Fundamental Barriers to Green Energy Production in Selected EU Countries

Abstract

Most EU countries are trying to develop new sources of energy to meet local power requirements due to energy shortages. The most popular renewable energy developments include biogas stations, wind turbines, water turbines, and solar systems. This article focuses on reviewing studies concerning the utilization of solar energy systems, especially photovoltaic (PV) ones, in European countries such as Germany, Italy, Spain, and Poland, which are leaders in PV installations. The review identifies factors influencing the development of PV investments and the energy situation in these countries. Economic, market, environmental, and infrastructural barriers, as well as driving factors, are presented. In all countries, the majority of installations were in the prosumer sector, with only a very small percentage in the state-owned sector. The methodology of the study covered the mentioned barriers, which were identified using scientific databases such as Scopus, Web of Science, and branch organizations websites like the International Renewable Energy Agency (IRENA). The novelty of the article lies in its examination of special barriers concerning green energy production in chosen EU countries. Normally, when reading articles on PV installations, as presented in the References section, one primarily observes a description of the construction process without deep involvement in the presented ideas.

1. Introduction

The growing demand for energy worldwide, coupled with limited fossil fuel resources and increasing prices of raw materials such as coal, oil, and natural gas, is driving the development of methods, production, and application of renewable energy [1].

In recent years, information systems, data centers, cryptocurrencies, and artificial intelligence have significantly increased energy consumption [2].

Solar energy (SE) is among the most important renewable energy sources (RES), alongside wind, water, and biogas derived from bio-wastes [3]. The increased generation of electricity from wind and solar power contributes to reductions in emissions across sectors such as industry, agriculture (both plant and animal production) [4], and transportation, thereby reducing dependence on fossil fuels [5].

In recent years, there has been an increase in investments in RES [6], leading to reductions in greenhouse gas (GHG) emissions. According to Ellaban et al. [7], the CO₂ equivalent emissions over the entire life cycle of photovoltaic (PV) systems amounted to a maximum of 0.148 per 1 kWh. Despite disadvantages such as dependence on weather conditions, lack of continuity, and unpredictability of RES [6], these are offset by their advantages.

Traditional energy prices are notably high and are expected to continue rising in the future. As a new member country of the European Union, Poland has undertaken new strategic commitments in energy planning. Even leading SE producers in Europe like Germany and France are compelled to adapt their national energy production strategies due to the geopolitical situation between the EU and Russia.

In 2023, most EU countries, including Germany and Poland, experienced a decline in electricity demand compared to the previous year [2]. The economic downturn and lower consumption in the industrial sector contributed to this decline in electricity demand across the EU. However, these factors did not have a major negative impact on investment in new PV installations.

Many aspects in the fields of economics, markets, policies, governance, infrastructure, and technologies can potentially influence PV investment decisions made by actors such as individual households, companies, or administrations at different levels.

Currently, there are no review articles in the literature simultaneously addressing all potential factors crucial to increasing investment in the PV sector. Therefore, this article aims to review available technologies and identify factors influencing the development of the PV sector in selected European Union countries with leading installed capacities, namely, Germany, Italy, and Spain, in comparison to the situation in Poland.

Figure 1a–e show the total installed PV power during the past 13 years in chosen EU countries. For further analysis, only the four leading countries were chosen: those with the highest (Italy and Spain) and lowest (Germany and Poland) values of solar irradiation. However, while France has average values similar to Poland regarding the cumulative power installed.

As a result of the analysis of the literature in question, a number of different reasons were identified as obstacles to the wider development of investments in PV installations. These were mainly scientific databases. Therefore, the research problem was formulated as a question: Is it possible to rank the groups of existing barriers to the development of PV installations, and in which of the EU countries does a particular group of factors predominate?

2. Materials and Methods

Articles, mostly of the review type, were searched using the most popular and extensive scientific knowledge database, Scopus, along with other sources such as Google Scholar, statistical databases, and web pages, including well-known publishers. Keywords used during the search for appropriate literature were as follows: solar systems, PV systems, PV panels, PV modules, perovskite, and solar market in the EU. The obtained results were collected in a table, giving information about such indicators as IF, SCI, citation rate, and number of views/reads (regarding conference materials).

The next step was to systematize the information received and to identify barriers to the development of photovoltaic power as well as opportunities to increase the dynamics of “green energy” production.

