Talking with wind energy engineer Fort Felker about turbine manufacturing is like taking a breath of fresh air. A hearty fellow with a big voice and a slight southern drawl, he doesn't come across as someone who holds a patent in winglet technology, a PhD in Mechanical Engineering from Stanford University and was instrumental in the design of the modern wind turbine. He comes across as someone who believes in the power that renewable energy has to change the world – and the important role that solid mechanical design and analysis tools play in order to make that happen.
Felker started his career at NASA, performing research on helicopters at the Ames Research center but switched over to work with Kenetech Wind Power in 1994. According to Felker, Kenetech was a powerhouse early on in the wind industry. “Some of the things that the rest of the industry is just now getting to, Kenetech was doing in the early 90s,” he said.
His work at Kenetech centered on turbine dynamics analysis. He said that when he joined the company, the simulation tools for wind turbine design weren’t that good. Having done simulation work for helicopters, he had “a pretty strong toolkit to transfer that technology into the wind industry,” he said.
Felker’s crowning achievement at Kenetech was his work as part of the Tiger Team design group that built the KVS-45. The KVS-45 was a 500-kW machine, which was big for the day. Felker said that the KVS-45 was the first turbine designed from scratch to have all the modern features that we see today. It was the first turbine that combined variable speed, full power conversion, variable pitch and tubular towers.
He is quite proud of how quickly the machine went from concept to prototype. “In a space of 10 months, we went from a clean sheet of paper to having two prototypes up and operating and acquiring test data. It was an amazing accomplishment to do all that in 10 months. Just astonishingly fast,” he said. “I’m really proud to have been part of the design team that pulled that off.”
But soon after the KVS-45 was up and running, the company closed up shop – a result of poor management and other factors, said Felker. “It was a number of things that really came together at the wrong time. Deregulation of the electricity industry was occurring at the time and it became very, very difficult to secure a long-term PPA because there was so much uncertainty associated with the deregulation process,” he said.
But other companies survive tough times. And Felker thinks Kenetech management could have done more. “[Deregulation] shouldn’t have been enough to bring the largest wind turbine manufacturing company to its knees. I fault the leadership for not being sufficiently flexible to adapt to the realities of a fast-changing marketplace,” he said.
So Felker left Kenetech and started a six-year entrepreneurial stint during which he founded Winglet Technology, a company based on his patent. The company is still thriving today but Felker is no longer involved.
For Felker, wind power was in his blood and once he noticed that the wind industry was on solid ground, he immediately returned to it. “I had always wanted to return to wind. You know, as an engineer, it gives me such a positive feeling to work on a technology that is making the world a better place and I hated leaving that and I wanted to get back to it.”
Engineer AND businessman, he chuckles stating that when an industry can boast global annual sales in the $100 billion range, it’s probably here to stay. And that’s what landed him where he is now, as the director of the National Wind Testing Center (NWTC), which is part of the Department of Energy.
The NWTC is an R&D execution center based at the National Renewable Energy Laboratory that delivers world-class research results for the DOE. “We focus on innovation that will reduce the cost of wind energy, on ways to improve the power production of wind turbines, ways to reduce the structural loads on wind turbines through advanced controls that allow you to put bigger rotors on and get more power out,” he explained.
One area that the center has focused on is gearbox reliability, an issue that Felker said was hard to pin down because manufacturers didn’t like to talk about problems they were experiencing in their gearboxes. “There were warranty issues, lawyers were involved, there was a lot of finger pointing about whose fault it is,” he said. To get beyond that, the NWTC had to develop its own non-proprietary, open-engineering architectured gearboxes that were representative of modern gearboxes, he said. Once the design was in the public domain, Felker said the center could then provide results to the wide range of stakeholders responsible for gearbox reliability: “turbine manufacturers, gearbox manufacturers, bearing manufacturers, consultants, universities, there’s got to be over 50 participants,” he said.
The results of the center’s testing have been very revealing, according to Felker. The center compared its actual controlled laboratory results and field test results to blind analysis results to see if the simulation tools that are in use in the industry reflected actual data. And they didn’t.
“These tools that would predict the dynamics of a gearbox are quite complex, quite sophisticated computer programs and there are a lot of choices available to the analyst about how to proceed with a test,” he explained. It is the choices that those analysts are making when conducting simulations that revealed the inconsistencies, he said.
In addition, the center has found that two nominally identical gearboxes can actually behave a lot differently, which also means more work for the engineer.
“It means that the engineers that are designing the system can’t just consider the average – you have to look at the normal variation that you are going to see in a production line, he explained. Since routine, acceptable production variations can make a difference in how a turbine operates, “you can’t just look at the nominal design case,” he said. “You have to look at it and say, ‘well if the tolerances happen to stack up this way, or the other way, how does that change things?’ People need to start considering that,” he said.
Felker considers these results very interesting.
In addition to gearbox testing, the NWTC is looking to make advances in the aerodynamics of turbines and reducing the noise associated with turbines. A less noisy turbine can spin a little faster, he explained.
Felker said that tip speed is a fundamental parameter for turbine noise. “The lower it is, the less noise it makes, the higher, the more noise it makes.” Felker explained that you want that tip speed to be as high as possible with acceptable noise. Higher tip speeds mean lighter turbines and lower torque on the gearbox and the generator. “The whole system gets lighter when you push up that tip speed,” he said.
A lighter system costs less, and lower costs are what will ultimately advance the industry, said Felker. “When we are investigating noise, we can actually take dollars out of the capital cost of the turbine so I think that’s a real important opportunity,” he said.
Felker said that another area that needs further study is advanced control systems and the center has “a couple of wonderful test beds,” on which to conduct those tests. Further, the NWTC is developing a 5-10 MW grid simulator. “Over voltages, under voltages, frequency droop, face-to-face faults, ground faults – all kinds of real-world bad things that happen out there – we’ll be able to test those explicitly here,” he explained.
For Felker, the real challenge for the wind power industry is simple. Get the cost of wind power low enough so that it can really compete with fossil-fuel generation. “We shouldn’t rely on policy or subsidies—we just need to beat the fossil fuels on price,” he said.
He’s optimistic about the future, indicating that over the next 10-20 years wind power costs will drop and soon fall in line with those of fossil fuel generation. He believes that once that happens, we’ll see the fossil fuels dropping in price in order to compete, which will put pressure even further downward on both technologies. “That’s going to be really interesting.” he said.
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