Materials science breakthroughs in wind turbine blade technology could drive down the costs of building wind farms and help put the renewable energy technology on a stronger economic footing to compete with coal- and natural-gas-fired electricity.
Early-stage research by General Electric Co., with support from the Department of Energy and Virginia Polytechnic Institute and State University, aims to use tensioned architectural fabrics rather than fiberglass as the primary material for turbine blades, thus driving down costs by 25 to 40 percent, according to officials involved in the research-and-development effort.
"The fabric we're developing will be tough, flexible, and easier to assemble and maintain," said Wendy Lin, a GE principal engineer and leader of the estimated $5.9 million research effort funded in part by an Energy Department program. "It represents a clear path to making wind even more cost competitive with fossil fuels."
GE's turbine blade research was one of 66 projects selected by DOE's Advanced Research Projects Agency-Energy (ARPA-E) to share in a $130 million competitive grant program to advance cutting-edge energy projects that are in the early stages of development.
"With ARPA-E funding and active program management, GE's innovative tensioned fabric wind blades have the potential to be a real game changer in reducing the manufacturing and transportation costs associated with today's fiberglass turbine blades," agency Deputy Director Cheryl Martin said in a statement. "GE's innovative approach to use fabric stretched across a frame is a perfect example of how ARPA-E funds innovative energy R&D that is early stage, but could change what's possible."
In addition to lowering costs, GE scientists say, the new blade technology -- which involves wrapping advanced fabrics around a metal space frame resembling a fish skeleton -- would also aid in the development of larger, lighter turbines that can capture more energy from wind, even at lower wind speeds.
Assembly in the field
Such fabric-based blades also could be manufactured in sections and assembled in the field, enabling the construction of much larger wind turbines. "That's not our primary intent, but ultimately that's where we see the technology going," Lin said in an interview.
Current technology does not easily allow for turbines with rotor diameters exceeding 120 meters (394 feet) because of design, manufacturing, assembly and transportation constraints. Wider, longer wind blades are also difficult to move, and molds used to form the current generation of fiberglass blades cost millions of dollars.
Officials with GE say the company's fabric-based technology would all but eliminate such barriers and allow the industry to take hold in regions with lower wind speeds. "Developing larger wind blades is the key to expanding wind energy into areas we wouldn't think of today as suitable for harvesting wind power," Lin said.
Meanwhile, a new study from the London-based energy consulting firm GlobalData finds that wind farm developers are increasingly gravitating toward simpler, direct-drive turbines to generate power rather than gearboxes, which the industry has widely deployed in recent years.
A wind turbine's gearbox allows the electricity generator's internal shaft to spin 50 to 250 times for each rotation of the turbine's blades, and it provides advantages over other direct-drive technologies, including reduced noise and higher efficiency ratings.
However, drawbacks to gearboxes include considerable maintenance requirements and lower reliability, according to GlobalData.
Direct-drive turbines gaining favor
In contrast, direct-drive technology allows for continuous slow movement of all parts of a wind turbine, allowing for reduced wear and tear and superior reliability. "Direct drive turbines have been in the wind power market for a long time, but have gained increasing popularity in recent years due to the low reliability and high refurbishment costs of gearbox components," GlobalData states in its report.
The share of global wind turbine installations relying on direct-drive turbines has grown from 18 percent in 2006 to 22 percent in 2011, according to GlobalData. That share is expected to increase to nearly 29 percent by 2020, with manufacturers such as Siemens AG and GE shifting from gearbox turbines to permanent magnet direct-drive turbines.
Enercon GmbH of Germany and Xinjiang GoldWind Science and Technology Co. Ltd. of China are the current leading manufacturers of direct-drive turbines.
One potential drawback to direct-drive turbines using magnet technology, according to GlobalData, is that the technology requires use of rare earth materials such as neodymium, which are less abundant and can be costly during periods of high demand.