Gas grid
The gas grid in Germany ensures that the natural gas extracted at the respective production sites reaches the end user. The article explains the system of gas supply in Germany, where our gas comes from and what the gas grid of the future might look like. In particular, it looks at the importance of hydrogen for the gas network.
How does the gas grid work?
In Germany, a total of 443,000 kilometers of pipelines ensure that the natural gas from the production sites is available wherever it is needed. The gas used in this country is part of a large european gas network and comes mainly from Russia, Norway and the Netherlands, with smaller gas suppliers being Denmark and the UK. A small proportion of our gas comes from production sites in Lower Saxony – but with a share of 11 percent of total natural gas demand in 2010, domestic supplies play a minor role.
The mostly imported gas takes its route via so-called long-distance gas companies, which include Shell, Exxon, RWE, VNG and Wingas, among others. They feed the gas into the gas grid, whereupon it is transported to the local gas suppliers in the respective supply areas. These ensure that the gas reaches the end user. There are also numerous underground storage facilities across the country to protect the gas grid from load fluctuations.[1]
What is the pressure in the gas line?
There are different pressure levels for the gas grid: high pressure, medium pressure and low pressure. Since the higher the gas pressure, the more gas can be transported, producers feed the natural gas into the pipelines or trunk lines at high pressure (up to 200 bar).[2] However, over long distances, the gas loses pressure power. Therefore, compressor stations maintain the pressure and thus the flow of the gas.[3]
The pressure levels in the gas grid in Germany vary widely. For example, gas pressure in regional networks ranges from 1 to 70 bar. Gas pipelines at the municipal level have a pressure of less than one bar, and gas pipelines for house connections have a pressure of up to 30 millibars.[3]
How do I get connected to the gas grid?
In Germany, almost half of all houses are heated with natural gas. However, a connection to the municipal gas grid is essential for natural gas heating.
To find out whether there is a natural gas pipeline near your house, contact your natural gas supplier. Particularly in the case of newly built residential areas, these are nowadays usually immediately supplied with natural gas connections.
The network operator lays the gas connection right up to the house, but naturally charges for this service. The price the operator charges for the connection depends on the distance to the nearest main supply line. If the distance is within a certain range, the operator usually charges a flat rate. For each additional meter, the network operators charge the installation costs.
As a rule, the so-called main shut-off device is installed near a wall breakthrough. From there on, it is the homeowner’s responsibility to have the pipes laid in the house with the help of a specialist company.[4]
What are the advantages of using hydrogen in the gas grid?
Hydrogen is considered the cleanest known energy source to date because the only by products of hydrogen production are heat and water. Hydrogen fuel cells generate electricity by combining oxygen and hydrogen.[5] Direct methanol fuel cells are also already being used in modern fuel cell technology .
Hydrogen is thus being treated as an important helper in achieving climate protection targets. It is considered "green hydrogen" if it is produced from renewable energies such as wind turbines or photovoltaic systems. However, there are still difficulties in transporting the hydrogen.
It would be conceivable to transport the gaseous hydrogen in the already existing natural gas pipelines. Pilot projects are already attempting to accommodate hydrogen in the gas grid – by mixing the gas with the local gas grid in some locations. Subsequently, the hydrogen can be used as needed for e-mobility, household or industrial purposes.[6]
However, there is one difficulty: When hydrogen is converted back into electricity – i.e. electricity produced from the gas – around half of the energy is lost again.[1]
What will the gas grid of the future look like?
To drive forward the energy transition, both the German electricity grid and the gas grid need to be expanded. Experts are banking, among other things, on feeding more biogas into the existing gas grid. Today, however, no one knows exactly what the technical and economic implications of this project will be. Thus, the extensive injection of biogas into the German gas grid poses a major challenge.[1]
Many hopes are also pinned on hydrogen in the gas grid. The reason: By converting renewable electricity into hydrogen, it is possible to store and transport the electricity to the end user. Thus, in the long term, the gas could gradually replace fossil fuels in the heat supply, industry and transport sectors. This is good news especially for the decarbonization of industry, since industrial processes are usually difficult to electrify.[7]
Reversible fuel cells will also play an increasingly important role as storage technologies for the storage and reconversion of hydrogen. This type of cell is suitable for temporarily storing electricity in the form of hydrogen and converting the hydrogen back into electricity at a later date. The technology could be used to compensate for the fluctuations in renewable energies that occur in some cases.[8]
Conclusion
Hydrogen fuel cells have no negative impact on the environment and are therefore currently considered the cleanest energy source. Reversible fuel cells are also able to store electricity in the form of hydrogen and convert it back into electricity later. Such a storage technology could help to convert surplus electricity from wind and solar energy into hydrogen and use it for the existing gas grid. However, since there are still difficulties in converting hydrogen into electricity, the degree to which hydrogen can be blended into the gas grid is still limited.
