A full-size superconducting generator could be the future for wind turbines

via IOP Publishing

A superconducting rotor has been successfully tested on an active wind turbine for the first time.

The EcoSwing consortium designed, developed, manufactured a full-size superconducting generator for a 3.6 megawatt wind turbine, and field-tested it in Thyborøn, Denmark.

They report their results in the IOP Publishing journal Superconductor Science and Technology.

Corresponding author Anne Bergen, from the University of Twente, The Netherlands, said: “Wind turbine size has grown significantly over the last few decades. However, today’s technology has trouble keeping up with the trend towards ever-increasing unit power levels.

“Permanent-magnet (PM) based direct-drive (DD) generators offer a solution in state-of-the-art multi-megawatt generators, but the feasibility of 10+ megawatt PM-DD turbines requires significant weight reduction. Pseudo-magnetic direct-drive (PDD) machines, integrating magnetic gearing and generator functions are a possible solution to this, but they can be expensive and highly complex to produce.”

To tackle this challenge, the team employed rare-earth barium copper oxide (ReBCO) high-temperature superconducting generators. These require a smaller amount of rare-earth materials than PM machines, resulting in a lower cost. Superconductors can also carry high current densities, which results in more power-dense coils and a lower weight.

Ms Bergen said: “The field test of the generator was extremely successful. When the generator was installed at Thyborøn, the turbine achieved its targeted power range, including more than 650 hours of grid operation. This shows the compatibility of superconductive generator technology with all the elements of an operational environment such as variable speeds, grid faults, electromagnetic harmonics, and vibrations.

“The project made several other substantial pieces of progress. It demonstrated that HTS coil production is not limited to specialised laboratories, and constitutes a successful technology transfer from science to industry. The HTS rotor was also assembled in an industrial setting, showing superconducting components can be deployed in a `standard’ manufacturing environment.

“Now the concept has been proven, we hope to see superconducting generator technology begin to be widely applied on wind turbines.”

Learn more: Superconducting wind turbine chalks up first test success


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Oil rigs and wind turbines may end their days as valuable artificial reefs

There are plenty of cod around a sunken oil rig. Photo: Jon Svendsen

A large group of international researchers have just published a scientific article in which they encourage environmental authorities across the globe to rethink the idea of removing oil rigs, wind turbines and other installations in the sea when they are worn out.

A submerged camera at an old worn out oil rig shows an extensive life of flatfish, cod and bottom fauna in all its forms. A life usually not see in these parts of the North Sea, where the oil rig awaits decommissioning after 25 years’ of loyal service in pumping oil and gas from the ground.

“We also see many more porpoises around oil rigs than in the surrounding sea,” says senior researcher Jonas Teilmann from Aarhus University, who has been involved in the studies that have just been published in the international journal ‘Frontiers in Ecology and the Environment ‘.

“It’s easy to understand why the porpoises enjoy the area. One can’t throw a fish hook without catching one of the many cod around the legs of the oil rig,” says Jonas Teilmann.

Artificial reefs form oases in the sea

An oil rig or other artificial installations are typically present for 20-30 years in the sea. Through this period, the tubes, bars, concrete bricks and much more turn into beneficial substrate for adhering plants and animals. And this rich environment attracts fish and mammals.

Internationally, it has been decided that all artificial installations in the sea must be removed when they are no longer in use. But now almost 30 international researchers say that this decision perhaps should be reconsidered.

“In, for example, the North Sea, an old oil rig will have the same function as a natural stone reef,” Jonas Teilmann explains.

And stone reefs are in short supply as stones have been removed and used for, among other things, pier construction or been destroyed and spread due to use of heavy trawls.

“We have observed a significantly increased biodiversity around the old facilities and encourage the authorities to consider, in each individual case, whether an exemption from the demand for removal can be granted. When making the assessment, the environmental conditions must, of course, be of sufficient quality,” says Jonas Teilmann.

Avoid trawling

Around the world, there are more than 7,500 oil and gas platforms and between 10,000 and 20,000 wind turbines that need to be removed at some point. It is estimated that it will cost up to EUR 100 billion to remove these installations.

