Tech Insights

X-Shaped Rotors: The Future of Wind Turbine Innovation?

April 24, 2024 by John Nieman

To reach renewable energy goals, the wind sector is exploring rotor designs like the X-Rotor to spur development. 

Solar energy has been at the forefront of the energy transition, but wind power has an increasingly important role in the collective strive toward net-zero carbon emissions. Although the wind power industry has been growing, radical innovation is needed to overcome industry obstacles related to supply chain shortages, turbine tower transportation challenges, and maintenance struggles associated with offshore wind farms that operate in harsh maritime environments. 

Reconsidering the material used to manufacture wind turbines and component design can help the wind sector make the necessary leap forward to meet looming renewable energy goals. Earlier this year, Modvion, a Swedish engineering company, launched the first commercially viable wooden wind turbine to help overcome steel supply shortages and shipping challenges. Now, engineers are exploring more complex turbine designs, including an X-shaped rotor combining vertical and horizontal rotors. 

 

X-Rotor prototype rendering

X-Rotor prototype rendering. Image used courtesy of X-Rotor

 

The Pressing Need for Wind Power Growth and the Logistics of Wake Challenges

The power grid will be increasingly taxed as renewable technology comes online in the coming decades. All renewable energy sources, including the wind power sector, must expand to accommodate this growth. The European Union has established an emissions reduction goal of 55% by 2030. To meet this goal, renewables must leap from 23% of the energy market share to 42.5%. 

In the U.S., the Department of Energy’s (DOE) Wind Energy Technologies Office (WETO) has determined wind energy is currently contributing about 10% to the grid’s total power and notes that growth must occur to meet projected demands. 

As the wind sector expands, turbine towers grow taller, blades get bigger, and wind farms sprawl across larger spaces. There are defined limitations in how topography impacts wind flow, so wind farms cannot be readily accommodated in any region. 

 

Geographical variations in wind speed.

Geographical variations in wind speed. Image used courtesy of the National Renewable Energy Laboratory

 

In some locations like harsh ocean environments, maintenance becomes much more challenging as wind farm size expands. 

Part of what drives wind farms' sprawling nature is the logistics of dealing with wake challenges. Each turbine produces a wake behind it that can easily slow down and disrupt the productivity of any turbine in close enough proximity, and this impact is significant. A wind turbine’s power performance can be reduced by up to 40% if the wake of another turbine impacts it. 

The wake created by a turbine is largely created by its axis, and most commercial turbines in operation are horizontal-axis wind turbines. Experimenting with vertical-axis wind turbines (VAWTs) and perhaps even hybrid models might be the most innovative path to wind power’s future, especially given the growth in offshore wind farms and how hybrid design can serve the unique challenges of maritime environments. 

 

How Innovative Rotor Design Can Optimize Spatial Logistics and Improve Performance 

Two professors at the University of Strathclyde in Glasgow are developing an innovative hybrid rotor design capitalizing on the affordances of horizontal and vertical axes. This design, the X-Rotor, aims to lower energy costs by combining a unique VAWT configuration with a secondary rotor power-take-off system, potentially reducing operations and maintenance costs by up to 55% and turbine capital costs by up to 32%, which could lead to energy cost savings of up to 26%.

 

Early version of a V-rotor turbine

Early version of a V-rotor turbine. Image used courtesy of ResearchGate

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The X-Rotor's primary rotor features a double V configuration, which maximizes the swept area and minimizes the overturning moment—a common issue with V-rotors. This design also provides attachment points for the secondary rotors, which are power-take-off mechanisms that replace conventional drive trains. This innovative approach helps to avoid the torque ripple and the challenges associated with low-speed/high-torque drivetrains inherent in traditional VAWT designs.

The X-Rotor is still in the simulation, research, and development phase, so no constructed or commercially available model exists. Still, this research offers significant promise for how design innovations for wind turbine components can advance the entire sector.