Hybrid solar-geothermal energy systems: Technological developments, challenges, and scientific research dynamics

The integration of solar and geothermal energy technologies presents a promising pathway to enhance the reliability and efficiency of renewable energy systems. By combining the intermittency of solar power with the stability of geothermal energy, hybrid solar–geothermal systems can deliver more consistent outputs while reducing greenhouse gas emissions. Although individual technologies have been extensively studied, integrated configurations remain underexplored. Despite their advantages, widespread adoption is still limited by various economic, technical, and environmental challenges. This study provides a comprehensive examination of integrated solar–geothermal technologies, focusing on recent technical developments, key performance indicators, and major deployment barriers. A two-stage methodology is applied: qualitative and bibliometric analysis. First, a detailed technical assessment investigates design elements, configurations, and operational principles of standalone and integrated systems, highlighting technological progress. The second stage involves an in-depth bibliometric analysis using the Scopus database, processed through Biblioshiny and VOSviewer to analyze scientific research since 2000 up to mid-2025. The integrated approach shows that hybrid configurations are considerably progressing, reflected by the consistent rise in publications, reaching 809 in 2024. Findings confirm that while solar-geothermal energy systems offer significant potential, deployment is hindered by high capital costs, integration complexity, operational expenses, land-use demands, water consumption, and limited policy and financing support.