Summary

The study points out that as wind turbine unit capacity continues to break new ground (>20 MW) and wind power expands into deeper waters, direct drive HTS generators, with their advantages of high-power density, high reliability without a gearbox, and adaptability of modular design, have become a significant development direction for high-power offshore wind power. The paper focuses on the enhanced cost competitiveness brought by the declining price of HTS tapes, the potential of reduced-ferromagnetic topology, the key technical challenges in thermal management and mechanical design, and proposes a development path for prioritizing the improvement of technology readiness level (TRL) over the next five years.

• Background and Opportunities

Offshore wind power is a crucial route toward carbon neutrality. The continuous increase in single-unit capacity boosts energy capture capability and reduces the capital cost per kilowatt, while also enabling expansion to deep waters with superior wind resources. However, wind turbine maintenance in offshore installations is expensive, imposing stringent reliability requirements for a 25-year design life. Direct drive generators eliminate the gearbox, have become the preferred scheme for deep-water areas. But their volume and mass increase with power growth, posing challenges for offshore transportation and assembly. Modularization provides a viable route. The high current-carrying capacity of high-temperature superconducting (HTS) tapes enables field magnets to generate magnetomotive force (MMF) far exceeding that of permanent magnets(PM), resulting in increased air-gap flux density and power density, thereby achieving miniaturization and lighter generators.

In 2018, the EcoSwing project's 3.6 MW HTS generator prototype demonstrated the application potential of this technology, achieved a 24% mass reduction and reduced its outer diameter from 5.4 meters to 4.0 meters compared to a permanent magnet generator of the equivalent capacity.

Picture 1.Compact and lightweight HTS generators in deep wates

• Existing Challenges and Potential Solutions

Current technical advancement of offshore direct drive high-temperature superconducting (HTS) wind turbine generators faces multiple challenges:

In terms of rated frequency, the increased blade length in large-capacity units leads to lower rated speed. To meet the input frequency requirements of grid-connected converters, the number of pole pairs needs to be increased. However, both HTS coil width and mechanical assembly space limit the lower bound of pole pitch, therefore, power density gains are typically achieved by shortening the axial length than reducing the diameter.

Regarding ferromagnetic topologies, while using structures with iron tooth and iron yokes can achieve saturation with medium MMF, it introduces issues like tooth harmonics, vibration, and eddy current losses. Removing ferromagnetic materials can reduce mass and increase power density but requires extremely high MMF to compensate for increased magnetic reluctance and faces mechanical challenges such as electromagnetic forces and self-field stress in air-core structures. As the price of HTS tapes decreases, reduced-ferromagnetic structures are becoming a feasible direction for exploration.

In thermal design, the current scheme involves superconducting filed excitation paired with a conventional conductor armature. It requires systematic optimization of cryogens, cooling power, thermal interfaces, and heat transfer paths, with a focus on addressing AC losses caused by time-varying magnetic fields. Thermal-induced quench is a core risk. Reasonable thermal conduction design and bypass current paths are needed to increase the minimum quench energy (MQE) and temperature uniformity.

Regarding mechanical issues, it is necessary to comprehensively consider the stress and strain of materials under complex loads, matching thermal expansion coefficients, support structure stiffness, and control of air-gap deformation. Simultaneously, resonance risks should be avoided by predicting magnet’s natural frequencies and conducting vibration tests. For floating offshore generators, the influence of the magnet’s attitude under various operating conditions also needs to be evaluated.

Conclusion and Outlook

High-temperature superconducting (HTS) generators hold significant advantages in power density, system reliability, and modular manufacturing. Driven by the fusion industry, the declining price of HTS tapes has effectively reduced manufacturing costs, enhancing market competitiveness. Among the main current challenges, thermal design is the key to ensuring safe operation. Over the next five years, priority should be given to promoting the technology readiness level (TRL) of modular HTS generators, accelerating the transition from prototypes to standardized, certifiable mass-produced products, and promoting the practical application of models above 20 MW specialized for deep waters. They are expected to become a mainstream technology for high-capacity offshore wind power, significantly reducing the levelized cost of energy (LCOE), decreasing reliance on rare-earth materials, and improving overall system reliability.

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Original link：https://www.sciencedirect.com/science/article/pii/S277283072500081X

This research achievement, titled "Opportunities and challenges of offshore direct drive high-temperature superconducting wind turbine generators" was published in Superconductivity17, 100230 (2026). The first author and corresponding author is Zhen Huang from the School of Electrical Engineering, Shanghai Jiao Tong University. This research received support from the National Natural Science Foundation of China and the Shanghai Natural Science Foundation.

DOI: https://doi.org/10.1016/j.supcon.2025.100230.

Citation format：

Huang, Z., Ke, Z. & Coombs, T. A. Opportunities and challenges of offshore direct drive high-temperature superconducting wind turbine generators. Superconductivity 17, 100230 (2026).

Introduction to the First & Corresponding Author

Zhen Huang, Founder of NeuPower, Associate Professor in the Department of Electrical Engineering, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University.

He is a visiting researcher at MIT, a Shanghai Science and Technology Expert, a specially appointed Shanghai Bai Yu Lan Expert, Shanghai Eastern Talent, Shanghai Science and Technology Rising Star, Shanghai Pu Jiang Talent, and Shanghai Chen Guang Scholar. He has dedicated over 15 years to HTS wind turbine generators research. During his Ph.D. studies at Cambridge, he received 18 scholarships, including a full Ph.D. scholarship, and participated in helping Rolls-Royce^® build the world's first all-high-temperature superconducting synchronous wind turbine generators prototype. In recent years, he has led 18 vertical and horizontal projects related to superconducting motors, with cumulative R&D funding exceeding tens of millions of RMB.

About the Journal Superconductivity：

Superconductivity is an international academic journal focusing on the latest research in the field of superconductivity, aiming to promote academic exchange and knowledge dissemination. The journal encourages innovative thinking, supports high-quality research, strives to build a top-tier international academic journal dedicated to superconducting application research, and provides a platform for global researchers to showcase their achievements.

It is currently indexed in several globally authoritative academic databases, including ESCI, EI, Scopus, and DOAJ. It is classified as a Chinese Academy of Sciences Zone 1, Top journal, with a latest Impact Factor of 6.2 and a JCR Quartile of Q1. It is currently the journal with the highest impact factor in the global superconductivity field and the only one ranked in JCR Q1.