Green hydrogen for RES energy storage and natural gas system decarbonization: a case study in central-southern Italy

The increase of the electricity production from non-programmable RESs generates criticalities in the balance between the energy supply and demand, due to the intermittency and uncertainty of these energy sources. To tackle this problem, significant storage capacities of the electricity produced in excess of demand will be required in the coming years. These capacities could be ensured by exploiting the NG transport, distribution and storage infrastructures through the implementation of PtG technology. This technology can allow, on the one hand, the energy storage mitigating the asymmetries between renewable electricity production and energy demand and, on the other, the decarbonization of the NG infrastructure by the hydrogen injection into the grid. The objective of this work is to analyze the actual feasibility of distributed production systems of green hydrogen and its injection into the national NG transport network. In particular, a mathematical model has been developed to assess the dynamic operation of a PtH2 integrated system for the production of hydrogen using photovoltaic-powered electrolyser and its injection into the NG transport network downstream of an RMS present in central-southern Italy. The model developed is based on the hourly irradiation data and on the real NG consumptions of a section of the transport network. A scenario of increasing photovoltaic production is considered and the effects on NG infrastructure has been evaluated. The results show that the highest fractions of hydrogen in the NG mixture can be fed into the grid during the summer period, when the consumption of NG is lower and the production of electricity from photovoltaics is maximum, confirming the effectiveness of the PtG technology for the accumulation of excess electricity produced by distributed photovoltaic systems.