sustainability Article Correlation Analysis of the Spread of Household-Sized Photovoltaic Power Plants and Various District Indicators: A Case Study Nóra Heged ˝usné Baranyai 1,*, Henrik Zsiborács 1, András Vincze 1,Nóra Rodek 1, Martina Makai 2 and Gábor Pintér 1 1 Renewable Energy Research Group, Soós Ern˝oResearch and Development Center, Faculty of Engineering, Nagykanizsa Campus, University of Pannonia, 8800 Nagykanizsa, Hungary; [email protected] (H.Z.); [email protected] (A.V.); [email protected] (N.R.); [email protected] (G.P.) 2 Faculty of Business and Economics, Nagykanizsa Campus, University of Pannonia, 8800 Nagykanizsa, Hungary; [email protected] * Correspondence: [email protected] Abstract: As efforts are made worldwide to meet the growing energy needs of the population in a more sustainable way, harnessing weather-dependent renewable energy sources is becoming more and more important. One of the available technologies is photovoltaic energy production. In the last decade, there has been a growing need among households, institutions, and businesses to reduce the use of fossil-fuel-based electricity from the public grid. In order to meet their electricity demand in Hungary, investors prefer using household-sized photovoltaic power plant (HMKE) systems. The novelty of this study is that it examines the number and total power of photovoltaic HMKEs at the district level in the service areas of different electricity distributors, taking into account the social, economic, infrastructural, and welfare dimensions of these districts as well. The study seeks Citation: Heged˝usnéBaranyai, N.; to uncover whether there is a correlation between the number and total power of these types of Zsiborács, H.; Vincze, A.; Rodek, N.; power plants and the indicators of the districts, and if so, how strong these relationships are. The Makai, M.; Pintér, G. Correlation examination of the relationships also involved, in addition to correlations by pairs, the relationships of Analysis of the Spread of the ranking of the districts according to the complex indicators created from the district indicators and Household-Sized Photovoltaic Power the ranking of the districts based on the number and power of photovoltaic HMKEs per 1000 members Plants and Various District Indicators: of the population. By exploring correlations, the paper seeks to establish a regression model for the A Case Study. Sustainability 2021, 13, number of photovoltaic HMKEs and the territorial (district) indicators. 482. https://doi.org/10.3390/ su13020482 Keywords: economic and infrastructural indicators of the districts; Hungary; photovoltaic system; small-scale power plant; solar energy Received: 30 November 2020 Accepted: 30 December 2020 Published: 6 January 2021 Publisher’s Note: MDPI stays neu- 1. Introduction tral with regard to jurisdictional clai- 1.1. The Global Aspects of Photovoltaic Technology ms in published maps and institutio- In the last decade, climate change has posed a significant challenge to countries nal affiliations. around the world. One solution to the problems that arise is the use of renewable energy sources: By 2017, more than 150 countries had committed themselves to using alternative energy sources. This will automatically lead to the gradual expansion of the utilization of renewable energy sources worldwide. It is estimated that renewable energy sources Copyright: © 2021 by the authors. Li- censee MDPI, Basel, Switzerland. (RESs) will provide 60% of total energy consumption by 2050 [1] and more than 60% of the This article is an open access article newly installed global electricity capacity by 2040 [2,3]. All this shows that while more and distributed under the terms and con- more countries are facing the negative, harmful effects of climate change, its mitigation has ditions of the Creative Commons At- become a global goal. Today, the question is no longer whether we need to take action to tribution (CC BY) license (https:// reduce the problem, but what measures have to be taken. At the global level, the goal is ◦ creativecommons.org/licenses/by/ to limit the temperature rise to less than 2 C above pre-industrial temperatures, which ◦ 4.0/). means that humankind must aim at a maximum increase of 1.5 C to attain that [4]. Sustainability 2021, 13, 482. https://doi.org/10.3390/su13020482 https://www.mdpi.com/journal/sustainability Sustainability 2021, 13, x FOR PEER REVIEW 2 of 28 Sustainability 2021, 13, 482 2 of 24 goal is to limit the temperature rise to less than 2 °C above pre-industrial temperatures, which means that humankind must aim at a maximum increase of 1.5 °C to attain that [4]. The above objective can be achieved by developing energy systems aimed at reduc- The above objective can be achieved by developing energy systems aimed at reducing ing the greenhouse effect, in which weather-dependent renewable energy sources (VREs) the greenhouse effect, in which weather-dependent renewable energy