irradiance and the dynamics of the topography could help project better topographical regions for solar power plants. In Slovakia, the annual sum of clear sky solar irradiance on a horizontal plane is about 900–1800 kWh/m2/year. The optimization of solar tilt angles could increase energy output by 30% during winter months, e.g., in December compared to June [19]. One study shows that “Komarno” and “Nove Zamky” have the highest potential to harness solar energy on the district level. In contrast, the other districts which have good potential seem to be economically backward. Thus, further investigation is also needed on potential economic reforms and support by concerned state authorities [19].

2.4. Hungary The primary energy consumption through RES in Hungary is 21% by the year 2030. The existing policies forecast that the electricity-producing capacity in Hungary will be more than 4000 MW in the coming decade. The production capacity is estimated to be exceeding 6500 GWh, more than 70% of which will be harnessed through photovoltaics [20]. A recent study in Poland (which receives solar radiation of 1000 kWh/m2/year) was conducted to understand potential solar energy technology (SET) utilization, as per EU directives. Results suggested some new innovative SET applications with rotating solar towers and artiﬁcial photosynthesis [21]. RES and the cohesiveness of its production mainly revolves around supply security, energy saving, and environmental protection with sustainability. These three parameters are essential for the long-term energy independence goals of Hungary [22]. The percentage share was selected as a growth parameter to observe the recent growth in various RES production trends. The last decade’s share in percentage is depicted in Table1 and Figure3. Based on the available data, analysis was performed to generate the regressive trendlines. The other signiﬁcant sources, apart from solar, in Hungary are biomass, biogas, wind, and hydro. Among these sources, biomass has been a major RES in energy production over the last decade. The results show that the percentage share of biomass has reduced drastically from 67.4% to 48.1%.

Table 1. The percentage share of various RES in Hungary (2010–2018, denomination in %) (based on the data of the Hungarian Central Statistical Ofﬁce).

2010 2011 2012 2013 2014 2015 2016 2017 2018 Biomass 67.4 56.4 50.4 51.3 54.0 51.4 45.8 47.3 48.1 Biogas 3.9 7.9 8.0 9.6 9.1 9.1 10.2 10.0 8.8 Wind 17.7 23.1 29.1 25.7 20.8 21.5 21.0 21.8 16.2 Hydro 6.2 8.2 8.0 7.6 9.6 7.2 8.0 6.3 5.9 Solar 0.0 0.0 0.3 0.9 2.1 4.4 7.5 10.1 16.6 Sustainability 2021, 13, x FOR PEER REVIEW 5 of 18

Table 1. The percentage share of various RES in Hungary (2010–2018, denomination in %) (based on the data of the Hungarian Central Statistical Office).

2010 2011 2012 2013 2014 2015 2016 2017 2018 Biomass 67.4 56.4 50.4 51.3 54.0 51.4 45.8 47.3 48.1 Biogas 3.9 7.9 8.0 9.6 9.1 9.1 10.2 10.0 8.8 Wind 17.7 23.1 29.1 25.7 20.8 21.5 21.0 21.8 16.2 Sustainability 2021, 13, 5462 5 of 16 Hydro 6.2 8.2 8.0 7.6 9.6 7.2 8.0 6.3 5.9 Solar 0.0 0.0 0.3 0.9 2.1 4.4 7.5 10.1 16.6

share 40

% 20

0 2010 2011 2012 2013 2014 2015 2016 2017 2018 Year

biomass biogas wind hydro solar 2 per. Mov. Avg. (solar)

Figure 3. GrowthFigure trendline 3. Growth of solar trendline energy of share solar in energy Hungary share (2010–2018) in Hungary (based (2010–2018) on the data (based of the on Hungarian the data of Central the Statistical Office).Hungarian Central Statistical Ofﬁce).

On the otherOn hand, the other the other hand, bio-based the other bio source‐based increased source increased slightly fromslightly 3.9 from to 8.8%. 3.9 to 8.8%. Wind and hydroWind maintained and hydro their maintained share. Intheir contrast, share. solarIn contrast, energy solar emerged energy with emerged the biggest with the big‐ growth, fromgest an almostgrowth, negligible from an almost share tonegligible a relevant share share to ofa relevant 16.6%. Solarshare share of 16.6%. in the Solar last share in decade grewthe from last almost decade 0 grew to 16%. from If almost the same 0 to trends16%. If arethe same observed, trends it are could observed, reach moreit could reach than 30% if themore given than conditions 30% if the given remain conditions the same. remain Also, the new same. technological Also, new advancementstechnological advance‐ could affect long-termments could goals. affect long‐term goals.