Further, an analysis of factors with a positive or negative impact on the situation in the photovoltaic industry was carried out according to the following criteria: technical and technological, market, infrastructural and environmental, management, economic, and policy circumstances. In conclusion, an attempt was made to forecast the development of photovoltaic systems in selected countries and to identify the courses of action needed to increase synergies.

3. Results

As a result, some 57 scientific articles on photovoltaic energy were found. These publications came from 27 different, recognizable, open-access peer-reviewed journals. The majority of them originated from the Scopus and Elsevier databases, while other knowledge sources such as Google Scholar, EU services, and particular publishers’ websites of journals with high impact factors were in the minority (

Table 1. Citation rates and impact factors of the analyzed publications in open-access journals as well as conference materials.

Journal	IF	Cite Score (Scopus)
		Cs	Citescore Highest Percentile Cs-hp’23
Advanced Energy Materials	24.4	41.9	98
Applied Energy	10.1	21.2	99
Clean Technologies	4.0	6.1	80
Cogent Engineering	2.1	4.0	70
Current Opinion in Green and Sustainable Chemistry	9.3	16.0	97
Energies	3.0	6.2	85
Energy and Buildings	6.6	12.7	95
Energy Exploration and Exploitation	1.9	5.4	85
Energy Research and Social Science	6.9	14.0	98
Energy Strategy Reviews	7.9	12.8	85
Geoforum	3.4	7.3	94
IEEE Journal of Photovoltaics	2.5	7.0	82
International Journal of Energy Economics and Policy (IJEEP)	0.0	3.2	75
iScience	4.6	7.2	90
Journal of Hazardous Materials	12.2	25.4	99
Journal of Water and Land Development	0.0	2.1	56
Nature Communications	14.7	24.9	97
Photonics	2.1	2.6	43
Process Safety and Environmental Protection	6.9	11.4	95
Renewable and Sustainable Energy Reviews	16.3	31.2	97
Results in Engineering	6.0	5.8	82
Science	44.7	61.1	99
Science of the Total Environment	8.2	17.6	95
Solar Energy	6.0	13.9	89
Sustainability	3.3	6.8	88
Sustainable Energy Technologies and Assessments	7.1	12.7	92
Toxics	3.9	4.5	53
Conference Proceedings
Energy Procedia (Book Series). PV Asia Pacific Conference 2012	772 times cited in all databases
15th International Conferences and Exhibition on Nanosciences and Nanotechnologies (NN) 2019 Materials Today-Proceedings	43 times cited in all databases
Future Energy	Read counter: 6698; downloads: 176

). Other sources included government databases and industry web portals. First, the general circumstances for PV sector development were described, followed by an analysis of specific countries.

3.1. General Topics Overview

Solar PV systems directly convert SE into electricity. A typical PV system consists of PV cells (semiconductors) that form PV modules connected with other devices (inverters, batteries, energy storage). A solar system consists of the following elements: panels, electronic charge controllers, battery storage units, testing and monitoring methods, and solar-powered portable devices [9]. Storage and backup are necessary when discussing a complete PV system [7].

A characteristic feature of PV systems is the periodicity of production, leading to temporary oversupply. P2G (power-to-gas) technology enables surplus renewable energy to be converted into hydrogen gas via PEM electrolysis, offering a potential solution to the oversupply problem in addition to energy storage [10].

Due to favorable circumstances, energy production from photovoltaics is becoming increasingly profitable. PV markets are experiencing rapid growth in countries like China, India, the USA, Japan, and Australia [11].

Analyses by Heffron et al. in 2021 indicated that, in developing countries, new legislative regulations did not lead to an increase in PV installations [12].

Alongside the U.S., the European Union is the largest importer of PV panels, with the majority of the world’s exports originating from China and South Asia [13].

Although the electricity demand per citizen in Poland, Italy, and Spain is lower than the EU average [2], they are among the leaders in the number of PV installations.

The development of the SE industry results from advancements in technological solutions, economic factors, and political circumstances, as well as environmental and climate protection targets established by governments [14]. There is an expected increase in the use of solar irradiance to generate environmentally friendly electricity to meet the increasing demand.

