Exploration of Research Hotspots and Trends in Photovoltaic Landscape Studies Based on Citespace Analysis

Abstract

This study examines the photovoltaic (PV) landscape-related literature indexed in the Web of Science database from 2005 to 2024, employing a combination of bibliometric analysis software and a manual review to analyze, explore, and summarize the development trajectory and future trends in PV landscape research. Over the past two decades, PV landscape research has progressed through three stages: the foundational stage from 2005 to 2008, during which studies primarily focused on the environmental impacts of PV installations; the developmental stage from 2009 to 2020, characterized by interdisciplinary integration, with research shifting its focus to the combination of PV systems with living and production environments, advancements in PV landscape technologies, and innovations in PV materials; and the maturity stage from 2021 to 2024, which has seen heightened requirements for energy conversion efficiency and stability in PV systems, along with the establishment of a systematic research framework for PV landscapes, enabling more diverse explorations of its development. Based on this analysis, this study summarizes key research frontiers in PV landscapes, including the impacts and assessment of PV installations on the ecological environment, the deep integration of PV systems with living environments, and the visual aesthetic impacts and evaluation of PV landscapes. Finally, this study proposes three future prospects for PV landscapes and briefly discusses the limitations of this research.

1. Introduction

Global climate change and the depletion of fossil fuels pose serious challenges to the public. The adoption of clean energy to replace traditional fossil fuels has become an inevitable choice for achieving emission reduction and environmental protection goals. Solar energy, as one of the most common and abundant clean energy sources, has garnered unprecedented attention worldwide [1]. However, many researchers, such as Kapetanakis, I. A. [2], Tsantopoulos, G. [3], Patel, S. [4], and Ko, I. [5], generally believe that photovoltaic systems can have negative impacts on the landscape environment, including effects on community life, environmental benefits, land use, and ecological value. This perception has directly slowed the global promotion of photovoltaic systems. In this context, scholars like Bishop, I. D. [6], del Carmen Torres-Sibille, A. [7], and Ladenburg, J. [8] have proposed a series of indicators, parameters, and assessment methods to evaluate the environmental impacts of large solar photovoltaic facilities. Their goal is to identify opportunities for integrating photovoltaic systems with the landscape environment, thereby minimizing these negative effects as much as possible.

The term “photovoltaic landscape” is relatively new and has emerged as a modern energy concept. For instance, researcher Kapetanakis, I. A. [2] used the term “photovoltaics’ landscape” in his 2014 paper titled “Parametric analysis and assessment of the photovoltaics’ landscape integration: Technical and legal aspects” to explore the relationship and integration criteria between photovoltaic systems and the landscape environment. In 2016, Scognamiglio, A. [9] and colleagues formally introduced the concept of “Photovoltaic landscapes” through an “inclusive” design approach, creating a bridge between energy and the landscape environment. This approach integrates photovoltaic systems as a landscape element in design, aiming to mitigate their impact on the landscape. Subsequent researchers have proposed similar concepts, such as “solar landscapes” and “solar photovoltaic landscapes”, to reinforce and enhance the study of photovoltaic landscapes. For example, Sarvghad, M. [10] (2018) advocated for the spatial arrangement of solar power plants in harmony with local landscapes, introducing the concept of the “solar landscape”. Yadav, P. [11] (2019) introduced the term “solar photovoltaic landscape”, while Oudes, D. [12] (2022) developed a typology of “solar landscapes” from four dimensions: energy, economy, nature, and landscape, further expanding the vocabulary surrounding solar landscapes. As the concept of photovoltaic landscapes continues to evolve, it has increasingly become a focal point for researchers and designers, with a steady growth in the number of systematic studies and implementation projects [13]. Today, photovoltaic landscapes have gradually formed a substantial and multidimensional interdisciplinary research field [12]. In light of this, this paper will review the development of photovoltaic landscapes, aiming to reveal its evolution and future trends, thereby providing references and insights for subsequent research in this area.

Based on a comprehensive review of the relevant literature, this paper employs CiteSpace software 6.4.R1 to conduct a bibliometric and scientific knowledge mapping analysis on the existing literature from the Web of Science core collection. The aim is to elucidate the fundamental content of past and current research on photovoltaic landscapes, as well as to identify the current research directions and future trends in this field. This study hopes to provide valuable insights for future research on photovoltaic landscapes by presenting a comprehensive and systematic literature review, attracting the attention of peers, promoting in-depth development in photovoltaic facility landscape research, and contributing meaningful summaries of academic value. The research content of this paper is divided into four main sections: Section 2 introduces the relevant research methods, including data collection and an overview of the research methodology; Section 3 visualizes the results using CiteSpace software and discusses the findings; Section 4 analyzes and summarizes the research hotspots and frontier trends in photovoltaic landscapes; and Section 5 provides a conclusion and outlook on related research in the field of photovoltaic landscapes.

2. Methodology

2.1. Data Collection

This study employed the Web of Science (WoS) core collection platform for the literature retrieval, with the search conducted on 5 October 2024. Using the search formula (TS = (solar OR PV OR “solar energy” OR “solar power”)) AND (TS = (landscape)), a total of 2926 relevant articles were found, with the earliest publication dating back to 1991. Furthermore, the literature types were limited to articles, conference proceedings, and review papers, focusing on research frontiers and trend topics from the past 20 years (2005 to 2024) to enhance the timeliness of this study. Other relevant criteria followed the default settings of the WoS core collection platform. After filtering, a total of 2832 articles were identified, which were then exported in six batches, including full records and citation references, to serve as the foundational dataset for this study.