2.5. Hungary2.5. as a Hungary Case Study as a for Case Solar Study Energy for Solar Potential Energy Potential There are certainThere are parameters certain parameters which affect which the affect solar the PVsolar potential PV potential analysis analysis of of any any coun‐ country or region.try or region. Among Among these several these several factors, factors, the solar the solar irradiance, irradiance, temperature temperature profiles, profiles, and and weatherweather conditions conditions play a significantplay a significant role [23 role]. To [23]. understand To understand the regional the regional potential potential of of PV-basedPV energy‐based generation, energy generation, geographical geographical maps andmaps thermal and thermal profiling profiling could could be an be an im‐ important toolportant in making tool in accurate making predictionsaccurate predictions for the region’s for the energyregion’s capability energy capability [24]. Site [24]. Site specific irradiancespecific forecast irradiance supported forecast withsupported temperature with temperature profiling helpsprofiling in understandinghelps in understanding the forecast forthe PV forecast regional for potential.PV regional The potential. sum of theThe energy sum of falling the energy on a surfacefalling on on a earth surface for on earth a given timefor period a given is called time period irradiation. is called The irradiation. power or instantaneous The power or instantaneous energy rate received energy rate re‐ by a surface areaceived on by earth a surface is known area on as irradiance,earth is known and as is irradiance, generally calculatedand is generally on an calculated hourly on an basis. The irradiancehourly basis. is correlated The irradiance with is cloud correlated cover with predictions. cloud cover Thus, predictions. correct analysis Thus, correct of anal‐ ysis of irradiance can be considered in compliance with the sky cover [25]. For under‐ irradiance can be considered in compliance with the sky cover [25]. For understanding the standing the irradiance distribution of the Visegrád Countries, the PV–GIS interactive tool irradiance distribution of the Visegrád Countries, the PV–GIS interactive tool was used was used to observe the distribution in the four countries [26]. The capital cities, namely to observe the distribution in the four countries [26]. The capital cities, namely Warsaw, Warsaw, Bratislava, Prague, and Budapest, were considered as the irradiance in the re‐ Bratislava, Prague, and Budapest, were considered as the irradiance in the respective spective countries. Figure 4 gives a brief estimation of horizontal and direct irradiance countries. Figurevalues4 ingives the four a brief countries estimation over ofthe horizontal period of 2005–2016. and direct The irradiance monthly values solar radiation in the four countries over the period of 2005–2016. The monthly solar radiation data analysis reveals that the irradiance of Warsaw, Bratislava, and Prague lies below the range of 200 Kwh/m2, even during the peak value months. In contrast, for Budapest, Hungary, it could be observed that, during the peak irradiance months, the values cross the range of 200 Kwh/m2. The evident higher values reveal a higher solar potential of the Hungarian region. Along with irradiation data, the performance of grid-connected PV systems also plays an important role in analyzing solar potential. The European Commission PV–GIS tool gives a monthly energy output for a fixed angle PV system. Figure5 gives an estimate of energy output throughout the year in KWh. We analyzed the four nations based on their respective capital cities. It can be seen that Bratislava (Slovakia) and Budapest (Hungary) give an output of more than 125 KWh during the peak summer. Meanwhile, Warsaw Sustainability 2021, 13, x FOR PEER REVIEW 6 of 18

Sustainability 2021, 13, 5462 6 of 16

data analysis reveals that the irradiance of Warsaw, Bratislava, and Prague lies below the range of 200 Kwh/m2, even during the peak value months. In contrast, for Budapest, Hun‐ (Poland)gary, it could and Praguebe observed (Czech that, Republic) during the managed peak irradiance to reach months, an output the ofvalues 125 KWhcross the during summer.range of 200 The Kwh/m analysis2. The is based evident on higher a database values of reveal PVGIS–SARAH a higher solar with potential a slope of angle the of 35Hungarian degrees. region.

SustainabilityFigureFigure 4. 4.Solar 2021 Solar, irradiation13 irradiation, x FOR PEER trendline trendline REVIEW ofof monthly values values for for optimal optimal inclination inclination angle angle in capital in capital cities cities of Visegrád of Visegr Countriesád Countries 7 of 18 (2005–2016)(2005–2016) [26 [26].].

Along with irradiation data, the performance of grid‐connected PV systems also plays an important role in analyzing solar potential. The European Commission PV–GIS tool gives a monthly energy output for a fixed angle PV system. Figure 5 gives an estimate of energy output throughout the year in KWh. We analyzed the four nations based on their respective capital cities. It can be seen that Bratislava (Slovakia) and Budapest (Hun‐ gary) give an output of more than 125 KWh during the peak summer. Meanwhile, War‐ saw (Poland) and Prague (Czech Republic) managed to reach an output of 125 KWh dur‐ ing summer. The analysis is based on a database of PVGIS–SARAH with a slope angle of 35 degrees.

FigureFigure 5. Performance 5. Performance of grid-connectedof grid‐connected PV PV with with energy energy outputoutput fromfrom a fixed ﬁxed angle angle PV PV system system in in the the capital capital cities cities of of VisegradVisegrad Countries Countries (based (based on Europeanon European Commission Commission PV PV GIS GIS analysis analysis tool tool updated updated in 2019) [26]. [26].

