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Developments and prospects of wind energy made from composites

Developments and prospects of wind energy made from composites

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Developments and prospects of wind energy made from composites

Developments and prospects of wind energy made from composites

 

Wind energy is the fastest growing energy sector and has recorded consistent growth of over 20% over the last ten years as per Research and Markets. Wind energy promises to be of great interest as it is highly environment friendly and uses a renewable resource. Most of the critical components of a wind turbine use composites and the need for bigger size turbines means more composite usage per turbine. Findings include:
* Global cumulative installed wind energy has grown with a CAGR of 26.45% for the period of 1990 to 2007.
* Annual installed wind energy of top five countries US , Spain , China , Germany and India made up to 77.26% to the world's total wind power capacity in the year 2007 compared to 62.06% in the year 2006.
* Denmark cumulative installed wind energy declined by 11 MW in the year 2007 compared to the previous year 2006 but its future forecasts are optimistic.
* German wind industry is showing a sign of slow growth as it is expected to grow with a CAGR of 4.82% for the period of 2008 to 2010 compared to 20.27 for the period of 2000 to 2007.
* From the year 2000 Iran has registered the second highest growth of 19 MW in the year 2007.
* US Senate passed the one-year extension of the crucial wind energy production tax credit (PTC) through Dec. 31, 2009. The bill also would create a new investment tax credit for purchases of small wind systems used to power homes, farms and small businesses.
* In 2007, top 10 countries of world contribute more than 90% to the annual wind energy
* US, China and India are going to drive the wind energy industry in future.
Government support through incentive schemes and strong research budget allocations such as in Europe, where two thirds of the non-nuclear research budget has been allocated to research on renewable and energy efficiency systems, is expected to sustain the wind industry. Furthermore, sustained price volatility of fossil fuel and supply constraints due to sociopolitical issues in the production regions have pushed governments to look at wind energy as both a supplementary and complementary source of energy supply rather than just for green house gas mitigation. Moreover, this volatility in fossil fuel has reduced the price difference in cost of generation between conventional and wind energy systems. The wind energy industry has over the years, witnessed growth at nearly 24% largely due to incentive driven markets of Europe. Recently supply problems of essential components such as gearbox and reluctance to increase production capacity among original equipment manufacturers have acted as major restraints for growth. However, despite these constraints, steady growth in the wind industry is expected mainly due to extension incentive programs.
Wind energy is a rapidly growing market segment for the composites industry and is a fastest growing energy sector. On average, the global wind energy market is growing at a rate of 23% pa since last ten years. The wind energy market provides great opportunities to product manufacturers as well as material suppliers of the composites industry to expand their businesses. It consumes millions of pounds of composite materials every year. Composites consumption in the global wind energy market has grown 23 times in last 12 years. Wind turbine requires the manufacture of large rotor blades, nacelles and other components using wet lay-up, VARTM, prepreg lay-up and other processes. The future of the wind energy market looks great until 2010 and beyond. A growing sensitivity for the environment and depleting reserves of fossil fuels are all fueling the growth of wind energy in 21st century.
Wind capacity worldwide has quadrupled in the past five years. Wind power now exceeds 31,000 megawatts, enough for 7.5 million average American homes. Last year, overall wind generating capacity grew by 28%, which is worth US$7.3 bln. European nations added 5,871 megawatts last year while the United States added 410 megawatts. Germany has the largest wind generating capacity followed by Spain. According to the American Wind Energy Association and the European Wind Energy Association, building new global wind power could generate US$26.8 bln pa by 2010 if growth trends continue.