2.2. Overview of the Method

CiteSpace is a key tool for visualizing and analyzing bibliometric information, providing researchers with powerful technical support for uncovering knowledge network structures and tracking the dynamics and directions of research frontiers. This study primarily utilizes the CiteSpace bibliometric analysis software developed by Professor Chen Chaomei for data processing and visualization [14]. The software constructs knowledge maps that visually display the structural relationships within a research field, enhancing the intuitiveness and systematic nature of academic research. By conducting in-depth analyses of citation relationships, CiteSpace can reveal the intrinsic connections between different pieces of the literature, helping researchers identify classic works and core theories within the field [15]. In this study, CiteSpace version 6.4.1 is used for the data visualization analysis of the relevant literature, with a time frame set from 2005 to 2024 and time slices of one year. The node selection employs the g-index method, and the k-value and time slice years are adjusted according to the specific requirements of different data visualizations to maintain a relatively appropriate data density. Other parameters remain at the software’s default settings. The data visualization analysis focuses on aspects such as annual publication numbers and citation indices, collaboration networks, keyword co-occurrence analysis, and keyword time zone maps, which collectively provide a clear illustration of the progress and dynamic hotspots in photovoltaic landscape research.

3. Results

3.1. Publication Volume and Citation Trends

As shown in Figure 1, this study focuses on journal articles published between 2005 and 2024, and the research on photovoltaic landscapes can be roughly divided into three phases (Figure 1): (1) initial development stage (2005–2008). During this period, research on photovoltaic landscapes was still in its nascent stage, with fewer than 100 articles published annually. (2) Stable growth stage (2009–2020). In this phase, research on photovoltaic landscapes received further development and attention. Although there was a decline in publication numbers in 2016, growth resumed in 2017, with an average of about 150 articles published per year. This growth is evidently linked to the signing of the Paris Agreement by 195 countries at the Paris Climate Change Conference in 2016 [16], which spurred rapid development in photovoltaic landscapes during this time. (3) Rapid production stage (2021–2024). In this stage, the number of published papers in 2021 experienced explosive growth, with an average of over 250 articles published annually. Through calculations and statistics, it is found that the publications in this stage constitute approximately 50% of the total records. Since the beginning of 2020, the COVID-19 pandemic has swept across the globe, severely impacting the global economy. In the subsequent economic recovery process, countries around the world have announced various development strategies and policy measures in the energy sector, focusing on carbon neutrality and launching green recovery plans, positioning clean energy as the engine for economic recovery. As a result, many countries have promoted the rapid development of renewable energy, such as wind and solar power, leading to a renewed surge in research related to photovoltaic landscapes during this period.

Moreover, the trend in citation counts for these papers closely aligns with the number of publications and the stages identified, indicating that as the volume of published work increases, the research impact in this field continues to grow. Through data analysis with CiteSpace, this study has compiled a list of the top 15 publications that are closely related to the content of photovoltaic landscapes. These include studies on innovations in photovoltaic technology and solar cell technology [17,18,19,20]; the development potential of photovoltaics in urban settings and local microclimate issues [21,22]; public acceptance of sustainable energy and future developments [23,24]; and the application of photovoltaics in agroforestry and their mutual benefits [25,26]. This compilation serves as a reference for readers (

Table 1. Top 15 documents and their citations.

Publications		Citations
			Nearly Three Years			Average per Year	Total
			2022	2023	2024
Sort	Total	Year	11,489	12,643	11,081	2456.03	83,505
1	Opportunities and challenges for a sustainable energy future	2012	1290	1297	973	662.77	8616
2	Lessons from nature about solar light harvesting	2011	110	103	79	107.14	1500
3	Defect migration in methylammonium lead iodide and its role in perovskite solar cell operation	2015	154	136	90	129.7	1297
4	A comparative technoeconomic analysis of renewable hydrogen production using solar energy	2016	80	102	74	72.22	650
5	The urban heat island effect, its causes, and mitigation, with reference to the thermal properties of asphalt concrete	2017	119	107	94	71.5	572
6	A comprehensive review of state-of-the-art concentrating solar power (CSP) technologies: Current status and research trends	2018	109	86	62	72.57	508
7	Impact of urban form and design on mid-afternoon microclimate in Phoenix Local Climate Zones	2014	58	36	37	38.09	419
8	Tailoring the Energy Landscape in Quasi-2D Halide Perovskites Enables Efficient Green-Light Emission	2017	50	46	37	50.88	407
9	Public acceptance of renewable energies: Results from case studies in Germany	2008	39	27	20	23.35	397
10	A geometric solar radiation model with applications in agriculture and forestry	2002	31	16	26	16.52	380
11	A Critical Review of Machine Learning of Energy Materials	2020	102	75	59	69.4	347
12	Monolithic Perovskite Tandem Solar Cells: A Review of the Present Status and Advanced Characterization Methods Toward 30% Efficiency	2020	91	91	67	69	345
13	Agrivoltaics provide mutual benefits across the food-energy-water nexus in drylands	2019	65	100	91	55.67	334
14	Quantum-size-tuned heterostructures enable efficient and stable inverted perovskite solar cells	2022	70	124	105	100	300
15	Solar energy potential on roofs and facades in an urban landscape	2013	28	19	12	21.83	262

).

3.2. Author Collaboration Analysis Chart

In the academic field, the number of papers published by core authors in leading journals often reflects the development level and trends within that field [27]. The author co-occurrence analysis chart provides a visual tool for identifying collaboration relationships among scholars, revealing core research teams and key figures in a specific area. In the author co-occurrence analysis chart generated by CiteSpace, each node represents an author, with the size and color of the node typically indicating the author’s influence and the frequency of collaboration, while the lines connecting the nodes reveal direct collaborative relationships among authors. As shown in Figure 2, the author co-occurrence analysis chart contains 341 nodes and 454 connecting lines (Figure 2). Notably, researchers such as Pokorny, J., Cook, B., Mcgehee, Michael D., and Vandewal, K. are among the most prolific authors in this field, with several other authors also demonstrating a high level of activity. Additionally, the centrality of the vast majority of authors is close to zero, indicating that, at present, researchers in this field have not yet established a closely connected network of collaborative relationships. Thus, strengthening connections and collaboration among authors is a pressing need in the field of photovoltaic landscapes. It is noteworthy that the co-occurrence relationships among researchers were primarily concentrated between 2014 and 2016, a period that coincides with the stable growth phase in the number of published papers, demonstrating a positive correlation between the two.