sources (VREs) also also play an increasing role. Thanks to the rapidly evolving technology, more and more play an increasing role. Thanks to the rapidly evolving technology, more and more solutions solutions that use solar energy as an alternative energy source with ever-increasing effi- that use solar energy as an alternative energy source with ever-increasing efficiency are ciencybeing developedare being developed [5]. A significant [5]. A significant proportion proportion of the world’s of the world population’s population lives in lives cities, in cities,so it is so an it importantis an important result result that many that many cities cities around around the world the world have have launched launched their their own ownsolar solar energy energy programs programs for for the the purpose purpose of of protecting protecting the the environment environment andand promoting sustainablesustainable devel development.opment. Solar Solar energy energy is isgaining gaining ground, ground, on on the the one one hand, hand, because because it is it essentialis essential for formany many processes processes in nature, in nature, and on and the on other the otherhand, hand, because because it is a clean, it is a abun- clean, dant,abundant, sustainable sustainable,, and—most and—most importantly importantly—universally—universally available available resource resource[6–14]. What [6–14 is]. more,What th ise more, amount the of amount solar energy of solar reaching energy reachingthe surface the of surface our planet of our is planetthousands is thousands of times greaterof times than greater the current than the energy current need energy of the need population of the population [15–17]. Thanks [15–17 ].to Thanks all this,to recently all this,, anrecently, expansion an expansion of solar systems of solar ( systemsphotovoltaic (photovoltaic (PV)) can(PV)) be observed: can be observed: Their total Their capacity total worldwidecapacity worldwide was already was about already 627 aboutGW by 627 the GW end by of the2019, end which of 2019, played which a key played role in a keythe globalrole in efforts the global for sustainability, efforts for sustainability, green growth, green and growth, a higher and share a higher of low share-carbon of low-carbon economy. Overeconomy. the last Over decade, the last the decade, support the schemes support (e.g. schemes, the (e.g.,Feed- thein-Tariff Feed-in-Tariff system), system),on the one on hand,the one and hand, a decline and ain decline initial capital in initial expenditures capital expenditures due to the due boom to thein innovation boom in innovation and tech- nology,and technology, on the other on hand, the other have hand, had a havepositive had impact a positive on the impact spread on of the solar spread systems of solar[18]. Examiningsystems [18 the]. Examining map of the the global map annual of the global PV power annual generatio PV powern potential, generation it can potential, be con- it cludedcan be concludedthat the annual that theamount annual of amountPV energy of PV that energy can be that produced can be producedvaries, on varies, average on, betweenaverage, 700 between and 2400 700 andkWh/kWp 2400 kWh/kWp by geographical by geographical location (Figure location 1) (Figure. In the1 ).case In theof Hun- case gary,of Hungary, values vary values between vary between 1050 and 1050 1250 and kWh/kWp 1250 kWh/kWp (Figure (Figure1) [19]. 1)[19]. FigureFigure 1. 1. TheThe photovoltaic photovoltaic power power potential potential—world—world [19]. [19]. InIn Hungary, Hungary, according according to data data from from the the last last three three years, years, the the total total installed installed PV PV capacity capacity waswas approximately approximately 0.3 0.3 GWp, GWp, 0.7 0.7 GWp, GWp, and and 1.3 1.3 GWp GWp in 2017, in 2017, 2018 2018,, and and at the at end the endof De- of cemberDecember 2019, 2019, respectivel respectively,y, representing representing a growth a growth of of over over 400%, 400%, mainly mainly due due to to legislative legislative amendmentsamendments [20,21] [20,21].. In thethe longlong term,term, the the spread spread of of PV PV systems systems is expectedis expected to increaseto increase sig- significantlynificantly in Hungaryin Hungary as well:as well: The T Hungarianhe Hungarian transmission transmission system system operator operator has preparedhas pre- paredthree differentthree differen scenarios,t scenarios, based onbased which on thewhich PV capacitythe PV capacity is projected is projected to reach to 2.5–6.7 reach GWp 2.5– 6.7in 2030GWp and in 2030 4.3–12 and GWp 4.3– in12 2040GWp [22 in– 204024]. [22–24]. Sustainability 2021, 13, 482 3 of 24 1.2. The Regulatory Environment of Photovoltaic Technology in Hungary—Overview In the last decade, green-energy-related subsidies have become more and more widespread around the world. However, the regulatory environment varies consider- ably from country to country.