Solar Energy: Applications, Trends Analysis, Bibliometric Analysis and Research Contribution to Sustainable Development Goals (SDGs)

The study is motivated by rapidly rising global energy demand, environmental impacts of fossil fuels, and the abundant potential of solar irradiance. It aims to synthesize the state of the art in solar photovoltaic (PV) technologies and applications, and to assess how solar research contributes to the UN Sustainable Development Goals (SDGs). Specifically, it reviews PV generations and key application domains (large-scale plants, residential PV, green hydrogen, water desalination, and transportation) and conducts a bibliometric analysis (2011–2021) to map publication trends to SDGs, identify dominant focus areas (notably SDG 7: Affordable and Clean Energy), and reveal research gaps in underrepresented SDGs (e.g., SDGs 1, 4, 5, 9, 10, 16). The purpose is to inform future research directions for maximizing solar PV’s role in sustainable development.

The paper provides an extensive review of PV fundamentals and technology generations: first-generation (mono- and polycrystalline silicon), second-generation thin films (amorphous silicon, CdTe, CIGS), and third-generation (organic PV, concentrated PV), including typical efficiencies, advantages, and limitations. It further surveys major application areas—utility-scale PV plants, residential PV (grid-tied and stand-alone with storage), PV-powered HVAC and water pumps, PV-coupled green hydrogen via electrolysis, solar-powered desalination (RO, EDR, MD), and PV for transportation and EV charging—highlighting component choices (modules, mounting/tracking, inverters, transformers, grid interface), performance considerations, and representative statistics and examples from the literature.

A bibliometric analysis was conducted using the SCOPUS database. Search strategy: (1) initial keyword “solar” within titles, abstracts, and author keywords; restrictions to English language, journal publications; time span 2011–2021; yielding 276,989 publications. (2) Combined the “solar” query with each UN SDG term individually to identify overlaps; aggregated results produced 126,513 documents related to both solar and SDGs. (3) Repeated the combined searches for five focal applications: large-scale solar PV, residential PV, green hydrogen, water desalination, and transportation. Data processing involved exporting records to Microsoft Excel for cleaning (e.g., removing duplicates/repeated words), descriptive statistics, keyword extraction, and dashboard creation illustrating publication counts per year, top countries, open-access share, and patents. The analysis quantified distribution across SDGs and extracted most frequent keywords for SDG 7 within each application.

- Corpus size: 276,989 SCOPUS-indexed solar publications (2011–2021). When combined with SDG terms, 126,513 documents remained. - Distribution across SDGs (solar+SDG set): SDG 7 (Affordable and Clean Energy) dominated with 91,708 documents (≈72.49%). Next highest: SDG 13 (Climate Action) ≈11.46%. Very low contributions for SDG 4 (Quality Education) with 32 documents (≈0.03%) and generally weak representation for SDGs 1, 5, 9, 10, and 16. - Temporal trend: steady growth in annual publications from 5,179 (2011) to 20,392 (2021). - Applications ranking by publications (solar+SDG): (1) large-scale solar power generation (e.g., 4,451 docs cited in text), (2) transportation, (3) residential PV, (4) water desalination, (5) green hydrogen (lowest with 201 docs; no papers found for SDGs 1, 3, 4, 5, 8, 10, 16 within green hydrogen). - Application-specific highlights: water desalination—SDG 6 had 89 of 723 docs (second highest); transportation—SDG 11 had 73 of 1,898 docs (second highest). - Frequent keywords (SDG 7 focus per area): Solar overall—“Solar Power Generation” (23,169 docs); Power Plants—“Photovoltaic Cells” (1,633); Residential—“Photovoltaic Cells” (563); Green Hydrogen—“Hydrogen Production” (141); Water Desalination—“Desalination” (475); Transportation—“Electric Vehicles” (625). Least frequent examples included “Photocatalytic Activity” (1,166) solar overall; “Solar Heating” (59) Power Plants; “Hydrogen” (23) Residential; “current” (3) Green Hydrogen; “Water Conservation” (11) Desalination; “Electric Load Management” (27) Transportation. - Country contributions: Solar overall—China (66,823), USA (57,266), India (24,632). Large-scale plants—China (671), India (403), USA (382). Residential—USA (263), India (172), Australia (146). Green hydrogen—China (43), USA (14), Germany (14). Desalination—USA (66), Egypt (64), Saudi Arabia (53). Transportation—China (243), USA (224), India (220). - Patents and open access (examples from dashboards): Solar overall—310,009 patents; 35.9% OA. Large-scale—6,945 patents; 39.4% OA; publications 3,776. Residential—4,439 patents; 43.3% OA; publications 1,439. Green hydrogen—541 patents; 30.9% OA; publications 181. Desalination—1,005 patents; 26.8% OA; publications 549. Transportation—12,398 patents; 44.2% OA; publications 1,662. - Technical focus predominant: most literature emphasized technical and environmental aspects; social and economic dimensions were less examined.

The bibliometric mapping shows that solar research overwhelmingly targets SDG 7, directly aligning with clean energy objectives, while contributions to many other SDGs remain limited. This concentration answers the study’s central question by revealing both strengths (robust technical advancement and deployment in energy) and gaps (insufficient integration with social and economic development goals). The analysis indicates rising global scholarly and patent activity, with China, USA, and India as lead contributors, suggesting strong innovation ecosystems. Application-level findings reinforce the centrality of SDG 7 but also show relevant linkages: SDG 6 for desalination, SDG 11 for transportation/EVs. The discussion underscores that solar energy can positively affect broader SDGs—e.g., climate action (SDG 13), life below water (SDG 14), life on land (SDG 15), health (SDG 3), water and sanitation (SDG 6), poverty (SDG 1), education (SDG 4), gender equality (SDG 5)—through cleaner air, reliable electricity for services, and enabling technologies (e.g., irrigation, cold chains, digital access). However, the current literature’s emphasis on technical aspects leaves social inclusion, equity, job creation, and governance linkages underexplored. Therefore, aligning solar research agendas with broader SDG targets and measuring socioeconomic outcomes are crucial for maximizing solar’s systemic sustainability benefits.

The paper synthesizes PV technology status and applications and quantifies solar research contributions to SDGs via a decade-long SCOPUS-based bibliometric analysis. Key contributions include: (1) a comparative overview of PV generations and major application domains; (2) evidence of strong growth in solar publications and patents; (3) identification of a heavy focus on SDG 7 with notable gaps in SDGs 1, 4, 5, 9, 10, and 16; (4) country-level leadership by China, USA, and India; and (5) application-specific patterns (e.g., desalination’s linkage with SDG 6, transportation with SDG 11). The study recommends expanding research toward underrepresented SDGs, strengthening social and economic analyses (e.g., jobs, GDP effects, gender impacts), increasing focus on emerging applications (green hydrogen, EVs), aligning funded research with national SDG priorities, and enhancing open-access publishing to broaden impact.

- Data source limited to SCOPUS; results may omit works indexed elsewhere. - Language restricted to English and publication type to journals; conference papers and non-English outputs excluded. - Time window limited to 2011–2021; newer or earlier trends not captured. - SDG linkage based on keyword/search co-occurrence; potential for misclassification or undercounting where SDG relevance is implicit. - Analysis primarily descriptive; causal impacts on SDG outcomes are not assessed. Social and economic dimensions are relatively underrepresented in the source literature, constraining insights.