Assessment and economic analysis of photovoltaic power generation potential on highway slope: a case study of Guangxi, China

Highway slope photovoltaic (HSPV) systems represent a significant approach to achieving transportation-energy integration and reducing carbon emissions, as well as a crucial utilization method for renewable energy. Given the complexity of assessing the installable area of photovoltaic (PV) panels on highway slopes across large spatial scales, a regression assessment analysis was conducted using Random Forest. The results demonstrated that as of 2024, the total installable PV area on highway slopes across 14 cities in Guangxi is 0.989 km2. Furthermore, accounting for regional variations in PV system efficiency, the power generation efficiency of HSPV systems in different areas was evaluated by integration of the Analytic Hierarchy Process (AHP) and Entropy Weight Method. Based on these assumptions, the estimated installed capacity of HSPV in Guangxi reaches 155.93 MW, with an annual power generation potential of 169.03 GW · h. After conducting an economic analysis, the project is economically feasible, as evidenced by a net present value > 0, an internal rate of return > 8%, a benefit-cost ratio > 1, and a payback period < 10 years. The proposed integrated framework—combining random forest-based slope-area extrapolation with AHP-entropy efficiency evaluation—remains reliable even without high-resolution imagery, offering replicability and scalability for highway-slope PV assessments. The findings provide actionable guidance for PV siting and economic appraisal in other provinces or linear infrastructures (e.g., railways, transmission corridors).