Managing and Optimizing Hybrid Distributed Energy Systems: A Bibliometric Mapping of Current Knowledge and Strategies

Abstract

Hybrid renewable energy systems (HRESs) play a key role in the decarbonization of many sectors of the economy and, thus, in achieving ambitious climate goals. Due to the complexity of the issues and the impact of many factors on the efficiency of these systems, it is necessary to ensure that they are properly designed, managed, and optimized. Many techniques and methods are used to achieve an optimal multi-source energy system. In recent years, there has been a growing interest in HRESs. Taking this into account, a comprehensive review of scientific literature was carried out, based on bibliometric analysis. Professional software was used for the research: Bibliometrix and VOSviewer. The bibliographic database was created using the international scientific platform Web of Science. The evolution of research trends and the dynamic development of research on the management and optimization of HRESs in the years 2010–2024 were presented. The results of the analysis confirmed the growing importance of integrated energy management systems and optimization strategies in the context of the global energy transformation. The analysis also indicated that, despite the growing interest in this topic, further development of advanced energy management strategies and optimization methods is necessary to effectively use renewable energy sources and enhance the stability of HRESs.

1. Introduction

The well-being of society, its further development and its general functioning depend on the provision of reliable, safe, sustainable and affordable energy. The continuous increase in energy demand leads to the widespread use of fossil fuels, which in many regions of the world are still the main source of energy, contributing to significant environmental pollution. Over the past 20 years, nearly three-quarters of human-caused emissions have come from burning fossil fuels [1]. To minimize the effects of excessive fossil fuels exploitation, it is necessary to transform the energy sector toward near-zero-emission energy production. The need to achieve this goal has been reflected in many legal acts, including the European Union development strategy “European Green Deal” aimed at creating the world’s first climate-neutral economy in 2050 [2]. The plan for such a drastic reduction in greenhouse gas emissions has serious implications for energy systems, which were neither designed nor modernized to meet these challenges. As emphasized by the European Commission, energy networks are aging and need billions of euros in investments in order to adapt them to new requirements [3].

A solution to cover the continuously growing energy demand and to reduce dependence on conventional fuels is the implementation of renewable energy systems [4,5], such as photovoltaic panels [6], wind turbines [7], biomass [8], geothermal energy [9] and wastewater heat recovery [10,11,12]. However, to maximize the benefits of renewable energy, it is necessary to hybridize energy sources to overcome their stochastic and intermittent nature [13,14]. On the one hand, implementing HRESs is essential; on the other hand, integrating them with outdated electrical networks often leads to technical and operational issues, such as overload, voltage surges, and an increased risk of power outages [15,16]. This is mainly due to the variable energy production dependent on weather conditions, which may consequently lead to periodic shortages or surpluses. Instability of the energy supply, the high costs of expanding local distribution networks, and the exhaustion of connection capacities are the main challenges that arise when managing HRESs. Basing the energy mix on renewable sources requires the development of energy storage systems (ESSs) and appropriate demand management, leading to improved flexibility of the energy system and an increased capacity to balance demand and supply [17,18,19]. A promising solution is an integrated system of multiple energy storages (electrochemical, thermal and hydrogen), which can improve the stability of HRESs not only on a daily basis, but especially on a seasonal scale [20,21].

Such systems have attracted the attention of scientists worldwide for many years. However, the last decade has seen a significant intensification of research on HRESs, which is due to technological progress and international legal acts obliging individual countries to reduce CO₂ emissions. Taking into account available energy sources and technical solutions for energy production and storage, HRESs can be designed as centralized/decentralized, off-grid (autonomous)/on-grid and with/without energy storage systems [22,23,24]. Each of the systems has its advantages and disadvantages, and its design depends on local climatic conditions and the technical, financial and environmental criteria that are set for it.

