Wind power can be a cheaper alternative to selling power on the stock exchange for Ü20 plants.
A idea that makes methane from hydrogen and carbon dioxide from biogas production shows this.
Wind millers may prefer producing hydrogen to selling power on the exchange. True at least during “average” electricity pricing times. Two institutions have created an idea that uses biogas plant carbon dioxide. The two universities are Brandenburg University of Technology Cottbus-Senftenberg (BTU) and Flensburg University of Applied Sciences (FSU).
A power-to-gas concept for a renewable energy station in Nordhackstedt, Schleswig-Holstein, was engaged. The idea is to keep two wind generators running that no longer get guaranteed electricity payments. The calculations showed that low-cost methane generation is feasible if the energy transition regulatory framework is adjusted.
In the neighborhood, Nissen Biogas GmbH & Co. KG operates a 900 kW biogas plant, two 400 kW satellite CHP units, a local heating network, and two 600 and 1.5 MWel wind turbines. The Renewable Energy Sources Act (EEG) compensation period for the two wind turbines is about to end. However, the operators Bernd and Dirk Nissen only receive trade electricity prices for these turbines, making their operation unprofitable. To prevent closure, the Nissens sought alternative business strategies.
To this goal, BTU researchers devised a power-to-gas (PtG) concept. The idea is to use wind turbines to power an electrolyzer. The biogas plant supplies raw biogas, which reacts with hydrogen to generate methane (CH4, natural gas equivalent). In this case, anaerobic bacteria called archaea produce methane and heat in an innovative trickle-bed reactor.
Unlike catalytic methanation, the method is less difficult and more technologically robust. It doesn’t need high temperatures or high pressure. It also uses little energy because it doesn’t need an agitator. Finally, the procedure produces pure gas. The synergistic coupling with biogas plants is aided by the fact that the microorganisms in the trickling bed can be fed nutrients from the biogas plant’s liquid fermentation wastes, and the decoupling reaction heat can be used for fermenter heating.
The researchers studied numerous plant combinations for the Nordhackstedt site and evaluated possible methane production costs. Raw biogas was proved to be a viable CO2 source for biological methanation. The researchers produced 7 Nm3 CH4 per m3 reaction volume each day with a 95% methane content in the product gas.
The economic studies show the plant can be run profitably. The legislative framework and plant technology must be optimized.
Farmers and researchers in Nordhackstedt aim to build an electrolyzer and a trickle bed reactor to test the concept. For now, they only intend to use the older of the two wind turbines. The electrolyzer’s connected load is 333 kWel. Gicon, a Dresden-based engineering firm, will help implement the notion. Together with the BTU, they invented the trickling bed method of biological methanation. Nordhackstedt would have the world’s first continuously operating pilot plant for biological methanation with raw biogas, which might serve as a model for commercial operations.
