Many in the composites industry are aware that making use of carbon fiber can greatly decrease one’s carbon footprint, such as through the manufacture of lighter automobiles. But when it comes to green energy, composites are ideal for more than just conserving energy – they also can enable the generation of energy through alternative sources, such as wind and solar.
Major population growth and urbanization are increasing the world’s energy demands. According to the U.S. Energy Information Administration, International Energy Outlook 2013, without action, energy demand is expected to continue to grow at an average rate of 2.2 percent annually until 2020. That may not sound like a lot, but at that pace the world could increase its oil use per year by 20 percent, using more than 300 sextillion barrels of oil per day by 2020. The U.S. alone used approximately 48.7 million barrels of oil per day in 2013, according to Lawrence Livermore National Laboratory.
Rising greenhouse gas emissions from fossil fuel energy are linked to escalating surface temperatures, creating a great need for a range of sustainable energy sources. Composites may not be ideal for every application – for instance, geothermal energy, which uses heat from the Earth to generate energy, requires materials to withstand extremely high temperatures. But for other applications that require moving parts and high corrosion resistance, composites enhance efficiency.
Towering Wind Turbines
People have harnessed wind power for thousands of years to pump water and grind grain. Since the 1980s, the wind industry has grown very rapidly. With today’s technology, wind energy has the potential to generate 20 percent of America’s electricity with turbines installed on less than 1 percent of the country’s land area. “What you’ve seen over the past years is 15, 20, even 25 percent GDP growth a year,” says Chris Skinner, director of product platforms at Owens Corning in Toledo, Ohio. Now that wind is an established technology, the era of hyper growth is ending, says Skinner. But the industry still grows 5 to 9 percent per year.
The movement of turbine blades and their requisite to withstand various weather conditions is what makes GFRP and CFRP composites made with epoxy resins preferred choices for wind energy applications. “They offer the highest level of stiffness to the lowest weight,” Skinner explains. “Composites really fit into environments where you see a requirement for stiffness or corrosion resistance where typically the material is moving.”
These stiffness-to-weight advantages are particularly important as designers create even larger blades. Samsung Heavy Industries has commissioned the first prototype of the world’s largest wind turbine with 83.5-meter blades, currently being tested at the Fraunhofer Institute in Germany. Each blade skin was produced in a female mold using a combination of vacuum assisted resin transfer molding (VARTM), prepreg and hand lamination with DIAB’s ProBalsa150 end grain balsa wood and Divinycell H80 polyurea and polyvinyl chloride for the core materials.
Each turbine can generate 6.2 MW of energy, says Flemming Sørensen, director and general manager of SSP Technology, designer and manufacturer of the blade. The new design will be used in South Korea’s first offshore wind energy project, a construction of 12 units in an 84 MW offshore installation in the Korea Strait.