Sandia innovation eliminates reliance on rare-earth magnets for large-scale wind turbines
12 September 2022
Motivated by the need to eliminate expensive rare-earth magnets in utility-scale direct-drive wind turbines, Sandia National Laboratories researchers have developed a fundamentally new type of rotary electrical contact. Sandia is now ready to partner with the renewable energy industry to develop the next generation of direct-drive wind turbines.
Sandia’s Twistact technology takes a novel approach to transmitting electrical current between a stationary and rotating frame, or between two rotating assemblies having different speeds or rotational direction, ideal for application in wind turbines.
Twistact technology comprises a pure-rolling-contact device that transmits electrical current between a stationary and rotating frame (or two rotating assemblies having different speeds and/or direction of rotation) along an ultra-low resistance path (e.g., 1 milliohm). Twistact devices accomplish this pure-rolling-contact galvanic connection using a flexible, electrically conductive belt and a matching set of epicyclic sheaves.
The technology proves beneficial in lowering costs, improving sustainability and reducing maintenance.
Graphic illustration of the basic principle of the Twistact operation. (Graphic courtesy of Sandia National Laboratories)
Twistact originated by asking ourselves some really challenging questions. We knew it could be game-changing if we could find a way to get around the limited service lifetime of conventional rotary electrical contacts.
I started thinking that maybe not every conceivable rotary electrical contact architecture has been thought of yet. We spent a lot of time considering if there was another plausible way.—Jeff Koplow, Sandia research scientist and engineer
Eliminating reliance on rare-earth metals. Most of the current utility-scale wind turbines are dependent on rare-earth magnets, Koplow said. These materials come at a high initial cost and are vulnerable to supply chain uncertainties.
In 2011, for example, there was a rare-earth materials supply chain crisis that caused the price of neodymium and dysprosium, the two rare-earth elements widely used for such magnets, to skyrocket. This had the potential to block growth of the wind industry. The Sandia team began developing Twistact at the time as a hedge to protect the growing wind industry from future disruptions.
When you weigh in the fact that rare-earth metals have always been in short supply, that their mining is notorious for its adverse environmental impact, and that competing applications such as electric vehicles are also placing demand on rare-earth metals, the value proposition of Twistact becomes clear.—Jeff Koplow
Additionally, Sandia’s Twistact technology addresses two physical degradation processes common to high-maintenance brush or slip ring assemblies: sliding contact and electrical arcing. These limiting factors reduce the performance of traditional rotary electrical contacts and lead to short operating lifetimes and high maintenance or replacement costs.
A two-channel Twistact device for a multimegawatt direct-drive wind turbine application, designed at Sandia National Laboratories. (Graphic courtesy of Sandia National Laboratories)
Twistact, on the other hand, has been proven through laboratory testing to be capable of operating over the full 30-year service time of a multimegawatt turbine without maintenance or replacement.
Other potential applications for the technology include synchronous motors and generators, electrified railways and radar towers. Twistact could also be used in replacing brush or slip rings in existing applications.
Sandia is now exploring opportunities to partner with generator manufacturers and others in the renewable energy industry to assist with the transfer of Twistact technology into next-generation direct-drive wind turbines. Further, Sandia is open to partnering on the development of high-RPM Twistact technology for applications such as electric vehicles or doubly fed induction generators.
The thing that smacked me in the eye as someone who has not got a background in technology, is the illustration showing it is only 60cm long for a multi-magawatt installation!
What? Is that comparable to current devices or way smaller?
Posted by: Davemart | 12 September 2022 at 02:36 AM
This effectively removes material constraints for the expansion of wind energy.
The same has happened for solar. as agrivoltaics mean that you don't have to substitute solar for growing food, as it can actually provide shelter from excessive heat and reduce evaporation.
Here is an early installation in Germany, showing the learning curve we are on for deployment:
And if you use the heat from rooftop pv for hot water, you not only drastically improve the total electrical plus thermal efficiency, but you actually extend the life and improve the electrical efficiency of the panels:
The only part of the chain we are still a bit weak on is energy storage, with batteries way too expensive for some of the uses enthusiasts imagine.
Amongst a number of possible solutions, I am eagerly awaiting the results from Hydro-Quebec to see how they get on scaling Kubagen's manganese hydride solution up from the lab bench:
As a side perk, apart from solving distributed storage for renewables, it would also make electric cars actually competitive for the hundreds of millions of people on modest incomes looking for their first family car, instead of a luxury item for the wealthy looking for tax breaks
Posted by: Davemart | 12 September 2022 at 04:02 AM
Posted by: yoatmon | 12 September 2022 at 09:51 AM
Very welcome if it pans out.
We have a lot of ideas using all sorts of tech at early stages, but nothing as yet to hand for mass deployment where we can say:
'Yep, that will do the job for long term storage of renewables'
except hydrogen and various liquids derived from it, but many folk including yourself point out the still considerable obstacles in implementing those too.
Posted by: Davemart | 12 September 2022 at 10:38 AM
It may be that long term storage of energy is a pipe dream and we should not try to do it. By all means use short term storage for load shaping, and perhaps buffering solar over the night, but seasonal storage of electricity is crazy so leave it.
You can store chemical fuels (coal, oil gas) for long periods and use these to generate electricity when the renewables are off and to fly aircraft.
You don't have to eliminate them completely, just reduce their usage by say 70-80%.
Or just build lots of nuclear reactors (in safe places).
The problem with solar thermal is that it is complicated to install and tends to be faulty (says my brother in law architect).
Combining solar PV and solar thermal sounds good, but might turn out to be a maintenance nightmare for homeowners.
Solar PV, while less efficient, is a lot simpler (no plumbers involved).
Posted by: mahonj | 13 September 2022 at 12:17 AM
Here is something, that in my estimation, goes beyond wishful thinking.
Posted by: yoatmon | 13 September 2022 at 02:30 AM
Efforts to tap the thermal arrays reliant on liquids have been plagued with all sorts of issues, of leakage, freezing and so on.
And here is another idea I don't fancy, certainly for residential use:
Solar vacuum tubes, so you have new tech needing to ramp to get volume, with all sorts of fancy stuff to get the angles of the pv bits right.
Sunovate in contrast using air could not be simpler.
Stick a conventional solar array in some sort of shallow box, and blow air across it.
More accurately on a sloping rooftop, if you extract the air at the top, convection will do almost all the work.
You then pipe the warmed air down to the water tank, and use a bog standard heat exchanger to transfer the heat.
The cooled air is then recycled back up to the solar panels.
Check out the videos on the link I gave.
Posted by: Davemart | 13 September 2022 at 02:57 AM