Decentralized Renewable-Energy Desalination: Emerging Trends and Global Research Frontiers—A Comprehensive Bibliometric Review

Abstract

Decentralized desalination systems driven by renewable energy sources have surfaced as a feasible way to alleviate water scarcity in arid and rural areas. This bibliometric study aims to clarify the research trends, conceptual frameworks, and cooperative dynamics in the scientific literature on decentralized renewable-powered desalination techniques. Using a thorough search approach, 1354 papers were found. Duplicates, thematically unrelated works, and entries with poor information were removed using the PRISMA 2020 framework. A selected 832 relevant papers from a filtered dataset were chosen for in-depth analysis. Quantitative measures were obtained by means of Bibliometrix; network visualisation was obtained by means of VOSviewer (version 1.6.19) and covered co-authorship, keyword co-occurrence, and citation structures. Over the previous 20 years, the data show a steady rise in academic production, especially in the fields of environmental science, renewable energy engineering, and water treatment technologies. Author keyword co-occurrence mapping revealed strong theme clusters centred on solar stills, thermoelectric modules, reverse osmosis, and off-grid systems. Emphasizing current research paths and emerging subject borders, this paper clarifies the intellectual and social structure of the field. The outcomes are expected to help policy creation, cooperative projects, and strategic planning meant to hasten innovation in sustainable and decentralized water desalination.

1. Introduction

Access to secure and sufficient freshwater represents a significant global challenge of the 21st century. The United Nations World Water Development Report states that more than 2.3 billion people already live in water-stressed countries, a number that is expected to increase four-fold by 2050 if effective and sustainable strategies are not adopted [1]. In arid and semi-arid regions, like the Middle East, North Africa, and specific parts of South America, conventional freshwater resources are becoming insufficient, which is prompting governments and scholars to investigate alternate sources like seawater desalination [2,3].

Desalination offers a technological remedy for freshwater scarcity, particularly for coastal and off-grid communities [4]. The International Desalination Association (IDRA) reported that, by 2021, over 300 million people globally relied—at least partially—on desalinated water, the total operational capacity of which exceeds 95 million cubic meters per day [5]. Traditional desalination techniques, such as reverse osmosis (RO), multi-stage flash (MSF), and multi-effect distillation (MED), are recognized for their considerable energy usage and environmental impact. Desalination currently consumes about 75 TWh annually, leading to the emission of more than 76 million tons of CO₂ per year. These data underscore the pressing need to transition to more sustainable and decentralized alternatives [6].

Decentralized renewable-powered desalination (DRPD) systems have emerged as efficient and adaptable solutions for remote and energy-scarce regions. These systems employ renewable energy sources—namely solar, wind, and biomass—to power small- to medium-sized desalination units. They provide autonomy from centralized networks while significantly reducing carbon emissions [7,8]. The versatility of DRPD makes it especially attractive for humanitarian applications and community-level deployment in areas with high solar irradiation and insufficient infrastructure [9].

Recent advances in renewable energy integration and desalination technology have made DRPD systems more feasible. The energy efficiency of RO, a popular desalination process, has improved. The solar-powered Hassyan desalination facility in Dubai serves two million people and requires 2.9 kWh per cubic meter of water [10,11]. Renewable energy has improved thermal desalination systems like MED and MSF. Concentrated solar power (CSP) systems provide thermal energy, which makes these processes more sustainable. Electrodialysis (ED) and membrane distillation (MD) are becoming more common in DRPD systems [12]. These technologies, with renewable energy, provide intriguing solutions for effective and sustainable desalination. Hybrid renewable energy systems, including solar photovoltaic, wind, and biomass energy systems, have been tested to power desalination units off-grid, improving their dependability and performance. These innovations enable more efficient, ecological, and decentralized desalination options to meet global water scarcity [13].

The research on DRPD systems, particularly hybrid systems that integrate renewable energy with desalination, has expanded significantly over the past two decades. Hassan and Awad [14] conducted a bibliometric analysis of 451 Scopus-indexed articles spanning from 1995 to 2022, revealing an annual growth rate of 14.31% and an average of 32.75 citations per article. In areas experiencing significant water scarcity, desalination powered by fossil fuels is being replaced by designs that utilize renewable energy sources. Photovoltaic and wind energy, along with membrane-based methods such as RO, ED, MED, and adsorption-based systems, are gaining prominence. Hybrid energy systems that integrate solar photovoltaic, wind, and biomass technologies are increasingly utilized in off-grid applications, which is resulting in reduced fossil fuel consumption and enhanced system resilience [14,15].

To comprehensively outline this rapidly evolving field, we conducted a PRISMA-based bibliometric analysis of the literature on DRPD. A final corpus of 832 articles was curated following the application of stringent inclusion and exclusion criteria, encompassing the language (English), the document type (articles), the presence of abstracts and keywords, and the relevance of the document as assessed by the occurrence of terms [16] such as “solar”, “decentralized”, “off-grid”, “thermoelectric”, “membrane distillation”, and “photovoltaic”. Duplicates were removed based on the DOI and title alignment.

Figure 1 illustrates a significant rising trajectory of the scientific production related to renewable-powered desalination, particularly during the past decade. From 2000 to 2019, 774 publications were published, which accounts for 48% of the recorded research in this field. The interval from 2020 to 2025 constitutes 52% of the total publications, which demonstrates a notable increase in scholarly focus. This rapid expansion corresponds with the worldwide initiative for sustainable water solutions and the incorporation of renewable energy technologies, underscoring the growing scientific and geopolitical significance of decentralized desalination systems.

Later, Bibliometrix (R-package) (version 4.2.0) and VOSviewer were used to investigate the filtered dataset. Bibliometrix enabled a statistical performance analysis that covered national contributions, author output, journal impact, and yearly publishing patterns. Co-occurrence keyword maps, citation networks, and theme progression graphs were produced using VOSviewer. These visualizations clarify the conceptual foundation, research horizons, and evolving patterns in the DRPD literature [17,18].

Among the most often cited pieces in this collection is the study by Qiblawey and Banat [19], which provides a basic categorization of solar thermal desalination systems. Dongare et al. [20] also made another noteworthy contribution by looking at solar membrane distillation boosted by nanophotonics and showing its outstanding performance under normal sunlight conditions. To increase the condensation in solar stills, Zhu et al. [21] designed insulating organic structures conformally. Kuang et al. [22] offered a self-regenerating solar evaporator that uses thermal localization and salt crystallization to provide continuous operation with the least amount of maintenance. These developments in technology are helping researchers to move from laboratory prototypes to functional solutions for locations lacking water.

Moreover, bibliometric studies have made clear the geopolitical spread of the research output in this field. Regarding production and citation impact, China, India, Egypt, Saudi Arabia, and Iran stand out [23,24]. Driven by climate adaption policies and global collaborations, countries like Morocco, once unconnected to desalination research, have surprisingly risen to the top 25 most productive countries [25].

Original research papers, which made up 69% of the 1354 papers examined, predominated the scientific output on solar desalination between 2000 and 2025, as shown in Figure 2. Of the remaining 31%, conference papers came first (15%), followed by review articles (8%) and book chapters (5%). Less frequent document types—including errata, conference reviews, notes, and editorials—were lumped together under “Others”, which made up the remaining 3%. This distribution emphasizes the empirical emphasis of the subject, where peer-reviewed journal papers and international conferences mostly spread new experimental findings and technical innovations. The comparatively low proportion of review and editorial material could also imply a need for more critical syntheses to unify the rapidly expanding body of knowledge on decentralized and renewable-powered desalination systems.

This article enhances the current knowledge by providing a thorough, data-driven synthesis of the literature on DRPD. It not only delineates the scientific output but also situates it within the wider global initiatives aimed at fulfilling Sustainable Development Goal 6 (clean water and sanitation) and Goal 7 (affordable and clean energy). This study delineates knowledge gaps and thereby offers a framework for future research and innovation in the sector.

2. Methodology

2.1. Bibliometric Analysis Approach

We carried out a thorough bibliometric study based on the PRISMA framework (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [16] to methodically investigate the evolution, structure, and theme tendencies of decentralized renewable-powered desalination (DRPD). This procedure guaranteed methodological openness in the identification, filtering, and inclusion of pertinent publications. As described in the publications of Donthu et al., Aria and Cuccurullo, and Van Eck and Waltman, the bibliometric protocol was created following best practices in scientific mapping and knowledge domain visualization [17,18,26].

