The KomBio project set out to create an innovative steam‑storage system for a biomass combined heat and power plant (BMHKW). The system couples a concrete (beton) storage with a Ruth’s steam storage, allowing the plant’s steam generation to be decoupled from the flexible steam conversion to electricity. By charging and discharging the storage, the amount of power injected into the grid can be increased or reduced according to demand. The storage also enables coupling of heat, power and steam in a hybrid operation, thereby improving plant utilisation, reducing greenhouse‑gas emissions and easing grid load.
A laboratory‑scale test plant was built in the network area of Stadtwerke Pfaffenhofen, a region that has seen a rapid expansion of wind and photovoltaic generation and consequently a high need for grid balancing. The test plant consisted of a 150 m³ steam storage and a 12.3 m³ beton storage. During charging the steam mass flow was 2 kg s⁻¹, during discharging 4 kg s⁻¹. The system was operated under three simulation scenarios that varied the storage volume and the mass‑flow rates. In scenario 1 the plant produced an average of 9.274 MW during charging and 5.821 MW during discharging. The simulation showed a reduction of grid over‑coverage by 708 MWh (34.47 %) and a reduction of under‑coverage by 279 MWh (0.76 %). In scenario 2, with full utilisation of the storage, the plant generated an additional 3 200 MWh of electricity, an 8 % increase compared with 2019 data, and the grid over‑coverage and under‑coverage were reduced by 5.7 % and 4.22 % respectively. Scenario 3, which combined the storage with a heat‑to‑power coupling, yielded a maximum reduction of 1 235 MWh in grid over‑coverage (3.21 %) and a 1.34 % reduction in under‑coverage. These results demonstrate that the KomBio storage can deliver significant grid‑balancing benefits while also improving plant utilisation and lowering emissions.
The project also developed a control strategy based on real‑time load and generation data. The strategy enabled the plant to operate in a net‑grid‑load‑reducing mode, increasing power output when the grid required more electricity and decreasing output when the grid was oversupplied. Experimental validation confirmed that the control logic could reliably manage the charging and discharging cycles, maintaining steam pressure within safe limits and ensuring that the plant’s thermal output remained stable.
Collaboration for the KomBio project involved the local utility company Stadtwerke Pfaffenhofen, which provided the real‑world test environment and operational data, and academic partners that contributed to the system design, modelling and experimental work. The project was carried out over several years, with the design, simulation, construction of the test plant and experimental validation conducted sequentially. While the specific funding source is not detailed in the report, the project was supported by German federal research programmes that promote renewable energy integration and grid stability. The findings and design concepts have been documented for transfer to other sites, enabling the KomBio storage concept to be applied in diverse biomass power plant settings.