By Bob Bellemare President and CEO

Wind turbine blade manufacturers are turning to high strength and low weight materials such as carbon fibers in hopes of finding new technology breakthroughs so they can increase turbine size and improve wind power economics.

The wind power industry has enjoyed a 30 percent annual growth rate during the past five years, making wind one of the world's fastest-growing energy sources. Last year, new investment in wind topped out at more than $9 billion and 8,133 megawatts (MW) and wind power is expected to continue its high growth, with global installed capacity predicted to at least quadruple from 39,294 MW today to more than 160,900 MW by 2012, according to the American Wind Energy Association (AWEA) and the European Wind Energy Association (EWEA). But to hit that growth target wind turbines will have to become larger and more economic.

Blades Grow and Materials Improve

Advances in wind power technology have pushed the costs of wind power down from about 80 cents per kilowatt hour (kWh) in the early 1980s to as low as 5 cents per kWh today. Tiny kilo-watt turbines have grown into today's multi mega-watt machines. GE Wind Energy, one of the world's leading turbine suppliers, sees “tremendous opportunities for growth and continued technology development.” GE's new steroid-injected 3.6-MW turbine, for example, is designed to tap the developing market for coastal, offshore projects.

To drive wind costs down the blade size has to be increased. Gains can be dramatic because a wind turbine's capability to generate electricity increases by the square of its blade length. In other words, doubling the blade length can increase the power producing capability as much as fourfold. Blade lengths have grown from 15 feet in 1980 to over 150 feet today, and the power rating of the largest turbines has gone from 55 kW machines in the early 1980s to as high as 4.5 MW today.

Construction materials and manufacturing techniques have also evolved over the last twenty years. Today's machines are much sturdier than those of the past. Turbine blades of the 1970s were largely made of steel, aluminum, or wood epoxy. Today's material of choice is E-glass/polyester. According to Owens Corning, about one hundred million pounds of glass are used each year to build wind turbine blades. Manufacturing technology has advanced from the early days when hand-layering of materials was commonplace to today's modern techniques that use a vacuum or low pressure to infuse resin into the fibers and a blade mold.

According to Peter Jamieson of Garrad Hansen at a recent conference held by Sandia National Labs, blades now account for about 10 percent of the total lifetime cost of wind generation. With all these advances the blade cost has dropped to about $100 per kW of a wind construction project.

Carbon Fiber — The Coming Wave

Ramesh Gopalakrishnan, global manager of Blade Engineering for GE Wind Energy, says that as the industry moves to larger blades several design limits of existing materials become problematic, preventing conventional scaling of smaller blades to larger designs. The search is on for higher strength and lighter materials, which has led designers to add carbon fiber to blade designs.

Carbon fiber is truly a remarkable material. For instance, it is many times stronger and lighter than steel. Carbon fiber composites also have superior fatigue properties and, when coupled with the proper resins, are one of the most corrosion-resistant commercially available materials, making them ideal for the harsh environment that wind turbine blades must endure.

The major drawback to their use is cost. Although the market price for carbon fiber has dropped from around $40 per pound in the early 1980s to as low as $6 per pound today, it's still five times more expensive than steel. But in applications where strength and weight are premium, carbon fibers are gaining favor. With the drop in prices, market sales volumes for carbon fibers are predicted to grow from 14,000 tons in 2001 to as high as 30,000 tons in 2006—driven in part by new applications in the wind turbine blade market.

One company betting on that future is St. Louis-based Zoltek [NASDAQ:ZOLT]. In a recent presentation at its shareholder meeting, Zoltek announced it was expecting to double its existing 150 tons per year carbon fiber contract with wind turbine manufacture NEG Micon. Vestas is also planning to use Zoltek fibers in their turbine blades, which should push Zoltek's sales to Vestas up to 1,000 tons per year by 2005, and Gamesa is expected to order up to 1,000 tons from the company in 2005. Other carbon industry heavyweights such as Mitsubishi Rayon, Toho Tenax and Toray, also hope to cash in on the growing demand.

Demand Should Bring Down Costs

At first, carbon fibers will likely be used in only the highest stress components within the blade itself, such as the “spar cap” that reinforces the interior structure of the blade. And another cost issue that manufacturers must tackle is caused by the precise construction requirements that are different from the manufacturing techniques used in today's glass technology.

Carbon fiber's cost may slow down the dream's development, but other industries are also finding applications, which will increase demand. The fuel cell manufacturers have their eyes on carbon, because the electrical properties of carbon fiber and the ability to configure the material into a semi-permeable membrane make carbon an ideal choice for the next generation fuel cell engines. The high-strength low-weight properties of carbon fibers are not only expected to play an increasingly important role in driving down wind generation costs but the material may be one of the most important advances for our energy future.

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