Ongoing wind power research and development will help the industry harness more wind, more efficiently and at lower costs in the future.
The biggest factors in boosting wind turbine productivity — longer blades and taller towers — are fueling much of the next-generation research and development push to build a more powerful, efficient, durable and cost-effective turbine. Other important innovations are emerging to make turbine manufacturing easier and cheaper; create intelligent turbines that collect and interpret real-time data; and model and adjust wind plant flows and turbine configurations to maximize wind harvest.
Image: Todd Griffith shows a 50-meter blade cross-section that could be the basis for 50-MW offshore wind installations. Credit: Randy Montoya/Sandia.
Unprecedented Turbine Size
Perhaps the most ambitious R&D is seeking to create a rotor blade longer than 650 feet for a 50-MW offshore wind turbine. That’s 2.5X longer and over 6X more output than the largest blades and turbines now in operation.
The project, led by Sandia National Laboratories, uses Segmented Ultralight Morphing Rotor (SUMR) technology in an aerodynamically-sophisticated load alignment that could substantially reduce peak stress and fatigue on rotor blades and make such a gigantic turbine structurally and economically feasible.
Image: The machine at ORNL that will 3D print molds to be used for manufacturing turbine blades. Credit: Oak Ridge National Laboratory.
The light, segmented blades bend in the wind without losing stiffness. This reduces blade stress, so there’s less mass required to stiffen them. In high winds, the SUMR blades are stowed and align with the wind direction so they are less vulnerable to cantilever force damage. In low winds, the blades fan out for maximum wind energy.
Manufacturing and Materials Solutions
The challenge is making larger and taller – but not heavier or costlier – turbines that are no less effective and can withstand the wind stresses that longer blades would encounter. “You need to ramp up the size of these turbines,” said John Larson, Director at Dominion Resources, an advisor on the Sandia initiative. “But how do we get the weight reduced and advance turbine performance?”
One approach is to make the bigger blades lighter to lessen aerodynamic and gravity loads on the other turbine components, like the drivetrain, and lessen materials costs. GE’s answer here – building blades onsite by wrapping very strong architectural fabric around a metal space frame – could generate more power from slower wind speeds and yield much bigger blades. GE is using this same principle for a fabric-covered, five-legged lattice tower as tall as 139 meters.
Image: Research is being conducted on how to reduce the expense of transporting large steel turbine towers such as this one. Credit: v.schlichting / Shutterstock.com.
How to make the blades is changing, too. “By exploring ways in which 3D printing capabilities can benefit wind, we’re beginning to identify cost and saving options with manufacturing blades, while improving their design flexibility,” said Jose Zayas, director of the DOE’s Wind and Water Power Technologies Office. Specifically, DOE, Sandia and Oak Ridge National Laboratory are investigating 3D printing to manufacture turbine blade molds, eliminating costs and time in mold manufacture.
Today, it’s easier to transport towers by building them in segments made of thick, costly steel. But DOE is researching three simpler, less expensive possibilities: using concrete; shipping partially unrolled steel and welding it onsite; and fashioning corrugated steel segments onsite – which would require up to 30 percent less metal.
A big barrier to taller towers is that, at some point, they’re too big and expensive to transport by land under bridge overpasses. But the National Renewable Energy Laboratory (NREL) is collaborating with a company on a spiral welding process to build taller steel towers onsite and bypass the travel and cost constraints.
Gearbox, Hub and Foundation
Where other turbine components are concerned, NREL led development of new gearbox technologies that replace roller bearings with journal bearings – to improve gearbox reliability and lifespan and reduce size and weight – and use flex pins to increase load sharing between gears in a sun/planet configuration.
The wind that hits the blade hub is wasted, but GE is developing an ecoROTR turbine with a dome that covers the midpoint to capture that wind and deflect it out to the blades. The projected 3 percent performance increase would add up across a wind farm.
Image: The GE digital wind farm uses embedded turbine sensors that gather and analyze data in real time on factors such as temperature, misalignments or vibrations. Credit: GE.
To improve offshore foundations, Sandia is studying how to reduce the support structure costs, including the development of floating vertical axis machines. Since most of the U.S. offshore wind supply is in deep water, where large fixed steel piles or lattice structures are impractical, several U.S. companies are developing less-expensive spar-buoy, tension leg and semi-submersible floating wind platforms that maintain stability and motion control.
Smarter Turbines and Plants
Intelligent wind turbine R&D is centering on enhanced sensing for loads, turbine condition monitoring, wind farm controls and smart rotors with active control surfaces that use built-in blade intelligence to reduce rotor blade loads and turbine costs. “Making turbines smarter and able to sense and optimize energy capture while knowing the state of the turbine’s health – if it’s sound or damaged – will become more important,” said Todd Griffith, lead blade designer on Sandia’s SUMR research.
For instance, GE’s wind farm model pairs 2-MW wind turbines with a digital twin modeling system that can assemble up to 20 turbine configurations at every wind farm pad for peak power generation. Embedded turbine sensors gather and analyze data in real time on factors such as temperature, misalignments or vibrations and relays it to advanced networks that make adjustments to improve efficiency.
It’s not just the turbine that’s getting smarter. NREL is concentrating on what Daniel Laird, director of NREL’s National Wind Technology Center, calls “high-fidelity simulation at the wind plant level.” This uses intelligent plant-wide controls to operate the plant as a whole system, instead of on a turbine-by-turbine basis. “If you can yaw a turbine perhaps a degree or two off of its default setting, you could possibly steer the wake, or turbulence, between turbines in the next row within the plant rather than directly at another turbine,” he said. “Your wind power generation might decrease slightly for that particular turbine, but you may increase production of a subsequent row in the plant.” NREL hopes to test the theory on a commercial wind farm.
Image: The Carbon Trust’s scanning LIDAR technology test was launched in February 2016. Credit: Carbon Trust.
To better understand how the wind is blowing for a plant, DOE is trying to couple regional forecasting and localized wind resource models. “You would make the box bigger around the wind plant to really capture some of the interactions between the atmospheric boundary layer and the flow through the wind plant,” said Laird.
Offshore Wind Resource Assessment Without MET Towers
The Carbon Trust launched an ambitious wind resource measurement project in mid-February with a three-month test – the world’s largest ever – of scanning Light Detection and Radar (LIDAR) technology. LIDAR has the potential to migrate calculation of a wind farm’s potential energy yield away from fixed steel met masts by giving a more detailed picture of the wind resource over a larger portion of the wind site. The economic implications are enormous, since wind measurement accounts for about 45 percent of an average wind farm’s overall project cost.
“In information terms [scanning LIDAR technology] is the difference between taking a still photo compared to having a three dimensional video with full sound,” said Megan Smith, Project Manager, Wakes Research at the Carbon Trust in a press release.
Project partners include RES, Irish Lights, Leosphere and Lockheed Martin.
By some estimates, global installed wind capacity could grow to 2,000 GW by 2030 and meet almost 19 percent of global electricity demand. These innovations will certainly help the wind energy industry to get there.