REFWIND: Reference Wind Turbines and Wind Plants

Objectives

Reference systems are a key element of wind energy research and development because they act as benchmarks to evaluate technology innovations. Reference systems are popular in academia and research laboratories where students, professors, and researchers do not typically have access to design and operational data from real machines. Reference systems are also often adopted in collaborations between industry and academia, where they help to overcome limitations on data sharing. As reference systems improve and become more realistic, they are used in collaborations among industrial partners, again to minimise the use of intellectual property and the associated risk of data breach or loss of competitiveness. The rigorous definition of the system implemented in the windIO ontology is instrumental to the success of the reference wind turbine and plants.

Given this background, the objectives of the IEA Wind TCP Task 55 REFWIND are to:

1. Define novel land-based and offshore reference wind turbines that anticipate designs released by wind turbine manufacturers.
2. Define novel land-based and offshore reference wind plants that anticipate future installations.
3. Refine, maintain, and spread the use of a rigorous ontology to commonly define wind turbines and wind plants across fidelities and disciplines.
4. Maintain existing land-based and offshore reference wind turbines that are representative of today's installations and are widely used by researchers, students, and industrial stakeholders worldwide.
5. Conduct workshops in the areas of wind systems engineering and multi-disciplinary and multi-fidelity design optimisation.

Participation

The mailing list of Task 55 includes 124 people from eight participating countries, namely, Denmark, France, Germany, The Netherlands, Italy, South Korea, United Kingdom, and United States. The LinkedIn page lists 769 followers as of May 6th, 2026.

Progress, Results, and Impact in 2025

In 2025 research activities focused on advancing the standardised description for next-generation wind energy systems, highlighted by the release of windIO v2.0, which is the common ontology for wind turbines and wind farms and is fully documented at https://ieawindsystems.github.io/windIO/main/index.html. windIO v2.0 supports the detailed aero-servo-hydro-elastic definition of wind turbines as well as the full ontology of land-based and offshore wind farms. Both turbine and plant ontologies have been adopted in a variety of numerical tools, as witnessed by the 24 citations collected by the technical report documenting the theoretical background of windIO (DOI 10.2172/1868328). windIO was also presented at the 2025 Wind Energy Science Conference (WESC2025), which took place in Nantes, France, in June 2025 [1].

In parallel, the team that designed the 22-MW offshore reference wind turbine actively maintained its GitHub repository, addressing questions and improving weaknesses. Quite notably, a team at the Massachusetts Institute of Technology (MIT) successfully redesigned the floating tower to address critical fatigue constraints; their new design solution was independently verified by the original Task 55 designers, passed all expert checks, and will be made publicly available in 2026. The model of the 22-MW wind turbine is being used widely, and its technical report has accumulated 125 citations as of May 6th, 2026, since publication in 2024, demonstrating widespread scientific uptake and validation. The impact of reference wind turbines can also be verified by monitoring the number of citations collected by older technical reports. The report describing the 15-MW offshore reference wind turbine has collected more than 1,100 citations since publication in 2020, and the report describing the 3.4-MW land-based and the 10-MW offshore turbines has collected 241 citations since publication in 2019.

Among other notable results, the design of a new 2,200-MW array of three offshore wind farms was finalised by Samuel Kainz at the Technical University of Munich in Germany. Two journal publications derived from this work are currently in preparation, and an almost-final design was presented at WESC2025 [2]. Figure 1 shows the visualisation of the Dutch cluster used for the design of the new 2,200-MW array of three offshore wind farms and the surrounding existing and future offshore wind plants. Figure 2 shows an aerial view of the optimised layout of the array.

These results combined benefit research participants and the broader scientific community by providing openly available reference systems that reduce duplicated effort and accelerate innovation.

The Task 55 team held a virtual annual meeting spread over two days on 3–4 September 2025. The two meetings were attended by dozens of participants and were used to discuss recent accomplishments and plan future activities. Four new topics of interest were identified, namely, reference precursors for wind farm simulations, reference 3D blade finite element models, new reference land-based wind turbines, and reference maintenance strategies for offshore wind farms.

Next Steps

2026 is the third year of Task 55 REFWIND, which is scheduled to end on 30 September 2027. In 2026, Task 55 will finalise two publications describing the 2,200-MW array of three offshore wind turbines and will advance the design of three new land-based wind turbines with ratings of 6.3–7.2 MW, rotor diameters of 175–200 m, and specific power values of 200–300 W m⁻². Additional efforts include the development of standardised reference large-eddy simulation precursors to support high-fidelity wind farm simulations and the creation of reference operation and maintenance strategies tailored for floating wind farms.

References

1. Bortolotti, P., Barter, G., Bay, C. J., Mudafort, R., Lønbæk, K., Quick, J. A., & Zahle, F. (2025). windIO v2.0: A New Release for the Common Schema of Wind Energy Systems. In Proceedings of 2025 Wind Energy Science Conference, European Academy of Wind Energy.
2. Kainz, S., Quick, J., Arasteh, A., Souza de Alencar, M., Rodrigues, R. V., Kapila, A., Nguyen, B., Réthoré, P.-E. M., Bottasso, C. L., Bortolotti, P., & Bay, C. J. (2025). The IEA Wind 2200-22-MW Reference Offshore Wind Plants: Sequential vs. Cooperative Design. In Proceedings of 2025 Wind Energy Science Conference, European Academy of Wind Energy.