3. Materials and Methods 3.1. Indicators of the Analysis Solar energy, and especially solar power, has emerged as a major contributor in the context of renewable energy solutions. The contributions of renewable energy in the context of the sustainable growth plan of any country is significant. The role of government administration is crucial in the implementation of such policies, which favor sustainability. In the future, the concern is also on the creation of better bridges in the demand and supply chain of renewable energy sources. The last decade has seen a notable increase in RES, and solar energy research has been a prime investigation subject. The harnessing of solar energy potential has been discussed widely. Photovoltaics (PV) and photovoltaic-thermal (PV/T) modules are under investigation throughout the world. A study suggests PV/T collectors have marked better efficiency in overall efficiency considerations. This is because PV/T not only rises the temperature difference, but the water temperature enhances overall efficiency. This is also a reason for higher demand of combined PV–heat pump hybrid systems [27]. Solar energy, though being one of the most sought out renewable technologies, faces many challenges. Apart from the technical and economic analysis of solar sources, a significant consideration is their availability. The solar radiation available on the ground, which could be utilized for electricity generation or thermal applications, is the key factor [28]. The regional potential thus becomes important in harnessing solar RES for a long-term plan. The two important solar setup parameters are irradiance, which is defined as the amount of solar energy falling on a given unit area per unit time (W/m2), and irradiation, which is described as the area of solar energy falling in a given period (W/m2)[29]. The estimation of these two parameters thus becomes essential in creating solar operating plants for power generation. Implementing solar energy technology in a socioeconomic context is crucial in recent times. In the future, the depletion of fossil fuels is evident. In such times, national energy independence is a priority for policymakers. SET as a solution supports energy security and creates a nexus of the energy market in the economy of the nation [30]. Monthly clearness indices and annual average sunshine hours can be used as parameters in potential site analysis. A study of potential sites in Iran was done to develop geographic information system (GIS) maps based on horizontal radiation [31]. The compilation of radiation data and geospatial restrictions can help in optimal site selections for solar power plants and other solar utilities. According to Eurostat data, energy sharing from renewable sources in the European Union rose from 10.23% in 2005 to 19.27% in 2019. For Hungary, the percentage share of renewable sources made progress from 6.93% to 12.61% in 2019 [32]. Thus, in comparison to the EU, Hungary’s needs lag behind the RES share in energy sources. SET can play a vital role in the national energy independence of the country. There are several factors which influence the SET implementation possibility, namely geographical, technical, and economic factors. In this paper, the aim is to review the recent developments in Hungary for solar power production and SET implementation prospects. The investigations involved trend assessment using the available literature and data. There are around 20 cities in Hungary, which have a populous density as consumers of power.

3.2. Data and Analysis Curve fitting and regression analysis have long been used for data analysis. T-curve fitting works on the basic methodology of converting the available data in the form of the equation y = f(x), where x is the independent variable, y is the dependent variable, and f is the function. To understand the curve fitting’s accuracy, R2 values were generated by the tools available in Excel [33]. In the last decade, numerous solar parks with small- and high-power capacity were installed throughout the country. According to the Hungarian Solar Association, the growth parameters have doubled in the last few years. The potential to unfold the capacity is much higher in comparison with its neighboring countries. Germany today has the Sustainability 2021, 13, 5462 8 of 16

highest number of solar panels in the region, though Hungary’s solar radiation is 50% higher than that of Germany through the year [34]. Table2 and Figure4 represent the present list of operating solar parks with more than 10 MWp capacity. Table3 and Figure5 show the list of parks with less than 10 MWp capacity. MWp or Megawatt-peak is used to measure the rated power output of a solar plant. The plant’s MW value could be lesser than the MWp value due to DC (direct current) load ratio. In general, for solar plants, the MWp values are also used to analyze the plant’s cost upfront [35]. Apart from the previously mentioned categories, several more plants are under construction. Various solar-producing groups propose solar parks in Füzesgyarmat, Tiszaújvaros, Bátonyterenye, etc.

Table 2. List of Solar parks with capacity >10 MWp in various parts of Hungary.

Rank Solar Park Capacity (MW) Location Established in Year 1 Kaba Solar Park (UC) 43 Kaba 2020 2 Kapuvár Solar Park 25 Kapuvár 2020 3 Paks Solar Park 20.6 Paks 2019 4 Mátra Solar Power Plant 20 Bükkábrány 2019 5 Fels˝ozsolcaSolar Park 20 Fels˝ozsolca 2018 6 Duna Solar Park 17.6 Százhalombatta 2018 7 Szügy Solar Park 16.5 Szügy 2019 8 Mátra Solar Power Plant 16 Visonta 2015 9 Tiszasz˝ol˝osSolar Park 11.6 Tiszasz˝ol˝os 2019 10 Pécs Solar Park 10 Pécs 2016

Table 3. List of Solar parks with capacity <10 MWp in various parts of Hungary.

Rank Location Capacity M.W. Established in Year 1 Csepreg 5.5 2018 2 Vep 4.5 2018 3 Monor 4 2018 4 Sajóbábony 0.5 2016 5 Szombathely 0.385 2015 6 Bojt 0.49 2014

Tables2 and3 are the visualizations of ranking and share, based on capacity, in various parts of Hungary. The compilation of all this recent information on solar park developments could be used in further studies and research. The potential regional analysis could help with data visualization if such graphs and data on recent developments are available. The opening of more solar parks brings with them a lot of potential in economic growth. The rise of parks is coupled with competitiveness in the energy market. In addition, this newly formed market is likely to look for data analysis and relative forecast depending on the weather.