Considering the numerous factors affecting the efficiency of these systems requires proper planning, management and optimization of energy systems. For many years, researchers have been using various optimization approaches, the main goal of which is to design a technically and financially optimal HRES, which is friendly to the environment and society. An important stage in designing a renewable energy system is the appropriate selection of the sizes of its individual elements. Undersizing or oversizing HRESs can lead to serious operational problems and ultimately reduce its efficiency. HRESs can be dimensioned using traditional methods or various types of software tools. The traditional methods include the analytical method, the iterative method, the probabilistic method and artificial intelligence. Optimization can also be performed using various approaches: classical methods (e.g., Linear Programming, Nonlinear Programming, dynamic programming, the Newton Method, the Gradient Method, and Quadratic Programming), artificial intelligence-based techniques (e.g., Artificial Neural Networks and meta-heuristic algorithms), fuzzy logic, and hybrid methods [25]. Currently, due to advances in computational technologies, software methods which significantly accelerate and facilitate the process of dimensioning and optimization of multi-source energy systems are becoming increasingly popular. Many commercial programs are available, such as HOMER (Hybrid Optimization Model for Electric Renewable), iHOGA (Hybrid Optimization by Genetic Algorithm), RETScreen, TRNSYS, and INSEL (Integrated Simulation Environment Language) [26,27]. Depending on the optimization goals, the authors focused mainly on obtaining optimal financial parameters of HRESs (the levelized cost of energy LCOE, net present cost NPC, simple payback period SPP, internal rate of return IRR) and/or maximizing the reduction in the amount of pollutants emitted into the environment, mainly CO₂ [4,28,29].

However, the key to ensuring a continuous and stable supply of energy to end-users is effective and intelligent management of energy systems (EMSs). This is especially important in HRESs based on solar and wind energy, the production of which is unstable and irregular. In order to control, coordinate and save energy in renewable energy systems, various techniques are used, both traditional and smart [30]. Regardless of the technique used, the primary objectives of HRESs management are to ensure system stability (through voltage and frequency control), provide system protection (via power flow monitoring), and achieve power balancing (by operating the system as efficiently as possible) [25,31,32]. A well-designed EMS maximizes the use of renewable energy sources, minimizes the unit cost of energy, extends the life of the system and protects its components from damage [33]. Energy management models for standalone and grid-connected systems are mainly based on the Linear Programming Approach and Artificial Programming Approach, including Fuzzy Logic Controller. In the case of smart grid, SCADA and ZigBee are usually implemented [25].

Over the past decade, many studies have been published which apply a range of approaches, strategies, models, and techniques aimed at optimizing, controlling and managing hybrid renewable energy systems. The large number of different solutions and related studies means that the number of articles increases significantly year by year. This highlights the need to update the literature reviews conducted so far in this area and to examine current global trends in the energy sector. Moreover, there are few studies focusing on a comprehensive bibliometric analysis covering the issues of modeling, optimization and management of HRESs, including energy storage. A comprehensive review of the literature covering many aspects of HRESs design and operation was presented in [34], but it concerned only off-grid systems. Many literature reviews on these systems were conducted in a much narrower scope, in which the authors mainly focused only on selected aspects or configurations of energy systems [35,36,37].

Table 1. Review of bibliometric publications selected from the Web of Science regarding distributed energy systems.

Title	Year	Citation	References
A Survey and Evaluation of the Potentials of Distributed Ledger Technology for Peer-to-Peer Transactive Energy Exchanges in Local Energy Markets [38]	2019	256	84
A Survey of Energy Management in Interconnected Multi-Microgrids [39]	2019	140	92
Home Energy Management System Concepts, Configurations, and Technologies for the Smart Grid [40]	2020	93	118
Overview of the Optimal Smart Energy Coordination for Microgrid Applications [41]	2019	61	274
Optimization Models under Uncertainty in Distributed Generation Systems: A Review [42]	2022	12	224
Microgrid Energy Management with Energy Storage Systems: A Review [43]	2023	34	163
Review of Computational Intelligence Approaches for Microgrid Energy Management [44]	2024	6	226
Energy-Sharing Economy with Renewable Integration and Management in Communities—a State-of-the-Art Review [45]	2024	1	124
A Comprehensive Review of Sizing and Energy Management Strategies for Optimal Planning of Microgrids with PV and Other Renewable Integration [46]	2024	2	146

presents a list of the 5 most frequently cited review articles from the analyzed database. In most cases, bibliometric analysis, which is a very effective and useful tool in exploring current trends and research directions, was not used.

