The transition towards a decarbonized energy system necessitates the integration of low-carbon gases such as hydrogen and biomethane into existing natural gas infrastructure. This presents two key challenges:
• Operational challenge: How to manage the impact of varying gas mixtures on pipeline pressures and the stability of the gas distribution network
• Commercial challenge: How to bill customers fairly for the energy they use, which involves accurately tracking the gas’ Calorific Value (CV)

This paper presents and demonstrates a comprehensive solution in the form of an online simulation tool, or "digital twin," designed to address both challenges in real-time. By integrating live data from gas injectors and strategic network sensors, the system simulates the hydraulic behavior and propagation of blended gases. It overcomes the practical challenge of sparse pipeline instrumentation by utilizing state estimation techniques to create a complete, real-time picture of the entire gas distribution network.

The tool helps network operators ensure the safe and reliable delivery of gas by analyzing how different blend concentrations will affect pipeline pressure. At the same time, it calculates the precise, real-time Calorific Value (CV) for each customer, enabling accurate billing.