4. Results and Discussions 4.1. Regression Analysis Observations based on growth data through regression analysis on Excel are depicted in Tables2 and3. The two lines of different colors project the growth of solar parks with more than 10 MWp and less than 10 MWp capacities. This observation validates the growth potential status of solar parks in the Hungarian region. Observations in solar power production growth with the newly developed solar parks around Hungary are discussed in the study. From 2008 to 2020, regression analysis of the data is depicted in Figure6. The values of the coefﬁcient of determination predict Sustainability 2021, 13, 5462 9 of 16

the growth potential of plants as linear. These values confirm the substantial increase of solar parks in Hungary during the specified time frame with lower boundary values. For further investigation, the power plants’ clusters were segregated into two clubs with less than 10 MWp capacity and more than 10 MWp capacity. Figure7 depicts the regression analysis of two clusters separately. The study confirms the growth of larger solar parks

Sustainability 2021, 13with, x FOR 10 PEER MWp REVIEW capacity if solar park development is maintained through the years to10 come.of 18 The analysis provides a brief idea of the status of development in the region’s solar sector. The data analysis could not be the only parameter for a holistic viewpoint on the country’s total solar energy development. Hence, geographical gaps in the situation were analyzed Sustainability 2021, 13, x FOR PEER REVIEW 10 of 18 based on the regional developmentRES Trendline ofin parksHungary,2020 in various areas of the nation. 80.0

RES Trendline in Hungary,2020 70.0 80.0 biomass

60.0 70.0 biogas biomass wind 50.0 60.0 biogas hydro R² = 0.7785 wind 50.0 40.0 hydrosolar R² = 0.7785 40.0 solar Poly. (biomass) 30.0 Poly. (biomass)Poly. (biogas) 30.0 Poly. (biogas) Poly. (wind) 20.0 Poly. (wind) 20.0 R² = 0.5077 Poly. (hydro) R² = 0.5077 Poly. (hydro) R²R² = =0.8495 0.8495 Poly. (solar) 10.0 10.0 Poly. (solar)

R² =R² 0.9902 = 0.9902 R²R² = =0.6367 0.6367 0.0 0.0 2009 20102009 2011 2010 2012 2011 2012 2013 2013 2014 2014 2015 2015 2016 2016 2017 2017 2018 2018 2019 2019

Figure 6. Critical regression line analysis of various RES trends in Hungary (2010–2018). FigureFigure 6. Critical 6. Critical regression regression line line analysis analysis of various of various RES REStrends trends in Hungary in Hungary (2010–2018). (2010–2018).

2020 2019 2020 2019 2019 2018 y = 2.4366ln(x) + 2011.2 2019 R² = 0.3594 2018 2018 y = 2.4366ln(x) + 2011.2 2017 R² = 0.3594 (Years) (Years) 2018 2017 in in 2017 2016 (Years) (Years) Time Time

2016 2017 > 10 MW in y = 1.2814ln(x) + 2016 in

R² = 0.8643 20152016 2015 Time 2016 Time < 10 MW y = 1.2814ln(x) + 2016 > 10 MW 2014R² = 0.8643 2014 2015 2015 0 1020304050Size < 10 MW Figure 7. Critical regression line analysis of solar park future growth trends in Hungary (2010–2020). 2014 2014 4.2. Regional Map Analysis 0 1020304050Size Regional map analysis helps with the visualization of the current scenario of irradi‐ ance falling on the region. Global irradiance data can be a powerful tool in the accurate FigureFigure 7. Critical 7. Critical regression regressionprediction line analysis line of the analysis ofsolar solar potential park of solar future of a parkregion growth future[36]. trends The growth global in Hungary horizontal trends (2010–2020). inirradiation Hungary data (2010–2020). can give a brief idea of the yearly irradiation observed in the region. Meanwhile, the optimally 4.2. Regional4.2. Map Regional Analysisinclined Map irradiation Analysis data is based on the tilt angle for maximum output from the PV. The Regionaltilt angle map is generally analysis the helps latitude with of the the region visualization of focus. However, of the currentthough the scenario irradiance of irradi‐ Regional mapdata analysis can help helpsin predictions, with it the is also visualization recommended to of perform the current onsite calculations scenario [37]. of irradiance falling on the region. Global irradiance data can be a powerful tool in the accurate ance falling on theThe region. regional Global maps were irradiance generated to understand data can the be solar a powerful irradiance falling tool in inthe theregion accurate prediction of the solar potential of a region [36]. The global horizontal irradiation data can prediction of the solar potential of a region [36]. The global horizontal irradiation data can give a brief idea of the yearly irradiation observed in the region. Meanwhile, the optimally give a brief ideainclined of theirradiation yearly data irradiation is based observedon the tilt angle in the for region. maximum Meanwhile, output from the the optimally PV. The inclined irradiationtilt angle data is generally is based the on latitude the tilt of angle the region for maximum of focus. However, output though from the the PV. irradiance The tilt angle is generallydata can the help latitude in predictions, of the region it is also of recommended focus. However, to perform though onsite the calculations irradiance [37]. data can help in predictions,The regional maps it is were also generated recommended to understand to perform the solar onsite irradiance calculations falling in the [37 region]. The Sustainability 2021, 13, 5462 10 of 16

Sustainability 2021, 13, x FOR PEER REVIEW 11 of 18 regional maps were generated to understand the solar irradiance falling in the region of Visegrád Countries. Figure8 represents the global irradiation and solar electricity potential for horizontally mounted PV modules. It was observed that Hungary receives a yearly of Visegrád Countries. Figure 8 represents the global irradiation2 and solar electricity po‐ sumtential of irradiation for horizontally in the mounted range of PV 1200–1400 modules. It KWh/m was observed, which that isHungary the highest receives range a in the region.yearly The sum yearly of irradiation sum of in electricity the range of generation 1200–1400 KWh/m potential2, which was is also the thehighest highest, range with the 2 rangein ofthe 900–1050 region. The KWh/m yearly sum. Similarly, of electricity Figure generation9 depicts potential the globalwas also irradiation the highest, forwith optimally inclinedthe range PV modules, of 900–1050 with KWh/m the2. highestSimilarly, observations Figure 9 depicts from the global Hungary. irradiation Moreover, for opti the‐ yearly summally of irradiation inclined PV was modules, recorded with as the in highest the range observations of 1300–1600 from Hungary. KWh/m Moreover,2, and the the yearly sum 2 of electricityyearly sum generation of irradiation potential was recorded was 975–1200 as in the range KWh/m of 1300–16002 [38]. KWh/m , and the yearly sum of electricity generation potential was 975–1200 KWh/m2 [38].

