Friday, January 4, 2019

Wind turbines like palm trees?

Design for 50MW Offshore Wind Turbine Inspired by Hurricane-Resilient Palm Trees

Blades for a 50-megawatt turbine would be at least 200 meters long, equal to two football fields.




When the wind doesn't blow, it's a problem for wind farms.  To keep the current flowing you'll need batteries, or solar farms or to ship in electricity from a place a few hundred kilometres away where the wind is blowing.  But when the wind blows too strongly, you have all those problems plus one more.  At very high winds, the wind turbines have to be stilled because they can burn out; worse, if the wind is strong enough they can break.

From GreenTech Media:

A team of researchers is working to complete the design for a novel 50-megawatt offshore wind turbine, nearly six times more powerful than a record-setting 8.8-megawatt turbine recently deployed off the coast of Scotland. Testing will begin on prototype blades this summer in Colorado.

The massive turbine marks an about-face from conventional wind turbine design. The standard wind turbine installed today is a three-bladed machine positioned with the blades facing incoming winds.

The blades for the so-called Segmented Ultralight Morphing Rotor (SUMR) wind turbine would, conversely, face downwind. The “go-with-the-flow” design was inspired by palm trees, which have evolved to withstand hurricane gales.
Just as palm fronds bend and yield to the direction of the wind, the segmented blades for the SUMR turbine will fold together, aligned with the wind direction, in strong winds.

“We’re trying to have the turbine blades be more aligned along the load path, so we can get away with lower structural mass and have less fatigue and less damage,” said Eric Loth in an interview. Loth is chair of the department of mechanical and aerospace engineering at the University of Virginia and the SUMR project lead.

The research team believes the downwind design will make it possible to deploy extreme-scale offshore wind turbines in parts of the United States, such as the South Atlantic and Gulf of Mexico, where wind speeds can reach 200 mph during severe storms.

A primary goal of the project is to shed weight in the turbine blades. Added weight increases the “global loads” transferred from the blades to the turbine hub and, according to Griffith, is the main limitation to building ever-larger blades for conventional upwind offshore wind turbines.
“Weight reduction is a big driver in the design,” said Griffith, who began researching 100-meter blades a decade ago as a member of the offshore wind technical team at Sandia National Laboratories.

Conventional turbine blades are made mostly of fiberglass with some carbon fiber. You could incorporate more carbon fiber into the design to add strength, but it comes at a cost.
There are good reasons why fiberglass is the industry standard. It’s inexpensive and has good stiffness properties, said Loth.
Griffith is encouraged by ongoing research, funded by the U.S. Department of Energy, to reduce the cost of carbon fiber. “It’s something that may be perfectly tailored for our blades,” he said.

The research team is convinced that the standard upwind design with conventional blades won’t work for extreme-scale offshore wind turbines envisioned by the project.

“Conventional upwind blades are expensive to manufacture, deploy and maintain beyond 10 to 15 MW. They must be stiff, to avoid fatigue and eliminate the risk of tower strikes in strong gusts,” Griffith said in a statement announcing the ARPA-E grant.

Another concern is logistics. With turbine blades trending beyond 100 meters — the 12-megawatt Haliade-X turbine unveiled by GE last month will be outfitted with 107-meter-long blades — shipping the blades from the factory to the project site becomes challenging.

Blades for the 50-megawatt SUMR turbine are expected to be at least 200 meters long. A trunnion hinge near the hub would enable the blades to fully fold and stow in hurricane-force winds. And because each blade will be fabricated in five to seven segments and assembled at the project site, project developers will avoid having to figure out how to transport blades as long as two football fields.

The ultralight blades would be capable of morphing downwind, or as the researchers put it, “deforming into the direction of the flow.”

[Read more here]

Every time I think wind power has reached the limit of its cost declines, a new technological innovation comes along.  Wind power will likely just keep on getting cheaper and cheaper.


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