But perhaps the money can be saved and conditions for marine life improved instead.

“By leaving the rig in place, we may ensure greater biodiversity in the sea. The physical structures also ensure that the areas will not be trawled. The heavy trawls turn the seabed into a uniform desert with poor biodiversity,” says Jonas Teilmann.

Learn more: Oil rigs may end their days as valuable artificial reefs



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Vertical axis wind turbines offer electricity solutions for urban and suburban areas

Figure 3 illustrates the computer-aided design model for design configuration #13. The turbine blades are assumed to be made of carbon fiber and the turbine shaft and blade supports are made of Aluminum 2024.
CREDIT: Lam Nguyen and Meredith Metzger, Department of Mechanical Engineering at the University of Utah

Researchers model optimal configurations of vertical axis wind turbines and find they can offer a future where electricity costs are lowered, or even eliminated, in urban and suburban areas

According to a prediction made by the U.S. Department of Energy, wind energy could provide 20 percent of electricity in the U.S. by the year 2030. This has motivated researchers from the University of Utah’s Department of Mechanical Engineering to investigate the performance capabilities and financial benefits of vertical axis wind turbines (VAWTs) in urban and suburban areas.

A VAWT is a wind turbine design where the generator is vertically oriented in the tower, rather than sitting horizontally on top. While there are many VAWT designs, the one used in this study is called the straight-blade Darrieus type or H-rotor turbine.

According to the researchers, small VAWTs possess the ability to effectively operate in the presence of high turbulent flow, which makes them ideal energy harvesting devices in urban and suburban environments. In an article in this week’s Journal of Renewable and Sustainable Energy, from AIP Publishing, the authors present results indicating that an optimally designed VAWT system can financially compete with fossil-fuel based power plants in urban and suburban areas, and even spearhead the development of a net-zero energy building or city.

To establish their results, the team input actual, time-resolved wind speed data into a numerical simulation that determined the total amount of energy captured by a turbine over a year of operation. Their wind data was accrued over the year 2009 from 3-D sonic anemometers mounted on the top of traffic posts, about 9 meters, or 30 feet, above ground, and positioned at nine different urban and suburban sites around Oklahoma City, Oklahoma.

The researchers simulated 13 different wind turbine configurations, with a focus on four particular design parameters: height-to-diameter aspect ratio (H/D), blade airfoil shape, turbine solidity and turbine moment of inertia. The main performance measure used to identify the optimum design configuration was the percent of energy captured by the turbine over the course of the year relative to the available energy in the turbulent wind during the same time period.

Of the 13 design configurations, the optimal turbine design had the lowest moment of inertia. Interestingly, however, the researchers confirmed that even with the moment of inertia eliminated as a design parameter, this configuration was still the most ideal.

They also analyzed the various turbine designs for the levelized cost of energy (LCOE) at one of the test sites and found the values for blade characteristics necessary for economically viable options. The optimal design configuration at this site produced electricity at a cost 10 percent lower than the average national electricity unit price.

“This is not the end of our research, and I think that we have more to study on the turbine design configuration and its operating conditions that would allow for enhancing the amount of energy captured by the turbine. […] It’s exciting,” said Lam Nguyen, one of the lead researchers on the project. Nguyen is currently expanding his research with a former advisor.

Following their conclusion that an optimal design configuration for VAWTs could lead to a lower electric cost, the team knows the work is not finished.

Learn more: Vertical Axis Wind Turbines Can Offer Cheaper Electricity for Urban and Suburban Areas


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Argonne coating shows surprising potential to improve reliability and vastly reduce costs in wind power

Researchers from Argonne’s Surface and Lubrication Interaction, Discovery and Engineering initiative developed a novel “diamond-like” coating that could prove of great benefit when used to coat equipment for wind turbines, like the bearing in this photo. Pictured from left, Levent Eryilmaz, Giovanni Ramirez, Ali Erdemir and Aaron Greco.

