Abdirahman Sheik Hassan, Neha Chandarana, Rainer Groh, Terence Macquart
The Big Picture
Multi-rotor wind turbines (MRWTs/MRs) are a promising solution to many of the problems facing the wind energy industry in its mission to scale up renewable capacity and address the ongoing climate crisis. MRWTs use an array of smaller rotors on one support structure, as shown in Figure 1, in place of the ever-growing single-rotor concept. The inherent scaling advantage of this architecture can offer significant mass and cost savings, while simultaneously alleviating challenges in transportation, manufacture and aeroelastic stability associated with large wind turbine blades. From the launch of the OceanX dual-rotor platform in China, to the planned construction of the Wind Catching demonstrator in Norway, the concept is moving up the technology readiness levels from theoretical economies of scale to practical solutions. While these demonstrators will shed light on the practical feasibility of the concept, little is known about the true extent of the benefit it can offer over the existing single-rotor paradigm.
Our work aims to provide further confidence in the feasibility of the multi-rotor concept through detailed modelling, analysis and by employing coupled aeroelastic optimisation to minimise the levelised cost of energy. We recently published a review on multi-rotor technology (tinyurl.com/4b4pnypm) and highlighted the need for comprehensive design studies to quantify the benefits of the multi-rotor concept in comparison to conventional designs.
An Open-Source Library to Support Research in the Multi-Rotor Concept
To address this gap, the ATOM aeroelastic software package from the University of Bristol has been expanded to model and design MRWTs, using blade element momentum theory coupled with multi-body dynamic finite element analysis. Enabling this process requires detailed virtual rotor models fit for the MR context. We tackled this problem with our recent work presented at the Multi-Rotor Seminar in Hamburg (tinyurl.com/4vpwbp64) on the generation of an open-source library of reference rotors for use in MRWT modelling. Optimised rotor models with ratings ranging from 100kW to 1MW are generated and shared in the OpenFAST format, allowing researchers to study and compare a large range of multi-rotor configurations.
Holistic Concept Design
Aiming to achieve a “globally optimised” MRWT, the individual rotor-level optimisation enables the assessment of optimal rotor number for a given overall rated power. Figure 2 demonstrates the use-case of these models – the ability to assess the optimal number of rotors by rapidly exploring a large number of different configurations with detailed rotor and support structure models.
An Opportunity for Greener Wind Energy
Working in collaboration with the National Composites Centre we are exploring the potential of MRWTs as an enabling technology for the use of sustainable materials in wind turbine blades, due to their smaller rotor size and reduced structural requirements. Ongoing work investigates the dual-objective optimisation of the rotor models in the rotor design library for the minimisation of both cost of energy and environmental impact.
[1] Mingyang Smart Energy. Retrieved October 2nd, 2025, from https://en.myse.com.cn/
[2] Wind Catching Systems. (n.d.). Retrieved September 23, 2025, from https://www.windcatching.com/