Figure 8. FigureHorizontally 8. Horizontally mounted mounted PV potential PV potential in the in the Visegr Visegrádád Countries Countries based based on global global irradiation irradiation and and electricity electricity gener generation‐ Sustainabilityation data 2021 [38]., 13, x FOR PEER REVIEW 12 of 18 data [38].

Figure 9. Optimally inclined PV Potential in the Visegrád Countries based on global irradiation and electricity generation Figure 9. Optimally inclined PV Potential in the Visegrád Countries based on global irradiation and electricity generation data [38]. data [38]. To better understand the PV potential, another map analysis was performed to un‐ derstand the PV output using SOLARGIS maps available online. Figure 10 represents a long time PV potential of the regions during the period of 1994–2018. The southern regions of Slovakia represent higher values, with the overall country yearly values of 876–1241 KWh/KWp. Hungary, on the other hand, had the highest values 1095–1314 KWh/KWp. Poland and Czech Republic had a similar range of 949–1168 KWh/KWp, which is compar‐ atively lower than Slovakia or Hungary. Sustainability 2021, 13, 5462 11 of 16

To better understand the PV potential, another map analysis was performed to understand the PV output using SOLARGIS maps available online. Figure 10 represents a long time PV potential of the regions during the period of 1994–2018. The southern regions of Slo- vakia represent higher values, with the overall country yearly values of 876–1241 KWh/KWp. Hungary, on the other hand, had the highest values 1095–1314 KWh/KWp. Poland and Sustainability 2021, 13, x FOR PEERCzech REVIEW Republic had a similar range of 949–1168 KWh/KWp, which is comparatively13 of lower18

than Slovakia or Hungary.

FigureFigure 10. 10.PV PV potential potential inin the Visegrád Visegrád Countries Countries [39]. [39].

FromFrom the the aboveabove analyses analyses of of regional regional maps, maps, it could it could be understood be understood that Hungary that Hungary has hasthe the highest highest irradiation irradiation falling falling on the on region. the region. The PV The output PV output potential potential of the last of thetwo last dec‐ two decadesades also also confirms conﬁrms the thehighest highest yield yield for Hungary. for Hungary. The interesting The interesting observation observation from from FiguresFigures8– 8,10 9,is and that 10 the is southern that the southern region of region Hungary of Hungary has highest has potentialhighest potential of the combined of the Visegrcombinedád region. Visegrád The region. area marked The area in themarked dotted in linesthe dotted in all ﬁgureslines in couldall figures be easily could seen be as havingeasily theseen highest as having values the highest based on values color based combinations. on color combinations. To further investigate To further the investi current‐ scenario,gate the thecurrent regional scenario, map the analysis regional of map present analysis solar of parks present was solar carried parks out was to carried observe out solar parkto observe clusters solar in various park clusters Hungarian in various regions. Hungarian As shown regions. in Figure As shown6, the presence in Figure of 6, a the solar presence of a solar power plant was distinguished with a blue or red color on the map, power plant was distinguished with a blue or red color on the map, based on the power based on the power capacity. The image reveals the highest presence of parks were ob‐ capacity. The image reveals the highest presence of parks were observed in the northern served in the northern and eastern parts of Hungary. The northeast region dominates the and eastern parts of Hungary. The northeast region dominates the more extensive capacity more extensive capacity solar parks with more than 10 MWp capacity. The southern re‐ solar parks with more than 10 MWp capacity. The southern regions with counties, namely gions with counties, namely Baranya, Bács‐Kiskun, Bekes, Szeged, and Tolna, have a rel‐ Baranya,atively nominal Bács-Kiskun, presence Bekes, of solar Szeged, parks andfor power Tolna, generation. have a relatively To further nominal analyze presence the po‐ of solartential parks regions for power for better generation. solar harnessing To further facilities, analyze a thetemperature potential graph regions analysis for better study solar harnessingwas performed facilities, with a the temperature recently available graph analysis weather study forecasts was of performed the year 2020. with Figure the recently 11 availableshows solar weather park forecastspresence in of various the year regions 2020. Figure of Hungary 11 shows based solar on power park presence capacity. inIn variousthat regionspicture of is Hungary also highlighted based onarea power with higher capacity. potential In that and picture with islesser also solar highlighted parks. area with higher potential and with lesser solar parks. Sustainability 2021, 13, 5462 Sustainability 2021, 13, x FOR PEER REVIEW 14 of 1812 of 16

Figure 11. SolarFigure park 11. Solar presence park presence in various in various regions regions of of Hungary Hungary based basedon power on capacity. power capacity.