Researchers from Argonne’s Surface and Lubrication Interaction, Discovery and Engineering initiative developed a novel “diamond-like” coating that could prove of great benefit when used to coat equipment for wind turbines, like the bearing in this photo. Pictured from left, Levent Eryilmaz, Giovanni Ramirez, Ali Erdemir and Aaron Greco.

Despite the rigors of scientific inquiry and the methodical approaches of the world’s most talented researchers, sometimes science has a surprise in store.

Such was the case when a group of researchers from the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory and the University of Akron discovered that a particular form of carbon coating not necessarily designed for wind turbines may indeed prove a boon to the wind industry — a serendipitous finding that was recently highlighted in the journal Tribology International.

Prolonging the life of these components could greatly reduce the cost of wind power, the fastest growing source of energy in the world, thereby making it an even more attractive energy source.

Due to the strenuous environment inherent in wind turbine drivetrains, key components such as actuators, bearings and gears are prone to failure, meaning turbines require regular maintenance that helps drive up the price of wind energy. Prolonging the life of these components could greatly reduce the cost of wind power, the fastest growing source of energy in the world, thereby making it an even more attractive energy source.

These failures are often due to a phenomenon known as micropitting in which the repeated rolling and sliding cycles in the gears and bearings of turbines lead to cracks on the surface of drivetrain components. Further contact only exacerbates the cracking once it begins, chipping away at the metal and increasing the severity of the existing cracks until costly maintenance is necessary or, even worse, the drivetrain fails.

Enter Argonne’s Tribology and Thermal-Mechanics Section and its Surface and Lubrication Interaction, Discovery and Engineering (SLIDE) initiative, which investigates how lubricants and materials interact and develops novel lubrication and coating concepts that reduce friction, and therefore micropitting, prolonging component life across a range of energy technologies.

And sometimes they get a little lucky. Such was the case when SLIDE researchers applied this “diamond-like” (some of the carbon-to-carbon bonding in the coating is similar to that of diamonds) coating to wind turbine components, which was not the intended use.

“We felt that if it was working under other sliding conditions, it might work in wind turbine drivetrains as well,” said SLIDE’s Ali Erdemir, an Argonne Distinguished Fellow. “Initially, our expectations were low, as we thought the coating would wear out due to the high stresses inherent in wind turbines, but that didn’t happen.”

So far the coating, named N3FC, has proven its worth through more than 100 million testing cycles with no appreciable micropitting.

Erdemir admits that they don’t know exactly how far it could go, as it has surpassed the time limit of SLIDE’s benchtop micropitting test rig. If the coating performs similarly under real-world conditions, it could mean huge savings in terms of maintenance and prevention of failure in wind turbines nationwide — to the tune of millions of dollars, said Erdemir.

But first, he added, they need to learn exactly why it works.

“We don’t yet understand the exact mechanism,” said Erdemir. “The general belief is that component wear life extension requires a much harder coating, as more hardness reduces wear. But in this case the coating has less hardness than the base steel, so conventional thought doesn’t apply.”

The team is now eager to work with companies and see how N3FC performs in the field. Until then, they will stay busy trying to discover the mechanism behind this surprising scientific development. “We would love to get to the bottom of this and design even better coatings,” said Erdemir.

The team is also testing the coating in sealing applications for compressors. As a low-friction surface coating, it may also prove beneficial in natural gas and hydrogen environments. “It appears to have multiple capabilities in terms of performance,” said Erdemir.

Learn more: Gone with the wind: Argonne coating shows surprising potential to improve reliability in wind power



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A New Type of Wind Turbine

Michael Carruth via University of Colorado at Boulder

Michael Carruth via University of Colorado at Boulder

Since childhood, Michael Carruth, a junior in the environmental design program at CU-Boulder, has been fascinated with nature. Long hours spent playing outdoors, observing swirling leaves, clouds scudding across the sky and the way seed pods spin in the wind: experiences like these inspired Carruth to design a new type of wind turbine.

Drawing on nature for inspiration, his wind turbine design utilizes flexible sails that open and close depending on which direction the wind blows to maximize energy production efficiency. The result is his design project, which he calls Vertical-Axis Sail-Turbine (VAST).