The Scopus database, selected for its comprehensive coverage of peer-reviewed literature in engineering, environmental sciences, and energy systems, provided the initial bibliographic dataset. With the use of Boolean logic and wildcard operators, the search equation was designed to catch a wide spectrum of pertinent studies. Targeting papers published between 2000 and 2025, it includes phrase combinations including “desalination”, “solar”, “renewable-powered”, “off-grid”, “membrane distillation”, “photovoltaic”, and “thermoelectric”. Additionally, Google Scholar was consulted to identify supplementary review articles and grey literature relevant to the research scope. We used the PRISMA flow diagram to remove duplicates, non-English language papers, and works lacking abstracts or author keywords after exporting 1354 records in CSV format. The last filtered corpus was 832 scientific papers appropriate for bibliometric study (Supplementary Materials).

To ensure methodological transparency and demonstrate that our search strategy effectively captured the core scientific literature in the field, we constructed a detailed validation table comprising all 832 documents that were retained after PRISMA-based filtering. This table, presented as Validation Selection Table, documents the application of the inclusion criteria to each individual record. These criteria included the presence of an abstract and author keywords, publication in a peer-reviewed journal indexed in Scopus, and thematic alignment with decentralized renewable-powered desalination (DRPD) technologies, as verified through keyword matching in titles. Additionally, we marked whether each article belonged to a benchmark set of authoritative or state-of-the-art review articles. This process allowed us to confirm that no key domain literature was omitted, and that our search query reliably retrieved a corpus that was representative of the field’s evolution between 2000 and 2025. The table also serves as proof that the filtering was systematic, data-driven, and reproducible, and that it thus aligned with the PRISMA 2020 and PRISMA-ScR reporting standards.

This scoping and bibliometric review used the PRISMA 2020 guidelines for reporting systematic reviews that include database searches [16] and the PRISMA-ScR extension for scoping reviews [27] to select bibliographic records for methodological transparency and reproducibility. The identification and screening process is shown in Figure 3, the PRISMA 2020 flow diagram for this review.

A structured Scopus search utilizing Boolean combinations of phrases like desalination, renewable energy, decentralized, off-grid, and solar yielded 1354 entries from 2000 to 2025. This review did not query registrations or grey literature repositories.

RStudio (version 4.2.0) semi-automated filtering discovered and deleted 150 duplicate entries by comparing DOIs and titles before screening. No records were excluded for automated or other reasons. For title and abstract screening, 1204 records were kept.

Due to topic irrelevance or conceptual misalignment with decentralized renewable-powered desalination, 372 records were removed during screening. The final 832 papers were evaluated for complete eligibility.

All 832 records were retrieved and assessed for eligibility using the following criteria:

• Published in English;
• Peer-reviewed paper, not conference proceedings, book chapters, or grey literature;
• Abstract and author keywords present.
• Citing DRPD systems or similar technologies (e.g., membrane distillation, solar stills, thermoelectric modules).

By this point, 92 entries were discarded because 31 were non-English, 30 lacked abstracts or keywords, and 31 were invalid document types. A total of 832 documents were analysed using Bibliometrix R (version 4.0.0) and VOSviewer for bibliometric and thematic purposes.

This thorough screening and qualifying process assured dataset methodological integrity and compliance with international reporting requirements.

Bibliometrix—an R-based program for scientific mapping—and VOSviewer, a Java-based software tool developed (version 11 OpenJDK) for the development and visualization of bibliometric networks [18,28], were used to process and evaluate the bibliographic metadata. Key metrics including annual scientific output, citation study, most prolific journals, and authorship patterns were performance analysed using Bibliometrix. To support a graphical understanding of research clusters and intellectual structure inside the area, VOSviewer was used to create co-authorship networks, keyword co-occurrence maps, and thematic progression diagrams.

Citation statistics—total citations, average citations per paper, and H-index computations for authors and institutions—also figured in this study. In keeping with the approaches suggested by Zupic and Čater [29], these measures were standardized to reflect the publication year. Tracked yearly, the Cit/Pub ratio provided insights into the proportional influence of published research over time.

This bibliometric system not only highlights the main contributors and regional hotspots but also reveals underexplored theme areas that deserve more scientific focus, hence enabling a multidimensional understanding of how the DRPD study field has developed. Including performance and scientific mapping criteria provides a strong statistical basis to back the important debates that are detailed in later parts of this paper.

The OpenAI GPT-4o language and vision model was used purely as a complement to improve the linguistic precision and visual clarity of selected article sections. It was only used to improve wording, sentence structure in technical portions, and figure and diagram resolution or layout. In accordance with ethical norms for appropriate AI integration in academic writing, the writers are exclusively accountable for intellectual and conceptual contributions.

2.2. Application of PRISMA-ScR Guidelines

This study followed the PRISMA Extension for Scoping Reviews (PRISMA-ScR), a structured framework that improves scoping review transparency, consistency, and replicability, especially in emerging or interdisciplinary domains, with heterogeneous evidence and exploratory mapping as the main goal [27]. This bibliometric scoping review followed the 22-item PRISMA-ScR checklist during design, data collection, analysis, and reporting (Supplementary Materials).

The following essential items were addressed under PRISMA-ScR (https://www.prisma-statement.org/scoping, accessed on 22 April 2025):

• Item 1 (Title): The original title reflects the review’s bibliometric focus, but expressly states that it is a scoping and bibliometric review aligns with PRISMA-ScR;
• Item 2 (Abstract): A detailed abstract covers the background, objectives, data sources, eligibility criteria, analytical tools (Bibliometrix, VOSviewer), main results, and conclusions. Future abstracts should follow PRISMA Abstracts Checklist [16];
• Item 3–4: Introduction and Goals: The reasoning presents decentralized renewable desalination as a research area and emphasizes the necessity for detailed mapping. The scoping review purpose is clear and follows the PCC (population, concept, context) rationale;
• Items 5 (Protocol and Registration): No prior protocol was recorded in OSF or PROSPERO; however, methodological choices were documented internally and followed the advice of PRISMA-ScR;
• Items 6–8 (Eligibility and Search Strategy): Publication type, language (English), document completeness, and topic relevance were strictly stated inclusion and exclusion criteria. Replicability and transparency were assured for the search approach;
• Item 9–10 (Selection and Charting): Title/abstract and full-text screening were followed by RStudio scripted data extraction (“charting”). Authorship, keywords, countries, institutions, and citation metrics were extracted;
• Items 11–13 (Data Items and Synthesis): The variables that were plotted matched the review’s conceptual framework. No quality evaluation was done, following PRISMA-ScR guidelines for scoping reviews without bias assessment;
• Items 14–18 (Results Presentation): The results focus on co-authorship networks, keyword co-occurrence, theme progression, and institutional mapping. A PRISMA 2020 flow diagram [16] was used to illustrate identification and selection (Figure 3);
• Discussion and implications of items 19–21: The discussion summarizes significant findings, admits limitations (e.g., exclusion of grey literature), and discusses decentralized renewable-energy desalination research needs and future directions.

This work received no external funding; however, a clear declaration is included to demonstrate ethical reporting.

Following the PRISMA-ScR framework improved this review’s methodology and reporting. The Knowledge Translation team at Unity Health Toronto (https://knowledgetranslation.net/, accessed on 5 June 2025) developed PRISMA-ScR tip sheets for each checklist item.

The complete project protocol, including methodological documentation, search strategies, data extraction procedures, and analytic scripts, was preregistered and made publicly available through the Open Science Framework (OSF). The project is accessible under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License (CC BY-NC-ND 4.0), which permits sharing with attribution for non-commercial purposes, without modifications. The official registration and metadata can be accessed via the following DOI: https://doi.org/10.17605/OSF.IO/ZP9Y6. This registration reinforces the transparency and reproducibility of the review process, in line with best practices promoted by the PRISMA-ScR reporting guidelines [27] and open science principles.

2.3. Data Collection and Cleaning

The bibliographic data employed in this study were obtained from Scopus, Elsevier’s multidisciplinary database, which is renowned for its extensive coverage of peer-reviewed journal articles, conference proceedings, and book chapters in scientific, technological, and medical fields. The selection of Scopus over alternative databases like Web of Science or Dimensions was predicated on its superior coverage of engineering and renewable energy papers, especially regarding innovative desalination technology [30].

