Hourly carbon intensity of natural gas combined cycles compared to the current and future electricity mixes in Italy

The current solutions for power generation include a wide range of technologies, each providing specific advantages and limitations. In a decarbonization perspective, their carbon intensity will represent a crucial factor in determining their success towards a future low-carbon electricity mix. Today, natural gas combined cycles are among the most efficient plants, especially when operating in combined heat and power mode. This paper presents the analysis of the actual carbon intensity of a large-scale natural gas combined cycle, calculated on an hourly basis over several years of operational data, compared with the average hourly emissions of the Italian power grid both with the most recent electricity mix and the forecast to 2030 and 2040, based on the decarbonization targets that are currently in place. The results of this study highlight the very low carbon intensity of the electricity produced in CHP mode, with average monthly values as low as 242 g/kWh during the winter months, compared to around 350 g/kWh when operating in full-electric mode in summer. These values are lower than the current performance of the Italian electricity mix in winter, although the opposite is true in summer, confirming the importance of the cogeneration in decreasing the carbon intensity of the energy output. However, in a future low-carbon electricity system, fossil gas CHP units will have higher carbon emissions than the average mix. In order to achieve the decarbonisation objective it is necessary to take these considerations into account. The availability of a high-resolution estimate of the performance of power generation will support policy makers in developing strategies to deploy the most effective technologies to decarbonize the energy system.