Reducing the Cost of Future Turbines with Active Lift Control

Wind turbine tower height and swept area has increased dramatically over the last 20 years

It’s an exciting time for the US wind industry. Advancements in technology are allowing us to tap into new generation potential across the country, as well as off our Eastern shores. As we work to reach the DOE’s goal of 20% and 35% penetration by 2030 and 2050, the industry is turning to ultra-large turbines. Vestas, for example, recently announced plans for a 15 MW offshore turbine, joining SGRE and GE as the latest to hit the teens in nameplate rating. These new designs are over 50% taller with blades that are twice as long as turbines of 15 years ago. The Vestas 15 MW design reaches 236 meters in rotor diameter and has a tower that is taller than the Washington monument. Installing larger turbines allows wind farms to use fewer per wind farm, and is expected to reduce net operations and maintenance costs and some other outlays incurred by wind farm owners and operators. But these cost savings are not guaranteed to continue to be realized with ever-increasing turbine size.

While ultra-large turbines can capture significantly more energy per turbine than their predecessors, wind experts agree that increasing the hub height and rotor diameters could lead to higher costs on a per-watt basis. This is a result of the so-called “square-cube-law” which states that the power captured by a wind turbine grows with the square of the rotor diameter while the material costs grow at a faster rate, closer to the cube of the diameter than its square. Thus far, the largest turbines have continued to do better than the projected square-cube-law through a combination of new control and manufacturing technologies, supply chain efficiencies, and higher sustained winds available to taller turbines. All these innovations have led to the cost of wind energy continuing to fall year by year. Eventually, though, as the manufacturers continue to build larger and larger turbines, the cost of energy will likely increase as material costs outpace power output.

At Arctura, we are working to address this problem by developing new aerodynamic controls on the blades that will reduce the impact of unsteady aerodynamic forces caused by turbulence, wind shear, gusts and wake effects. These added controls will give turbine designers another tool to reduce fatigue loads before they have a chance to develop, allowing wind turbines to be built with less material and at a lower cost. This could enable the next generation of turbines in the 15-20 MW range and beyond.

A number of on-blade active load control technologies have been proposed by different organizations, including mechanically actuated trailing edge flaps, pneumatically-driven trailing edge flaps, and shape-morphing blades. But manufacturers have yet to adopt any of these technologies, primarily because of concerns around reliability and the high costs of maintaining mechanical components mounted inside the blade. In addition, predictive tools have not been sufficiently developed and validated to project the potential impact of such technologies.

Arctura is in the process of addressing each of these concerns. In 2019, the company (which was then called Aquanis) won a highly competitive ARPA-E award to develop and test an active lift control device.  The device itself, called a plasma actuator, is unique in that it uses no mechanical components and has no moving parts. As such, it is not subject to mechanical fatigue and does not require hidden mechanical components to be mounted in hard-to-reach locations inside the blade. And the approach is proving to be effective – reducing peak-to-peak blade bending stresses by 30% in simulations.

The device consists of a controllable Gurney Flap – essentially a bump on the pressure side of the blade (facing the wind) near the trailing edge. The local sectional lift on the blade can then be controlled by activating the plasma actuators that are mounted on the surface of the bump. The concept is currently being validated in a state-of-the-art wind tunnel at the University of Texas at Dallas and next year will be installed and tested at Sandia National Laboratory’s Scaled Wind Farm Technology (SWiFT) test facility in Lubbock, Texas.

The work has been featured in several conference presentations and upcoming peer-reviewed journal articles, including here and here.

Contact Arctura today to learn more about our active lift control technology and other exciting innovations our team is bringing to the wind industry.