Wooden windmills are picturesque but modern composite materials enabled wind to become the first commercially viable source of renewable energy. New fabrication facilities for blades continue to be built around the world as designs evolve and blades get longer. The most common blade size today - about 2.5 meters in length - uses as much as six metric tons of composite material. Wind blades may also be the fastest growing market for composites ever, having gone from an emerging industry 15 years ago to having more than 120 gigawatts (GW) of installed capacity today. More than 400,000 people are now employed in the wind industry and that number is expected to be in the millions in the near future. The Global Wind Energy Council expects the market for wind turbines to grow by more than 155 GW, from 94 GW in 2007 to 240 GW of total installed capacity by 2012. This success has prompted many in the composites industry to ask, "What is the next wind blade?"