In general terms, PV technologies are currently divided into Generations I, II, and III. The first generation includes monocrystalline and polycrystalline silicon panels, which are relatively inexpensive and widely popular. These are followed by second-generation thin-film solutions, namely, perovskite, silicon-free cells such as CIGS (copper indium gallium selenide) and CdTe (cadmium telluride), and cells based on amorphous silicon. The latest advancements in cell solutions include nanocells containing synthetic chlorophyll-like dye [15].

Shubbak lists the following PV technologies: c-Si general, c-Si mono-Ingot, c-Si Mono-cells, c-Si Poly Ingot, c-Si Poly-Cells, c-Si:HIT, c-Si:Micro, Common, Thin-film: General, Thin-Film: CIGS, Thin-Film CdTe, Thin-Film a-Si, GaAs, Multijunction, and Emerging technologies [9].

According to the WEEE Directive, PV equipment falls under the category of waste electrical and electronic equipment, requiring an 85% efficiency in the recovery of secondary raw materials [16,17]. Panel producers are responsible for covering the costs of collection and recycling. At present, there is a deficiency in a developed and implemented waste management system, along with insufficient human resources and infrastructure. It is predicted that the PV industry worldwide will generate more than 4.5 million tons of waste panels by 2050, although a sensitivity analysis conducted by Ovaitt et al. showed reduced material requirements due to an expected increase in PV lifetime by 2050 [18].

3.1.1. Management, Economic, and Policy Circumstances

Table 2. Overview of factors influencing the development of photovoltaic investments concerning management, legal, and political environments.

Characteristics of the Problem Group/Barriers	Advantages/Opportunities
Management
PV installations in cities on new buildings require planning from early stages (Formolli et al. [19]).	Distributed energy systems (DES) offer several advantages over centralized energy systems [11].
Conventional planning of optimal decentralized energy systems (DES) is not as suitable as artificial intelligence techniques [11].	Sustainable energy transition focuses on 4 dimensions: decarbonization, decreased use, decentralization, and digitalization [20].
Generally, around the world, there is a lack of proper waste management policies and programs like decommissioning, even in countries that are the biggest consumers of PV modules [21].	The usage of LCA helps on all levels of PV system planning [22].
Law and governmental policies
New legislation sometimes does not lead to an increase in the share of solar energy [12].	The future of PV was discussed during the Paris COP21 climate change negotiations [23].
There are problems with setting up recycling facilities and building a closed solar recycling market.	WEEE Directive, the Waste Electrical and Electronic Equipment Directive [24], indicates that potentially harmful substances will be contained, rare materials will be recovered, materials with high embodied energy value will be recycled, and recycling processes will consider the quality of recovered material.
Concerns involve an unclear policy framework and regulations [12] and an urgent need to institutionalize regulations regarding PV waste management.	The policy frameworks show photovoltaic (PV)-based DES (decentralized energy systems) as good alternatives for centralized energy systems [25]

summarizes the identification of various factors influencing the development of PV investments within the legal, economic, and management conditions. In developing countries, there is a lack of favorable and stable policies and strategies with assured incentive schemes that could accelerate decisions about PV investments. However, in developed countries, a challenge lies in regular planning by management organizations regarding the amount of certain types of PV installations in particular regions. These evaluations should consider local possibilities of selling energy overproduction to local electricity systems. It is also important to assess the state of the grid where energy will be bought or sold. At this stage, government institutions should play a more active role in preparing for future PV installations. The success of initial local energy investments can serve as a good example for the future success of new energy projects.

Table 3 presents the economic and market situation relevant to future investments in PV systems concerning the certain region or countries under evaluation. There are notable differences between investing in developing countries and investing in developed countries like the EU, where special energy programs often provide subsidies of up to 90% for projects.

In some developing countries, such as Iran, reduced government-guaranteed rates for renewable energy have resulted in a slowdown in PV investment [26]. Introducing systems similar to those in developed countries, such as net billing, where PV energy producers receive a reduced bill for the electricity consumed by accounting for the energy produced, could contribute to faster development of PV investment in developing countries.

Besides the financial support, it is possible to participate in a special training program, typically organized close to the customer, which can facilitate investments in the countryside where PV locations are most popular. When planning the investment, one should also consider the waste management program, including placement of such wastes as well as the cost and who will pay for it.

Table 3. Overview of factors influencing the development of photovoltaic investments concerning economy and market.

