Ok, I’m sorry for the headline, it’s just…
You know how sometimes you see an innovation that’s so obvious, you wonder why it wasn’t just always done that way? Maybe this is my ignorance speaking, but this feels like one of those times.
Traditional upwind turbines face the incoming wind, and to avoid being blown into the tower, their blades must be sufficiently stiff. It requires a lot of material to build these relatively thick and massive blades, which drives up their cost. Turbine blades on downwind rotors, however, face away from the wind, so there’s less risk of them hitting the tower when the winds pick up. This means they can be lighter and more flexible, which requires less material and therefore less money to make. These downwind blades can also then bend instead of break in the face of strong winds—much like palm trees.
Over the past six years, in conjunction with collaborators at the University of Virginia, the University of Texas at Dallas, the Colorado School of Mines, and the National Renewable Energy Laboratory, Pao’s team has collaborated to develop the SUMR (Segmented Ultralight Morphing Rotor) turbine, a two-bladed, downwind rotor to test the performance of this lightweight concept in action. On June 10 at the American Control Conference, the CU researchers presented results from a new study of four years of real-world data from testing their 53.38 kilowatt demonstrator (SUMR-D) at the National Renewable Energy Laboratory’s (NREL) Flatirons Campus, just south of Boulder, Colorado.
They found that their turbine performed consistently and efficiently during periods of peak wind gusts—a satisfactory result.
This seems unequivocally good. I talk a lot about how we need to be preparing for a much more hostile climate, even as we work to reduce that hostility. A huge part of that is going to be having electricity that keeps working even when disaster strikes. Power plants that shut down during heat waves are already getting people killed, as is energy infrastructure that breaks in the cold. Conditions are changing, and our best shot at saving lives is to change our infrastructure ahead of that change.
Wind turbines that keep working in high winds, plus a grid that can withstand hurricanes, could move us from storms meaning a power outage, to storms meaning a power surplus!
I also like this because it goes into the design of the controller that makes sure the blades are facing the correct direction. The oldest windmills had to be directed manually. I think the next upgrade after that was a sail that could align the rotor to the wind like a weathervane. After that, we got fascinating arrangements of wooden gears and the like. All of those innovations are cool in their own right, but it’s good that we’ve got more advanced systems, to deal with a more chaotic climate.
One of the trickiest elements of wind energy generation is dealing with not enough or too much wind at one time. When wind speeds are too low, a turbine can’t produce a useful amount of energy. When gusts are too fast, they can push the limits of a turbine’s capacity, causing it to shut down to avoid a system overload.
The inconsistency of wind speed has plagued wind energy since its inception; the lost time spent shutting down the system leads to less energy generated and less efficient production.
Key to Pao’s innovative contributions are improvements to the controller—the part of the turbine that determines when to be more or less aggressive in power production.
“We like to think of the controller as essentially the brain of the system,” said Pao, senior author on the study and fellow at the Renewable and Sustainable Energy Institute (RASEI).
This hidden brain aims to produce efficient wind energy at low cost and with low wear and tear. The feedback controller does this by using measurements of how the system is performing, and then adjusting to better improve the performance, said Pao.
The yaw controller makes sure the turbine is facing the correct direction, the blade pitch controller determines the direction of the blades (dependent on the wind speeds), and the generator torque controller decides how much power to pull off the turbine and onto the grid. While it controls physical components of the turbine, these controllers are essentially a software algorithm that tells the motors what to do.
Pao’s group is not only turning the turbine around to reduce damage from strong winds, but working behind the scenes on its software to maximize the system’s ability to keep running during peak wind events.
“Our work attempts to predict the likelihood or the probability of peak wind gusts occurring, and then tries to mitigate the speed peaks by acting before they happen,” said Phadnis.
NREL’s Flatirons Campus’ was the perfect place to test this in action, as it’s strategically placed to receive the strong winds which shoot out across Highway 93 and onto the mesa, after being funneled through Eldorado Canyon directly to the west.
There, the researchers found that, even through extensive experimental testing, peak generator speeds were below the threshold for their operational controller to keep the turbine running.
In a separate collaboration, Pao and her research group have been working with the University of Oldenburg in Germany to assess the utility of sensors that scan ahead of the turbine to measure the wind coming in and of advanced controllers that command the turbine to respond proactively.
I remember reading a while back about how concentrated solar thermal plants were getting better because advanced sensors and computing meant you could have a field of small (relatively), flat mirrors that would re-align themselves to keep the reflected light focused on the same point throughout the day. Prior to that, solar furnaces had to use large parabolic mirrors , which work, but which are harder to construct and transport, and less efficient at tracking the sun. It stands to reason that similar advances have been made for wind energy, but I honestly hadn’t thought much about it till now.
I hope this team gets all the support they need to advance this. The article is cautious about the likelihood of their design being adopted over the turbines we’re used to, and I’m sure that the problems of capitalism will be a big obstacle, beyond whatever engineering problems may exist. That said, the possibility of wind power that uses less material, while also working in a wider variety of conditions, feels like an obvious win.
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I think the tradeoff is that in a downwind turbine, when the blades pass through the wind shadow of the tower, they flex from fully loaded to lightly loaded. This repeated bending leads to earlier blade failure. Upwind or downwind is an engineering problem and maybe these people have found a new solution that favors downwind, but it’s not a new idea.
John Morales says
This sort of thing is ongoing.
People tend to forget those older technologies have had 100 or more years head start, and are mature technologies.
Emerging tech, not-so-much.
Generation, storage, distribution — all are subject to serious research right now.
Abe Drayton says
@SchreiberBike – good point, and I guess it makes this work all the more important.
regardless, I’m glad we’re at the point where we might be able to actually get some benefit from the superstorms we’ve summoned.
Oggie: Mathom says
Over the years, I have run across many ideas that, in retrospect, seem so bloody obvious that I wonder (fleetingly) how all the great minds in the world could have missed that. I think that one of the working definitions of genius (not just the stupid IQ idiocy) is being able to spot the obvious. Then, of course, comes the hard work.
Wind shadowing is a problem for both downwind horizontal axis turbines as wel as for a lot of vertical axis turbines.
It’s one of the reasons why vertial axis wind turbines aren’t more popular.