Design and techno-economic feasibility study of an innovative solution for gas preheating in Re.Mi. stations through an ambient air heat exchanger

This thesis examines the deep and rapid transformation of the European natural gas sector, a change accelerated by the 2021–2022 energy crisis and the Russia–Ukraine conflict, which highlighted the high dependence on imports (about 83% for the EU and 96% for Italy) and the resulting need to diversify supplies (LNG and African corridors) and to reinforce an infrastructure often considered “vintage” but still central to energy security. The core of the work was the study of innovative solutions, developed within Italgas’ Open Innovation framework, aimed at improving the energy efficiency of the Italian distribution network. Specifically, the thesis focused on reducing the natural gas consumption used for preheating in Regulation and Metering stations (Re.Mi. or IPRM). Preheating is crucial because pressure reduction (for example, from 65 bar to 5 bar) causes a sharp temperature drop (down to about −25 ◦C) that must be prevented for safety and metering reasons. The proposed solution is the integration of an ambient-air heat exchanger (AAV) in order to use outdoor air as the primary thermal source and relegate the gas-fired hot-water system to a backup/integration role. Thermo–fluid-dynamic simulations showed a 73.4% saving in gas consumption, validated by comparison with real data that confirmed an actual reduction of 62%. This translates into annual savings of 42 tonnes of CO2 emissions. From an economic standpoint, the project proved solid: the initial investment, estimated at €77,040, generates annual operating savings of about €10,800, yielding a positive Net Present Value (NPV) of €17,865.54 (at a 6% discount rate) and a simple Payback Time (PBT) of 7.9 years, making the intervention compatible with the decision criteria of a network operator. The positive outcome of the study led to the filing of a patent and to the planning of a pilot project to be carried out by the end of the second quarter of 2026, indicating the concrete possibility of replicating the solution on other stations and thereby contributing to the modernisation and progressive decarbonisation of the national gas infrastructure.