Assessment of Carbon Emission Reductions from a Rural Rooftop PV System Based on SAM

To investigate the effects of model selection, time-varying parameters and climatic differences on the carbon emission reduction performance of rural rooftop photovoltaic (PV) systems, this study selected a typical rural residential rooftop PV system in Beijing as the research object. Hourly simulations using the System Advisor Model (SAM) and an operational-period baseline method were employed to optimize the PV array parameters and conduct a multi-factor analysis of carbon emission reductions. The results show that the first-year electricity generation was 15,902 kWh, corresponding to an annual carbon emission reduction of 12.60 tCO2. The carbon emission reduction estimates obtained using the three irradiance models differed, with a maximum deviation of 0.51 tCO2. When both PV module degradation and changes in the grid emission factor were considered, the cumulative carbon emission reduction decreased by 68.37 tCO2 relative to the ideal scenario. Moreover, the faster the grid transition speed, the lower the cumulative carbon emission reduction over the system’s operational period. In addition, extending the analysis from a single region to multiple regions revealed that the annual carbon emission reductions in representative rural residential rooftop PV systems in Beijing and Wuhan differed by 2.94 tCO2, with differences also observed in their seasonal variation patterns. The assessment of rural rooftop PV systems should comprehensively consider irradiance model selection, module power degradation, grid transition pathways, regional climatic conditions and economic feasibility.