3.3. Collaboration Analysis by Country or Region

As shown in Figure 3, the collaboration network among countries or regions consists of 55 nodes and 224 connecting lines (Figure 3). The size of each node represents the number of papers published by each country, while the thickness of the lines between nodes reflects the degree of collaboration between countries. When the centrality index exceeds 0.1, a purple circle is added around the node to indicate the importance and influence of that country in the specific field; the larger the purple circle, the more significant the country’s bridging role in the network. The statistical results reveal that ten countries have a centrality index exceeding 0.1, including Germany, England, Australia, Canada, and France, indicating their critical bridging roles in the field of photovoltaic landscapes. Furthermore, by observing the radius of the node circles, one can discern the publication volume of each country in this area. Notably, scholars from the United States and China stand out with publication counts of 898 and 448, respectively, while other countries with significant publication volumes include Canada, Germany, and France (

Table 2. Countries or regions with more than 100 articles.

Serial	Number	Central	Year	Country
1	898	0.09	2005	USA
2	448	0.04	2005	China
3	231	0.15	2005	England
4	217	0.11	2005	Germany
5	197	0.03	2006	Italy
6	162	0.16	2006	Australia
7	162	0.12	2005	Canada
8	150	0.11	2006	Spain
9	143	0.17	2006	France
10	112	0.02	2009	India

). Through the Belt and Road Initiative, China shares photovoltaic technology and project experiences with countries along the route, facilitating the internationalization of photovoltaic products. For example, cooperation projects with African countries have helped improve local energy self-sufficiency by providing relevant PV system technologies and have promoted the development of both local and regional PV landscapes. In the field of PV landscape construction, Germany possesses advanced technology and research experience, providing a benchmark for other countries. The collaboration between Chinese and German research institutions and enterprises has addressed technical challenges in the PV landscape field, enhancing production processes and product quality for both parties and driving technological upgrades in the photovoltaic industry. Overall, in the context of globalization, close cooperation between countries is a crucial force in the development of the PV landscape field and serves as an inexhaustible driving force for its long-term development.

3.4. Distribution of Related Research Disciplines

From Figure 4, it can be observed that the research primarily encompasses disciplines such as environmental sciences, energy and fuels, ecology, geosciences, environmental studies, and materials science (Figure 4). Notably, the connections between environmental studies and ecology, as well as between materials science and energy and fuels, are particularly prominent, indicating a close relationship between these pairs of disciplines in the field of photovoltaic landscape research. As a novel concept that integrates renewable energy technology with ecological aesthetics, photovoltaic landscapes are attracting increasing attention and research globally [9]. Photovoltaic landscapes not only represent one aspect of the energy transition but also result from the interdisciplinary integration of fields such as materials science, electrical engineering, energy technology, landscape design, and ecological restoration. Furthermore, the study also analyzed disciplines with over 200 published papers, finding that nine disciplines have a centrality greater than 0.1. This further confirms the high degree of interdisciplinary crossover in photovoltaic landscapes, which is conducive to the rapid dissemination and promotion of future research in this area (

Table 3. Statistics of related disciplines with more than 200 articles published.

Serial	Number	Central	Year	Wos Discipline
1	564	0.37	2005	Environmental Sciences
2	523	0.22	2006	Energy and Fuels
3	294	0.12	2005	Ecology
4	282	0.11	2005	Geosciences, Multidisciplinary
5	276	0.11	2007	Materials Science, Multidisciplinary
6	229	0.11	2006	Environmental Studies
7	223	0.1	2009	Green and Sustainable Science and Technology
8	203	0.03	2009	Chemistry, Physical

).

3.5. Analysis of Research Institutions and Organizational Collaboration

This study visually presents the collaboration relationships between various institutions and organizations involved in this field through an organizational cooperation analysis chart. A total of 558 nodes and 831 connecting lines represent the institutions and organizations participating in the research. The font size and node size reflect the number of publications for each institution (Figure 5). The Chinese Academy of Sciences ranks first with the highest number of publications at 107, making a significant contribution to the development of photovoltaic landscapes. The top five organizations all have more than 30 published papers, including the Chinese Academy of Sciences, US Geological Survey, University of Chinese Academy of Sciences (38 papers), University of Arizona (37 papers), and NASA (30 papers) (see

Table 4. Top 5 research institutions and organizations in terms of the number of published articles.

Serial	Number	Central	Year	Organization
1	107	0.11	2005	Chinese Acad Sci
2	38	0.05	2009	US Geol Survey
3	38	0.03	2014	Univ Chinese Acad Sci
4	37	0.06	2008	Univ Arizona
5	30	0.07	2005	NASA

). From a specific research content perspective, Chinese Academy of Sciences (CAS) is prominent in research on photovoltaic materials. Articles with high citation frequencies, such as “Material and Device Design of Flexible Perovskite Solar Cells for Next-Generation Power Supplies”, highlight significant progress in solar cell technology related to flexibility, stability, and power conversion efficiency, providing new possibilities for the further development of PV landscapes. Additionally, in “Effect of Solar Farms on Soil Erosion in Hilly Environments: A Modeling Study From the Perspective of Hydrological Connectivity”, the institution also focuses on the importance of landscape ecology, hydrology, and geomorphological feedback in improving the environmental impact assessment of solar power stations. On the other hand, the US Geological Survey (USGS) is more concerned with the impacts of PV facilities on the local environment and biodiversity when introduced. For example, in “Solar Energy Development Impacts Flower-Visiting Beetles and Flies in the Mojave Desert”, the article discusses how deserts are prioritized as reception environments for ground-based solar development and the loss of biodiversity that can be mitigated through careful site selection. In “Wind, Sun, and Wildlife: Do Wind and Solar Energy Development ‘Short-Circuit’ Conservation in the Western United States”, the article reviews the current state of the relationship between wildlife conservation and energy development in the western United States since 2010 and explores ways to mitigate the impact of renewable energy development on wildlife.