“I was curious about air and wind and being able to use it for energy,” said Carruth. “I took ideas of capturing air energy from things like birds and sail boats. You get an amazing sense of motion looking at the clouds and how they interact with the terrain. And you can get a good understanding of the wind by looking at creeks and water flow.”

Carruth and his six siblings grew up having adventures on their family’s ranch near Austin, Texas. His connection to the natural world developed as they were exploring, building bridges across the creek, climbing trees and walking through pastures.

On his way to CU-Boulder as a freshman, originally to study economics, Carruth drove past a wind farm in north Texas that had the tall, three-blade conventional turbines. He noticed the turbines were spinning at different speeds while some weren’t spinning at all. As he observed differences in how the turbines were performing, Carruth wondered if he could design a turbine that generated power more efficiently, could be used in small-scale applications and would be aesthetically pleasing.

As Carruth settled into his coursework in economics, he couldn’t get the turbine idea out of his mind, so he worked on sketches in his free time.

“In my classes, instead of taking notes I was drawing sketches of turbines,” he said. “I wasn’t interested in studying economics anymore. It took a leap of faith to check out the environmental design program, which turned out to be a better fit for me. I like the freedom of expression that comes with design.”

There are two basic types of wind turbines, which are determined by the direction the turbine turns. The more common type has rigid blades that rotate around a horizontal axis, like a windmill. A vertical axis turbine rotates on an axis perpendicular to the ground, which is what Carruth’s design is based on. While the horizontal axis variety must be oriented to the prevailing wind direction, the vertical axis allows the turbine to collect wind energy from any direction.

The main structure of Carruth’s design will be constructed from aluminum; the bottom sail will be made from carbon fiber and the top sail will be made from rip-stop nylon. He designed the flexible sails to open in order to collect the wind and then fold closed to optimize aerodynamic performance. Even the design is drawn from nature, mimicking a wing or a flower caught in the air.

Environmental design is the process of integrating the artificial built environment into the natural world, says Justin Bellucci, an instructor in the environmental design program and Carruth’s advisor on the VAST project. Students are taught to blend social, ecological, cultural and ethical concerns in their approach to design.

“Michael was looking at biomimicry, taking inspiration from the natural world to build something that’s beautiful, efficient and sustainable,” said Bellucci. “We teach our students to use natural systems to influence design, because design is inherent in everything. ENVD students have a broader picture of the world.”

Carruth is so passionate about his project that he reached out to the College of Engineering and Applied Sciences at CU to find students to help him build a prototype of his turbine. Six mechanical engineering students chose VAST for their senior design project.

“This is something new and innovative in the renewable energy field,” said Jeffrey Gay, fifth-year senior working on VAST. “All of us on the team are very interested in wind turbines, renewable energy and sustainable energy. We’re excited to build a wind turbine and do it in a novel way that’s never been done before, which furthers the technology.”

In 2014, Carruth’s design earned a $1,000 Undergraduate Research Opportunities Program (UROP) grant for preliminary research and a feasibility study resulting in a prototype proving the concept of its design. He recently received a $1,500 grant from the Engineering Excellence Fund. Bolstered by the positive feedback, he is pursuing more funding.

“The engineering team I’m working with has been amazing,” he said. “What we can expect in terms of this initial prototype isn’t going to change the world in terms of the amount of energy we’ll be able to produce, but the way it changes the thinking of how wind turbines interact with the wind will hopefully make a difference.”

Carruth’s plans after graduating include possibly pursuing a graduate degree in architecture or working in the design field. His long-term goal is to have a design firm that focuses on solving some of the serious problems plaguing the world.

“I want to make the world better in terms of exploring new ways of doing architecture,” he said. “Philosophically changing our relationship with problems, which requires a different level of design. I feel a deep connection with trees, wind, water and light. A lot of that is what drives my desire for change.”

Learn more: Drawing Inspiration From Nature, Student Designs a New Type of Wind Turbine



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