Increasingly developing wind energy has catalyzed developments of blades from composite materials. Wind power plants are more developed in USA, China and Spain. The global wind energy market has grown 23% pa for the last 10 years. Long-term growth will require technical innovation to make wind more competitive with other forms of energy. One of the key trends is the push to improve productivity. Blade manufacturing via vacuum infusion or prepreg molding is labor intensive and producers are seeking ways to reduce cycle time and cut costs. Robotic lay-up, enhanced finishing techniques, two-piece or segmented blades, and on-site manufacturing are potential tools to trim labor and logistics costs. New prepreg molding techniques are said to improve surface appearance and facilitate finishing. And resin and prepreg suppliers are introducing materials that cure faster and at lower temperatures.
As wind generating capacity increases, there is also a trend to bigger and lighter blades. Observers envision greater use of carbon fiber�despite disadvantages of higher cost and tight supplies�due to its higher stiffness and lighter weight than standard E-glass. Meanwhile, traditional E-glass and specialty glass products are holding off competition from carbon fiber through new chemistry and optimization to meet higher performance requirements.
A wind turbine is composed of several composite parts; but the blades, made of fiber-reinforced epoxy or unsaturated polyester, represent the largest use of material. Other turbine parts made of polyester include the nacelle (housing for the gearbox, generator, and other components) and the hub. The dominant processing method is vacuum resin infusion. It generates low VOCs and can evenly wet out large parts with a controlled amount of resin, thus facilitating production of lighter and less expensive blades. Prepreg molding with a woven or unidirectional glass fabric is more costly but offers greater consistency because it already contains the matrix material (typically epoxy). Depending on blade size, either vacuum infusion or prepreg molding takes 12 to 24 hr. Typically composed of 70-75% glass by weight, these aerodynamically designed blades must meet very strict mechanical requirements such as high rigidity and resistance to torsion and fatigue. High static and dynamic loads over a wide temperature range are typical during a 20-yr service life. A standard 35- to 40-meter blade for a 1.5-MW turbine weighs 6 to 7 tons. Both epoxy and polyester, and to a lesser extent vinyl ester, shared the wind blade business in the early days but epoxy earned preferred status as blades grew longer. Polyester is easier to process and is less expensive, but epoxy offers stronger mechanical performance�particularly tensile and flexural strength�for blades longer than 26 m (85 ft). Unlike epoxy, polyester needs no post-curing but the blades are generally heavier.
E-glass is by far the most used reinforcement, while more costly carbon fiber is employed on a limited basis for greater stiffness and reduced weight in longer blades. The barriers to entry for wind blade manufacturing are formidable. They include the physical scale of the parts, the need for competitive technology and manufacturing know-how, a good supply base, global presence, and heavy investment. There are about 12 global wind turbine suppliers and the top four hold about 72% of the market. Most of these top manufacturers make their own blades, but some, like GE Energy, contract out to firms like Molded Fiber Glass Companies (MFG), Ashtabula, Ohio, and TPI Composites, USA. The world�s leading wind turbine maker is Denmark�s Vestas Wind Systems A/S (23% market share), followed by GE Energy, Spain�s Gamesa (17%), Germany�s Enercon, India�s Suzlon (10.5%), and Germany�s Siemens. The world�s leading blade maker is Danish-based LM Glasfiber A/S, which makes between 8000 and 9000 blades/yr and has 25% market share. The company started manufacturing in 1978 and has expanded operations worldwide with new U.S. plants in Grand Forks, N.D., and Little Rock, Ark. It claims to have the largest total installed base of blades today: Every third turbine worldwide is fitted with its blades. LM uses vacuum infusion to produce polyester wind blades that are less costly than epoxy but still boast high performance. The process has been optimized to create a strong, uniform laminate with more rapid hardening, which reduces production time by several hours. LM has adapted its technology to produce the industry�s longest wind blade. The 61.5-m (202-ft) blade, built for a 5-MW turbine from Germany�s REpower Systems, weighs 17.8 tons. The turbine has a rotor diameter of 126 m (413 ft) and the three blades cover an area almost the size of two football fields. Most remarkable is LM�s ability to use E-glass for stiffness and light weight above the threshold length of 40 m where carbon fiber is generally considered.

 
 
 
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