Taking the above into account, research was conducted to analyze the bibliometric scientific literature on the broadly understood optimization and management of distributed energy systems integrated with energy storage, in which the main energy sources are photovoltaic installations and wind turbines. This article presents publications on the modeling and optimization of HRESs, energy management strategies, analysis of their impact on infrastructure and the environment, and the economic profitability of implementing these solutions.

The novelty of this paper lies in conducting an in-depth bibliometric analysis focused on the management and optimization of hybrid renewable energy systems. Unlike previous studies, this research not only identifies key technological and research development directions but also analyzes the evolution from traditional energy management methods toward modern digital and AI-driven solutions. Additionally, it highlights emerging patterns of international collaboration and draws attention to geopolitical factors that may influence future research trends in this field.

The structure of the article is as follows: Section 2 describes the methodology used in the bibliometric analysis; Section 3 presents the results and a discussion of the research results; Section 4 summarizes the research and presents the most important conclusions.

2. Materials and Methods

A literature review on the management and optimization of hybrid renewable energy systems, with a focus on systems based primarily on photovoltaic (PV) and wind turbine (WT) installations, was conducted using bibliometric analysis. This method is often employed to examine and evaluate large volumes of scientific literature. It enables the identification of research trends, emerging areas of interest and existing knowledge gaps in a given discipline [47,48].

To ensure a comprehensive and reproducible analysis, a dedicated bibliographic dataset was created using the Web of Science (WoS) platform. Bibliographic records were retrieved specifically from the Science Citation Index Expanded (SCI-EXPANDED, covering the years 2012–2024) and the Emerging Sources Citation Index (ESCI, covering the years 2010–2024), which together cover a wide range of peer-reviewed journals and high-quality sources. These sub-databases were selected based on expert recommendations to ensure completeness, transparency, and scientific rigor [49].

The research methodology consisted of four main stages, illustrated in Figure 1. In the first stage, the bibliographic source was selected. In the second stage, relevant keywords such as “hybrid renewable energy systems”, “optimization”, and “management” were defined and used to perform the initial search, resulting in a database comprising 904 publications. During the third stage, the content and metadata of these records were reviewed to classify each publication into one of six thematic categories: (1) distributed energy systems, (2) power engineering, (3) smart grids, (4) electric vehicles, (5) energy security, and (6) economics. Publications that did not match any of these categories were placed in a separate group labeled as irrelevant topics. Filtering and classification reduced the dataset to 416 relevant entries. In the final stage, the filtered database was analyzed using specialized bibliometric software tools.

The search was conducted in the Web of Science Core Collection using a structured query with Boolean operators (AND and OR) and wildcard symbols, such as the asterisk, to account for variations in word forms. The query was applied to three fields: title (TI), abstract (AB), and author keywords (AK). To ensure thematic relevance, the results were further refined by subject areas including Energy Fuels, electrical engineering, Sustainable Technology, Environmental Engineering, Software Engineering, and artificial intelligence. The query formulation, illustrated in Figure 1, was iteratively refined to ensure an optimal balance between precision and recall, and it followed established principles of bibliometric analysis.

From over one million initial results, specifically 1,007,214 records, the dataset was narrowed down through the use of field filters and manual screening. The final set consisted of 416 publications that met the defined criteria. Only peer-reviewed journal articles and conference papers published in English between 2010 and 2024 were included. Records lacking essential metadata, such as author affiliations or keywords, were excluded to ensure the quality and integrity of the dataset.

The final collection, summarized in Figure 2, included 409 articles and 7 conference papers. These works were authored by 1647 individuals and published across 82 different sources. Bibliometric analysis was conducted using the Bibliometrix R package (version 4.4.3) and VOSviewer (version 1.6.20). The scope of the analysis included co-occurrence mapping of author keywords, co-authorship network analysis, institutional collaboration patterns, thematic clustering, and the evolution of research topics over time. For clarity in the generated visualizations, only keywords that appeared at least three times were included. Linkages between nodes were weighted using the association strength method.

