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Making Way for a Bigger Turbine

They stand as looming testaments to innovation, growing ever more prominent and powerful. Yet for much of 2011, wind installations remained somewhat obscured, eclipsed by the media storm surrounding the solar industry.

The truth of the matter is, however, that the wind industry bounced back from a disappointing 2010 with a surge in both installations and sales. The wind industry quietly and methodically continues to forge ahead, and today it dominates the renewable energy landscape in new installations.

Through October (the most recent numbers available by press time), the wind industry placidly posted three strong quarters behind a steady drop in prices and the realization that Congress may not extend the Production Tax Credit (PTC) past its December 2012 expiration date. According to the American Wind Energy Association (AWEA), through the first three quarters of 2011, the wind industry installed 29 wind farms larger in total capacity than the biggest solar project installed during that same period.

With the wind industry eager to continue its momentum with or without the PTC, two things are clear: turbines must get bigger and engineers must work to drive down costs. It’s a proven formula that’s paying dividends beyond the traditional stronghold of the Midwest, as the technology becomes a bigger part of the landscape in places like New York, Massachusetts and Maine.

But how to get there, and from where will the cost gains come? Dan Shreve, a partner with Make Consulting, says his company is looking at just that and has come out with a new report on wind turbine trends. The report breaks down the materials used for components like hubs and blades, and projects how a component’s cost impacts its performance. Sometimes, more costly materials can open the door to cost-savings with other components. Engineers have found this to be the case with rotors, where new materials and novel approaches are pushing costs down and performance up. The result, though, is a turbine capable of better returns.

How Big Can They Get?

Fort Felker, Director of the National Renewable Energy Laboratory (NREL) Wind Technology Center, remembers a time when many questioned whether the industry had hit the ceiling with the height and capacity ratings for wind turbines. Today, those same folks might be shocked to learn that companies like GE are actively working to build turbines that reach into the 10- or even 15-MW range. Few are skeptical anymore that eventually we’ll get to those scales.

“The landscape is littered with people who predicted turbines couldn’t get any bigger,” said Felker. “They said that at 50 kW. They said that at 100 kW. They said that at half a MW and they said that at 1 MW. It’s just silly to predict a limitation because again and again, the industry has found ways to innovate to get past technology barriers that are perceived at any given size.”

Technological barriers aside, it is market conditions that serve as the real driving force behind the growth of turbine capacity. To become more powerful, turbines must get bigger. But there’s a growing friction between developers coming to town with wind behemoths and local residents questioning how the turbines will impact the landscape. Nowhere is this conversation as vocal as it is in places like bucolic New England, which prizes its rolling hills and its scenic views.  

Today, it’s not unusual to see the installation of a 3-MW turbine, though most remain smaller than that. We’re seeing 5- to 7-MW turbines in the offshore markets of Europe. The giants we’re likely to see in the future will mostly be offshore, where there are usually fewer logistical constraints and not-in-my-backyard objections. Eventually, mega-turbines will be installed in deep water far offshore on floating platforms. Their assembly will be done on land and they’ll be shipped relatively intact to their final destination where they’ll “drop anchor,” so to speak. This convergence of large turbines and, eventually, of floating platforms and new transmission, could also make assembly far easier.

Wind turbine manufacturer Gamesa, though, is bucking the notion that large turbines will be pushed offshore. It has recently introduced a 4.5-MW onshore turbine that is taking an innovative approach to common transportation and assembly hurdles that larger turbines face. As rotors get bigger, they can handle much longer blades. But the longer the blades get, the more difficult it becomes to transport them on roads, rails and bridges, and around power lines and curves. Gamesa gets around this by shipping the blades in two pieces and assembling them on site.

For Felker, this is further evidence that companies will find creative ways to get around perceived limitations and build bigger and bigger turbines. It does, though, bring up a new set of challenges, according to Shreve. “Construction costs money and it adds complexity. Wind farms are generally not the most hospitable environments and having to take on larger levels of on-site assembly presents a great deal of new challenges to project developers.”

