Cost-optimal investment decision for the natural gas infrastructure of Piedmont with biomethane distributed sources.

The aim of this study is to identify the different evolution paths of the gas infrastructure in Piedmont region considering, on the one hand, the perspective decrease of natural gas consumptions (according to European and national decarbonization targets for 2030 and 2050) and, on the other hand, the development of the biomethane sector as a distributed source of renewable gas. An optimization model is used to determine the most cost-effective decision that the Transmission System Operator should take about decommissioning or replacement of existing pipelines in the regional gas network. The Piedmontese network has been first represented on GIS software from open-source data. Then, a preliminary fluid dynamic analysis has been performed using MATLAB for the determination of pipelines capacities. Input data, such as the current network configuration, gas demands at the nodes, gas sources, pipeline capacities, and investment costs, are provided to the Python optimization model. This model is available in literature and has been modified to consider the perspective connections of the biomethane plants, that have been estimated according to the evolution of the revamping of existing biogas power plants following the new incentive schemes on biomethane production. The primary outputs of the model consist of network configuration, including divestments and new pipeline diameters, as well as gas dispatch, gas demand, and the costs’ Present Value in 2050. Two main evolution scenarios are considered: one without renewable gas penetration and one with the injection of biomethane from domestic production. All scenarios have shown partial refurbishment and partial decommissioning of the infrastructure, with smaller diameter pipelines to be needed in the future. A scenario with variable injection of biomethane have been considered, resulting in reduced costs with respect to the base scenario, favoring the injection of part of the available biomethane sources. Furthermore, it has been observed that including all potential sources of biomethane reduces the share of decommissioned infrastructure, resulting in higher costs.