Sewage treatment plants not only ensure that wastewater is cleaned, they also produce energy and thus make a contribution to the energy transition. How biogas can be generated more flexibly in the plants and also contribute to the stability of the power grid is being researched by scientists at the University of the Federal Armed Forces in Neubiberg led by Christian Schaum, Professor of Urban Water Management and Waste Management, in the “FLX-Synergy” joint project.
Sewage treatment plants generate energy by producing biogas from the biomass produced there, the sewage sludge, according to a press release from the university. This gas can be transformed into electricity and heat in the combined heat and power plant. Ideally, the sewage treatment plant covers its own needs. The storage of energy is an important building block. “If you need electricity at 12 o’clock, for example, you would add the sewage sludge as needed and produce gas at that time and convert it into electricity,” says Schaum. Heat can also be used as required, since the heated digester tank can also be used as a seasonal heat store.
The energy from the sewage treatment plants can not only cover the company’s own needs for electricity and heat or cold, but can also be made available to external consumers. With the combined heat and power plants in combination with gas storage or emergency power generators, sewage treatment plants could contribute to the stability of the power grid, according to the university. In order to ensure this, a constant frequency of 50 Hertz is required. In the event of deviations, the network operator can throttle or increase the output of the units if the system participates in the control energy market. “This requires a high level of flexibility, and here, too, sewage treatment plants can operate on the market,” says Schaum. This is exactly what the FLX Synergy project is about.