Characteristics of the Problem Group/Barriers	Advantages/Opportunities
Economy
High costs of waste management	High initial costs, but only in developing countries; in EU countries, there are many programs for financial support of PV
PV installations of the off-grid type, with their own energy storages, are more expensive and less popular compared to the on-grid type [27]
Capital costs of the system, maintenance costs, and energy produced are necessary to calculate the value of economic indicator LCOE (cost of kWh delivered by the energy system) [28]	Regardless of the billing system (net-metering, i.e., cashless or net-billing where prosumer sells and buys electricity from the grid), there is a possibility of building energy storage systems [27]
Unclear economics and methodologies in countries
Market
Unfamiliarity of consumers [29]	Increase in urbanization; well-developed countries observe higher investment levels (i.e., China, Japan, and Germany) [30]
Lack of energy awareness	Population growth
Unclear market	Increase in energy consumption and production [16,31] EIA foresees a 50% increase in world energy needs by the year 2050 [32] Increase in prosumers sector Conventional technologies based on silicon are more expensive than the new third-generation PV solutions [33]

Table 3. Overview of factors influencing the development of photovoltaic investments concerning economy and market.

Characteristics of the Problem Group/Barriers	Advantages/Opportunities
Economy
High costs of waste management	High initial costs, but only in developing countries; in EU countries, there are many programs for financial support of PV
PV installations of the off-grid type, with their own energy storages, are more expensive and less popular compared to the on-grid type [27]
Capital costs of the system, maintenance costs, and energy produced are necessary to calculate the value of economic indicator LCOE (cost of kWh delivered by the energy system) [28]	Regardless of the billing system (net-metering, i.e., cashless or net-billing where prosumer sells and buys electricity from the grid), there is a possibility of building energy storage systems [27]
Unclear economics and methodologies in countries
Market
Unfamiliarity of consumers [29]	Increase in urbanization; well-developed countries observe higher investment levels (i.e., China, Japan, and Germany) [30]
Lack of energy awareness	Population growth
Unclear market	Increase in energy consumption and production [16,31] EIA foresees a 50% increase in world energy needs by the year 2050 [32] Increase in prosumers sector Conventional technologies based on silicon are more expensive than the new third-generation PV solutions [33]

Table 4. Overview of technological and technical factors in manufacturing and at the operation stage influencing the development of photovoltaic investments.

Characteristics of the Problem Group/Barriers	Advantages/Opportunities
Technological and Technical Factors (Production and Operation)
Voltage regulation, power quality problems, malfunction of protection systems, and islanding [34]	Natural cooling in FPV leads to an increase in the efficiency of the modules at about 12% [35]
Crystalline silicon technologies (c-si) have some issues to be solved in order to increase the energy effectiveness. The most promising technology is HIT (heterojunction with intrinsic thin layer) [9]	Perovskite-based solar cells (PSCs) are the fastest-growing solar technology to date since their inception in 2009
Still low effectiveness: from 18% for mono-crystalline silicon cells to 26.1% for perovskite technology [36] and up to 40–41% for three-junction concentrator cell (GaInP/Ga(In)As/Ge) [37]	Perovskite: an opportunity to produce panels with multifaceted applications
Effectiveness depends on technology used: a multijunction system has 10% higher effectiveness compared to a single-junction construction [33]	Production of transparent panels allows their application on horticultural tunnels
The higher the concentration of PV, the higher the solar energy efficiency [38]	Fully printable, carbon-based, multiporous-layered-electrode perovskite solar cells (MPLE-PSCs) are easy to fabricate and have excellent durability and high stability over long periods [36]
Some technologies, like PSCs, are expensive because they require the use of gold or silver for back electrodes and expensive materials for the hole transport layer [36]	Some coverings on the PV modules are semi-transparent
Problem with temperature increase, which causes early damage [39]	Increasing longevity of panels: 25–30 years is guaranteed by 3rd-generation technologies [40]
Cooling methods need to be developed, especially when ground-based PV is used [41]	OPVs (organic photovoltaics) can use roll-to-roll manufacturing [9]
Problems with overshadowing: Fully covered single cells cause power loss of the module, even up to 79% [42]

presents the possibility of choosing different PV manufacturing technologies, focusing on factors such as material costs, product simplicity, operational service ease, spare parts costs, and procurement distance. An example of expensive technology is PSCs (perovskite-based solar cells), which require gold and silver for back electrode production. When planning a PV investment, it is important to prepare a project that facilitates easy installation at the final operating location. Higher concentrations of PV panels in rural areas correlate with increased system efficiency overall.

