Power-to-gas plants use surplus green electricity to produce hydrogen, allowing large quantities of renewable energy to be stored and further utilized.
“I don’t like it when energy is wasted,” Stefan Ficht says. The electrical engineer manages production development for the Energiedienst Group, which supplies green hydropower energy to over 270,000 customers in Germany and Switzerland. In times of increased power generation through renewable energy, it can happen that more energy is produced than is currently needed, leading to an imbalance between supply and demand. Hydropower plants must then reduce their production by allowing water to flow that is partially unused. “We therefore came up with the idea to do something else with this electricity and store the surplus renewable energy,” Stefan Ficht says.
This is made possible by a power-to-gas plant. It is one of Germany’s 35 plants and has been operating on the site of the run-of-the-river power plant in Wyhlen am Rhein since December 2019. Green electricity is used for electrolysis in the plant, in other words to split water into oxygen and the energy carrier hydrogen. Endress+Hauser not only supplied measurement devices for the electrolyzer but also for all of the upstream and downstream processes in addition to an attached research electrolyzer. “It is important to us that everything works,” Stefan Ficht says. “I know from my own experience that Endress+Hauser pays for itself – I have been building process plants in the energy sector for 25 years.”
The facility, which produces approximately 200 cubic meters of hydrogen per hour with an output of one megawatt, is considered to be a flagship project in energy transition in southern Germany. To begin with, the gas is being used by a nearby chemical company. It replaces hydrogen from fossil fuels in their production process. “The aim is to run fuel cell vehicles with it in future,” says Energiedienst Project Engineer Dagmar Kaiser. The process can also be linked to other industry sectors: When combined with carbon dioxide, hydrogen creates synthetic fuels for conventional combustion engines or methane that can be fed directly into the natural gas grid.
How green electricity turns into green gas
1. A direct route Through a switching station and a transformer, the electricity is fed directly from the plant into the power-to-gas facility and used for electrolysis.
2. Electrolytic splitting During alkaline electrolysis, purified water (H2O) is split into oxygen (O) and high-purity hydrogen (H2) with the help of electricity.
3. Effective compression The hydrogen is then compressed, increasing the pressure from 30 to approximately 300 bar, allowing the gas to be transported more efficiently.
4. Many opportunities The hydrogen can now be used for mobility, heating or industrial processes. It is stored in tanks until it is collected by truck