Analysis of the impact of Combined Cycle in the energy transition

The energy transition of the Italian electrical sector is balancing the objective of renewable energy sources generation increase and the need of maintaining a proper electrical system stability. In the next years, the phase-out of the coal will be covered by an increase of the renewable energy source exploitation supported by natural gas and biogas backup production. In this context, the production of electricity from natural gas, mainly produced by Combined Cycles Gas Turbines (CCGT) plants, that in 2019 covered 48.2% of the Italian electricity generation, will maintain its relevance at national level, even if a more flexible operating profile is envisaged. The use of Combined Cycles as backup power plants will further increase the frequency of transient operating conditions (i.e. start and stop), reducing their load factor and increasing the weight of the emissions related to transient operation with respect to those related to normal operation. In this paper, the operating profile of 45 Italian power-oriented CCGTs are analyzed showing the similarities of management in the different market zones and identifying the main operating patterns. Then a statistical analysis of the emission during normal and transient operation is performed basing on the public available yearly emission statement and highlighting the effect of the CO catalyzer during the transient. Finally, the yearly environmental impact of the flexible operation was assessed and compared to the yearly emission considered during the Environmental Impact Assessment, the Italian VIA (Valutazione di Impatto Ambientale).