4.3. Performance Assessment4.3. Performance of Assessment a Grid-Connected of a Grid‐Connected PV System PV System The climatic conditions,The climatic conditions, other than other irradiation, than irradiation, can can sometimes be of be inference of inference in un‐ in derstanding a region’s solar potential. The overall climatic changes can have severe effects understanding aon region’s the regional solar potential potential. [40]. Similar The to overallthe country climatic‐based assessment changes of grid can‐connected have severe effects on the regionalPV systems potential output, the [40 regional]. Similar cities of toHungary the country-based were analyzed. The graphs assessment of monthly of grid- connected PV systemsenergy output,output in KWh the regionalare shown in cities Figures of 12 Hungary and 13. Figure were 12 shows analyzed. the graphs The for graphs cities in the western region, and Figure 13 shows cities in the eastern region of Hungary. of monthly energyThe output analysis inis performed KWh are for showna crystalline in silicon Figures‐based 12 PV and system. 13. The Figure slope angle12 shows con‐ the graphs for cities insidered the western is 35 degrees region, and the azimuth and Figure angle is 13 0 degrees. shows The cities cities ininvestigated the eastern for the region PV of Hungary. The analysisoutput are is mentioned performed below: for a crystalline silicon-based PV system. The slope  Budapest; angle considered is 35Debrecen; degrees and the azimuth angle is 0 degrees. The cities investigated for the PV output are Gyor; mentioned below: •  Kecskemét; Budapest;  Nyíregyháza; • Debrecen;  Pecs; • Gyor;  Siófok;  • Kecskemét; Kekesteto. • Nyíregyháza; • Pecs; Sustainability 2021, 13, x FOR PEER REVIEW 15 of 18 • Siófok; • Kekesteto.

Figure 12. FigurePerformance 12. Performance of grid-connected of grid‐connected PV in PV the in capitalthe capital city city and and in in West West Hungary Hungary (based on on European European Commission Commission PV GIS analysisPV tool GIS analysis updated tool in updated 2019). in 2019).

Figure 13. Performance of grid‐connected PV in the capital city and in East Hungary (based on European Commission PV GIS analysis tool updated in 2019).

The results of the graph analysis predict similar results to the PV output. The yearly PV production range is between 1100 and 1250 KWh. The yearly plane radiation value is Sustainability 2021, 13, x FOR PEER REVIEW 15 of 18

Sustainability 2021, 13, 5462 13 of 16 Figure 12. Performance of grid‐connected PV in the capital city and in West Hungary (based on European Commission PV GIS analysis tool updated in 2019).

Figure 13. Performance of grid-connected PV in the capital city and in East Hungary (based on European Commission PV Figure 13. Performance of grid‐connected PV in the capital city and in East Hungary (based on European Commission PV GIS analysisGIS analysis tool tool updated updated in 2019). in 2019).

TheThe results results of of the the graph graph analysis analysis predictpredict similar results results to to the the PV PV output. output. The The yearly yearly PVPV production production range range is is between between 1100 and and 1250 1250 KWh. KWh. The The yearly yearly plane plane radiation radiation value value is is in the range of 1400–1600 KWh/m2. The eastern city Kecskemét observes the highest yearly irradiation of 1543 KWh/m2. However, the overall variation is not very high, which supports the fact that eastern and southern portions of the Hungarian region have untapped potential for future solar plants.

5. Conclusions Each country has its own available resources and own assessments on which the state authorities frame national policies. The European Commission’s NECP reports give a brief insight on the major plans of the V4 nations about increasing the renewable energy consumption share by 2030. The Czech Republic report projects a 68% increase in the heating and cooling sector, but only 17% for electricity generation using renewable energy. This approach could contradict the EU projection of 32% and become a barrier to energy entrepreneurs. Poland is working significantly on the prospects of decarbonization. Wind energy could be a driving force in the growth of renewable usage in the energy sector. The fast development of photovoltaics landed the country the fifth position in the European continent. Slovakia has lower targets to achieve by 2030 compared to other counterparts of the Visegrád Group. The countrywide plan to shift towards renewables is commendable, especially on wind and solar productions. The self-consumer producers and small photovoltaic plants can breed nationwide with minor modifications and subsidies from state authorities. The geospatial study reveals potential in the southern ranges of Slovakia for solar potential power plants in the future. Among the four countries of the V4, Hungary reflects the highest potential in terms of irradiation and temperature profiling. The southern region of Hungary had specifically shown better results, so it may be considered an untapped potential site for future solar parks. In Hungary, there has been a slight reduction in the share of renewable sources from the year 2013. A significant downfall in the percentage of biomass-based energy share has been observed and, in contrast, a soaring high in solar-based power plants. In the study, data regression analysis was performed on available statistics to verify the data’s Sustainability 2021, 13, 5462 14 of 16

fitting curves. The results are promising regarding solar power production in the future. In the regional map study, exciting insights were revealed in the map analysis, which was carried out to understand the distribution of power plants set up around the nation. It could be observed that there is a cluster of solar parks with more enormous capacities in the northeastern region. Very few power plants could be seen in the lower southern parts of the country. The study recommends utilization of the untapped potential of the southern and eastern parts of the country. The yearly irradiation values reflected that eastern cities of Hungary also have similar PV outputs as western and northern cities. These profiles were produced from the PV–GIS tool of the European Commission, which was last updated in the year 2019. A similar analysis could be done for the sky clarity index for Hungary’s southern region and eastern cities. This data analysis could be helpful for government agencies and industrial observers for potential unmasking opportunities.