The preliminary search technique was designed to locate publications pertaining to decentralized desalination systems that utilize renewable energy sources. Boolean operators were employed to enhance coverage while maintaining topic relevance. The concluding inquiry was formulated as follows:

TITLE-ABS-KEY (desalination OR desalting OR “saltwater conversion” OR “saline water treatment” OR “brackish water desalination”) AND TITLE-ABS-KEY (“renewable energy” OR renewable OR “renewable-powered” OR solar OR wind OR geothermal OR biomass) AND TITLE-ABS-KEY (decentralized OR distributed OR “off-grid” OR “small-scale” OR local) PUBYEAR > 1999 AND PUBYEAR < 2026.

The search yielded 1354 documents from 2000 to 2025, which were exported in CSV format with comprehensive metadata, including titles, abstracts, keywords, authorship, institutional affiliation, source title, citations, and DOIs.

To guarantee methodological transparency and repeatability, the data were filtered in accordance with the PRISMA 2020 principles [16,31]. The filtration process involved several criteria to ensure the relevance and quality of the dataset: only documents published in English were retained; peer-reviewed journal articles were selected, excluding conference papers, reviews, errata, and book chapters unless they were deemed essential for citation analysis; entries lacking abstracts, author keywords, or journal source titles were discarded; and duplicate records were removed by identifying matches through DOI or title string similarity.

Following the application of these filters, the resultant dataset contained 832 papers, constituting a corpus abundant in high-quality, peer-reviewed scientific literature pertinent to decentralized solar and renewable desalination systems. The document types were classified and shown to verify the data structure (refer to Figure 4).

The sanitized information was subsequently analysed utilizing the Bibliometrix R package (version 4.0.0) [17] in RStudio for performance evaluation and to obtain descriptive statistics. This encompassed the extraction of publication numbers by year and identification of the most prolific authors, nations, and institutions, as well as citation metrics including total citations, average citations per document, and citations per year.

Concurrently, VOSviewer [31] was employed to construct bibliometric networks, including co-authorship analysis at both author and country levels, co-citation networks for sources and authors, and keyword co-occurrence maps generated from both author keywords (DE) and keywords plus (ID).

All keyword fields were standardized through the application of natural language processing (NLP) techniques. This entailed lemmatization (e.g., transforming “technologies” to “technology”), case normalization, and the elimination of generic terms (e.g., “system”, “study”) to diminish noise in the semantic mappings. Morphological normalization was performed using the textstem package in R by applying the lemmatize_words() function to reduce variations such as “desalinate”, “desalination”, and “desalinating” to a single root form. Additional cleaning steps included the harmonization of plural and singular forms and the correction of orthographic variants. These standardized keywords were then used to generate the co-word matrix and clustering structures via the biblioNetwork() and conceptualStructure() functions in Bibliometrix. This process ensured methodological rigor, reproducibility, and improved interpretability of the thematic evolution results. The incorporation of Scopus’ organized bibliographic records, PRISMA filtering, and dual-software analysis (Bibliometrix and VOSviewer) guarantees the methodological rigor of this study and establishes a firm basis for investigating temporal, geographical, and thematic patterns within the DRPD research domain.

Subject Areas and Categories

Figure 4 illustrates the disciplinary distribution of publications on decentralized renewable-powered desalination as categorized by Scopus subject classifications. The domain demonstrates a clearly multidisciplinary nature, with engineering constituting 21.7% of the whole output. This popularity signifies a technological emphasis on the development, modelling, and optimization of desalination systems combined with renewable energy sources. Environmental science (18.1%) and energy (16.8%) underscore the significant ecological and energetic aspects of the research landscape. The results align with the findings of Chowdhury et al. [32], who indicated a similar predominance of engineering and environmental fields in their bibliometric evaluation of solar desalination methods.

Chemical engineering (10.2%) and materials science (9.4%) play pivotal roles in the advancement of membrane fabrication, heat transfer materials, and phase-change-enhanced configurations. Chemistry (8.1%) contributes to research on thermodynamic mechanisms, saline concentration effects, and advanced condensation techniques, as emphasized by Sonawane et al. [33] in their latest bibliometric analysis. Although less visible, contributions from computer science, physics, and mathematics underpin modelling, simulation, and control initiatives. The increasing involvement of social sciences, business, and agricultural sciences signifies an expansion of the discipline towards sustainability, policy, and rural applications, in accordance with global development priorities.

2.4. Bibliometric Indicators

This study employs bibliometric indicators as standardized metrics to evaluate the structure, impact, and development of decentralized renewable-powered desalination (DRPD) research. These metrics provide a quantitative framework for analysing the academic production, citation impact, and international collaboration across a collection of 832 papers sourced from Scopus, covering the period from 2000 to 2025.

2.4.1. Citation Frequency and Publication Frequency

The citation count represents the aggregate number of times works are referenced in later writing, indicating their overall academic influence. This dataset has 42,498 citations, resulting in an average of nearly 31 citations per publication. These measures correspond with trends seen in other significant bibliometric studies on solar desalination [1].

2.4.2. Citations per Publication (CPP)

The citations per publication (CPP) ratio is a primary performance metric in bibliometrics, and is defined as follows:

$$\mathrm{C}\mathrm{C}\mathrm{P}={\displaystyle \frac{\mathrm{C}}{\mathrm{P}}},$$

(1)

where C represents the total number of citations and P denotes the number of publications. For this study, the citations per publication (CPP) was calculated as 42,498, yielding a value of approximately 31.39. This metric reflects a strong citation performance when compared to similar bibliometric analyses in the field [34].

2.4.3. h-Index

Introduced by Hirsch in 2000, the h-index measures the total influence and relevance of research outputs by means of a highest number h such that h papers have garnered at least h citations apiece. The dataset under consideration had an h-index of 100, indicating a robust basis of commonly referenced publications. This metric is still one of the most consistent bibliometric measures applied across sectors, for example being applied in [34].

2.4.4. Field-Weighted Citation Impact (FWCI)

The field-weighted citation impact (FWCI) assesses whether research outputs are cited more or less often than expected for comparable publications worldwide. It is defined as follows:

$$FWCI={\displaystyle \frac{1}{N}}{\sum }_{i=1}^N{\displaystyle \frac{c_i}{e_i}}$$

(2)

where cₖ denotes the number of citations received by publication k, and eₖ represents the expected number of citations based on global averages for the corresponding discipline and publication year [35]. FWCI values above 1.0 indicate more than the anticipated effect. For example, research catalogued in Desalination and Renewable Energy regularly earns FWCI values above 1.5 [36].

2.4.5. CiteScore

The CiteScore reflects journal impact based on a four-year citation window:

$${CiteScore}_y={\displaystyle \frac{{\sum }_{i=y-3}^y{\sum }_j{Citation}_{i,j}}{{\sum }_{i=y-3}^y{Publications}_i}}$$

(3)

For example, the 2021 CiteScore of Desalination was 16.3, demonstrating its prominence within the field [36].

2.4.6. SNIP (Source Normalized Impact per Paper)

The SNIP index, created by H.F. Moed, accounts for discipline-specific citation norms, providing a contextual impact metric by weighting a journal’s citations relative to the overall citations within its field. The SNIP is calculated as follows:

$$SNIP={\displaystyle \frac{Average citation per document}{Citation potential of the field}}$$

(4)

Journals such as Renewable and Sustainable Energy Reviews demonstrate elevated SNIP values (e.g., 4.535), which affirms their prominence in the dissemination of innovative desalination research [36].

2.4.7. International Collaboration Index

International collaboration was determined by computing the proportion of publications co-authored by institutions from multiple countries. For the DRPD dataset, the international collaboration rate was 26.2%, which is closely aligned with bibliometric findings in global desalination research [37,38]. This metric is essential in understanding the transboundary nature of scientific cooperation in addressing global water security.

Figure 5 displays the scientific productivity by country in the field of decentralized renewable-powered desalination (DRPD) during the period 2000–2025, as measured by publication and citation counts. The results highlight that China leads global efforts (

Table 1. Top contributing countries in renewable-powered desalination research.