Bigger Rotors, Better Materials

There’s a race on right now as manufacturers push to dramatically increase wind turbine’s power and economics and to do that, many are focusing on increasing the size of the rotor while being mindful of load and costs.

One way to cut costs and/or increase performance is through innovative materials. Many turbine makers are analyzing the cost benefits of switching from fiberglass to alternative materials like carbon fiber, which is prized for its ability to reduce weight and increase performance. Because it’s been prohibitively expensive, most manufacturers that use carbon fiber do so exclusively in the blade spar and the spar caps, an area considered the primary structural element for the blade. “It’s about clever utilization of the material. Effectively, they’re doing this to get the best bang for the buck,” said Shreve. “They’re trying to achieve the rigidity, the stiffness required to enable the system’s operation. This is critical for larger rotor diameter.”

Though carbon fiber will remain expensive in the near future, Felker sees a couple of paths to significantly bring down its cost. One is an innovation being made in the airline industry. Boeing has introduced its 787 jet, which uses carbon fiber reinforced materials for about 50 percent of its airframe. The quantities produced to service that aircraft will create a more vibrant market for carbon fiber, and this should ultimately push down its cost. Felker also pointed to research being done at the Oak Ridge National Laboratory in Tennessee. There, researchers have launched a consortium with 14 companies to push the development and commercial application of low-cost carbon fiber.

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The interest in manufacturing wind turbines with alternative materials doesn’t end there. Traditionally, manufacturers use balsa wood in their blades to separate layers of fiberglass, resulting in light yet stiff structures. Many manufacturers are now starting to look to advanced materials like WebCore, which has been engineered specifically for wind blades. “People are asking, ‘What’s the real engineering need and let’s create a material from scratch that satisfies that need,” said Felker. “This will continue to be a trend over the next five years or so.”

Tremendous strides are also being made in blade geometry and systems and control analysis. In both cases, new approaches are being used to better manage loads on wind turbines under various conditions. A curve or a blend in the blade may not vastly increase performance, but it can reduce stress and even noise. And a sensor that measures incoming gusts could allow it to react to sudden conditions. These innovations may not reduce initial costs, but they add value and longevity to an installation.

“Over the 20-year life, are you going to reduce blade fatigue, such that you’d be able to minimize maintenance on blades, in the gearbox and in different areas within the drivetrain? It’s tougher to monetize and to truly put your arms around,” said Shreve.

Direct Drive Versus Geared Drives

Years ago, direct drive technology was a novel concept with serious cost limitations. Today, we’re starting to see direct drive turbines that are cost-competitive with geared systems.

While a vast majority of deployed wind turbines use geared technology, direct drive has been able to make inroads because of the potential for improve reliability. Since geared turbines come with many more parts, the thinking goes that direct drive technology with fewer moving parts offers the potential for improved reliability.

Siemens and GE are among those beefing up their direct drive products, joining a market that already includes Enercon and Goldwind.  Much of these turbines are destined for the offshore market, where there is less resistance to large turbines and a greater need for turbines that need less maintenance. According to Felker, the industry is still figuring out which environments respond best to geared technology, and which environments would be better served by direct drive turbines. Ultimately, though, there will be room for both.

And the technologies may in the end push each other to achieve new highs in capacity and new lows in cost.

“What that’s going to do is push the gear technology to get better, and that’s going to push the direct drive technology to get better,” said Felker. “A little competition in fact is going to do a lot.”

Chief among the biggest concerns with direct drive technology is the price volatility associated with rare earth minerals, which are central to everything from computers and military weapons to the magnets that power direct drive technology. China currently controls as much as 97 percent of these metals, and recently there has been a sharp spike in prices and a deep drop in availability.

Many corporations, desperate to maintain price stability and eager to wrestle the market control away from China, are investing heavily in new mining operations. While rare earths are not all that rare around the globe, finding locations with a high enough volume to support a profitable mining operation has been difficult. Mining giants Molycorp and Lynas are among those opening or expanding operations in places like the U.S., Australia and Malaysia. Ultimately, many expect these efforts will help stabilize prices and supply.

And that stability could further help the industry continue its momentum in both pricing and technology in 2012 and beyond.

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