Hydrogen |
Life expectancy of pipelines repurposed for H2
fracture mechanics tell us? Dr Johanna Steinbock*, Jan Sachse**, Dr Albert Großmann***, TÜV SÜD Industrie Service
Green hydrogen is one of the cornerstones of decarbonisation. As a promising alternative to fossil fuels, it further improves the economic potential of the offshore wind sector, which can use electrolysis to produce large volumes of green hydrogen that is both carbon-neutral and cost-effective.
Some energy intensive industries will use green hydrogen directly as a raw material, for example in the production of synthetic fuels or environmentally friendly chemicals. Where large volumes of hydrogen are generated, pipeline transport is more economic than conversion into electricity. In many cases, existing pipeline
infrastructure can be used for this purpose. And to cope with the fluctuating supply of wind energy, hydrogen can be stored in caverns in a similar way to natural gas.
Using the natural gas grid Germany is criss-crossed by more than half a million km of natural gas pipelines, with diameters of almost 1.5 m. These pipelines can withstand operating pressures of up to 100 bar and are thus also suitable for hydrogen distribution.
However, this requires expert planning and implementation of technical measures
in accordance with scientific findings for each pipeline section. Fortunately, some of the gas grid operators in Germany can look back on over 100 years of experience in the transportation of gas and so some of these pipelines have been in use for this length of time. The accumulated knowledge will be used to convert the pipelines to the next stage in their lives.
Until the mid-20th century they transported “town gas” manufactured from coal, which included methane, nitrogen, carbon monoxide and a large percentage of hydrogen (up to 50%). From the 1960s onwards, town gas was replaced by natural gas. Today most gas fed into the grid is natural gas, with a higher methane content and calorific value. In many regions, high-calorific gas (H-gas) is increasingly replacing low-calorific gas (L-gas). This shows that the existing natural gas grids tolerate fluids of different compositions and can also be used to transport hydrogen provided the appropriate measures have been taken.
Regulations governing conversion and new construction
In Germany, hydrogen pipelines primarily fall under the scope of the Energy Industry Act (Energiewirtschaftsgesetz, EnWG). The act aims at establishing a grid-based gas and electricity supply for the public, which is as safe, cost- effective, consumer-friendly, efficient, and as environmentally compatible as possible. In this context, renewable energy is increasingly becoming the focus of interest. However, significant changes to energy systems are subject to notification and approval for safety reasons.
For example, use of a different fluid with a maximum permitted operating pressure exceeding 16 bar requires the initiation of a notification procedure in accordance with Art. 5 of the German Regulation on High Pressure Gas Pipelines (GasHDrLtgV). In cases of conversion
Left: Laying of the NETG (Nordrheinische Erdgastransportgesellschaft) pipeline, Cologne region. (Photo copyright: OGE)
32 | January/February 2022|
www.modernpowersystems.com
: what does
Hydrogen transport does not necessarily require the construction of dedicated pipelines. In some cases, existing natural gas pipelines may also be suitable. However, if the fluid transported by the pipeline changes, the safety concepts for pipeline operation must be reviewed and revised. This includes verification that the pipeline is suitable for hydrogen transport as well as a service-life prediction. The integrity of steel pipes can be analysed using fracture mechanics, even in the case of cyclic load
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