Bibliometric analysis examines the existence of relationships between authors, keywords, journals, citations and other data [47]. Exploring and analyzing such large amounts of bibliometric data requires the use of advanced techniques to speed up and facilitate this process. There are many software tools which support bibliometric analysis, but Bibliometrix [50] and VOSviewer [51] are the most commonly used programs. Bibliometrix is a valuable tool for researchers requiring advanced methods for science mapping and bibliometric analysis. Bibliometrix R-package provides a set of tools for quantitative research in bibliometrics and scientometrics. It is written in R, which is an open-source environment and ecosystem [50]. VOSviewer, on the other hand, is a free computer program designed to construct and view bibliometric maps. Unlike other computer programs used for bibliometric mapping, VOSviewer pays special attention to the graphical representation of bibliometric maps [51]. In this paper, both VOSviewer 1.6.20 and Bibliometrix 4.4.3 are implemented to perform bibliometric analysis in the management and optimization of HRESs, where the main energy sources are PV and WT. The generation of bibliometric meadow maps is based on applying the equation that defines the association strength [52]. The association strength s_ij is a measure of the proximity of elements appearing in the map and is calculated according to Equation (1).

$$s_{ij}={\displaystyle \frac{c_{ij}}{w_i{w}_j}}$$

(1)

where c_ij represents the number of co-occurrences of items i and j, w_i is the total number of occurrences of items i, and w_j is the total number of occurrences of item j.

3. Results

The dynamic development of HRESs based on distributed energy sources results from the need to improve energy efficiency and to integrate renewable technologies. The optimal management of such systems is a challenge both technically and operationally, requiring advanced planning strategies and modern control methods. In the long term, their development can contribute to increasing the stability of the energy supply and reducing operating costs compared to traditional solutions. This study conducted a bibliometric analysis of existing studies on the management and optimization of hybrid renewable energy systems. The main research trends, key strategies used in this field and areas requiring further exploration were identified. The literature review also helps to identify research gaps and potential development directions in the implementation of intelligent control systems and energy storage methods.

There is a growing interest in hybrid systems, which enable efficient use of local energy resources and minimize losses related to energy generation and distribution. In the context of global challenges, such as energy market instability and the need to reduce carbon dioxide emissions, it is crucial to implement strategies that increase energy independence and improve the stability of the energy supply. Figure 3 shows the number of publications and the number of citations in the years 2010–2024 relating to the management and optimization of hybrid renewable energy systems. The blue bars represent the number of citations, while the orange bars indicate the number of new scientific publications in a given year. Trend analysis allows the assessment of the development of research on HRESs and the identification of key periods with the greatest scientific impact.

In the years 2010–2017, the number of publications remained relatively low (1 to 14 works per year), which suggests that the subject of HRESs was only just beginning to gain importance. At the same time, the number of citations was relatively stable, with the exception of 2013 and 2015, when it increased to 968, which may indicate the presence of influential works that became a reference point for further research.

Since 2018, there has been a clear increase in interest in the topic, with the number of publications increasing to 26 and citations rising to 1127. This trend may be the result of the growing importance of technologies related to renewable energy sources and their integration with energy management and storage systems. The largest jump occurred in 2019, when the number of citations reached 1709 and the number of publications increased to 46. This significant increase can be attributed not only to the growing importance of renewable energy technologies but also to structural changes within the Web of Science Core Collection (WoSCC). As noted in [53], the expansion of WoSCC, including the addition of new journals and the broadening of existing indices such as the Emerging Sources Citation Index (ESCI) and the Science Citation Index Expanded (SCIE), has contributed to the overall increase in indexed publications. This expansion has affected various research fields, including energy and electrical engineering, which are directly related to the management and optimization of hybrid renewable energy systems (HRESs). Furthermore, the introduction of Journal Impact Factors (JIFs) for all journals in WoSCC from 2023 onwards has further increased the visibility and citation potential of publications. In the following years, the number of citations remained high (1466 in 2021 and 1062 in 2022), suggesting that earlier research had a significant impact on the development of this field.

In 2021–2023, the number of publications remained high (53–74 works per year), indicating the continued development of research on the optimization and management of hybrid renewable energy systems. In 2023, the publication output remained high (74 works), but the number of citations dropped to 754, which may be attributed to a natural delay in the accumulation of citations for newer works.

