Scientists pursue better ways of making and moving enormous wind turbine blades
WASHINGTON - Each year the gleaming turbines reach higher into the sky to wrest more energy from the wind. Their blades are growing, too, now exceeding 200 feet - two-thirds the length of a football field.
Meanwhile, the logistical gymnastics involved in getting such oversized equipment to remote locations around Texas and other Western states are multiplying. A transport can take days and cost tens of thousands of dollars.
Now a team of scientists, drawing from the U.S. Department of Energy, engineering giant General Electric and a small Austin-area firm, Wetzel Engineering, is exploring whether there's a better way of manufacturing the giant turbine blades and getting them into the field.
"Many people thought (100 feet) was the largest we were going to get, except we always find a way to get around it," said Derek Berry, an engineer with the National Renewable Energy Laboratory in Colorado. "The ultimate measure of how competitive we are is our cost of energy. But at some point there is a limit where transportation and maintenance costs, plus other areas, outweigh the gains in efficiency."
Right now blades are manufactured as a single piece. With a foam or balsa-wood core, carbon fiber reinforcement and a fiberglass exterior, their composition resembles that of a giant surfboard, designed to spin and generate electricity even in light wind.
Manufacturing facilities have sprung up around those parts of the country areas where wind is strongest, places like Iowa and Texas. But turbine parts come from all over the world, and in a global marketplace Texas developers are just as likely to buy a blade manufactured in Germany or China and then shipped to the Gulf Coast.
Wherever their origin, the real logistical test is getting blades and turbine towers across roads and highways.
Permits must be obtained from each state the blade will pass through. Routes must be scouted by an advance driver looking for sharp turns and obstructions like stop signs that might need to be temporarily taken down. There must be truck stops capable of fueling a truck trailing a 200-foot-long load.
The trucks themselves are a marvel of design, a trailer with an independent back end similar to that of a fire truck, controlled remotely from a chase vehicle to allow the truck driver to make 90-degree turns.
Getting a blade from the Port of Houston to the Panhandle, usually a 10-hour drive, takes between three and four days, said David Ferebee, a vice president at Lone Star Transportation in Fort Worth, one of a handful of trucking companies that handle wind turbine loads.
"It takes time," he said. "When you pass under bridges, sometimes you have to stop and go a little bit at a time so you don't scrape the bottom of the bridge."
The Department of Energy reports a 1,000-mile truck trip can run more than $20,000. Considering the average wind turbine now runs $3.3 million, that's a relatively small piece of the overall cost. But multiply the trucking bill by the three blades per turbine and the 100 turbines that might make up a wind farm, and the pricetag rises quickly.
Developers are hopeful there will come a day when wind-turbine blades can be manufactured in pieces and assembled on site, said Jeff Clark, executive director of an Austin-based industry group, the Wind Coalition.
The team led by the Energy Department is pursuing two distinct prototypes through a $1.8 million federally funded project. Last year Wetzel was awarded a $1 million grant to develop a lightweight blade that can be built on site. GE is working on a more traditional blade that has a joint running through it, allowing it to be broken down for easier transport.
The struggle is that making something in pieces requires joints. And physics dictates that the more joints are added, the weaker the structure is, Berry said.
"It's not the big storm you worry about. It's the constant cyclical nature of fatigue loads over many, many years," he said.
For now, there is little sign the transportation hurdles are slowing anything down. Between 2008 and 2014, wind turbines accounted for more than 30 percent of the new power generation built in this country.
In Texas, which has more wind turbines than any other state, more than 22,000 truckloads were reported to the Texas Department of Motor Vehicles last year.
The vast majority of those trips go off without a hitch, state transportation officials said. But every once in a while, something goes awry.
Last summer, a truck hauling a wind turbine blade got stuck right off the town square in Goldthwaite, 100 miles northwest of Austin.
A wind farm was going up nearby, and for months the town had watched blades move through. Over that time maybe half a dozen of the trucks got stuck, requiring police to stop traffic to let them back up and try again, Mills County Chief Sheriff's Deputy Chris Green said.
"They'd have a couple escorts. It was a pretty neat little set-up," he said. "But this time the wheels came up on curb. The truck almost hit the traffic light. You can make the turn onto the highway, but this guy just didn't quite hit it right."