With the Production Tax Credit subject to the whims of a fickle Congress, U.S. windpower remains in an ongoing state of uncertainty. Will the United States embrace the technology?
In the Mainstream: Wind Turbines Take Off
New technologies are helping windpower mature as a viable power supply choice for utilities.
in the United States last year, and Mitsubishi supplied almost one in 10. Also, Vestas, Mitsubishi, Siemens, Gamesa, and Suzlon have developed workaround technologies that enable them to bring variable-speed machines into the United States, apparently without treading on GE’s intellectual property. GE’s patent itself has spurred innovation in finding new ways to accomplish variable-speed operation and VAR control, and to advance other goals.
“Almost all turbine manufacturers are now working toward more sophisticated control algorithms,” says Christina Aabo, international product manager with Suzlon in the company’s Denmark offices. “The turbine is becoming more intelligent, and has been for the past several years.”
Wind turbine technology is advancing at the front end, in control and automation systems, and at the back, in gearboxes and generators.
“We are spending our money to get higher efficiency turbines,” Gleitz says. “We want capacity factors at the highest levels, and that means we must focus on improving the efficiency of blades to capture kinetic energy from the wind. The key question is how to convert energy from wind, and lose less in energy transformation.”
As such, manufacturers are working on adaptive airfoil shapes that capture wind more efficiently across a range of wind conditions, as well as advanced materials that reduce various types of stress on the system.
“Well-designed blades are important,” Aabo says. “But the main thing to get higher performance is to improve how it is operated.”
Because wind speeds can vary substantially from the top to the bottom of a 90-meter rotor, adjusting pitch angle during the blade sweep to adapt to changing wind speeds can reduce the amount of stress being placed on the system. The result is less need to overrate components, and lower materials requirements and weight—which further reduce stress.
“We are working on optimizing individual blade pitch, as it goes through its sweep from top to bottom,” Aabo says. Suzlon calls the technique “micropitching.” “That’s caused headaches for our control people, but we’re getting it done.”
The idea of adaptive blades is not especially new, but automation and control systems are getting steadily more complex and powerful as technology marches forward. The same is true of wind-park operations and control systems. “The brain of the windpower plant is the SCADA system that can operate the wind park to a high degree of efficiency,” Aabo says. “Manufacturers are looking at projects as a power plant, taking a more holistic view.”
The next generation of control systems is applying more intelligence to entire wind parks, managing operations according to dynamic wind conditions as well as power loads, both active and reactive. And even more broadly, project engineers and planners are analyzing wind resources with more intensive data-crunching capabilities, to inform equipment and facility design decisions.
“We’re using historic weather data for 3-dimensional weather modeling, and combining that with the utility’s load and operational data, to re-create what a hypothetical wind plant would have produced if it had been there,” says Mark Ahlstrom, CEO of WindLogics Inc. in St. Paul, Minn. The models draw upon a huge database of historic