In 2024, the number of publications reached its highest recorded number (76), while the number of citations (279) was significantly lower, which was due to the short exposure time of the latest studies. These data suggest that interest in HRESs management and optimization remains strong, and that the growing number of publications reflects the maturity and dynamic development of this research area.

In the analyzed database, the most frequently cited article was “Robust Energy Management for Microgrids with High-Penetration Renewables” by Zhang et al. [54] with 592 citations.

The authors proposed a decentralized framework for robust energy management in microgrids with a high penetration of renewables. Their approach minimizes operational costs while accounting for uncertainties in renewable generation and ensures power balance through energy trading with the main grid. The second most cited article was by the article by Morstyn et al. [55] entitled “Multiclass Energy Management for Peer-to-Peer Energy Trading Driven by Prosumer Preferences”, in which the authors presented a peer-to-peer energy trading platform that considers prosumer preferences. Prediction and optimization models were used to reduce operating costs and better adapt to users’ needs. The third most cited publication was by the publication by Arcos-Aviles et al. [56] entitled “Fuzzy Logic-Based Energy Management System Design for Residential Grid-Connected Microgrids”, describing an energy management system based on fuzzy logic. This approach eliminated the need for complex mathematical models while offering high functionality.

Table 2. Articles with the highest number of citations in the years 2010–2024.

Authors	Title	Journal	Year of Publication	Citations	Impact Factor	JIF
Zhang et al. [54]	Robust Energy Management for Microgrids with High-Penetration Renewables	IEEE Transactions on Sustainable Energy	2013	592	8.6	Q1
Morstyn et al. [55]	Multiclass Energy Management for Peer-to-Peer Energy Trading Driven by Prosumer Preferences	IEEE Transactions on Power Systems	2019	358	6.5	Q1
Arcos-Aviles et al. [56]	Fuzzy Logic-Based Energy Management System Design for Residential Grid-Connected Microgrids	IEEE Transactions on Smart Grid	2018	216	8.6	Q1
Wu et al. [57]	Demand side management of photovoltaic-battery hybrid system	Applied Energy	2015	212	10.1	Q1
Li et al. [58]	Energy Management and Operational Control Methods for Grid Battery Energy Storage Systems	CSEE Journal of Power and Energy Systems	2021	208	6.9	Q1
Wu et al. [59]	Autonomous Active Power Control for Islanded AC Microgrids With Photovoltaic Generation and Energy Storage System	IEEE Transactions on Energy Conversion	2014	191	5.0	Q1
Talari et al. [60]	Stochastic-based scheduling of the microgrid operation including wind turbines, photovoltaic cells, energy storages and responsive loads	IET Generation Transmission & Distribution	2015	182	2.0	Q3
Krishan et al. [61]	An updated review of energy storage systems: Classification and applications in distributed generation power systems incorporating renewable energy resources	International Journal of Energy Research	2018	173	4.3	Q1
Hosseinzadeh et al. [62]	Power management of an isolated hybrid AC/DC micro-grid with fuzzy control of battery banks	IET Renewable Power Generation	2015	170	2.6	Q2
Nikmehr et al. [63]	Optimal operation of distributed generations in micro-grids under uncertainties in load and renewable power generation using heuristic algorithm	IET Renewable Power Generation	2015	152	2.6	Q2

lists the articles with the highest number of citations, each containing 150 or more citations. The selected works focus on various aspects of energy management in microgrids, including optimization of power system scheduling, control of renewable energy generation, and blockchain technologies in energy transaction models. The research results confirm that advanced energy control and management methods can enhance system stability, improve operational efficiency, and support the integration of distributed energy sources.

Figure 4 shows the keyword co-occurrence network in publications on the management and optimization of hybrid renewable energy systems (HRESs). The graph was generated using the VOSviewer software based on data from the Web of Science, considering both author keywords and keywords plus—keywords assigned by the authors of the publications and terms generated automatically based on the titles of cited sources, respectively.