3.6. Keyword Co-Occurrence Analysis Chart

Keywords typically serve as a concise summary of the core viewpoints and content of the literature, and their frequency of occurrence can reflect their influence in a particular research field to some extent [14]. As shown in Figure 6, the keyword co-occurrence analysis involves 558 nodes and 831 connecting lines (Figure 6). The nodes with a centrality greater than 0.1, indicated by a purple outer circle, primarily include four keywords: climate change (205 occurrences), model (152 occurrences), performance (118 occurrences), and solar radiation (170 occurrences). As shown in

Table 5. The frequency of the top 10 keywords.

Serial	Number	Central	Year	Keyword
1	205	0.14	2005	climate change
2	196	0.02	2010	renewable energy
3	185	0.09	2005	landscape
4	170	0.17	2005	solar radiation
5	163	0.09	2005	vegetation
6	152	0.11	2006	model
7	135	0.06	2011	solar energy
8	127	0.1	2005	climate
9	118	0.11	2012	performance
10	110	0.06	2008	temperature

, the top ten keywords also include renewable energy (196 occurrences), landscape (185 occurrences), vegetation (163 occurrences), solar energy (135 occurrences), and climate (127 occurrences) (Table 5). From a centrality perspective, although keywords such as solar radiation, model, and performance have relatively lower occurrence counts in the top ten, they still possess high influence. In contrast, keywords like renewable energy and landscape, which have a strong correlation with photovoltaic landscape research and appear more frequently, exhibit lower centrality. This indicates that while these keywords are commonly found in the literature, they do not exert significant influence in the field of photovoltaic landscapes and are often used as qualifiers and descriptors within the context of the photovoltaic landscape literature.

3.7. Keyword Cluster Analysis

The keyword cluster analysis using CiteSpace can help researchers identify hot topics, development trends, and knowledge structures within a research field, which is extremely valuable for grasping research frontiers and determining future research directions [28]. The keyword cluster analysis identified seven main clusters: #0 landscape scale, #1 renewable energy, #2 plant species richness, #3 perovskite solar cell, #4 urban green space, #5 characterization, #6 stability, and #7 European conquest (Figure 7). In cluster analysis, the modularity value (Q value) is an important indicator for measuring the significance of the clustering results. In this study, the Q value of the cluster analysis was 0.726, exceeding the threshold of 0.3, indicating that the clustering results are significant. Furthermore, the effectiveness of the knowledge map is usually evaluated based on network structure and clustering clarity, typically using the modularity value (Q value) and the average silhouette value (S value). When both the Q value and S value are within the interval [0, 1), and when the Q value is greater than 0.3 and the S value is greater than 0.5, the clustering results can be considered reasonable [27]. In this study, the Q value of the clusters was 0.4226 and the S value was 0.5475, indicating that the clustering degree in this study is good and holds high research value. This paper will integrate all clustering results and elaborate on them, mainly through three aspects.

The first cluster emphasizes the need for decision-makers to make informed decisions, designs, and implementations based on the current state of photovoltaic (PV) landscapes across different spatial and characteristic contexts. The “#0 landscape scale” highlights that decision-makers need to engage in comprehensive planning and layout according to the spatial environments of different landscape scales. This involves not only the installation and operation of individual PV facilities but also requires decision-makers to consider the integration of these facilities with the surrounding natural ecological environment and human living conditions at a macro level. For example, at the urban spatial scale, Florio, P. [29] proposed a multi-scale evaluation model for assessing building visibility, which not only integrates PV systems into the entire urban environment to capture significant solar energy but also avoids severely impacting public perception and social acceptance related to landscape changes. Similarly, Ioannidis, R. [30] utilized multi-scale standards to evaluate the visibility of facilities in urban planning, contributing to methods aimed at enhancing the social acceptance of solar energy in cities. In rooftop spaces, Dimond, K. [31] conducted landscape considerations for green roofs and PV roofs of varying scales, exploring which type can achieve the most sustainable impacts and benefits under different contexts. The “#4 urban green space” cluster emphasizes that urban green spaces frequently appear in the spatial environment where PV facilities are installed, marking these areas as crucial for spatial integration of PV landscapes. In urban green spaces, PV landscapes serve not only as a means of energy production but also as an excellent opportunity to create urban green open spaces. The combination of both can achieve dual benefits of energy production and urban ecological development. For instance, Lu, M. [32] employed visual Q methods to assess the visual impact of PV systems on urban landscapes in China, summarizing five factors through which PV facilities influence urban aesthetics. Redweik, P. [33] created digital surface models of urban areas based on LiDAR data, exploring the potential for PV development in building rooftops and facade landscapes. Sattler, S. [34] used interdisciplinary research methods to integrate PV systems into urban flat-roof gardens, concluding that PV rooftop gardens are particularly suitable as multifunctional spaces for green recreational activities and renewable energy development in cities. The “#5 characterization” cluster emphasizes the impact of different landscape environmental characteristics on PV facilities. For example, Moraitis, P. [35] assessed the influence of various urban features on PV facilities, demonstrating that urban environments significantly affect the overall performance and efficiency of solar energy systems. Schunder, T. [36] analyzed the internal structural characteristics of PV rooftops, finding that building design features greatly influence the feasibility of solar energy as an alternative energy source.

The second cluster emphasizes the role of emerging energy sources and photovoltaic (PV) technology development in advancing PV landscape research. The “#1 renewable energy” cluster clearly indicates that PV landscapes are an important branch of the renewable energy field. As a core component of renewable energy, photovoltaics play a crucial role in the global energy transition [35]. With increasing public concern over climate change and the energy crisis, countries around the world have intensified their support for the PV industry, promoting the innovation and application of PV technology. The “#3 perovskite solar cell” cluster highlights how the development and innovation of new solar cell technologies have improved the compatibility of PV materials with other facility materials. With higher conversion efficiencies [37] and lower costs [38], these advancements adapt to different installation environments and personalized needs, bringing new hope for the efficiency and popularization of PV landscapes. For example, regarding the high-temperature resistance of PV materials, Sarvghad, M. [10] discussed innovations involving heat transfer fluids, low eutectic salts, or metals, enabling PV plants to operate at higher temperatures (around 700 °C). In terms of material transparency, researchers have proposed using luminescent solar concentrators (LSCs) as a photovoltaic module to replace glass curtain walls of varying transparencies, seamlessly integrating into urban architectural landscapes, with their aesthetic qualities proving to be an excellent alternative to commercially available frosted glass [39]. In the area of morphological innovation in PV materials, Sharma, P. [40] described a new method for the maximum power tracking of curved thin-film flexible PV (FPV) modules, providing designers with more creative possibilities, including arched roofs, landscape features, tents, and building-integrated photovoltaics (BIPVs). Additionally, the “#6 stability” cluster emphasizes the importance of the efficiency and stability of new solar cells [41] in the process of developing PV landscape research, serving as the foundation for integrating PV facilities with the landscape environment.

