With total installed capacity reaching 250 GW at the end of 2011, wind is the most prevalent source of renewable energy today. Furthermore, increasingly strict renewable portfolio standard programs–33% by 2020 in California, 20% in Europe, and 15% in China–provide significant impetus for the wind industry. However, the proliferation of effective wind installations heavily hinges on advanced coatings and composite materials that are critical for maintaining efficient operation.
A recent study conducted by 3M and the University of Illinois found that weathering damage to wind turbines decreases energy generation by over 20% per year, costing developers an estimated $131,000 annually in lost revenues. Functional coatings that offer enhancements in hydrophobic, anti-icing, and anti-drag properties can enhance efficiency and reduce operating and maintenance costs. For instance, researchers at Battelle announced in January 2010 that its carbon nanotube (CNT)-based coatings prevent ice build-up. The coatings, essentially giant resistors composed of CNT networks, heat up when current passes through, preventing ice from adhering and water from freezing. Meanwhile, companies such as GE, CG2 Nanocoatings, Luna Innovations, and Seashell Technologies are developing competitive, yet passive (requiring no energy), anti-ice coatings.
In addition to functional coatings that enhance operation, protective coatings that combat performance degradation by means of corrosion, wear, and fouling are key to maintaining efficient operation, particularly offshore. Currently, large and longstanding industries such as oil and gas and marine get the most attention in regard to protecting offshore structures and vessels. However, as renewable sources continue to play a larger part in the energy portfolio, coatings for offshore structures of wind farms (and wave and tidal power stations) will become increasingly important. Corrosion and fouling will be major concerns for any component that resides in the water, so material developers should keep these emerging segments in mind when designing new coatings.
The average offshore turbine size is expected to rise from currently 3 MW to about 6 MW in 2020. This progression to larger power ratings is logical because offshore turbine construction requires foundations on the sea floor and power transmission lines, which consequently inflate installation costs per unit and make larger turbines more economical. Larger turbines mean bigger blades, thus necessitating use of lighter and stiffer materials that highlight the need for advanced composites.
The most commonly used structural materials in turbine blades are glass fibers in an epoxy resin. Many consider carbon-fiber reinforced plastics (CFRPs) the obvious choice for next-generation blades. In fact, Lux Research projects wind to become the dominant source of carbon fiber demand in this decade, growing at an average CAGR of 26% from 12,500 metric tons in 2011 to 97,600 metric tons in 2020. However, recent significant progress by nanocomposite developers makes this a more interesting game. For instance, startup Applied Nanotech is developing hybrid composites incorporating both glass fiber (about 1/5 the cost of carbon fiber) and multi-walled, carbon nanotube (MWNT) reinforcements in a vinyl ester resin (cheaper than epoxy but with lower performance). The materials have already demonstrated 31% and 20% improvements in flexural strength and modulus compared with the glass-fiber reinforced plastic (GFRP) analog. MWNT-reinforced GFRPs may make a more logical choice for wind-turbine developers if they are able to meet next-generation performance criteria at a lower cost than CFRP. Regardless, advancements in composite design essentially give material developers a palette of resins, reinforcing fibers, and nanomaterial fillers to work with to create the best price and performance for a given application. WPE
By: Ross Kozarsky, Lead Analyst of Advanced Materials team at Lux Research, www.luxresearchinc.com
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