Lived system transformation

Sometimes it's the small screws you have to turn to change the big picture. This is also the case with the two wood-fired power stations of Holzwerke Weinzierl GmbH. Initially, as producers of electricity from renewable energies, they fired the energy revolution with an output of over four MW. In the meantime, the power plants also act as participants on the balancing energy market and compensate for grid frequency fluctuations within seconds.

Case study of the wood-fired power plant in the VPP Case study of the wood-fired power plant in the VPP But in order to be able to assume this responsibility for security of supply, adjustments were necessary. "Of course, you often hear 'That's not possible' when you want to change something," recalls Josef Brauneis, head of electrical engineering at Holzwerke Weinzierl. "In our case, however, only minor changes had to be made to the system hardware so that the bypass flaps for the silicone oil vapor react more quickly. After the parameters and the system control had been adjusted, the rest of the process ran smoothly. In the meantime the procedure has become the standard at our generator manufacturer - also for other customers".

In more than 300 deliveries of short-term balancing energy, the two power plants, for whose daily operation Josef Brauneis is responsible, have demonstrated that renewable energies can make their contribution to system stability. They are switched via the Next Box telecontrol unit, which communicates via GPRS mobile radio with the central control center of the virtual power plant Next Pool in Cologne. The duration of power plant calls varies considerably depending on the grid situation. On some days, the balancing energy requirements of the transmission system operator last only a few minutes, but in rare cases it can also take up to 50 minutes to call up the two wood-fired power plants. "At the start of the project, we mentioned the technical and organizational restrictions to Next Kraftwerke, such as the minimum capacity that must not be undercut. These parameters are now taken into account in the control system of the virtual power plant, so that balancing energy call-offs, which are passed on to us by Next Kraftwerke, do not endanger the functionality of the plant," explains Josef Brauneis.

Holzwerke Weinzierl GmbH's motivation to become part of a virtual power plant was also based on economic considerations. "Of course, we have an interest in operating our wood-fired power plants with optimum economic efficiency. The investment costs are low and the necessary adjustments in everyday operation are manageable. And the additional revenues that we achieve through direct marketing and balancing energy justify our participation in the virtual power plant. The fairness of Next Kraftwerke has also convinced us, for example when it comes to short-term schedule changes."

Facts & Figures

Capacity turbine 1:1,6 MW
Capacity turbine 2:2,6 MW
Annual power generation:35,000 MWh (~8,500 households)
Rated thermal input:25,5 MW
Partner website: More about our project partner Holzwerke Weinzierl
Applied product:Direct marketing and balancing energy