As technology advances, offshore wind turbines can tower over 490 feet above ground, their spinning blades churning out up to 8 megawatts (MW) each, which is enough to power around 4000 homes in the U.S. However, their size becomes a risk as the U.S Atlantic coast faces hurricanes.
A team of CU Boulder researchers are taking inspiration from nature to make the turbines more hurricane-resilient.
“We are very much bio-inspired by palm trees, which can survive these hurricane conditions,” said Lucy Pao, Palmer Endowed Chair in the Department of Electrical, Computer and Energy Engineering.
Pao’s team have been collaborating over the past six years with the University of Virginia, the University of Texas at Dallas, the Colorado School of Mines, and the National Renewable Energy Laboratory, to develop the SUMR (Segmented Ultralight Morphing Rotor) turbine, a two-bladed, downwind rotor to test the performance of this lightweight concept in action.
The CU researchers presented results from a new study of four years of real-world data from testing their 53.38 kilowatt demonstrator (SUMR-D) which showed that their turbine performance was consistent and efficient through periods of peak wind gusts.
“The blades are manufactured to be lightweight and very flexible, so they can align with the wind loads. That way, we can reduce the cost of the blades and bring down the cost of energy,” said Mandar Phadnis, lead author on the new study in Proceedings of the 2022 American Control Conference, and a graduate student in electrical, computer and energy engineering.
One of the challenges of wind energy generation is the inconsistency of the wind’s speed. If they are too low, a turbine can’t produce a useful amount of energy; and if they are too fast, they can push the limits of a turbine’s capacity, causing it to shut down to avoid a system overload.
An important contribution made by Pao’s team are improvements to the controller, which determines when the turbine should be more or less aggressive in power production.
This hidden “brain”, as Pao refers to the controller, aims to produce efficient wind energy at low cost and with low wear and tear. This is achieved by a feedback controller using measurements of how the system is performing, and then adjusting to better improve the performance, said Pao.
The yaw controller makes sure the turbine is facing the correct direction, the blade pitch controller determines the direction of the blades, and the generator torque controller determines how much power to pull off the turbine and onto the grid.
While overseeing physical components of the turbine, these controllers are essentially a software algorithm that tells the motors what to do. Pao’s group is also working on its software to maximize the system’s ability to keep running during peak wind events.
There, the researchers found that, even through extensive experimental testing, peak generator speeds were below the threshold for their operational controller to keep the turbine running.
“The advantage of the downwind configuration, however, really comes about when you get to extreme scale turbines, and those are primarily for offshore,” said Pao.
Pao’s group is already addressing these great heights: With their collaborators, they have designed and modeled (but not experimentally tested) large-scale, offshore 25 MW and 50 MW SUMR (downwind) turbines.