The size of the nodes corresponds to the frequency of occurrence of a given term, while the thickness and length of the connections reflect the strength of the relationships between individual keywords. The network structure enables the identification of dominant research areas and the relationships between key concepts. The closer two nodes are to each other, the more frequently the analyzed terms co-occurred in the publications. The thickness of the lines connecting the nodes indicates the intensity of these relationships, allowing for the determination of the main research trends in the field of management and optimization of hybrid renewable energy systems.

The analysis of the keyword co-occurrence network revealed four distinct thematic clusters, reflecting the main research directions related to the management and optimization of HRESs. Due to the large number of analyzed keywords, only those that appeared in at least ten publications were included. Individual clusters were created based on thematic coherence, determined by the number of connections between specific terms, which allowed for grouping of the most closely related issues.

The red cluster includes issues related to distributed generation, demand management, as well as variability and risk in power systems. It focuses on aspects of network operation and system flexibility. The green cluster focuses on optimization, power balancing, and integration of renewable energy sources, emphasizing the importance of efficient design and management of energy systems. The yellow cluster addresses technological and economic aspects of hybrid systems, such as operational reliability, cost analysis and the role of energy storage in optimizing energy management, ensuring appropriate system performance and stability. The blue cluster covers microgrids, P2P systems and digital technologies for energy management. It refers to the implementation of modern solutions related to automation and intelligent algorithms. The network structure enables the identification of key research areas and the mutual dependencies between them, which is the basis for further analyses in the field of HRESs management.

The largest cluster, marked in red in the co-occurrence network, is described in

Table 3. The most frequently occurring keywords in the identified clusters.

Keyword	Cluster	Occurrences	Average Citations	Links
management	1	56	27.82	52
operation	1	53	7.75	51
demand response	1	47	21.31	54
generation	1	45	19.07	54
distributed power generation	1	37	28.27	48
model	1	37	16.33	47
uncertainty	1	31	30.36	45
distributed energy resources	1	28	14.43	47
strategy	1	28	10.00	45
energy	1	27	39.59	42
distributed networks	1	22	7.58	44
electric vehicles	1	22	9.72	41
wind	1	20	55.50	43
energy management systems	1	18	6.12	35
blockchain	1	16	34.50	29
dispatch	1	15	84.00	37
optimisation	1	15	12.94	35
reliability	1	13	7.66	35
demand	1	12	54.16	29
framework	1	12	7.60	29
virtual power plant	1	12	7.72	23
coordination	1	11	16.00	32
optimization	2	122	28.88	56
system	2	77	43.26	54
microgrid	2	57	31.08	51
distributed generation	2	40	30.03	51
smart grid	2	36	34.14	47
design	2	34	19.50	52
energy management system	2	34	20.83	49
algorithm	2	27	47.71	43
demand side management	2	22	43.85	45
demand-side management	2	21	20.42	37
battery	2	17	34.60	32
energy storage system	2	15	34.57	39
renewable energy resources	2	10	36.33	33
solar energy	2	10	47.60	31
technologies	2	10	6.50	31
energy management	3	88	34.98	57
renewable energy	3	63	14.17	53
storage	3	57	38.67	56
microgrids	3	52	35.82	50
systems	3	50	18.75	50
ac	3	12	3.00	41
distributed optimization	3	11	17.18	22
electricity	3	11	19.00	32
peer-to-peer	3	11	63.88	22
power management	3	10	5.50	26
pv	3	10	13.00	37
renewable energy sources	4	66	20.21	56
energy storage	4	34	30.58	52
integration	4	24	4.50	42
power	4	24	35.23	47
smart grids	4	22	16.52	42
batteries	4	15	17.68	36
costs	4	17	17.05	38
solar	4	11	25.20	34
flexibility	4	10	10.83	29
simulation	4	10	12.00	27

as cluster 1, where the most frequent keyword was management (56 occurrences). The most frequently appearing keywords for clusters 2, 3, and 4 were “optimization” (122 occurrences, green), “energy management” (88 occurrences, blue), “renewable energy sources” (66 occurrences, yellow), respectively. The terms “demand-side management” and “demand side management” are conceptually equivalent and refer to the same energy strategy.

The analysis also examined the distribution of the number of publications and directions of international cooperation in the field of management and optimization of hybrid renewable energy systems between 2010 and 2024.