3.1.2. Infrastructural and Environmental Circumstances Influencing PV Sector Development

Table 5. Overview of infrastructural circumstances influencing PV sector development.

Characteristics of the Problem Group/Barriers	Advantages/Opportunities
Infrastructure
Locations of solar energy infrastructure should be well planned [43,44,45]	In the majority of cases, no problem with distances or distribution infrastructure
Creation and usage of maps of the accessibility and potential of building surfaces (roofs and façades) due to overshading [46]	Only in some countries, especially developing countries such as Somalia, is the barrier the lack of infrastructure [47]. This problem does not apply to EU countries.
For FPV (floating photovoltaic) with BEES (battery energy storage systems), the accessibility of the national and local grids is important; sometimes it is lacking [28,48]	Versatility and ease of installation; some can be very thin for roofs and sidewalls of individual houses, public use buildings, and clusters of buildings [49]
The connection of new energy sources to the electricity system is limited by the state of the grid infrastructure and the availability of connection capacity	Diversity of usage: office buildings, gas stations, tunnels, and greenhouses type Agro [50]
Off-grid renewables-based DES (decentralized energy systems) require energy storage systems [11]	Advantages: lifespan of photovoltaic systems: after 25 years, they retain 80% of their original efficiency
	OPVs (organic photovoltaics) [51], semi-transparency [52], low weight, and flexibility in shapes and colors

presents an overview of factors influencing PV installation development, focusing on infrastructure.

Concerning infrastructure, the most important issue is the availability of the grid and easy access to it.

Sunlight is a clean and renewable source of energy that does not produce air or water pollution during its conversion into electricity. Organic photovoltaic (OPV) is particularly promising in environmental protection. Other types of PV could be sources of various harmful emissions.

Table 6. Overview of environmental circumstances in PV sector development.

Characteristics of the Problem Group/Barriers	Advantages/Opportunities
Environment
Crystalline silicon (c-Si) is the most popular PV technology used in the global market [53], and its share is around 90% [40]	Some PV technologies, like organic photovoltaics (OPVs), have a reduced negative impact on the environment in comparison with others [54]
Attractive support policies can lead to high increases in investing, but can also lead to problems with the recycling and disposal of photovoltaic waste [16]	Recovering process: physical and chemical treatments like separation, shredding, and chemical reactions [37]
	Rare substances and materials with high embodied energy value (e.g., silicon, glass) have high potential for reuse
Using floating PV leads to a reduction in water evaporation, while ground-based PV can cause a loss of agricultural land [48]	Possibility to produce very thin panels, i.e., in OPV flexible organic solar cells [33,51], is connected to a lower amount of waste
Only 10% of PV modules in the world are recycled [16]
Wastes occur at all four stages: production, transport, installation, and operation [21]
Main reasons for failures (cell degradation, micro-cracks, contact defects, glass breakage, and defective bypass diodes) are connected with changing ambient factors (precipitation, wind) and repeated mechanical and thermal load cycles [21,55]
Depending on the technology used for production of PV cells, the solar installation is built from different types of materials and often contains toxic chemicals, heavy metals [56], and rare substances like fluorine [57], which can be release into the environment (cadmium, lead, copper, nickel, zinc) [58,59]
PV panels contain heavy metals, and waste disposal is more difficult [60]

describes the potential for environmental protection at each stage of PV utilization: production, transport, installation, and operation. When considering PV production technology, choosing very thin panels can positively influence the amount of waste generated. Currently, only 10% of installed PV systems are recycled. Before planning an SE system, it is essential to analyze specific solar maps that can help to optimize energy capture from the sun in particular regions of the country.

3.2. Situations in Chosen Countries Regarding Photovoltaic System Development with Future Projections

The more electricity a specific installation can produce, the shorter the financial return time, which is advantageous in countries with high solar irradiance. In Sicily, for instance, the return time for installations using modules made from wafer-based silicon is only about 1 year [61].

The average share of RES in the EU27 in 2021 was 19%, while the total installed PV power in the EU reached 259.99 GW by 2023 [62]. Leading countries have made significant strides in integrating weather-dependent sources into the grid. For example, the Netherlands has achieved a share of 25%, Germany 29%, Spain 32%, and Denmark 58%. By the end of 2022, Germany led in total installed PV capacity with 67 GW, followed by Italy with 25 GW and Spain with 20 GW.

