The CycleTest project, carried out from 1 July 2019 to 30 September 2022, aimed to create and validate a realistic test cycle for wood‑central heating boilers that operate with automatic pellet or wood‑chip feeding. The core scientific outcome was a test methodology that reproduces the yearly load profile of a boiler in a proportional, real‑world manner, thereby overcoming the limitations of the DIN EN 303‑5 type‑test approach. A provisional test handbook, including the load cycle, measurement and evaluation procedures, and the required test fuels, was finalized in December 2020. The methodology was then subjected to a ring trial involving four experienced biomass‑boiler test institutes: the German Biomass Research Centre (DBFZ, Leipzig), the Danish Technological Institute (DTI, Aarhus), the Higher Federal Teaching and Research Institute Francisco Josephinum (BLT, Wieselburg), and the Gas Technology Institute (DBI, Freiberg). The ring trial confirmed the reproducibility of the method and led to minor adjustments that improved its robustness under varying operating conditions, including the use of buffer storage. The project’s technical deliverables also comprise a certification handbook and procedures that enable manufacturers to demonstrate the efficiency and emission performance of their boilers under realistic operating conditions. This certification framework will allow planners, installers, energy agencies, and funding bodies to compare different boiler technologies and to highlight advanced solutions. In addition, the method provides plant manufacturers with a tool for factory‑level testing and optimisation of boiler control and regulation, facilitating adaptation to the constantly changing heating demand of a permanent‑change heating supply scenario.

The project’s scientific impact extends beyond the specific test cycle. By providing an internationally applicable real‑measurement method, CycleTest addresses growing criticism of the low validity of existing type‑tests and the distortion introduced by the 2020 Eco‑Design Directive’s calculation methods for annual heating efficiency and emissions. The new method offers an alternative that can be used for normative purposes, thereby enhancing the reliability of performance data used in policy and market decisions. The data set generated through the ring trial will also serve as a benchmark for the state of the art under the defined test conditions, supporting further research and development in biomass heating technologies.

Collaboration was central to the project’s success. The Technology and Promotion Center Straubing (TFZ) coordinated the development of the test methodology (Work Package 2) and the validation (Work Package 3), working closely with its subcontractor Bioenergy and Sustainable Technologies GmbH (BEST). DEPI, the German Pellet Institute, led the market implementation side (Work Packages 4 and 5), ensuring that the certification program and its market rollout were aligned with industry needs. The ring trial’s participation of four external institutes expanded the project’s scope beyond the original plan of three partners, adding valuable expertise and enhancing the credibility of the validation results. The project was funded by the German federal government, with grant numbers 22039118 (DEPI) and 22038918 (TFZ). The coordinated effort of these partners, combined with the rigorous scientific methodology, positions CycleTest as a foundational contribution to the certification and optimisation of wood‑central heating systems in Europe.