Table 4. Number of research studies and scientific cooperations between individual countries in the field of management and optimization of hybrid renewable energy systems in 2010–2024.

From	To	Total Number of Publications
China	USA	16
China	Denmark	11
Iran	Finland	8
Pakistan	Saudi Arabia	8
China	Pakistan	6
Iran	Denmark	6
China	United Kingdom	5
Iran	Italy	5
Italy	Denmark	5
Spain	Colombia	5
United Kingdom	Saudi Arabia	5
China	Saudi Arabia	5

presents the results of the review, taking into account the number of publications and the most frequent co-authorship connections between countries. This enables the identification of dominant regions and key partners in research on these systems.

Figure 5 illustrates the global distribution of publications and the main routes of scientific exchange. The intensity of the colors reflects the number of publications in each country, while the thickness of the connections between countries indicates the strength of their cooperation. The pink lines represent the links based on the number of joint publications, illustrating the main routes of scientific exchange. The largest number of studies in this field were conducted in China (187), confirming its dominant role in research on modern energy systems. Iran (68), the United States (65), India (55), and Italy (50) also showed high activity. China and the US are key centers of research and cooperation, not only maintaining intensive scientific links with other countries, but also demonstrating strong bilateral cooperation in the field of hybrid renewable energy systems. Denmark and Saudi Arabia stand out for their active presence in the international cooperation network, underlining their growing importance in this field. In contrast, South America, Africa and Oceania are characterized by lower levels of international cooperation, indicating potential for further development and strengthening of global scientific collaboration.

The next step in the analysis involved identifying scientific journals that most frequently publish articles on the management and optimization of hybrid renewable energy systems. Figure 6 shows the number of publications in the five most productive scientific journals between 2010 and 2024.

The largest number of articles in this field was published in Energies, which has consistently ranked first in the number of publications on this topic over the past decade. This journal has shown a significant increase in interest in the subject of HRESs since 2015, confirming its role as a key source of literature in this field. Second place is occupied by IEEE Access, which has significantly increased its number of publications in recent years, becoming one of the leading journals dealing with this subject.

The next few positions are occupied by IEEE Transactions on Smart Grid, IET Renewable Power Generation and IET Generation Transmission & Distribution, which play a significant role in publications on technological aspects of energy management in hybrid renewable energy systems.

The journals not included in this list published fewer than five articles on the analyzed topic. The analysis also included the scientific institutions that made the greatest contributions to research on the management and optimization of hybrid renewable energy systems. Figure 7 shows the number of publications affiliated with the seven leading research units in the years 2010–2024.

The largest number of publications in this field was recorded by Aalborg University (Denmark) (25), which has shown a dynamic annual increase in the number of scientific papers since 2017, reaching its highest level in 2024. Islamic Azad University (Iran) (19) and the Egyptian Knowledge Bank (Egypt) (13) occupy the next few places, showing a systematic increase in research activity since 2019.

A significant contribution was also made by the University of Johannesburg (South Africa) (12), which noted an increase in the number of publications in 2016, indicating a growing interest in the subject of HRESs in Africa. Zhejang University (China) (9), Centre National de la Recherche Scientifique—CNRS (France) (9) and Aalto University (Finland) (9) noted significant activity after 2019.

Institutions not included in this list published fewer than nine articles on the analyzed topic. The absence of leading academic centres from countries which dominated in terms of the number of publications suggests that research on hybrid renewable energy systems in these countries is not concentrated in individual leading institutions but is dispersed among numerous universities and research institutions.

Using the Bibliometrix tool, a thematic evolution diagram was developed based on the authors’ keywords, which illustrates the dynamic changes in research on the management and optimization of HRESs from 2010 to 2024. The analysis revealed clear stages of development of this field, which reflect both the evolution of research topics and the progressive integration of new technologies in the context of energy solutions. These relationships are illustrated in Figure 8.

In the period 2010–2014, research focused on the basic issues of energy management, energy storage and the use of renewable energy sources laying the foundation for the further development of hybrid renewable energy systems.

The period 2015–2017 brought about a significant intensification of topics related to distributed energy generation, microgrids and demand-side management, which indicates the growing role of decentralization of energy systems and the adaptation of new solutions to increase flexibility and energy efficiency.

