Comparative Thermo-Economic Analysis of Standalone and Hybrid Geothermal-Solar Organic Rankine Cycle Systems

Geothermal-solar hybrid power generation has been widely recognized as a promising application within the realm of renewable energy, as such hybridization mitigates solar intermittency while enhancing the utilization of medium-temperature geothermal resources, thus enabling effective energy complementarity. To quantitatively investigate its performance enhancement over single-source systems, this study constructs and analyzes three Organic Rankine Cycle (ORC) based plants with a capacity of approximately 500 kW: a standalone solar ORC, a standalone geothermal ORC, and a hybrid geothermal-solar ORC system. A comprehensive analysis encompassing both design-point and annual off-design operations is conducted, followed by an economic assessment using key metrics. The Lhasa-Yangbajing region in Tibet, China, is selected as the case study due to its abundant geothermal resources and high solar irradiation, providing a representative testing scenario for hybrid energy utilization. At the design point, thermal efficiencies are 12.61% (solar), 6.66% (geothermal), and 9.14% (hybrid). Annual simulation results reflect the impact of solar intermittency, with power generation of 707.26, 4383.3, and 3488.9 MWh, respectively, demonstrating the hybrid system’s ability to balance output and stability. Economically, the specific investment costs are 6997.22, 3268, and 4978.4 USD/kWe, and the levelized costs of electricity (LCOE) are 14.09, 1.06, and 2.13 USD/kWh for the solar, geothermal, and hybrid systems. The hybrid configuration offers a favorable trade-off, significantly improving upon the geothermal-only efficiency while drastically reducing costs compared to the single solar system, confirming its substantial integrated application potential.