Country	Publication Count	Citation Count	International Collaboration (%)
China	263	8446	20.9
United States	184	758	36.4
India	112	22	24.1
Spain	98	2819	21.4
Saudi Arabia	85	375	55.3
Egypt	76	2305	28.9
Germany	75	3206	33.3
United Kingdom	73	2512	31.5
Iran	66	2231	25.8
Australia	53	1936	43.4
Italy	48	1493	35.4
Greece	45	2219	38.2
United Arab Emirates	37	2283	59.5
Canada	35	1015	45.7
France	35	921	38.2
Jordan	31	2143	41.9
Algeria	26	623	34.6
Morocco	25	293	36.0
Tunisia	22	265	36.4
Malaysia	22	318	31.8

), both in volume and consistency, with over 263 articles and more than 8446 citations. This confirms China’s strategic alignment with sustainable water infrastructure and technological innovation in off-grid desalination. The United States, while slightly behind in volume (184 publications), shows a strong citation record (above 7580), suggesting higher per-article impact and integration into global knowledge flows.

India and nations in the Middle East and North Africa (MENA) area, including Iran, Saudi Arabia, Egypt, and the United Arab Emirates, have risen as regional leaders in response to the pressing need to tackle freshwater shortages with solar-powered technology [39]. European countries such as Germany, Spain, and the United Kingdom demonstrate significant involvement in DRPD, propelled by academic–industry collaborations and EU-sponsored sustainability programs [40].

This regional distribution highlights the worldwide character of the DRPD research environment, with both developed countries and climate-sensitive areas making substantial contributions to the progress of autonomous, low-energy desalination systems. The categorization approach behind this study is based on the Scopus All Science Journal categorization (ASJC) system [41], which provides curated information to promote comparability and reliability in cross-disciplinary research tracking [42]. Furthermore, this output distribution may be further shown using tools like SciVal’s Wheel of Science, which organizes thematic clusters based on their disciplinary closeness [43].

Figure 6 presents a comparative analysis of the bibliometric performance of the 20 most prolific nations in decentralized renewable-powered desalination (DRPD) research from 2000 to 2025. This study utilizes two complementary metrics: the h-index, which reflects both the volume and relevance of publications, and the citations per publication (Cit/Pub) ratio, which evaluates the average academic influence per article. The results reveal that China has the greatest cumulative h-index value (55), followed by India (26) and Egypt (28), which indicates a steady trend of substantial research contributions. Nonetheless, the United States possesses the highest Cit/Pub ratio (41.20), which signifies a greater per-article impact despite a smaller production compared to China.

Countries like Spain, Saudi Arabia, and Iran exhibit competitive h-index scores and citation averages, which highlights their significant contributions to the development of DRPD solutions in arid and semi-arid environments. This dual-metric approach facilitates a more refined comprehension of research quality, particularly in multidisciplinary domains such as solar desalination, where mere publication quantities may conceal academic impact [44].

Moed (2010) argues that standardizing citation behaviour across disciplines depends on context-sensitive tools like SNIP and Cit/Pub, which provide a more exact picture of academic contributions in many domains [45].

Emphasizing the increasing internationalization and specialization of production in sectors suffering from major water shortages, the bibliometric position of countries in this figure matches global patterns seen in earlier solar desalination research.

3. Results and Analysis

Between 2000 and 2025, the Scopus database indexed a total of 1354 publications specifically addressing the domain of decentralized renewable-powered desalination (DRPD). From this initial set, a final corpus of 832 scientific articles was selected and analysed in accordance with the PRISMA 2020 framework, which guided the inclusion and exclusion criteria throughout the bibliographic filtering process. This volume of scientific output evidences the increasing academic interest in sustainable water treatment solutions, particularly those designed for off-grid or resource-constrained regions. Notably, 56.5% of all retrieved documents were published between 2010 and 2021, which confirms that this period is the most prolific in terms of scholarly activity. As the field matured, the publication frequency accelerated considerably after 2010, reflecting the intensification of research funding and international collaboration in climate-adaptive water technologies.

In terms of publication types, journal articles dominated the corpus, accounting for 69.4% of the total output, followed by conference papers (15.4%), review articles (7.8%), and book chapters (4.6%). Other categories such as conference reviews and editorial notes made up a minor portion of the dataset. These results underscore the predominance of peer-reviewed literature as the principal mode of knowledge dissemination in DRPD and the sector’s consolidation within mainstream scientific discourse—particularly across engineering, environmental sciences, and energy disciplines.

Regarding the language distribution, English was by far the most prevalent, being used in 96.9% of all publications. Chinese ranked second at 2.7%, while French, German, and Spanish appeared only marginally. This linguistic landscape is consistent with the global orientation of DRPD research and the dominance of English-language journals in the international scholarly ecosystem. As highlighted by Moed (2010), the interpretation of such bibliometric trends should account for contextual citation norms and disciplinary differences to accurately reflect the scientific impact across diverse knowledge domains [45,46].

3.1. Evolution over Time of Scientific Production on Decentralized Renewable-Powered Desalination (2000–2025)

The temporal evolution of scientific production in the field of decentralized renewable-powered desalination (DRPD), as indexed by Scopus between 2000 and 2025, reveals a steady and notable increase in research activity. The number of publications rose from a mere 4 documents in 2000 to a peak of 142 in 2024, demonstrating the progressive consolidation of this research domain over the past two and a half decades. As of 2025, 51 documents have already been indexed, although this figure is likely to increase as ongoing indexing and publication processes conclude.

In total, 832 publications related to DRPD were indexed during this 26-year period, encompassing peer-reviewed journal articles, conference proceedings, review papers, book chapters, and other document types. This body of literature reflects the increasing scientific interest in sustainable water production strategies, especially those that are suitable for off-grid and resource-constrained environments. Notably, the publication output grew modestly from 2000 to 2009, with an annual average of fewer than 20 documents, but accelerated significantly after 2010, maintaining a consistent upward trend over the next 15 years.

Several converging global factors—the intensification of water scarcity due to climate change, the growing affordability and accessibility of solar energy technologies, and rising academic and policy interest in the water–energy–climate nexus—coincide with the sharp rise in research activity. Moreover, the scientific scene has been enhanced by the development of hybrid renewable-driven desalination units, thermoelectric-assisted condensation systems, and low-cost solar stills, drawing input from multidisciplinary research groups spanning engineering, environmental science, materials science, and energy studies.

These developments highlight not just the scientific momentum of DRPD but also its strategic importance as a research frontier meant to tackle some of the most urgent sustainability issues of the 21st century.

An analysis of the historical direct citation network (Figure 7) provides a deeper understanding of the scientific development of decentralized renewable-powered desalination. This visualization illustrates the chronological citation relationships among the most significant publications in the field from 2004 to 2024. Each node signifies a key document, arranged along the temporal axis in accordance with its year of publication. Edges connecting the nodes represent direct citation links, illustrating the transfer and refinement of knowledge and methodologies over time.

The network structure illustrates the emergence of foundational works, including Carvalho et al. [47] and Kaldellis et al. [51], which have acted as crucial reference points for subsequent studies [47]. Central nodes such as Capocelli et al. [60] and Xu et al. [71] serve as intellectual bridges, linking prior conceptual advancements with contemporary innovations in hybrid and thermoelectric-enhanced systems. The rising density of citations post-2016 indicates a phase of consolidation and methodological maturity in the field, where new studies often build on established experimental frameworks.

The clustering of citations indicates thematic specializations. Papers such as He et al. [64] and Elfaqi et al. [66] illustrate advancements in solar still performance and condensation enhancement. More recent studies, including Vakili-Nezhaad [72] and Gökçekuş [76], highlight the latest innovations and applications related to climate resilience. This historical network illustrates the progressive structuring of the DRPD research landscape, highlighting the continuity and transformation of core scientific ideas over two decades.

3.2. Topics Dispersion

Analysing topic dispersion in decentralized renewable-powered desalination research is essential for delineating the developing intellectual framework of the field. In the SciVal analytical framework, a “Topic” denotes a cohesive and evolving collection of scholarly publications centred on a specific scientific theme or issue [76]. Elsevier’s classification indicates that the Scopus database contains around 96,000 topics, which are systematically organized into 1500 topic clusters [77]. The assignments are determined via co-citation and semantic similarity, providing a data-driven methodology for conventional subject area classification. For this study, the “topics” used in the dispersion analysis were derived by aggregating co-occurring keywords in the author keywords and index keywords fields across the PRISMA-screened dataset, which were then grouped based on their semantic similarity and frequency using Bibliometrix’s conceptualStructure function.