In 2018–2019, there was an intensification of research on fuel cells and further integration of renewable energy sources with energy storage systems, which have become key elements in the management and stabilization of hybrid systems.

In the period 2020–2021, there was a focus on the development of advanced analytical methods, such as dynamic programming and demand response strategies. These modern approaches enabled more precise and efficient energy management under changing operating conditions, system flexibility and adaptability.

From 2022 to 2024, research focused on further system optimization, including the implementation of blockchain technology in the context of energy management and the development of smart grids. An important research area remained the integration of renewable energy sources, with an emphasis on their integration with digital technologies supporting management and optimization of these systems.

The thematic evolution, shown in the diagram, indicates a clear transition from the original, basic concepts of energy management towards complex, technologically integrated, digitally supported systems that respond to the growing challenges of modern energy networks.

4. Conclusions

The conducted bibliometric analysis demonstrated dynamic development of research on management and optimization of distributed energy systems between 2010 and 2024. Key research directions, dominant scientific institutions and main centers of international cooperation in this field were identified. The results confirm the growing importance of integrated energy management systems and optimization strategies in the context of global energy transformation.

Analysis of keyword co-occurrence reveals the existence of four main thematic groups. The first one focuses on issues related to distributed energy generation, demand management, and variability and risk in power systems. This group emphasizes the aspects of network operation and system flexibility. The second group focuses on optimization, power balancing, and integration of renewable energy sources, emphasizing effective design and management of energy systems. The third thematic group includes technological and economic aspects of hybrid systems, such as reliability, cost analysis, and the role of energy storage in optimizing energy management, ensuring system efficiency and stability. The last group refers to microgrids, P2P systems and modern energy management technologies, such as automation and intelligent algorithms that support efficient operation of systems.

Research in this field is scattered across many countries, with dominant publications in China, Iran and the US. China and the United States stand out for their strong international cooperation, suggesting their dominant role in shaping the future of renewable energy systems. However, recent studies indicate that scientific collaboration between China and the US has been weakening, highlighting an ongoing decoupling between these countries [64], which could influence future cooperation patterns. Although Denmark and Saudi Arabia have also made important contributions, countries in South America, Africa and Oceania are characterized by less research activity, which creates room for increased cooperation in these regions.

Most of the publications in this field are published in the Energies journal, which has maintained its leading position for years. Since 2015, there has been a clear increase in interest in the topic of distributed energy systems, making it a key source of knowledge in this field. IEEE Access is in second place, significantly increasing the number of publications in recent years, making it one of the main journals in this field. Other important titles include IEEE Transactions on Smart Grid, IET Renewable Power Generation and IET Generation Transmission & Distribution, which focus on technological aspects of energy management in hybrid systems. In the institutional analysis, it was noted that key research institutions such as Aalborg University (Denmark), Islamic Azad University (Iran) and Egyptian Knowledge Bank (Egypt) have a significant impact on the development of this subject. The lack of a clear concentration of research in single academic centers in dominant countries indicates a broad interest in the management and optimization of distributed energy systems in various scientific institutions around the world.

The thematic evolution of research on distributed energy systems reflects a shift in interest from basic energy management issues towards integrated systems requiring modern digital technologies such as blockchain, artificial intelligence and smart grids. These changes respond to the growing need to adapt energy systems to changing conditions. Another important direction involves enhancing the operational efficiency and long-term reliability of HRESs, supported by advanced optimization techniques.

This analysis highlights several ongoing challenges in the field of hybrid renewable energy systems, including the lack of standardized optimization methodologies, the complexity of integrating distributed energy sources, and the variability of weather-dependent data. Future research should focus on developing hybrid optimization methods, enhancing system interoperability, and leveraging artificial intelligence technologies to improve energy system management. Expanding bibliometric analyses to include additional databases could also provide a more comprehensive view of global research trends [65].

Despite the comprehensive nature of this analysis, it is important to recognize certain limitations. The use of the Web of Science Core Collection as the sole data source may introduce language and regional biases, as well as potential gaps in metadata such as missing keywords or incomplete author affiliations. These factors should be considered when interpreting the findings of this study [66].