The third cluster emphasizes the importance of maintaining ecological balance and protecting biodiversity in the development of PV landscapes. The “#2 plant species richness” cluster highlights the need for decision-makers to systematically consider the potential impacts and threats to local flora and fauna diversity and ecological balance when introducing PV facilities. Research in this area primarily focuses on assessing the ecological effects of PV facilities on local environments and biodiversity. For example, Gómez-Catasús, J. [42] and colleagues investigated the impacts of PV facilities on arid biomes in certain regions of South Africa, finding that solar power plants had the most direct effects on ecological landscapes and bird populations, summarizing experiences for the future introduction of PV facilities in arid areas of South Africa. However, the impact of PV facilities on ecological environments and species diversity is not solely negative; for instance, the spaces beneath solar panels provide habitats for some small animals. Researcher Suuronen, A. [43] evaluated the effects of solar power plants on local microclimates and biodiversity in desert regions, with findings indicating that the shaded areas created under solar panels offer refuges for arthropods in the desert. This information is significant for the sustainable planning and construction of solar power plants in arid regions.

3.8. Keyword Time Zone Analysis Chart

The keyword time zone chart in CiteSpace visually illustrates the development trajectory of research directions over different periods [44]. As shown in Figure 8, the keyword time zone analysis chart contains 65 nodes and 224 connecting lines, covering the research period from 2005 to 2024 (Figure 8). Based on the overall time zone trends observed in the CiteSpace time zone analysis chart, the research trajectory of PV landscapes can be primarily divided into three developmental stages.

First stage (2005–2008): During this stage, the keyword nodes in the purple outer circle with a centrality greater than 0.1 are the darkest, indicating a dense concentration of keywords within this time zone. This period represents the core interval of PV landscape research, laying the foundation for its subsequent development. High-frequency keywords include climate change, solar radiation, climate, vegetation, leaf area index, model, forest, and landscape. Thus, the keywords from the first time zone indicate that related research during this period primarily focused on ecological environmental changes against the backdrop of global warming [44] and the increasing public emphasis on sustainable development [3]. For example, some researchers have suggested that by optimizing ecological indicators and models, PV landscapes can achieve a harmonious integration with natural landscapes, resulting in a win–win situation for energy production and ecological protection [45].

Second stage (2009–2020): Compared to the first stage, the number of keyword nodes in the purple outer circle with a centrality greater than 1 significantly decreased, and the overall distribution of keywords became relatively uniform. PV landscape research during this period was experiencing rapid development. High-frequency keywords included diversity, renewable energy, solar energy, performance, land use, water, biodiversity, systems, management, impacts, and community. Based on these keywords, the focus of PV landscape research in the second stage began to shift toward the systematic application of PV facilities and their impacts on human living environments. For example, in urban residential spaces, Vyas, M. [46] and others studied the use of novel solar photovoltaic trees to replace traditional urban solar power plants, which not only enhanced the aesthetic appeal of urban PV landscapes but also achieved the same power output with limited land use. In rural residential areas, PV landscape research trended towards a diversified industrial development model of “PV +”. Examples include “PV + agriculture” [47] and “PV + cultural tourism” [9]. These models, based on PV landscapes, not only promoted the development of related industries but also achieved regional industrial synergy and economic growth.

Third stage (2021–2024): In the third stage, compared to the previous two phases, the significance of current PV landscape research is relatively weaker, with the overall research in a stable development phase. High-frequency keywords include system, ecology, framework, optimization, efficiency, technology, stability, and classification. Based on these keywords, research related to PV landscapes in this phase places greater emphasis on the energy conversion efficiency and stability of PV technologies and materials. For instance, researchers such as Zhang, K. N. [41], Cha, J. [48], and Block, A. B. [49] continuously enhance the power generation efficiency and stability of PV systems through innovative research on new technologies and materials. Additionally, researchers are focusing on systematic investigations of PV landscapes, establishing a multidimensional development framework for contemporary PV landscapes. For example, Oudes, D. [12] conducted a systematic examination of different spatial configurations of contemporary multifunctional solar power plants through a comparative case analysis, creating and testing a typology of solar power plants from four dimensions: energy, economy, nature, and landscape. This work provides guidance for the future site selection, implementation, and decision-making of solar power plants.

3.9. Keyword Burst Analysis

This paper conducts a detailed exploration of the frontier dynamics in the field of PV landscape research through keyword burst analysis. Using CiteSpace’s keyword burst analysis, the twenty-five most frequently occurring terms were identified (Figure 9). Specifically, the length of the red bars in the keyword burst chart represents the duration of the keywords’ emergence, from the beginning to the end period. A greater burst intensity indicates that the frequency of the keyword is higher during a specific time period, reflecting more active related research [50].