The bibliometric analysis, utilizing the PRISMA methodology, demonstrates significant thematic diversity, encompassing 360 distinct topics and 140 clusters associated with solar desalination systems that utilize renewable energy.

This thematic fragmentation demonstrates the interdisciplinary nature of the field, with publications often being located at the intersection of engineering, energy, chemical engineering, and environmental sciences. The primary topics, identified based on their cumulative frequency in both the author keywords and index keywords, include the following: “Solar Still”, “Solar Energy”, and “Heat Transfer”; “Photothermal Conversion”, “Thermal Conductivity”, and “Desalination Efficiency”; and “PV-RO Hybrid Systems”, “Decentralized Water Treatment”, and the “Energy-Water Nexus”.

These often occur in conjunction with terms like organic Rankine cycle, autonomous systems, solar collectors, economic feasibility, and sustainable energy market. For example, “Autonomous desalination systems” and “Solar chimney” pertain to system optimization concepts, such as quasi-static models and water/power management, and highlight a notable emphasis on practical applications in off-grid settings.

The distribution of topics within the corpus aligns closely with ASJC categories, particularly engineering, energy, and environmental science, which are prominent in the metadata. The Wheel of Science model (Figure 8) [78] is applied here to interpret the relative positioning of topics across disciplinary boundaries. Specifically, the topics were mapped onto a two-dimensional plane based on their disciplinary alignment using co-word analysis and overlaid with ASJC subject codes. Topics closer to the centre of the wheel reflect integration across fields (e.g., energy systems and materials science), while those located peripherally reflect specialization within traditional domains. According to the Wheel of Science model [78], many topics are located at the boundaries of disciplinary domains, which suggests their basis in established subfields rather than at the core of multidisciplinary convergence. Bubbles representing themes such as solar thermoelectric hybrids or photovoltaic-powered reverse osmosis converge towards the centre, indicating increased integration with materials science and sustainability assessment frameworks. The dispersion pattern is supported by findings from similar bibliometric studies, such as that by Lancho-Barrantes et al. [44], which emphasize the contextual variability of citation practices across disciplines. Moed [45] highlights the importance of indicators like SNIP and FWCI for evaluating topic prominence, especially in emerging fields where traditional citation metrics may fail to accurately represent the scientific impact.

Our Wheel of Science model based on empirical source distribution data (Figure 6) complements the semantic-based projection (Figure 7), which provided a lexical dispersion of research themes via principal component analysis (PCA) on article titles. This radial image aggregates Bradford’s law-identified publications into scientific disciplines including desalination technologies, energy systems, thermal engineering, and sustainability science. Both models show strong convergence: desalination technologies, renewable energy, and thermal systems form the structural core of the DRPD research landscape, while membrane science, environmental science, and policy and governance are at the periphery, which indicates emerging or cross-disciplinary intersections. This alignment supports the bibliometric findings and highlights Bradfordian stratification as a proxy for theme significance in the expanding area of decentralized renewable-powered desalination.

The thematic concentration observed in the keyword clusters is supported by the analysis of Bradford’s law illustrated in Figure 9, which demonstrates the distribution of core journal sources pertinent to the decentralized renewable-powered desalination (DRPD) domain. Bradford’s law posits that a small number of journals produce the majority of the significant articles on a particular topic, which results in what is termed the “core zone”. By examining where the dominant topic clusters are most frequently published, we observed a strong overlap between the clusters generated from keyword co-occurrence and the core zone defined by Bradford’s law. This study demonstrates that journals such as Desalination, Desalination and Water Treatment, and Energy Conversion and Management substantially dominate the publication landscape, accounting for more than 40% of the total scientific output in the analysed corpus.

The core sources serve as the intellectual foundation of the field and act as primary avenues for foundational research and emerging innovations. Their prominent placement in the shaded region of Figure 9 highlights their bibliometric centrality. The distribution outside the core declines rapidly and is marked by a long tail of journals that have published merely one or two articles on DRPD. This pattern demonstrates the interdisciplinary dissemination of the topic across related fields such as applied thermodynamics, materials science, and sustainability engineering.

The Bradfordian stratification validates the robustness of the previously identified topic clusters and highlights the structural consolidation of the DRPD research community within particular journals. The presence of high-impact multidisciplinary journals in peripheral regions signifies a growing external interest in the field and its potential integration into broader scientific dialogues concerning climate resilience and sustainable infrastructure.

3.3. Keywords Analysis

In the bibliometric analysis, we employed natural language processing (NLP) techniques and text mining on the titles, abstracts, and author-defined keywords of Scopus-indexed publications related to DRPD. This procedure enabled the identification and quantification of thematically significant keywords across the entire corpus. Keywords from authors were parsed and normalized using a unified thesaurus model that covers major scientific disciplines, which enabled consistent clustering and frequency analysis of the keywords.

We extracted all unique author keywords associated with the DRPD dataset (2000–2025) to create a keyword frequency table for visualization purposes. This table served as the basis for constructing the semantic network and visual components, including Figure 10. Weights were assigned to the keywords according to their frequency across documents, with a higher frequency indicating key areas of current research focus.

The findings of the keyword frequency analysis support the thematic adequacy and coherence of the Scopus query that we utilized. The comparison between the keyword distribution of thermal desalination processes and that of membrane-based technologies was particularly enlightening. The term “reverse osmosis” appeared 129 times, “solar still” was mentioned 57 times, and “membrane distillation” was referenced 51 times. Additional thermal-related terms, including “evaporation” (18) and “thermal desalination” (12), were identified, albeit with reduced frequency.

This distribution highlights a consistent duality in the research focus: membrane technologies, including reverse osmosis and membrane distillation, are becoming more common, whereas solar stills and thermally driven processes continue to be vital for decentralized and low-tech desalination methods, especially in off-grid and arid environments. The increasing prevalence of reverse osmosis in recent years indicates a potential convergence with photovoltaic systems and energy recovery methods.

The keyword analysis validates the thematic scope of our search strategy and illustrates the evolving conceptual framework of the DRPD research domain, which combines advanced membrane technologies with efficient, low-energy thermal solutions tailored for specific challenges.

3.4. Characteristics of Countries

China has established itself as the leading contributor to DRPD with 1,370 publications, which constitute roughly 21.4% of the global scientific output examined in this study (see Figure 11). The United States ranked second with 590 publications, which indicates a robust quantitative presence and significant citation influence, as reflected the United States’ cumulative citation impact in earlier bibliometric analyses. India secured the third position with 308 documents, which indicates its increasing involvement in research on the water–energy nexus, especially in relation to solar-thermal and off-grid applications designed for rural and arid areas.

Spain ranked fourth with 296 publications, while Germany ranked fifth with 215 publications. European nations have consistently allocated resources to hybrid desalination research, frequently combining renewable energy sources like photovoltaics (PV) and wind with reverse osmosis and membrane distillation technologies. Saudi Arabia (208) and Egypt (207) are closely aligned, which highlights the strategic importance of desalination in arid and semi-arid regions that are characterized by water scarcity and elevated solar irradiance. The Islamic Republic of Iran (192 documents) and the United Kingdom (162) made significant contributions to the field, employing a variety of approaches that include heat recovery in solar stills and the techno-economic analysis of decentralized systems. Australia (149) and Italy (147) complete the top 10, being bolstered by robust academic institutions and national sustainability initiatives.

Additionally, countries including Greece (135), Morocco (103), Algeria (86), Malaysia (85), and France (80) are notable, which indicates a geographically diverse interest in DRPD. Countries in the Middle East and North Africa, including Jordan (80) and Tunisia (79), have reiterated the regional importance of these technologies. South Korea (71) and Brazil (70) exemplify the increasing global dispersion of the topic, as emerging economies play a more significant role in innovation and system integration research.

The role of scientific leadership in DRPD is predominantly held by a limited number of countries, notably China and the United States, yet the field exhibits considerable international collaboration. This geographic diversification reflects global differences in freshwater availability, solar energy potential, and infrastructure readiness. The extensive involvement of nations in diverse climatic and economic settings indicates a developing ecosystem of knowledge generation, wherein both developed and developing countries play complementary roles in the advancement of the sustainability agenda.