Poland stood out as the only country in Central and Eastern Europe among the top six EU countries with a total installed capacity of 12 GW. These leading countries have excelled in integrating weather-dependent sources into their grids. The development of PV investment in Europe is driven by the European Union’s SE strategy [63], coupled with increasing energy consumption and rising energy prices.

3.2.1. Germany

By the end of 2023, Germany had achieved 93 GW of installed power in PV [64], marking significant progress toward its planned targets, including climate targets for 2045 and GHG emission reductions of 65% by 2030 and 88% by 2040.

Facing restrictions on imported gas supplies, Germany has decided to expand its nuclear power plants, aiming to stabilize the energy market [64,65].

Germany has also prioritized expanding renewable energy infrastructure and enhancing energy efficiency. In 2023, the country generated 62 TWh from solar PV, with predictions indicating approximately 400 GW of installed PV energy by 2040 [64].

Recent reports suggest that Germany will continue to be a key market for home batteries, expected to reach a capacity of 1.3 GWh [64]. This growth is driven by an increasing number of solar systems and rising demand for electric vehicles (EVs). Additionally, new conditions for energy cooperatives will positively influence the increase in investments [66].

Germany’s method of integrating energy from PV into the grid has served as a model for other countries in recent years. The German PV market [30] is notably promising among all EU countries. As Germany progresses toward achieving its targets for GHG neutrality by 2045, rapid investment in PV installations is crucial [67]. The biggest potential for this growth has been identified in agri-photovoltaics, with floating PV and parking areas representing the next level of development [68].

3.2.2. Poland

The main driver behind the growth of PV investments in Poland and other countries is various types of subsidies, benefiting individual users, companies, and even government institutions. Among various RES, PV holds the highest share—99.96% of prosumer installations.

The PV market in Poland holds significant promise, with the installed capacity expected to reach 15 GW by 2025. Alongside Germany, Poland is among the countries experiencing systematic increases in investments in PV. Compared to other analyzed countries, Poland’s PV market is relatively young, with the first PV panels installed as recently as 2011, whereas in other European countries, such installations date back to the 1980s. Several factors have contributed to the growth of investments in micro-installations in Poland in recent years, including the availability of government support programs like “My Electricity” and the change from net metering to net billing in 2022 [69,70].

According to data from the Polish Energy Market Agency (ARE), in 2023, PV panels totaling more than 17 GW in capacity were installed in Poland, with approximately 3/5 of these installations being in micro-installations. In the previous year, 2022, the total installed capacity was 12.181 GW, of which about 3/5 were also in prosumer micro-installations [65]. On the other hand, state-owned PV plants covered only 599.8 MW of power in 2022.

3.2.3. Spain

Since 2015, Spain has experienced the largest increase in delivered PV energy, amounting to 31 TWh. The country’s total electricity demand in 2023 was 256 TWh [60]. Spain holds a leading position in the EU’s Power Purchase Agreement (PPA) market.

Statistics indicate that solar PV accounts for approximately 27.8% of all RES in Spain [64]. Despite achieving the largest increase in installed electricity capacity from PV systems in Europe in 2023, Spain faces several challenges.

The turbulence in Spain’s energy market, caused by the geopolitical situation since February 2022 and internal political events such as national and local elections, has coincided with high inflation and delays in implementing the National Recovery Program. However, amidst these challenges, the systematic increase in PV investments is driving the necessity for concurrent reforms. These reforms include improvements in distribution grid infrastructure, enhanced auction planning, policy adjustments, and updates to subsidy programs [71].

According to the National Energy and Climate Plan (NECP), Spain plans to install 76 GW of PV power by 2030.

The development of investment in solar PV in the country has recently been influenced by ongoing auctions in the energy market and the government’s promotion of investment benefits for individual consumers. In addition, the closure of the last coal-fired power station is planned for 2025, which will accelerate the development of RES [72].

One opportunity for PV development is to capitalize on the natural conditions offered by Spain’s high levels of solar radiation. Experiments conducted in southeastern Spain (Almería region) on greenhouses have shown that, in regions with high solar irradiance, it is possible to provide up to 44% shading for plastic greenhouses without reducing crop yields [72].

