Spatiotemporal potential and economic assessment of highway slope-based photovoltaics: A case study in Jiangxi, China

As the growing scarcity of available land for renewable energy deployment, highway fill slopes offer an innovative solution for land-efficient renewable energy integration. This study proposes a scalable, high-precision method for identifying PV-suitable slopes using high-resolution DEM, and evaluates the solar potential of these sites in Jiangxi Province across physical, geographical, and technical dimensions. A geo-techno-policy economic framework is developed to assess project feasibility under varying capital costs and subsidy scenarios, using the payback period as the core metric. The findings reveal strong spatial and seasonal heterogeneity in slope-based solar resources, with high-potential areas concentrated in southern Jiangxi. Despite the removal of cut slopes due to glare and instability concerns, fill slopes alone provide over 88.79 km2 of developable land, with an estimated technical potential of installable capacity of 12.3 GW and 14.5 TWh /year. Economic analysis shows that capital cost reduction has a stronger effect on viability than marginal subsidies in recent ten years, with payback periods below 9 years achievable in top-performing zones. These results underscore the need for tiered investment strategies, spatially differentiated policy tools, and regulatory frameworks that formally recognize slopes as infrastructure-integrated photovoltaic deployment surfaces.