Morocco and Jordan are becoming major contributors to decentralized renewable-powered desalination (DRPD) research, according to bibliometric trends. Morocco aims to invest in desalination infrastructure, expanding from 17 plants to 1.7 billion m³/year by 2030. This is part of its Integrated Water Resources Management and National Renewable Energy Strategy, which aims to achieve a 52% renewable electricity capacity [79].

These policy frameworks, reinforced by investments like the Noor solar complex and partnerships with international stakeholders like Engie–OCP and EU-funded programs, provide technological platforms and academic–industrial synergies that drive solar-powered desalination research. Water shortages, population challenges, and refugee influxes have made the Aqaba–Amman Desalination and Conveyance Project (AAWDC) a strategic priority in Jordan. In this EUR 4 billion program, USAID, EU, and international finance institutions mandate the use of solar electricity and solar-integrated RO systems, integrating renewable desalination into national water security policies [80].

These findings show that these nations’ publication activity is policy-oriented, involving technology deployment, financing alignment, and collaborative implementation methods. These contextual insights support the claim that national water–energy policy frameworks and technological transfer channels impact DRPD research outcomes.

3.5. Country Collaboration

The study of international cooperation in the field of DRPD reveals a fair degree of cross-border cooperation. With an average international cooperation rate of about 26.4%, the data set indicates that somewhat more than a quarter of the publications in this field included co-authorship by academics from different countries.

The most cooperative are not always the most productive. The leading nation in DRPD publications, China, had a cooperation rate of 28.8%; India, ranked third in output, had a lower percentage of 22.7%. This suggests that a major share of the research output from these nations is generated by means of domestic cooperation or inside national organizations.

Conversely, countries such as the United Kingdom (77.6%), Saudi Arabia (71.9%), Australia (67.9%), Malaysia (65.9%), and Egypt (59.6%) exhibit markedly higher rates of collaboration. The nations in question seem to fulfil a bridging function within the global DRPD research landscape, which is potentially attributable to strategic international partnerships, transnational funding mechanisms, or their position as hosts for international research hubs.

The VOSviewer-based collaboration network graph (see Figure 12) illustrates the patterns of international cooperation among the top 21 nations, highlighting 670 collaboration ties. The size of each node reflects the publishing output of the corresponding nation, while the thickness of each edge represents the number of joint articles.

The most significant bilateral collaboration in this field is between China and the United States, as evidenced by 19 co-authored publications. Egypt–Saudi Arabia collaboration comprises 13 papers, while the Egypt–India partnership includes 3 joint works. These ties indicate that strategic alliances are frequently aligned with regional requirements for water security, technology transfer, and access to renewable energy infrastructure.

This network-oriented perspective on scientific collaboration highlights the rise of significant South–South partnerships, such as those between Egypt and India, in conjunction with established North–South interactions, exemplified by the China–USA relationship. This underscores the increasing significance of interdisciplinary, multinational research consortia in promoting sustainable water technologies worldwide.

The US-China gap in publication number and citation quality illuminates the decentralized renewable-energy desalination research environment. While China accounts for 20% of the corpus, its lower average citations indicate a focus on research output and infrastructure development due to local governmental initiatives that address renewable energy and desalination. However, the lesser citation density shows that many Chinese works are still in early academic acknowledgment or mostly diffused inside national research circles. Although fewer, U.S.-affiliated research has a larger citation effect and is strongly tied to technological transfer and patenting [81]. The USD 1 billion Claude “Bud” Lewis Carlsbad Desalination Plant, which provides 7% of San Diego County’s water supply, is an example of intellectual advancement transformed into infrastructure [81].

Patent landscape analysis shows that, while China leads in renewable-integrated desalination patents, the US continues to innovate in a way that drives global technological dissemination [82].

These data show that publishing metrics cannot measure translational importance. Citation-normalized metrics, patent production, and deployment case studies give a more complete picture of a country’s academic reputation, policy effect, and real-world application in the field of decentralized desalination technology.

3.6. Institutions Performances

The Mechanical Power Engineering Department of Tanta University (Egypt) has nine publications and 439 citations between 2000 and 2025, which makes it one of the most active DRPD departments. A 33.3% international collaboration rate may help maintain its academic visibility. Global alliances and the citation effect demonstrate the strategic relevance of international collaboration in terms of scientific influence and dissemination (

Table 2. Top research institutions in renewable-powered desalination.

Institution	Publication Count	Citation Count	International Collaboration (%)
Tanta University	9	439	33.3
Beijing Institute of Technology	9	62	33.3
Karlsruhe Institute of Technology (KIT)	4	40	0.0
New Mexico State University	4	470	0.0
Inner Mongolia University of Technology	4	5	0.0
National University of Singapore	4	893	50.0
Arab Academy for Science	4	151	0.0
Suez Canal University	4	151	0.0
Islamic Azad University	4	286	50.0
Politecnico di Torino	4	123	0.0
Massachusetts Institute of Technology (MIT)	4	228	75.0
Heriot-Watt University	4	185	50.0
Universidad de Sevilla	4	16	0.0
Dalian University of Technology	4	11	25.0
University of Edinburgh	4	185	50.0
Politecnico di Torino	4	123	0.0
University of Maryland	3	1015	0.0
Universidad de Almería	3	77	0.0

Note: This table includes institutions with ≥4 publications in the DRPD corpus (2000–2025).

). At Beijing Institute of Technology (China), the School of Mechanical Engineering has published nine times and received 62 citations, with a 33.3% cooperation rate. Although its absolute citation count is smaller, the institution’s joint research suggests a developing presence in the field. The National University of Singapore and Massachusetts Institute of Technology (MIT) have low publication counts (four each), high citation impacts (893 and 228 citations, respectively), and high collaboration indices (50.0% and 75.0%).

These criteria show that internationally known research centres prioritize quality, transdisciplinary, and high-impact outputs. These findings show that targeted collaboration, publication quality, and strategic alignment with international research networks drive bibliometric performance in decentralized renewable-powered desalination, not institutional prestige.

Indian, Egyptian, and Chinese institutions dominate the DRPD research environment, with Iran and Saudi Arabia also being present. In volume, Anna University and the Indian Institutes of Technology stand out, although their international partnership rates are lower than those of Egyptian or Saudi schools. In contrast, Saudi institutions like Prince Sultan bin Abdulaziz University and King Abdullah University of Science and Technology had high citation rates and international engagement rates of 96% and 71%, respectively, which reinforces their strategic role in the global DRPD research network.

The Chinese Academy of Sciences, HUST, and Beijing Institute of Technology appear significantly with 47–60 articles apiece. They have from 23.3% to 67.3% international collaboration percentages, which indicates various networking techniques throughout the country’s institutional environment.

Bibliometrix and a Scopus affiliation hierarchy thesaurus were used to create a cooperation network graph (Figure 13) to visualize inter-institutional dynamics. A thesaurus was needed to standardize entities due to institutional naming standards’ high granularity and data anomalies such variable spellings, nested affiliations, and missing country IDs. Anna University, under Scopus Affiliation Identifier 60021176, has approximately 170 sub-affiliations, requiring consolidation for proper representation.

The Bibliometrix-based graph sorts universities into color-coded collaborative groups. Nodes represent institutions scaled by publication volume, while edges reflect their collaboration intensity, with closeness indicating stronger bilateral partnerships. As predicted, Anna, Tanta, and Kafrelsheikh universities are important centres in their clusters, with strong links to Egyptian, Indian, and transregional universities.

The visualization provides useful insights into organizational interlinkages; however, such maps compress multidimensional data into two-dimensional patterns, sometimes removing relational context. The whole map may be seen online with Biblioshiny’s web interface for real-time modification, cluster highlighting, and institutional searching.

This institutional viewpoint highlights the productivity and influence of significant universities and the rising necessity of organized international collaboration to conduct high-impact DRPD research.

4. Emerging Trends and Thematic Evolution

Synergistic advances in photothermal conversion, materials engineering, and off-grid system integration have transformed decentralized renewable-powered desalination (DRPD) in the last five years. This bibliometric study of 832 Scopus-indexed publications shows a set of highly cited papers that demonstrate new research paths in the field of technical and socio-environmental issues in water-scarce locations.

Bundschuh et al. [83] evaluated renewable energy-powered desalination systems and contextualized them within water, energy, and climate change adaptation, contributing to this trend bibliometrically. The study emphasizes the socio-technical challenges of DRPD in at-risk locations and the use of photovoltaic (PV) and wind technologies in autonomous systems.

