Together with Rhineland-Palatinate’s Minister for Economic Affairs Eveline Lemke, Ralph Rieker, Chairman of the Board of the Pirmasens Test and Research Institute (PFI), PFI Director Dr. Kerstin Schulte, and the Mayor of Pirmasens Dr. Bernhard Matheis inaugurated the power-to-gas pilot plant at Pirmasens-Winzeln Energy Park during a ceremony held on 24 June.
“Construction of PFI’s highly innovative pilot plant has dramatically raised the visibility of the energy turnaround in Rhineland-Palatinate”, Lemke commented.
The underlying concept of the PFI pilot plant is the novel power-to-gas process jointly developed by PFI and Mainz University. It utilises “biological methanation” as an innovative solution for long-term storage of excess power generated by wind turbines and photovoltaic installations in the natural gas grid. Having undergone successful engineering laboratory trials, the process is now to be tested on an industrial pilot scale and optimised in further research projects.
The pilot plant will produce up to 440,000 m³ of biomethane per year utilising wind and solar power and the carbon dioxide present in biogas. The excess power fed into the national gas grid by the power-to-gas process can be recovered by combustion of the methane in gas-fired power plants. The extensive pipelines and caverns of the German gas grid permit storage of the equivalent of 200 terawatt hours of electric power over a period of several months. That corresponds to about one third of Germany’s annual electric power consumption. Precisely this long-term storage aspect distinguishes power-to-gas from other storage technologies such as batteries, pumped hydro storage, or power-to-heat, which merely offer economic power storage for just a few days.
High-performance reactors for the biosynthesis of methane (CH4) from carbon dioxide (CO2) and hydrogen (H2) are the core components of the pilot plant. In contrast to the industrial synthesis of methane at relatively high temperatures (above about 300 °C) and relatively high pressure (10 to 30 bar) with associated high process costs, biological methanation utilises methanogenic microorganisms requiring operating temperatures of only about 35 to 65 °C and low pressure (1 to 7 bar), making the process far more economical. The CO2 present in the biogas produced by PFI’s research biogas plant at Pirmasens-Winzeln Energy Park serves as CO2 source for methane production. The hydrogen required is produced electrolytically by wind and solar energy and admixed with the biogas.
The thermophilic methane bacteria “digest” carbon dioxide and hydrogen to form methane (biogas) and water. The methane concentration increases steadily to over 95 percent by volume. The resulting high-quality biogas can be fed into the gas grid while the water and biomass produced are returned to the biogas plant.
PFI’s power-to-gas research project is thus an important contribution to the development of power-storage systems, one of the greatest challenges to be met in order to guarantee the success of the energy turnaround. Given the present rate of installation of renewable energy generation capacity, future electric power production will exceed immediate demand for increasingly long periods.
The new pilot plant is part of a biorefinery developed for R&D purposes. Total investment in the pilot plant has been about €3.1m, half of which has been met by PFI. The remaining €1.55m has been funded in equal parts by the European Regional Development Fund (ERDF) and the State of Rhineland-Palatinate. Moreover, Rhineland-Palatinate has funded development of the Energy Park by the City of Pirmasens to the tune of €1m. “We are confident that this is a good investment”, said Lemke. “There are very few places where expertise is so profound and effectively networked as at PFI: Here, development and innovation go hand in hand!”
On conclusion of the pilot phase, the Test and Research Institute plans to engage with partners to develop a business model for industrial-scale production of methane from excess power and to implement it at sites in Rhineland-Palatinate.