Both in Europe and in North America, the goal to use increasing amounts of renewable energy has created the need for electricity storage. One concept which aims to address this need is to produce hydrogen from surplus electricity, and to use the existing natural gas pipeline system to transport and store said hydrogen. Generally, the hydrogen content in the pipeline flow would be below 20%, thus avoiding the problems of transporting and burning pure hydrogen. The thermodynamic properties of hydrogen-natural gas mixtures, as well as their impact on the combustion process are briefly addressed.
To assess the impact of hydrogen addition in various concentrations to a natural gas pipeline, a realistic pipeline system is simulated. The pipeline hydraulic simulation provides the necessary operating conditions for the gas compressors and the gas turbines that drive these compressors. The impact on transportation efficiency in terms of energy consumption as well as the impact on the transport capacity of a pipeline where the equipment was sized originally for natural gas transport, are assessed.
The increased use of renewable energy will require the capability to store energy to balance the large fluctuations in the availability of renewable energy, thus balancing supply and demand. Generating green Hydrogen from surplus electricity using electrolysis and transporting this hydrogen together with natural gas in gas pipelines is a method to provide storage and transportation for hydrogen [1,2,3]. Mixing hydrogen into natural gas pipelines requires a number of considerations regarding the compression of this mixture, the use of the mixture as a fuel for the gas turbines that drive the pipeline compressors, and the impact of pipeline capacity and transport efficiency.
There are a number of other concerns, including safety concerns for gas compressor packages, and material issues related to hydrogen embrittlement on rotating parts like impellers, pressure containing vessels (like compressor bodies), and high-pressure pipes. .