Author Contributions: Data curation, G.S., Z.C.,ˇ and L.B.; formal analysis, B.K., M.K., Z.P., and Z.S.; funding acquisition, Z.C.ˇ and M.K.; investigation, B.K., L.B., and Z.S.; methodology, B.K., Z.C.,ˇ and Z.S.; project administration, G.S. and M.K.; resources, G.S.; validation, Z.P.; visualization, Z.P.; writing—original draft, B.K. and Z.C.ˇ All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by Slovak Research and Development Agency: APVV-19-0576 and Ministry of Education, Science, Research and Sport of the Slovak Republic and the Slovak Academy of Sciences: VEGA 1/0757/21. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not Applicable. Data Availability Statement: The data of the Hungarian Central Statistical Office is downloaded from the free-access STADAT system, available at: https://www.ksh.hu/engstadat?lang=en (accessed on 1 May 2021). Conflicts of Interest: The authors declare no conflict of interest.

Abbreviations EU European union MWp Megawatt peak NECP National Energy and climate plans RES Renewable Energy sources GDP Gross Development product PV Photovoltaic TWh Terawatt-hour MW Megawatt GW Gigawatt EUR Euro RES Renewable energy sources SET Solar energy technology PV/T Photovoltaic thermal GIS Geographic information system

References 1. Latawski, P. On Converging Paths? The Visegrad Group and the Atlantic Alliance. Paradigms 1993, 7, 78–93. [CrossRef] 2. Khanam, T.; Rahman, A.; Mola-Yudego, B.; Pelkonen, P.; Perez, Y.; Pykäläinen, J. Achievable or unbelievable? Expert perceptions of the European Union targets for emissions, renewables, and efﬁciency. Energy Res. Soc. Sci. 2017, 34, 144–153. [CrossRef] 3. European Commission. 2030 Climate & Energy Framework. Available online: https://ec.europa.eu/clima/policies/strategies/ 2030_en (accessed on 1 May 2021). 4. Nosko, A.; Orban, A.; Paczynski, W.; Cernoch, F.; Jaros, J. Energy Security. Policy Paper, Visegrad Security Cooperation Initiative. 2010. Available online: https://www.visegradgroup.eu/download.php?docID=139html (accessed on 13 May 2021). 5. European Commission. NECP HUNGARY. 2018. Available online: https://ec.europa.eu/energy/sites/ener/ﬁles/documents/ ec_courtesy_translation_hu_necp.pdf (accessed on 2 May 2021). Sustainability 2021, 13, 5462 15 of 16