Based on the three stages of PV landscape research development summarized from the keyword time zone analysis in Section 3.8, the following trends are observed:

In the first stage (2005–2008), the keywords mainly included vegetation, patterns, soil moisture, forest, remote sensing, energy balance, and classification. These keywords had the longest burst duration and almost completely overlapped, indicating that the research topics they represent were key areas of focus in the academic community during this period, with sustained attention and relatively stable research directions that did not shift significantly. For example, keywords such as vegetation, soil moisture, and forest emphasize that researchers in the PV landscape field began to explore the potential connections between various natural elements and solar energy. This was aimed at understanding the fundamental impacts of these natural factors on solar energy utilization, laying the groundwork for further in-depth research. Additionally, some researchers worked on integrating new technologies into PV landscape studies, which not only enriched the possibilities within this field but also facilitated interdisciplinary knowledge exchange and technological innovation, accelerating the widespread application and recognition of PV landscapes globally. For instance, the introduction of remote sensing technology [51] enabled researchers to observe and analyze large areas of PV landscape regions from a macro perspective, obtaining information about vegetation cover, soil conditions, and solar radiation distribution. Finally, research on energy balance in PV landscapes [52] helps the public understand the flow and transformation of solar energy within ecosystems. The establishment of classification [53] and radiation models [54] provides methodologies for the analysis and planning of PV landscapes. By classifying different types of PV landscapes, researchers can better understand their characteristics and applicable scenarios, predict solar radiation intensity and distribution, and provide scientific bases for the layout of PV facilities.

In the second stage (2009–2020), the keywords primarily included growth, dynamics, water, solar radiation, evapotranspiration, transport, radiation, model, urban heat island, solar cells, evolution, ecosystem services, and land surface temperature, totaling fourteen keywords. This stage had the shortest burst duration and the lowest overlap among keywords, indicating that research directions in the field of PV landscapes became more diverse and rapidly changing, with new research hotspots continuously emerging. With the continuous advancement of PV technology and the increasing societal demand for sustainable development, the term “evolution” in 2010 reflected that research related to PV landscapes had undergone a series of transformations and evolutions [18,55]. These changes often involved innovations in technology, expansions in application scenarios, and shifts in ecological impacts. Keywords like solar cells, transport, and solar radiation demonstrated researchers’ focus on the photovoltaic conversion performance of solar cells, highlighting that the transmission and conversion of solar radiation are crucial for achieving energy output in PV landscapes [56]. To enhance the efficiency of solar power generation, researchers in materials science can improve the photovoltaic conversion efficiency of solar cells through technological innovations. Meanwhile, PV engineers can optimize the design and layout of PV facilities to enhance radiation reception efficiency. For instance, some researchers study the transmission of radiation in the atmosphere, which aids in selecting appropriate installation locations and angles for PV facilities to maximize solar radiation capture [52]. The keywords “land surface temperature” from 2016 and “urban heat island” from 2017 reflect researchers’ concerns about urban issues, such as using PV landscapes to mitigate the urban heat island effect [25]. Installing PV panels on building rooftops and facades can reduce the amount of solar radiation absorbed by buildings [31].

In the third stage (2021–2024), the keywords include energy transition, buildings, PV, framework, and generation. The duration of their emergence is not yet known, but they exhibit significant overlap in their initial stages, similar to the first phase, which will not be elaborated on here. The keywords in this phase emphasize the deep integration of PV systems within the urban building sector during the energy transition process. The integration of PV systems with buildings enables self-sufficiency in energy, reduces reliance on traditional energy sources, and lowers carbon emissions, representing one of the most common and mature forms of practical application for PV landscapes [57]. Lastly, the term “framework” indicates that research in the field of PV landscapes is developing a systematic application framework [2,12]. This framework encompasses various aspects, including energy, economics, nature, landscape, technology, and legal considerations, providing comprehensive guidance for the planning, construction, and management of PV landscapes. Overall, the development of PV landscapes has progressed from initial explorations of natural factors to a focus on technological advancements and ecological values, culminating in a mature stage characterized by integrated applications and sustainable development.

4. Summary of Research Hotspots and Frontiers in Photovoltaic Landscape Studies

Through the analysis and discussion of the key words of CiteSpace, combined with the literature compiled in this paper, it is found that the research frontier of photovoltaic landscape in the past 20 years mainly focuses on the following hot spots.

4.1. Ecological Impact and Assessment

Research on the ecological impact assessment of photovoltaic systems has become a key focus in photovoltaic landscape studies. The evaluation results not only contribute to the sustainable development and construction of future photovoltaic facilities but also enhance their ecological performance. Guerin, T. F. [58] assessed the expected environmental and community risks at photovoltaic construction sites in Australia, identifying the ecological environment as one of the two most publicly concerned factors. Scognamiglio, A. [9] expanded the focus of photovoltaic landscapes to include ecological and landscape values, evaluating ecological impacts from the perspectives of land-use energy intensity and perceptual effects. Researchers like Suuronen, A. [43] and Lafitte, A. [59] evaluated the impact of photovoltaic facilities on local biodiversity, covering aspects such as animals, plants, fungi, and microorganisms, finding significant effects on species and ecosystems, particularly the degradation of natural habitats. Pringle, A. M. [60] assessed floating solar photovoltaics (WSPVs) from various angles, exploring their adaptability and impact on water source ecological environments. Chang, Y.-H. [61] evaluated the ecological effects of photovoltaic facilities in ponds, coastlines, lakes, and reservoirs, integrating them with vegetation for water purification and ecological engineering to enhance aquatic ecosystems. Additionally, some researchers have focused on the potential negative impacts of different planning and construction stages of photovoltaic landscapes, including noise, glare, water and soil pollution, and damage to archaeological sites or sensitive ecosystems. For instance, Tsoutsos, T. [62] detailed the negative environmental impacts of photovoltaic systems during construction, installation, and decommissioning, enabling decision-makers to make informed judgments and adopt optimized solutions for issues at various stages. Guerin, T. F. [58] also emphasized identifying or predicting a range of environmental and community risks during the planning stage to effectively mitigate impacts on animals, biodiversity, and infrastructure.

