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Biogas plants have everything that a flexible power plant needs: variable-speed motors, constant gas supply and their own gas storage. The German Renewable Energy Sources Act (EEG) 2012 paved the way to exploit this flexibility on the energy markets. Those who switch to power trading through independent power traders according to the so-called market premium model can offer the flexibility of their biogas plant both on the EEX`s spot market and on the control reserve markets organized by the German Transmission System operators. Gerd Clasen was immediately convinced by the new concept: "After one or two months, I understood that trading on the spot exchange is the right way to go and that sooner or later all operators will switch to the then new system.” Together with his four local business partners, he decided to bring KBB's biogas plant to the electricity markets as part of Next Kraftwerke's virtual power plant.

Gerd Clasen recalls that the integration into Next Kraftwerke's VPP went off without a hitch: “We had the contract with Next Kraftwerke reviewed by a lawyer, and after signing the contract the power trading through our new trading partner started quickly. The trading of our biogas electricity on the energy exchange is very transparent, we can calculate monthly on the basis of the invoices from Next Kraftwerke what additional revenues we have received through the market premium model compared to the old model, the fixed EEG feed-in tariff.".

But what about the supreme discipline, the provision of flexibility on the control reserve market? Here, in contrast to energy trading, the virtual power plant intervenes in the plant operation and dispatches the the biogas plant according to the specifications of the transmission grid operators in order to support the electricity grid. After the installation of the remote control unit, a so-called Next Box, it was networked with the headquarters of the virtual power plant in Cologne. Subsequently, various tests were carried out to prove the plant's dispatchability with the transmission grid operators ("pre-qualification"). KBB's biogas plant was ready to provide secondary reserves (aFRR) as early as mid-2013.

Gerd Clasen remembers the first activation of control reserve with a smile: "I sat with coffee and cake and received an SMS that there was a secondary reserve activation. I could watch live at my plant control interface how the CHP was ramped down within seconds from Next Kraftwerke's headquarters in Cologne. After the end of the activation, the CHP drove up again fully automatically. My coffee wasn't even cold yet." Since then, the two CHPs of the KBB biogas plant have repeatedly provided balancing energy for grid frequency stabilisation, both tertiary reserve and secondary reserve. The CHP units receive a signal via the Next Box to adjust the output - in the case of the larger of the two CHP units, for example, from the maximum output of 600 kW down to 360 kW. "When the contract was signed, we were able to decide for ourselves how far the CHP unit could be ramped down. So far, every activation has gone smoothly," explains Gerd Clasen. The remuneration for the balancing energy provided is made up of two components. On the one hand Gerd Clasen is paid a stand-by fee ("capacity price") and on the other hand he receives an activation remuneration ("energy price"). A good deal for him and for the energy grid which increasingly relies on bioenergy's flexibility.

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