6. European Commission. NECP of European Countries. Available online: https://ec.europa.eu/energy/topics/energy-strategy/ national-energy-climate-plans_en (accessed on 1 May 2021). 7. Eurostat DATA. 2020. Available online: https://ec.europa.eu/eurostat/cache/infographs/energy/bloc-4c.html (accessed on 1 May 2021). 8. Dyduch, J.; Skorek, A. Go South! Southern dimension of the V4 states’ energy policy strategies—An assessment of viability and prospects. Energy Policy 2020, 140, 111372. [CrossRef] 9. Renewables Networking Platform. Renewables in National Energy and Climate Plans of Visegrad Countries Challenging the Low Ambition. Available online: https://www.komoraoze.cz/download/pdf/169.pdf (accessed on 2 May 2021). 10. Papiez, M. CO 2 emissions, energy consumption and economic growth in the Visegrad Group countries: A panel data analysis. Math. Methods Econ. 2013, 2013, 696–701. 11. Wawrzyniak, D. CO2 emissions in the Visegrad Group countries and the European Union climate policy. Comp. Econ. Res. 2020, 23, 73–92. [CrossRef] 12. Zapletalová, V.; Komínková, M. Who is fighting against the EU’s energy and climate policy in the European Parliament? The contribution of the Visegrad Group. Energy Policy 2020, 139, 111326. [CrossRef] 13. Gulkowski, S.; Zdyb, A. Performance Assessment of Four Different Photovoltaic Technologies in Poland. Energies 2020, 13, 196. 14. IEO. PV MARKET IN POLAND. 2020. Available online: https://ieo.pl/en/pv-report (accessed on 3 May 2021). 15. Ministry of Energy. Extract from the Draft of Energy of Poland until 2040 (EPP2040). Available online: https://www.gov.pl/ attachment/376a6254-2b6d-4406-a3a5-a0435d18be0f#:~{}:text=The%20Energy%20Policy%20of%20Poland,delivered%20in%20 the%20medium%2Dterm (accessed on 3 May 2021). 16. Valentova, M.; Knápek, J.; Mikeska, M.; Vašíˇcek,J. Investment Needs for 2030 Energy and Climate Targets in Czechia, Buildings and Renewable Energy Supply Sectors Executive Summary. 2020. Available online: https://www.ikem.de/wp-content/uploads/ 2020/03/Valentova-et-al.-2020.-Investment-need-analysis-in-Czechia_Executive-Summary_in-English.pdf (accessed on 2 May 2021). 17. Macháˇc,J.; Zaˇnková, L. Renewables—To build or not? Czech approach to impact assessment of renewable energy sources with an emphasis on municipality perspective. Land 2020, 9, 497. [CrossRef] 18. Ministry of Trade and Industry of the Czech Republic. National Energy and Climate Plan of the Czech Republic. Eur. Comm. 2019, 437. Available online: https://ec.europa.eu/energy/sites/ener/files/documents/cs_final_necp_main_en.pdf (accessed on 1 May 2021). 19. Hofierka, J.; Cebecauer, T. Spatially distributed assessment of solar resources for energy applications in Slovakia. Acta Fac. Stud. Humanit. Naturae Univ. Presoviensis Prírodné Vedy Folia Geogr. 2008, 12, 97–114. 20. European Comission. National Energy and Climate Plan of Hungary. 2018. Available online: https://ec.europa.eu/energy/sites/ default/files/documents/ec_courtesy_translation_hu_necp.pdf (accessed on 1 May 2021). 21. Barwicki, J.; Kuboń,M.; Marczuk, A. New Developments of Solar Energy Utilization in the Aspect of EU Directives. Agric. Eng. 2017, 21, 15–24. [CrossRef] 22. Talamon, A. Global renewable energy trends and Hungary. Int. Rev. Appl. Sci. Eng. 2012, 3, 81–85. [CrossRef] 23. Pintér, G.; Zsiborács, H.; Baranyai, N.H.; Vincze, A.; Birkner, Z. The economic and geographical aspects of the status of small-scale photovoltaic systems in hungary—A case study. Energies 2020, 13, 3489. [CrossRef] 24. Vokas, G.A.; Zoridis, G.C.; Lagogiannis, K.V. Single and Dual Axis PV Energy Production over Greece: Comparison between Measured and Predicted Data. Energy Procedia 1490, 2015, 74–1498. [CrossRef] 25. Park, S.; Kim, Y.; Ferrier, N.J.; Collis, S.M.; Sankaran, R.; Beckman, P.H. Prediction of Solar Irradiance and Photovoltaic Solar Energy Product Based on Cloud Coverage Estimation Using Machine Learning Methods. Atmosphere 2021, 12, 395. [CrossRef] 26. European Commission. PHOTOVOLTAIC GEOGRAPHICAL INFORMATION SYSTEM. Available online: https://re.jrc.ec. europa.eu/pvg_tools/en/ (accessed on 2 May 2021). 27. Kumar, R.; Rosen, M.A. A critical review of photovoltaic-thermal solar collectors for air heating. Appl. Energy 2011, 88, 3603–3614. [CrossRef] 28. Šúri, M.; Huld, T.A.; Dunlop, E.D.; Ossenbrink, H.A. Potential of solar electricity generation in the European Union member states and candidate countries. Sol. Energy 1295, 2007, 81–1305. [CrossRef] 29. Sˆúri, M.; Hofierka, J. A new GIS-based solar radiation model and its application to photovoltaic assessments. Trans. GIS 2004, 8, 175–190. [CrossRef] 30. Tsoutsos, T.; Frantzeskaki, N.; Gekas, V. Environmental impacts from the solar energy technologies. Energy Policy 2005, 33, 289–296. [CrossRef] 31. Alamdari, P.; Nematollahi, O.; Alemrajabi, A.A. Solar energy potentials in Iran: A review. Renew. Sustain. Energy Rev. 2013, 21, 778–788. [CrossRef] 32. Eurostat DATA. Eurostat. 2019. Available online: https://ec.europa.eu/eurostat/databrowser/view/NRG_IND_REN__custom_ 29122/bookmark/line?lang=en&bookmarkId=15508b69-e68c-4d60-a6cf-f2e0d96d67d7 (accessed on 2 May 2021). 33. Brown, A.M. A step-by-step guide to non-linear regression analysis of experimental data using a Microsoft Excel spreadsheet. Comput. Methods Programs Biomed. 2001, 65, 191–200. [CrossRef] 34. Magyar Epitok. Available online: https://magyarepitok.hu/rohamtempoban-bovul-hazai-napenergia-felhasznalas (accessed on 2 May 2021). Sustainability 2021, 13, 5462 16 of 16

35. SOLAR BAY. Understanding How Solar Power Is Measured: MWp, MWac and MWh. Available online: https://solarbay.com.au/ portfolio-item/understanding-how-solar-power-is-measured/ (accessed on 1 May 2021). 36. Kam, O.M.; Noël, S.; Ramenah, H.; Kasser, P.; Tanougast, C. Comparative Weibull distribution methods for reliable global solar irradiance assessment in France areas. Renew. Energy 2021, 165, 194–210. [CrossRef] 37. Yu, C.; Khoo, Y.S.; Chai, J.; Han, S.; Yao, J. Optimal orientation and tilt angle for maximizing in-plane solar irradiation for PV applications in Japan. Sustainability 2019, 11, 2016. [CrossRef] 38. European Commission. Country and Regional Maps. Available online: https://re.jrc.ec.europa.eu/pvg_download/map_index. html (accessed on 2 May 2021). 39. Solargis. Solar Resource Maps and GIS Data for 200+ Countries. Available online: https://solargis.com/maps-and-gis-data/ download (accessed on 2 May 2021). 40. Power, H.C.; Mills, D.M. Solar radiation climate change over southern Africa and an assessment of the radiative impact of volcanic eruptions. Int. J. Climatol. 2005, 25, 295–318. [CrossRef]