The impact of Greenhouse Gases on climate change has led the natural gas industry to double down its efforts on cutting methane emissions. In natural gas transportation and distribution, such emissions are generally due to leakage. This work focuses on estimating the reduction of the intrinsic emissions in a natural gas distribution network in Tuscany (Italy) by regulating the pressure outlet setpoint of a City Gate Station. The developed model estimates the leakage of a network hourly and for each element based on a hybrid database of measures of several European test campaigns. Measurements are corrected on the pressure of the elements calculated by hourly steady-state fluid-dynamic simulations of the grid. The expected results aim at showing how the pressure output regulation in a City Gate Station as a function of the gas demand can avoid a percentage of the intrinsic leakage without affecting the standards required for a safe operation of the grid.

Introduction and Background

Global warming is the result of anthropogenic emissions of greenhouse gases, of which carbon dioxide (CO2) from the combustion of fossil fuels is the main contributor [1]. Methane is responsible for the second-largest contribution, after carbon dioxide, to climate change. In particular, methane is a climate-altering gas with a Global Warming Potential (GWP) over 100 years of 29.8 [2]. This means that the contribution of 1 kg of methane to the greenhouse effect is 29.8 times greater than that of 1 kg of carbon dioxide. The European strategy on non-CO2 climate-altering gas emissions envisages reducing methane emissions in the EU by 29% by 2030 compared to 2005 levels [3]. Globally, reducing anthropogenic methane emissions by 50% over the next 30 years could reduce the global temperature increase by 0.18 °C by 2050 [4]. In this scenario, the natural gas chain must redouble its efforts to reduce methane emissions. Natural gas transporters and distributors are therefore also involved in this process. One of the main causes of methane emissions during transport and distribution is linked to leaks in the infrastructure. In natural gas transport and distribution, fugitive emissions can be classified as:

- Intrinsic: due to wear and tear of joints, micro-cracks in pipes and physiological leaks of elements installed above ground (Above Ground Installation).

- Incident: linked to damage generated by third party activities such as excavations or road incidents.

- Operational: due to venting and purging phenomena (vent valves, purging of a section of the network during maintenance).

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