Engineers work to increase the role of wind in the nation's energy portfolio
Bringing technology up to speed with this need for workable wind power is a tall order, but it is achievable, according to Douglas Adams, professor of mechanical engineering. “Whenever we try to take a technology and rapidly advance it, that’s a challenge,” he says, “but that’s what makes wind power so interesting. It’s one of engineering’s ‘grand’ challenges.”
Adams’ colleague Sanford Fleeter, the McAllister Distinguished Professor of Mechanical Engineering, is an expert in gas turbine engines. He became interested in wind power not just because he thought he could “really make a contribution” to the rapidly advancing science, but also because he recognized its commercial potential.
“When I looked at wind power, I saw a growing business,” Fleeter says. “With energy costs going up, wind power is not only a green alternative.”
But it also makes sense economically, since it is not subject to supply-and-demand fluctuations of the marketplace. Fleeter notes that “when you put in a wind farm, you know what the power from that farm will cost in 20 years.”
Fleeter estimates that as he was entering the wind power arena about five years ago, 1,500 people attended the Windpower Conference and Exhibition. Two years ago, that number was up to 7,000. This year, 15,000 attendees and 1,200 exhibitors gathered for the meeting in the Windy City. A paper Adams co-authored with his graduate student Jonathan White was presented at the Chicago meeting, where “unbelievable attendance” excited Adams and his colleagues. It seems the winds of change are indeed blowing in energy innovation.
Better understanding, better design
Right now wind provides about 2 percent of the national energy supply. Adams admits there is risk in rushing to ramp up wind power capacity. “We’ve got a functioning technology,” he says, “but how do we get to 20 percent? Not by installing turbines that sometimes suffer reliability setbacks in the variable wind corridor of the American Midwest.”
To achieve the ambitious goal of 20 percent wind power by 2030, engineers like Adams and Fleeter are analyzing the things that can go wrong and figuring out a way to predict and manage problems with the wind
turbines and all their various parts.
What can go wrong? Adams, who hates to see a wind farm with its towers at a standstill has a list of potential problems for engineers to study and design around. That list includes a leak in the hydraulic seal
of the pitch actuator, structural failure of the blade itself, which could arise from rare but catastrophic cracks in the blade, failed bearings in the drive train, shafts that become misaligned, which in turn can have a negative
effect on the gear box, whose meshing gears can either lose energy or crack, damaged dampers, a faulty generator—even hail and lightning present a threat. These turbine assemblies are sometimes 200 feet off the ground, and Adams notes that when a turbine “goes down” it can take several thousand dollars to rent a crane and make the repairs, not to mention the loss in productivity.
Fleeter has constructed a model wind turbine facility at Purdue to study fatigue failure and other issues that arise from the dynamics of the turbine. He quantifies the interactions between the tower and the rotor in a wind
tunnel. Because the rotors have three blades that are revolving past a columnar tower, they create a three-beat impulse that affects operational reliability. These vibrations, plus phenomena like acoustic noise from the blade tips, are factors that need to be accounted for. “We’re trying to understand and monitor these vibrations, and hopefully become able to control them,” he says.
Adams wants the turbines to be able to “speak” for themselves, so to speak. “We need enough intelligence on board to manage the turbine’s reliability,” he says.
So Adams is working with Sandia National Laboratories to design “smarter” turbines that can quantify both static (centripetal) and dynamic (fluctuating wind) loads on the blades. They use a capacitive accelerometer
to measure acceleration directly related to force, something earlier sensors have not been able to do.
"The aim is to operate the generator and the turbine in the most efficient way, but this is difficult because wind speeds fluctuate,” Adams explains.
“You want to be able to control the generator or the pitch of the blades to optimize energy capture by reducing forces on the components in the wind turbine during excessively high winds and increase the loads
during low winds. In addition to improving efficiency, this should help improve reliability.”
Deciding where to build a wind farm is a big decision for a developer. The first step after a potential site has been identified is to erect an anenometer tower to collect wind data for one year before going ahead with construction. These calculations often overestimate the potential wind power generation at a site, says Fleeter, because they do not accurately account for the turbines that stand in the “wake” of other turbines. Fleeter is working to quantify the effects of this interaction of the turbines with the “atmospheric boundary layer” of the wind as it moves through the farm. Identifying and understanding subtle factors like these will help developers move forward on construction with a greater degree of confidence.
The next wave in wind
Fleeter sees a great interest in wind power among his students at Purdue. In the fall 2008, he offered a senior/graduate course in wind energy, expecting six students. Three times that many signed up. He and his
students also became involved in a senior design project: a self-starting vertical wind turbine. “In the space of one semester the students designed, built, and ran it. It worked,” says Fleeter proudly. “I thought it was
pretty amazing.” Several of those students have gone on to work for wind turbine companies.
Fleeter also worked with an Engineering Projects in Community Service (EPICS) group to do a feasibility study to put a small wind turbine on Purdue’s campus, with incoming students wanting to continue this EPICS project and actually get one installed. “There are definitely opportunities for engineers in wind power,” Fleeter says.
Adams is equally optimistic about wind power as a promising professional field. “Boilermakers will be in leadership roles in the green economy,” he says, “and wind energy stands to offer plenty of jobs.” From manufacturing to wind farm management to retrofitting existing wind farms with new technologies to quality control and beyond, the new wind power industry will make rewarding careers for many engineers. “And we’re not working on the fringe, with obscure technologies that will take decades to work,” says Adams. “The core technology is very feasible in the near term.”
The benefits of tapping the power of the wind are numerous. Approximately 40 percent of total U.S. CO2 emissions come from power generation facilities. Since substantial amounts of coal and natural gas fuels would be displaced by a 20 percent wind scenario, CO2 emissions in 2030 could be reduced by 825 million metric tons. Wind power saves water, too, by not using any of it in the generation of power. Unlike the water-thirsty processes of fossil-fuel and nuclear energy generation, generating 20 percent of U.S. electricity from wind would reduce water consumption in the electric sector in 2030 by 17 percent.
And then there is the economic impact. The US Department of Energy report entitled 20% Wind Energy by 2030: Increasing Wind Energy’s Contribution to U.S. Electricity Supply finds that, during the decade preceding 2030, the U.S. wind industry could:
- support roughly 500,000 jobs in the U.S., with an annual average of more than 150,000 workers directly employed by the wind industry.
- support more than 100,000 jobs in associated industries (accounting, law, steel work, and electrical manufacturing)
- support more than 200,000 jobs through economic expansion based on local spending.
- increase annual property tax revenues to more than $1.5 billion by 2030.
- increase annual payments to rural landowners to more than $600 million in 2030.
Special thanks to Mr. Dale J. Budreau for allowing our team to photograph the windmills on his land.