3.2.4. Italy

Italy’s current goal for 2030 is to cover 65% of its energy supplies through RES, requiring an additional 70 GW of installed power [73]. By the end of 2023, approximately 65.2 GW of power had been installed, which was three times more than in 2008. This significant increase was primarily achieved through large projects led by the country’s association for the PV sector [73].

Italy’s solar power capacity increased by 1.7 gigawatts (GW) in the first quarter of 2023, reaching 32 GW, thanks to developments in the PV sector. According to the NECP, Italy aims to increase its installed PV power to 131.3 GW by 2030. Four years ago, SE accounted for 8.2% of the country’s energy consumption, supplied by over 1.2 million systems [74,75].

Global predictions made by Haegel [76] show that the sustainable PV installation market grow rate should be around 25% year to year. We prepared our own figure showing the prognosis based on national declarations of individual countries (Figure 2). The data indicate that the market should speed up in order to achieve the intended rates of increase.

4. Discussion and Conclusions

Rapid progress in technically accessible solutions for consumers, growing demand, and society- and environment-friendly policies are important drivers of investments in RES, especially in solar PV.

Among environmental barriers, the lack of a coherent waste management system is the most critical issue affecting all countries in the study. Economical effectiveness heavily depends on national incentive systems.

Economic factors are strongly connected to legislative regulations because legislation introduces the basis for functionalizing the type of billing system, which directly influences final costs for energy PV producers and decisions about investments.

The payback period of a PV system depends on some parameters, such as the geographic location of the project, solar activity at the installation site, materials used for panel production, and the angle of solar incidence on the panels. PV systems typically operate at 80% efficiency after 25 years of activity. The greater the electricity output of a specific PV system, the shorter its financial return period, which is particularly beneficial in countries with high solar irradiance. For example, PV installations in the Sicily region can achieve a return time of about 1 year when using silicon panels.

There is still potential to decrease the global investment costs of PV installations through the creation of opportunities for global cooperation, particularly supporting underdeveloped and developing countries [14].

However, the amount of installed PV capacity in the analyzed countries and its growth rate indicate that favorable factors have broken barriers.

It is expected that global renewable electricity, including solar PV, will grow to 7300 GW by 2028 [2]. Among the four largest countries with the highest total installed PV power in 2023, totaling 31.7 GW, are Germany, Spain, Italy, and Poland [61].

In Europe, Germany leads in PV installation capacity, with over 66.6 GW installed in 2022, nearly three times more than Spain.

Although Italy and Spain experience more sunny hours per year, their PV capacity remains significantly lower compared to Germany. According to IRENA data, Italy ranks as one of the world’s leading countries in solar PV electricity consumption and PV market size [8]. Photovoltaics play a crucial role as one of the most important RES in Italy.

Poland faces a comparable situation in the PV market, which is expected to expand to 15 GW by 2025. Alongside Germany, Poland is among the countries experiencing a systematic increase in investments in PV.

The following conclusions are the results of our study:

-

The future of SE utilization looks very promising due to its clean energy usage. There are new challenges that countries should face, as countries are cautious in their approach to nuclear energy due to the increased risk. Not all countries can afford to develop wind power because there are problems with the necessary distances that matter to the environment and people. PV technologies are considered the least negative.

-

Concerning EU countries that have installed the most PV capacity in recent years, Germany stands out, with solar power plants built with a total capacity of 7.9 GW. This result is 1.9 GW higher than what was achieved in 2021. Germany is also the leading country in the EU in the field of energy derived from biogas and hydropower.

-

Starting from an installed capacity of 68.5 GW at the end of 2022, Germany aims to expand its PV fleet almost fourfold by the end of this decade. Furthermore, new measures outline solar installations averaging 22 GW per year post-2030, aiming to reach about 400 GW by 2040.

-

The installed capacity of photovoltaics in Poland amounted to 13,480.8 MW, including 599.8 MW from state-owned PV power plants and 12,881.0 MW from independent private PV power plants.

-

According to data from the Energy Market Agency, as of the end of August 2022, Poland had 1,131,973 PV micro-installations under 50 kW. The high popularity of home installations is largely due to very favorable financial conditions for prosumers that were recently in effect. Specifically, the country’s net-metering scheme allowed prosumers with systems up to 10 kW to feed 1 kWh into the grid and receive 0.8 kWh for free.