4.2. Deep Integration with Human Settlements

Driven by the concept of sustainable development, the integration of photovoltaic landscapes with human environments has reached an unprecedented closeness, deeply permeating various aspects of public life and intertwining with agriculture, public activities, architectural spaces, and cultural heritage. The combination of photovoltaic systems with agricultural production not only promotes the development of modern agriculture and enhances the efficient use of land resources but also broadens the application models of both photovoltaic technology and traditional agriculture, fostering their deep integration. Researcher Abidin, M. A. Z. [63] argues that the cohabitation model of photovoltaics and agricultural landscapes sets a precedent for the combination of renewable energy and agricultural production, providing a symbiotic strategy to mitigate global warming impacts and address food scarcity issues. Kim, T.-H. [64] examined the perceptions of the South Korean public regarding agricultural landscapes and photovoltaic power plants, suggesting that the expansion of renewable energy policies should balance multifunctionality and acceptability within local agricultural landscapes. Stremke, S. [65] effectively utilized renewable energy technologies by combining photovoltaic facilities, agricultural landscapes, and recreational tourism, creating a new approach to the development of photovoltaic landscapes and agriculture.

In the context of rapid new energy development, the integration of photovoltaic facilities with public activity spaces has become another focal direction and emerging trend in photovoltaic landscape development. For instance, Lindberg, O. [66] employed GIS and trend analysis to evaluate the multicriteria development and geographical assessment of solar photovoltaic parks in Sweden, identifying suitable resources and system-efficient locations for photovoltaic parks. Picchi, P. [67] used qualitative landscape structure analysis (QLSA) to establish design principles for large photovoltaic parks in the Netherlands and Germany, expanding the breadth of spatial research to include multi-criteria decision analysis and environmental impact assessment. Dorokhov, A. S. [68] integrated photovoltaic facilities into parks, gardens, and museums without disrupting the harmony of the surrounding nature and landscapes, enabling the facilities to adapt to various activity spaces. Photovoltaic facilities have become common elements in urban and rural construction, with the integration of photovoltaic systems and buildings being one of the most prominent hotspots in photovoltaic landscape research. Photovoltaic systems can not only be simply attached to building surfaces but can also be directly integrated into construction materials, enhancing both the aesthetic appeal and functional diversity of buildings, making them an essential component of green architecture and sustainable development. Ptak, T. [69] analyzed the structural framework of urban communities combined with photovoltaic systems from a geographical perspective, providing a new view for the energy framework of emerging communities. Scognamiglio, A. [52], through extensive case studies, aimed to construct a new cognitive framework for the integration of photovoltaic systems and buildings, thereby promoting the concept of zero-energy communities and anticipating potential outcomes, opportunities, and challenges of photovoltaic applications in new constructions. Dimond, K. [31] outlined the relevant factors to consider when integrating photovoltaic facilities with green roofs, comparing the environmental benefits and demands of plant roofs and photovoltaic roofs across nine aspects, and developing performance systems suitable for different projects. Research on the integration and preservation of photovoltaic facilities with cultural heritage has also garnered widespread public attention. Studies have shown that integrating photovoltaic systems into buildings with high cultural heritage value does not excessively distort or transform existing architectural envelopes and expressions. Lingfors, D. [70] explored methods for assessing photovoltaic potential in sensitive areas of natural and cultural heritage to balance the coordination between heritage protection and energy production. Lucchi, E. [71] emphasized the importance of originality and caution when addressing photovoltaic integration in heritage buildings and landscapes, noting that cultural, aesthetic, and economic interests are key issues affecting the acceptance of photovoltaics. Di Rocco, A. R. [72] analyzed potential influencing factors when integrating renewable energy with historical architectural heritage and landscapes, including aesthetics, landscape quality, community values, environmental issues, and perceptual changes. De Medici, S. [73] argued that architectural characteristics and environments could guide designers in balancing the energy generation of photovoltaic systems with the protection of architectural heritage, proposing a classification hypothesis for heritage buildings and integration standards for photovoltaic systems, thereby advancing the renaissance of architectural heritage value in Europe.

4.3. Research on Visual Aesthetic Impact and Evaluation

Research related to visual impact and assessment has become a core hotspot in current photovoltaic landscape studies. With the rapid development of global photovoltaic facilities, the negative aesthetic impacts on public visuals have been a persistent reason for public opposition to renewable energy project development [74]. Early researchers in this field, such as Tsantopoulos, G. [3] and Grêt-Regamey A. [30] have thoroughly explored the visual impacts of photovoltaic facilities on the public and their applications. Ioannidis, R. [75] and others conducted assessments of landscape impact indicators related to land use, visibility, and public perspectives on renewable energy, concluding that any form of renewable energy could have minimal visual impact under certain conditions, with hydropower having the least impact, followed by solar and wind energy. Building on this foundation, some scholars have investigated the factors contributing to the visual impacts of photovoltaic facilities on the landscape environment and developed evaluation systems and classifications for the aesthetic impacts of photovoltaic landscapes. For example, Sánchez-Pantoja, N. [76] and colleagues identified objective factors and assessment methods for the aesthetic impact of photovoltaic facilities, categorizing visual impact factors into two groups based on photovoltaic landscape characteristics: simple visual factors independent of other influences, such as color, shape, or transparency; and more complex visual factors that are integrative and ambiguous, such as visibility and coherence. Bishop, I. D. [77] demonstrated that when new objects (such as industrial or photovoltaic infrastructures) are introduced into a landscape environment, their visual impacts depend on the object itself, the surrounding environment, and the observer. Subsequent research, such as that by del Carmen Torres-Sibille, A. [7], Chiabrando, R. [78], and Kapetanakis, I. A. [2], has employed a combination of weighted sum formulas, quantitative analysis, and semantic analysis to evaluate the visual impacts of photovoltaic facilities on surrounding landscapes. They proposed four quantifiable indicators of objective aesthetic impact, including visibility, color, fractality, and consistency, to measure the differences between the initial landscape environment and the landscape after the installation of photovoltaic power stations. Additionally, Naspetti, S. [79] used a combination of quantitative and qualitative methods, employing the visual Q method to assess the visual impacts of photovoltaic systems in both urban and rural landscapes in Italy, summarizing different perspectives on the integration of photovoltaic systems in these settings. Lu, M. [32] and colleagues similarly applied the visual Q method to evaluate the visual impact of photovoltaic systems on urban landscapes in China, identifying five factors to consider in their integration, thereby promoting the development of photovoltaic landscapes in Chinese cities. Finally, as shown in

Table 6. Visual objective influencing factors of photovoltaic landscape and the related literature.