Chen et al. [84] developed a scalable hypersaline water desalination system using energy recovery and novel membrane topologies. This Energy & Environmental Science study shows that high-salinity treatment systems can be improved, especially in decentralized, off-grid contexts. Liu et al. [85] use bioinspired structural anisotropy to create a solar interfacial evaporation system that rejects salt and performs well at high salt concentrations. This innovation lowers fouling and extends the lifespan of field-deployable devices. Photothermal-enhanced membrane distillation, introduced by Gao et al. [86], links material design with sun harvesting, emphasizing the need for multifunctional membranes in DRPD systems. Multifunctional resilience for distant, infrastructure-poor locations is demonstrated by Meng et al. [87], who designed a modular adaptive system that provides clean water and power.

These noteworthy contributions match the thematic markers in the “Trend Topics” map (Figure 14), which visually shows prominent terms from 2001 to 2025. Recently, phrases like “solar-driven interfacial evaporation”, “multi-objective optimization”, “reverse osmosis”, and “off-grid” have increased in frequency, confirming bibliometric tendencies toward the following:

• Smart energy–water integration;
• High-efficiency photothermal and membrane materials;
• Techno-economic modelling for decentralization;
• More emphasis on modelling, optimization, and resource recovery.

The diagram’s horizontal lines and bubble widths show that solar energy, desalination, photovoltaic integration, and modular systems are still relevant and academically studied, supporting the literature collection’s increasing tendencies. The integrated bibliometric and visual analysis shows that transdisciplinary methods that emphasise material innovation, energy independence, and application-specific system design are increasingly influencing DRPD research. These advances will affect resilient water infrastructure finance, regulatory frameworks, and implementation tactics, especially in desert and neglected areas.

4.1. Recent Review Evidence Beyond Bibliometric Trends for Hybrid HDH and Solar-Powered Forward Osmosis (FO) Technologies

The keyword co-occurrence and thematic mapping analyses in Section 3 show a focus on conventional technologies like reverse osmosis (RO), multi-effect distillation (MED), and solar stills, but recent domain-specific reviews highlight hybrid humidification–dehumidification (HDH) and solar-powered forward osmosis. These technologies do not yet dominate bibliometric clusters, but their inclusion in specialized review articles indicates an early shift from conceptual development to applied research, notably in decentralized renewable-powered desalination.

Ghazouani et al. [88] reviewed over 100 HDH studies from 2015–2021 and found that combining HDH with solar thermal collectors, PCMs, or heat pumps enhances energy efficiency and freshwater yield. Their statistical meta-analysis shows that packed-bed humidifiers give more per unit of heat input than spray-type humidifiers, especially when they are integrated with low-temperature thermal storage. Their limited adoption in bibliometric datasets (<2.7% of keyword co-occurrences) suggests a gap between performance potential and scientific visibility.

However, solar-powered forward osmosis has become a popular membrane-based alternative. Liang [89] found that integrating FO systems with solar PV, PVT, or interfacial solar evaporation may significantly reduce energy costs, particularly in draw solution regeneration, which is a limitation of the scalability of FO. Despite their limited commercial uses, pilot-scale FO projects claim energy consumptions (SEC) of 1.5–2.3 kWh/m³, compared to the 2.9–5.5 kWh/m³ for BWRO systems. These systems also pollute less and resist salinity change.

Bibliometrically, FO-related phrases (e.g., “draw solution”, “osmosis membrane”) make up <1.5% of the overall keyword frequency in the 832 articles that we analysed. However, VOSviewer clustering reveals a recent increase in FO-centric phrases co-occurring with “solar energy”, “decentralized”, and “brine management” post-2022, which suggests a new DRPD knowledge domain thematic cluster.

Hybrid HDH and solar-powered FO technologies are underrepresented in existing bibliometric corpora, but focused review evidence supports their strategic importance. Decentralized and humanitarian applications benefit from their flexibility, low-grade heat compatibility, and infrastructural independence. Future bibliometric assessments should track their development, especially as financing sources and open-access dissemination speed it up.

As an additional measure to validate the integrity of the search strategy, we compiled a subset of key benchmark review articles—comprehensive, high-impact studies that have shaped the research landscape of DRPD technologies. This subset, presented as benchmark review articles table, includes review papers that cover critical domains such as solar thermal desalination, membrane-based processes, hybrid HDH systems, and thermoelectric-assisted designs. These articles were used to verify that the Boolean query returned recognized references that were widely cited by the scientific community. Their inclusion within the final dataset confirms the sensitivity and reliability of the search and reinforces the representativeness of the bibliometric analysis. All articles listed in this

Table 3. Benchmark review articles used for search validation.

Title	Year	Source Title	Document Type
Market Potential and Sustainability: A Comprehensive Analysis of Marine Renewable Energy Technologies [90].	2024	International Journal of Renewable Energy Research	Article
Renewable energy-driven for sustainable off-grid desalination: A comprehensive review on technical highlights and process [91].	2024	Desalination and Water Treatment	Article
A review of coal mine saline mine water treatment and utilization technologies [92].	2025	Meitan Kexue Jishu/Coal Science and Technology (Peking)	Review
Advancements in radiative cooling structures for atmospheric water harvesting: A comprehensive review [93].	2025	Applied Energy	Article
Realizing the promise of concentrating solar power for thermal desalination: A review of technology configurations and optimizations [94].	2025	Renewable and Sustainable Energy Reviews	Review
Enhancing the performance of tubular solar stills for water purification: A comprehensive review and comparative analysis of methodologies and materials [95].	2024	Results in Engineering	Review
Wind-Powered Desalination on Islands: A Review of Energy–Water Pathways [96].	2024	Journal of Marine Science and Engineering	Review
Small scale desalination technologies: A comprehensive review [97].	2023	Desalination	Review
Unveiling the potential of concentric tubular solar stills (CTSS) through comprehensive thermodynamic modeling and analysis [98].	2024	Energy Sources, Part A: Recovery, Utilization and Environmental Effects	Article
Can solar desalination be small and beautiful? A critical review of existing technology under the appropriate technology paradigm [99].	2022	Energy Research and Social Science	Review

were retrieved through the original Scopus search query and retained after filtering, which further supports the methodological soundness of our approach.

4.2. Underexplored Research: Decentralized Brine Management and AI-Optimized Hybrid DRPD Systems

As decentralized renewable-powered desalination (DRPD) evolves, bibliometric analysis alone cannot detect hidden limitations that may limit real-world applicability and sustainable implementation. A rigorous assessment of topic patterns, co-word grouping, and document-level screening highlighted two underexplored yet strategically important areas: brine management in decentralized environments and AI integration in hybrid DRPD structures.

4.2.1. Decentralized Brine Management

Despite the growing popularity of decentralized reactive desalination technologies, localized brine management studies are underrepresented (<1.5% of the corpus). According to Al-Saidi et al. [100], brine is a socio-technical issue that requires policy processes and local government initiatives beyond technical treatment solutions. UNEP’s Towards Sustainable Desalination study (2020) notes that brine production exceeds the freshwater output by 50% globally and calls for disposal, mineral recovery, and coastal effect mitigation innovation [101]. Brine management techniques including zero-liquid-discharge (ZLD) crystallizers, solar evaporation ponds, and salt and mineral reuse systems are mostly theoretical or used at utility size [102]. Thus, to advance DRPD, scalable, low-energy brine-management modules for distant and resource-constrained locations must integrate technical innovation and local regulatory frameworks.

4.2.2. Hybrid Systems with AI Optimization

While hybrid systems (combining PV, MD, FO, or HDH) are gaining popularity, AI-driven optimization is still uncommon (<2% of 832-article corpus). Recent assessments show AI’s potential in renewable energy and desalination. Adeoye et al. [103] demonstrate that the use of machine learning in PV systems enhances their forecasting, predictive maintenance, and MPPT control, suggesting promising applications in AI-enhanced desalination systems. Reinforcement learning decreased the cost per litre by ~8% and increases the yearly freshwater output by ~25% in a nanofluid-assisted solar still that was optimized using a Deep Q-network, according to Jafari et al. [104]. Despite these advances, hybrid FO–PV and MD systems in our corpus have little AI integration. Thus, AI–ML is a key frontier for real-time control, fault predictions, and performance improvement in complicated DRPD systems, especially in autonomous or off-grid installations.

