Researchers at EPFL (Fédération École Polytechnique de Lausanne) used genetic learning algorithms to identify the optimal pitch profile for the blades of vertical-axis wind turbines. vertical axis wind turbine Due to its high energy potential, it has previously been vulnerable to strong wind gusts.
Explanatory paper published in open access Nature Communications.
Considering Today's industrial wind turbines, You probably imagine a wind turbine design, technically known as a horizontal axis wind turbine (HAWT). However, the first wind turbines were developed in the Middle East around his 8th century.th Centuries to grind grain, vertical axis wind turbines (VAWTs) were used, which rotate perpendicular to the wind rather than parallel to it.
VAWTs have lower rotational speeds, making them less noisy than HAWTs and delivering higher wind energy densities. This means less space is required to achieve the same power onshore and offshore. The blades are also wildlife friendly. The blade rotates sideways rather than cutting off from above, making it easier for birds to avoid.
Despite these advantages, why is VAWT so absent from today's wind energy market? Sébastien Le Fuest, researcher at the Faculty of Engineering's Unsteady Flow Diagnostics Laboratory (UNFOLD), explains We believe this comes down to an engineering problem of airflow control, which can be solved by combining sensor technology and machine learning. . In a recently published paper, nature communicationsLe Fouest and UNFOLD director Karen Mulleners explain two optimal pitch profiles for VAWT blades that achieve a 200% increase in turbine efficiency and a 77% reduction in structure-threatening vibrations.
EPFL’s experimental VAWT blade Image credit: © UNFOLD EPFL CC BY SA. Click on the press release link to see a larger image.
“Our study represents, to our knowledge, the first experimental application of a genetic learning algorithm to determine the optimal pitch of VAWT blades,” said Le Fouest.
Turn your Achilles heel to your advantage
Le Fuest explained that Europe's installed wind power capacity is increasing by 19 gigawatts a year, but this figure needs to approach 30 gigawatts to meet the United Nations' 2050 carbon emissions targets.
“The barriers to achieving this are not financial, but social and legislative. Wind turbines have very low public acceptance due to their size and noise,” he said. Ta.
Despite its advantages in this regard, VAWT has significant drawbacks. In other words, VAWT only works well with moderate continuous airflow. The vertical axis of rotation means that the blade's orientation relative to the wind is constantly changing. Strong gusts of wind increase the angle between the airflow and the wing, forming vortices in a phenomenon called dynamic stall. These vortices create temporary structural loads that the blades cannot withstand.
To address this lack of resistance to wind gusts, the researchers attached sensors to the working blade shafts and measured the aerodynamic forces acting on them. By pitching the blade back and forth at different angles, speeds, and amplitudes, a series of “pitch profiles” were generated. They then used a computer to run a genetic algorithm and repeated the experiment more than 3,500 times. Like an evolutionary process, the algorithm selects the most efficient and robust pitch profiles and recombines their characteristics to produce new and improved “descendants.”
With this approach, the researchers not only identified two pitch profile series that contribute to significant improvements in turbine efficiency and robustness, but also turned VAWT's biggest weakness into a strength.
“Dynamic stall (the same phenomenon that destroys wind turbines) can actually propel the blades forward on a small scale. Here, by directing the pitch of the blades forward to generate power, We are actually using dynamic stall to our advantage,” Le Feuste explained. “Most wind turbines tilt the force generated by the blades upwards, not helping them rotate. Changing that angle not only creates smaller vortices, but also allows the vortices to flow at the right time. is displaced, resulting in a second generation region ” downwind. ”
of nature communications This paper represents Le Fouest's doctoral research in the UNFOLD laboratory. Currently, he has received his BRIDGE grant from the Swiss National Science Foundation (SNSF) and InnoSwiss to build his proof-of-concept VAWT. The goal is to be able to install it outdoors and test whether it reacts in real-time to real-world situations.
“We hope that this method of airflow control will help mature and eventually commercialize efficient and reliable VAWT technology,” Le Festo said.
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We certainly hope that this development will provide an alternative to the many dangerous, ugly and noisy HAWTs. While wind is a notoriously intermittent power source, the industry has the power to suck up huge amounts of ratepayer and taxpayer money. Eliminating rent collection schemes like wind turbines could be an example of how badly politically forced rent collection schemes can harm the economy and the public.
It would be great if a developer could say that this technology can be economically self-sustaining. However, there is no such comment in the press release. In reality, these can only compensate a little when the wind blows.
Written by Brian Westenhouse new energy and fuel
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