09.07.07

New Twist Boosts Turbine Blades
Shipyard branches out into 'green' industry

SAN DIEGO, CALIFORNIA - Knight & Carver had a long-standing business building and repairing yachts and other vessels, when it got a cold call in 1997 with a curious request: Could the San Diego shipyard repair a broken wind turbine blade?

The question was raised because Knight & Carver has long built and repaired boats made from fiberglass, the same material used to construct wind turbine blades.

So Knight & Carver opted to give blade repair a try.

From that attempt the company has grown what it describes as a burgeoning business repairing wind turbine blades. And now, Knight & Carver believes it is on track to developing a breakthrough wind turbine blade.

The new Sweep Twist Adaptive Rotor, also called the Star blade, is designed to produce more electricity from a given wind turbine, without increasing wear and tear on the machine. It can produce electricity from wind blowing one to three miles per hour slower than conventional blades.

"If you can go down just a few miles per hour on the speed of wind needed to drive a turbine," said Gary Kanaby, who heads Knight & Carver's wind division, "the amount of land available for wind energy development goes up dramatically."

Kanaby said many of the areas that would be open for development are closer to places where there is heavy electricity demand, so the cost of building transmission lines would be reduced.

There's probably never been a time when a breakthrough in wind energy would be more welcome. The world has grown increasingly sensitive to reducing greenhouse gas emissions, particularly those created by burning coal and natural gas to product electricity. As a result, the wind energy business is growing rapidly in the United States and abroad.

Longer blades capture more wind and produce more energy. But the longer blades, with their greater leverage, put a greater load on the turbines and can shorten their life or increase failures.

How to design a longer blade without creating additional load on the turbine is a long-standing problem.

It's the kind of problem that Mike Zuteck, an industry consultant who teamed with Knight & Carver, has thought about for decades. Zuteck, a physicist who slipped into the wind energy business in the late 1970s, has a passion for wind, which he harnesses as an avid sailor.

As a prolific inventor and wind blade designer, Zuteck long wondered about the prospects for a curved wind blade that would twist slightly. The curve, he reasoned, would allow a blade to be longer and capture more wind energy - but during rotation it could stay within the same circumference as a shorter blade.

By keeping the blade's rotation within the same circumference, leverage and load on the wind turbine machine could be held constant.

Zuteck said other inventors have arrived at similar conclusions. But most others have proposed building the twist into a turbine blade by angling the fibers of glass that compose the blade.

"But in our way of seeing what is good in the world, you don't want to turn the fibers because then the blade is not as strong," Zuteck said.

So Zuteck came up with way of building blades with fibers that parallel its length, while still incorporating a twist. The design allows a blade length of 27_ meters to replace a blade of 25 meters.

The twist works in ways that mimic sailing techniques to keep the load on the turbine constant, despite the 10 percent increase in blade length.

In 2002, Zuteck submitted a proposal to Sandia National Laboratories for a grant to build a prototype. Sandia is a research unit of the U.S. Department of Energy.

Sandia has long sought technologies that can squeeze more energy from wind turbines and wind resources. Tom Ashwill, a member of Sandia's technical staff, says the Midwest has vast areas with winds of 13 to 18 miles per hour.

"We call it low wind speed, but it's still good wind," Ashwill said. "And we are looking at ways to make lower wind speed more cost effective (for electricity production)."

So Sandia agreed in 2004 to provide $2 million to the Knight & Carver team, including Zuteck, for development of the Star blade. The company agreed to provide an additional $800,000.

Zuteck said one of the toughest challenges was to design the blade as a replacement product, to be used on older 750-kilowatt turbines without modification.

Through multiple attempts and various design tweaks, Zuteck said, "My heart sank a time or two. It was real tricky to get everything to balance out - to get the twist and still keep it from getting heavy."

The inventor confessed that he began work on this project long before he submitted his proposal.

"I was thinking about this for years before I even did the study," he said. "What ends up happening is that the core of the idea stays in your head. Always asking yourself, 'Is there some way I can do this a little differently and get around the problem?' "

The tweaking continued as Knight & Carver began to build the blades in one of its airplane hangar-sized buildings along the National City bayfront.

First attempts morphed into a second phase, then third, fourth and fifth phases.

"I did a lot of work on the Star 5 and and Star 6 series," said Zuteck, whose firm is called MDZ Consulting. "We are now into Star 7-f."

Much of the work on prototypes involved taking the 27.5-meter Star prototypes and stressing them with weight to determine their strength and the degree to which they will twist under load.

Kanaby of Knight & Carver said it was important to build from conventional materials to hold down costs.

Kanaby said there are more than 500 wind turbines in the Midwest that could be candidates for the Star blades. And he said the booming business in wind turbine development has put companies such as Knight & Carver in a strong position.

"The industry can't build enough blades," Kanaby said. "It's a sellers' market."

The Star blade should result in at least 5 percent more energy production from a wind turbine, Kanaby said, which would more than justify the increase in cost expected for the blades. Knight & Carver said the blades should be priced at about $160,000 per set, or roughly $20,000 more than a conventional blade replacement.

A 750-kilowatt wind turbine typically produces about $180,000 worth of electricity per year, said Nancy Rader, of the California Wind Energy Association. So a 5 percent increase in the power production would yield $9,000 more in annual revenue and justify the additional cost of the Star in just a few years, assuming the increased energy production estimates are accurate.

Knight & Carver hopes to complete work on the Star prototype and begin marketing the blades by next year. But first it will test the blades on a turbine in California by comparing performance to a turbine using conventional blades at the same location.

Production of the blades will take place at Knight & Carver's new production facility in Howard, S.D., located near the wind resources of the Midwest and where many of the 750-kilowatt turbines are located.

Sam Brown, president of Knight & Carver, said employees at the new facility have already done blade repair work and should begin building Star blades next year.

Wind business, which amounted to about 25 percent of the company's revenue last year, will approach 45 percent this year, he said.

"Year-to-year growth was 199 percent, and we're projecting a doubling of the wind business over the next year," Brown said.

Knight & Carver has about 150 people working in the wind business, compared with 150 or more - depending on orders - working in the boat business. And the company has about 10 people working in the wind business outside the United States.

Tom Gray, a spokesman for the American Wind Energy Association, said the industry grew at 25 percent last year. He said growth in excess of 25 percent is expected this year, as more emphasis is placed upon developing energy sources that don't contribute to greenhouse gases.

Zuteck recalled that his leanest days in the wind energy business came during the Reagan administration, which placed little emphasis on renewable energy production. But now he is reveling in the boom.

"Part of the sailor's soul is to love the wind and the outdoors," Zuteck said. "If you could use the sailor's art to turn out clean power, isn't that the dream? If you could do that and make a living, it would be great."