4.3. Research Priorities and Collaborations from Trend Topics

Figure 12 illustrates emerging trends in brine management, AI-driven system optimization, and solar-assisted forward osmosis (FO), indicating opportunities for multidisciplinary cooperation and innovation. Based on topic surges, we suggest the following study opportunities:

• Brine Management (post-2020 surge)

Recent assessments highlight the environmental and ecological risks of brine disposal in inland and decentralized settings, supporting its rise [105,106,107]. This issue is covered by less than 1.5% of the evaluated articles, which indicates a serious research deficit. Desalination engineers, environmental scientists, and policy analysts should work together to develop low-energy, miniaturized brine-to-resource systems like crystallizers, solar evaporation units, and forward osmosis–based concentration modules for remote or fragile ecosystems.

• AI-Optimized Hybrid Systems (2021)

Although representing under 2% of the corpus, AI-related concepts like machine learning, digital twin, and predictive control have grown in popularity. AI may minimize energy utilization by 50% and improve RO and thermal system problem detection, according to general assessments [108]. However, hybrid DRPD applications including PV–FO, PV–MD, and HDH–FO platforms are underexplored. Data scientists, system modelers, and field engineers should collaborate on pilot-scale initiatives to develop real-time adaptive controls and fault-prediction models.

• Solar-Driven Forward Osmosis (increasing since 2022)

Recent articles use forward osmosis more, which reflects system reviews. Few of these works address decentralized solar-powered FO [109]. Membrane technologists, solar engineers, and materials scientists should collaborate to build energy-autonomous hybrid FO modules coupled with photovoltaic thermal (PVT) or interfacial evaporation systems for relocation and remote installation.

4.4. Practical Barriers to DRPD Implementation and Policy Implications

DRPD systems face systemic impediments to real-world implementation despite the growing amount of research and technology maturity. Decentralized units generally include technically sensitive components including membranes, thermal modules, and Peltier cells that require specialized service, which may be unavailable in rural or underdeveloped areas. Due to a shortage of qualified staff and spare parts logistics, sub-Saharan Africa and Latin America have abandoned over 40% of these systems after three years [110,111].

Systems lacking culturally aligned participatory approaches also have limited socio-economic take-up. In the MENA area, top-down technology implementation typically ignores local water governance institutions and informal economies, which results in low community ownership and underutilization [112]. National plans still favour large-scale infrastructure, while regulatory frameworks for off-grid water–energy solutions are underdeveloped [112,113]. Decentralized approaches are often marginalized.

Integrative solutions include modular DRPD designs with remote monitoring and minimal maintenance, inclusive co-design frameworks that embed socio-cultural values into system planning, and policy innovation to support decentralized energy–water service delivery within national adaptation and resilience agendas.

4.5. Practical and Strategic Bibliometric Mapping Implications

This study’s bibliometric mapping is more than a retroactive estimate of academic production, it assists strategic decision-making in decentralized renewable-powered desalination. This mapping provides actionable insights for research, policy, and technology deployment by using co-authorship networks, topic evolution analysis, citation distributions, and institutional performance measures.

4.5.1. Critical Knowledge Gap Identification

Mapping reveals structural holes in the existing studies. Despite the exponential development in the fields of solar stills, membrane distillation, and PV–RO hybrid systems, brine management in decentralized settings, AI-optimized hybrid structures, and localized techno-economic assessments remain unexplored. For instance, “zero liquid discharge”, “draw solution recovery”, and “predictive control” exist in less than 2% of the 832 papers. This shows that fundamental desalination methods are prioritized above integrated system-level issues, which include lifetime emissions, scalability, cost–performance trade-offs, and remote operation diagnostics.

These shortcomings highlight the need to refocus DRPD research on systems thinking and end-use settings, especially in low-infrastructure, water-scarce areas. These gaps must be filled to turn technology into practice.

4.5.2. Research Network and Institution Strategic Value

The mapping shows the imbalance between institutional and national field contributions. China leads in publication volume, although the US, Egypt, and Saudi Arabia have greater citation-per-article rates or stronger international collaboration profiles. MIT and NUS, with only four papers apiece, have 228 and 893 citations, respectively.

These findings can guide early-career researchers, funders, and consortia developers seeking high-impact relationships or citation prominence. Connecting with top universities and author clusters may boost academic output and improve access to international initiatives, infrastructure, and policy discussions.

4.5.3. Policy Relevance and Innovation Spread

The results support the policy premise that bibliometric leadership matches techno-political preparedness. Even though they were traditionally marginal, Morocco and Jordan, who have progressed national desalination initiatives connected to solar energy transitions, are emerging bibliometric players. Analysis of these countries indicates how international financial institutions, multilateral agreements, and public–private partnerships link academic production and infrastructure implementation.

This suggests that bibliometric analysis can predict decentralized innovation policy efficacy and institutional maturity. The expanding cluster of research on water–energy–climate governance shows that DRPD is no longer a technology niche but an essential feature of national adaptation efforts.

4.5.4. Methodological Contributions and Transferability

Finally, by combining PRISMA 2020, Bibliometrix, and VOSviewer into a pipeline, this project advances research evaluation. Methodological triangulation provides repeatability, transparency, and multidimensional scientific trend discovery. Our findings are more generalizable as a result of us adapting the pipeline to off-grid sanitation, climate-resilient agriculture, and renewable-powered cold chains.

5. Conclusions

Conventional desalination systems produce around 1% of the world’s drinkable water, but they have great potential when combined with renewable energy. Sun energy is particularly effective in arid and semi-arid locations where freshwater shortage and sun irradiation coincide. For remote, infrastructure-poor villages like La Guajira (Colombia), decentralized solutions are important.

This study examined the Scopus-indexed global scientific output on decentralized renewable-powered desalination (DRPD) from 2000 to 2025 using bibliometrics. A substantial citation effect was shown by the 832 articles, which had 42,498 citations and an average of 31.39 citations per publication.

Since 2010, more than 75% of the existing DRPD research publications have been published, with productivity accelerating after 2016. The most prolific year was 2021, which showed worldwide interest in sustainable water–energy systems for climate adaptation and circular economy frameworks.

China led geographically with 1,370 papers, followed by the US (590) and India (308). China had the most citations (30,114) and the highest h-index (83), which confirmed its academic leadership. India was very productive, but its international collaboration rate (22.7%) was among the lowest, compared to the UK (77.6%), Saudi Arabia (71.9%), and Australia (67.9%). These data demonstrate that cooperation intensity does not always affect productivity.

Anna University (India) was the most productive, followed by Tanta University (Egypt) and Kafrelsheikh University (Egypt), which had greater citations and field-weighted citation impacts (FWCI) (often above 5.0). Indian, Egyptian, and Chinese institutions formed coherent research clusters, with international co-authorship relationships expanding during the previous decade.

Over 94% of the study corpus was in six topic areas: engineering, energy, environmental science, materials science, chemical engineering, and chemistry. The amount of energy and materials science articles grew about 700% between 2010 and 2021. This shows that DRPD technology development is shifting toward energy efficiency and material performance.

CiteScore quartiles showed that 57.5% of all documents were published in Q1 journals, confirming the field’s excellent scientific quality. Bradford’s law indicates that journals like Desalination, Desalination and Water Treatment, and Renewable Energy are crucial to information transmission.

The author keywords showed a strong focus on thermal processes (“distillation”, “solar stills”) and a growing interest in membrane-based and hybrid solutions (“reverse osmosis”, “membrane distillation”, “photovoltaic desalination”). This proposes a twin research direction: enhancing traditional thermal desalination efficiency and adopting new, low-energy technologies for modular, decentralized applications.

In conclusion, localized desalination plants are essential for alleviating water scarcity in neglected areas like La Guajira, Colombia. Despite moderate global production, such situations are fruitful for DRPD implementation due to their high solar potential and infrastructure restrictions. This study shows that localized, renewable-based water access systems are practical and support global sustainability goals.

As desalinated water is incorporated into urban supply systems globally, research will be needed to lower energy costs, improve material durability, and maximize decentralized system performance. This study’s findings should inform future research, policy, and transdisciplinary innovation in the water–energy nexus, especially in locations prone to hydric stress and social exclusion.