Biogas ensures stable networks

Biogas plants are regarded as the jokers of the renewable energy system, as they can feed in electricity and heat flexibly and thus compensate for fluctuations. A plant in Bavaria proved that bottlenecks and overloads in the electricity grid can be avoided if photovoltaic and biogas plants feed in electricity in a coordinated manner.

Ensuring the stability of the electricity grids and thus the security of supply at all times is a major focus of the energy revolution in Germany. However, the increasing feed-in of fluctuating renewable electricity generators, such as wind power or photovoltaics (PV), is leading to increased bottlenecks or overloading of the distribution networks. The bottleneck to the medium-voltage distribution grid into which PV and biogas plants feed (up to 50 kV) is the so-called grid connection point, which is designed for maximum power feed-in. If this power is exceeded, the systems are shut down to ensure grid stability.

The Institute for New Energy Systems (InES), together with the project partners, has set itself the goal of reducing this burden without cost-intensive grid expansion in the project FlexFuture – Integration of biogas plants in grids with a high proportion of fluctuating electricity generators. The scientists used the controllability of biogas plants for load balancing. This means that short-term fluctuations in the electricity grid are compensated for by the controllable electricity production of the biogas combined heat and power plants (CHP units for the generation of electricity and heat). Load balancing is performed on the basis of PV supply forecasts.

“In real operation at the Zellerfeld biogas plant in Bavaria, we have shown that an intelligent system control system can prevent current peaks in the feeding of renewable electricity,” explains Prof. Wilfried Zörner, project manager at the Institute for New Energy Systems (InES) at the Ingolstadt Technical University. Together with the biogas technology manufacturer UTS Products GmbH and the location developer PROLIGNIS Energy Consulting GmbH, a control concept for the automated and distribution network oriented operation of biogas plants was developed, which can be transferred to practical plants.

By installing additional CHP units and appropriately dimensioned gas storage tanks at the biogas plant, additional capacities can be provided for the generation of electricity. In the case of a high PV feed-in, the power generation at the biogas CHP can be shut down or even suspended. During periods of low solar radiation, the CHP converts more biogas into electricity and heat.

Photo: THI (Technische Hochschule Ingolstadt)

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