Serial	Degree	Factor	Literature
1	Simple objective influencing factors	color	[16,17,18,20,22,23,80,81]
2		dazzling light	[26,66,82,83]
3		pattern	[13,17,40,81,84]
4		Fractal degree	[14,16,28,44,83]
5	Complex objective influencing factors	visibility	[2,3,12,13,16,20,36,37,46,83]
6		Integration degree	[17,32,33,34]

, this article summarizes the relevant literature on certain visual impact factors of photovoltaic landscapes, aiming to provide a reference for future research (Table 5).

5. Conclusions and Outlook

The study utilized CiteSpace software to organize and analyze the literature published from 2005 to 2024 in the Web of Science core collection related to photovoltaic (PV) landscapes. Through an in-depth analysis of publication volume and citation trends, author collaboration networks, regional distribution, interdisciplinary overlaps, research institution and organizational networks, and keyword co-occurrence, the study summarized the research hotspots and frontier trends in PV landscapes at different stages and time points. This includes the impacts and assessment of PV facility construction on the ecological environment, deep integration of PV facilities with living environments, and the visual aesthetic impact and evaluation of PV landscapes, providing a reference for subsequent research by other researchers interested in this field. With technological advancement, policy support, and the widespread recognition of sustainable development principles, PV landscapes are experiencing unprecedented development and opportunities. Based on the above analysis and discussion, the study concludes that the future development and potential of PV landscapes will primarily focus on the following areas:

(i)

First, the technological advancements in photovoltaic (PV) materials are moving towards higher efficiency, greater flexibility, and enhanced aesthetic value, aimed at better adaptation to various landscape environments. Notable achievements include transparent or semi-transparent solar cells [85], colored PV module technologies [86], and flexible solar films [87]. These innovations are significant directions for future PV material development. The innovation and development of PV materials are crucial for advancing PV landscapes, but they also come with some pressing issues. Recycling PV materials will be a key focus in the future of PV landscape research. It is estimated that by 2050, the demand for photovoltaic modules (PVMs) will approach 70 TW. Over the past 50 years, the PV industry has developed rapidly, maintaining an annual growth rate of at least 25% to meet the demand for solar energy [88]. The installation of PV cells and modules has been growing exponentially, and the scale of future waste will be massive, posing significant challenges for both the ecological environment and economic development. Countries around the world are responding actively to the recycling of PV materials. Specific implementation regulations regarding the recycling and utilization of PV materials have been established in countries like the European Union, the United States, China, India, and Japan. These regulations play a crucial role in handling, collecting, and recycling electronic waste, including waste generated by solar PV [89]. As PV landscapes continue to develop rapidly, research and efforts in the recycling and utilization of PV waste materials will become a hot topic for the public and researchers. Additionally, minimizing environmental impacts during production and disposal processes, and developing more easily recyclable, less toxic PV materials will be a new direction for the PV material industry.

(ii)

The development of photovoltaic landscapes in future living environments will become more intelligent and interactive. Photovoltaic systems will achieve real-time monitoring, smart scheduling, and efficient demand management of energy systems through deep integration with cutting-edge technologies such as the Internet of Things (IoT), big data, and artificial intelligence. This integration will significantly enhance energy utilization efficiency; for example, smart control systems can automatically adjust the operating modes of photovoltaic landscapes in different environments to enable intelligent energy management. Currently, photovoltaic landscapes are gradually evolving towards personalization, and creating interactive and engaging photovoltaic landscapes will be an important aspect of future development. For instance, incorporating photovoltaic interactive seating and photovoltaic fountains in public spaces can enhance public engagement and experience through features like automatic sensing and activation.

(iii)

Policies and regulations play a crucial role in balancing the ecological, social, and economic factors in supporting PV landscapes. In terms of ecological protection, strict regulations limit PV project construction in ecologically fragile areas, nature reserves, and other sensitive zones to prevent damage to the environment. Regarding social impact, policies and regulations focus on increasing public awareness and acceptance of PV landscapes through public education and outreach, thus enhancing environmental consciousness and participation. Economically, policies and regulations enhance the feasibility of PV landscapes by offering various incentives, such as investment subsidies, preferential loans, etc., which reduce project risks and costs, and improve the return on investment. The laws, regulations, and guiding policies that promote the development of photovoltaic landscapes still have a certain lag at present [2]. Due to the relatively large number of disciplines and technologies involved in research and practice in the field of photovoltaic landscapes, how to balance its relationship with land use, ecological protection, cultural heritage protection, perceptual impact, aesthetic impact, and other fields has become a difficult problem that legislative and decision-making departments of various countries must face and is not easy to solve in the short term. Some researchers have proposed integration rules and standards applicable between photovoltaic systems and landscape environments, but overall, they are still in the exploration and suggestion stage for both and have not formed a broad consensus and effective constraints or constraints. Therefore, future legal regulations and policy guidance for photovoltaic landscapes are a key direction that researchers and decision-makers need to pay attention to. In addition, the development time of photovoltaic landscape field is relatively short, but it involves a wide range of professional knowledge, and there is a great demand for professional talents. It is necessary to establish a specialized training mechanism and training system on a global scale to cultivate composite talents who not only understand the principles and material characteristics of photovoltaic technology, but also have expertise in landscape design aesthetics, environmental science, and other aspects.

Finally, this study has certain limitations and shortcomings. For instance, this paper aims to explore the research hotspots and frontier trends in the field of photovoltaic landscapes internationally, so the conclusions drawn are based on the WOS core database, which may lead to some data omissions. This could inadvertently exclude relevant research published in databases not indexed by WoS, such as the core paper data from the CNKI database in China, which are not covered in this discussion. Additionally, there is a degree of subjectivity and limitations in the data selection and software operation within CiteSpace; various quantitative analyses may not fully capture the complexities of qualitative aspects and interdisciplinary interactions in the field of photovoltaic landscapes. Therefore, this paper attempts to supplement these gaps through the extensive literature review.