SeaTwirl puts a new spin on offshore wind turbines


September 27, 2011

The SeaTwirl's vertical wind turbine (1), torus ring (2), float assembly (3) and generator (4)

The SeaTwirl's vertical wind turbine (1), torus ring (2), float assembly (3) and generator (4)

Image Gallery (6 images)

One of the main drawbacks of wind turbines is the fact that for maximum efficiency, the power that they generate must be fed into the grid right as the wind is blowing and their blades are spinning. While that power can be stored in batteries for later use, some of it will always be lost in the process. Sweden's experimental new SeaTwirl system, however, is designed to kinetically store wind energy until it's required - it's basically a seagoing flywheel.

The top of a SeaTwirl system consists of a vertical wind turbine, with a hollow torus ring attached to the bottom. This is the only part of the system that is located above the surface of the water.

An axle runs vertically through the center of the turbine and proceeds into the water. Mounted on that axle, just below the surface, is a hollow cylindrical float body. At the bottom of the axle is a generator. The whole system is held in place by anchoring lines attached to the bottom of the generator.

The wind causes the turbine to spin, regardless of the direction from which that wind is blowing. Because it's attached to the turbine, the axle also spins. The water itself acts as a sort of ultra-low-friction roller bearing, allowing the turbine and shaft to keep spinning even once the wind has lessened. Electricity is generated where the rotating axle meets the non-rotating generator axis. That electricity is fed to the shore via seabed cables.

When the wind is high, the turbine's vigorous spinning action causes water to be drawn up from the float, and into the torus ring. This added weight around the outside of the circular turbine adds to the centrifugal force, keeping it spinning longer. As the turbine slows, it folds down, and the water runs back down into the float. This drawing-in of mass is said to also help keep the turbine moving, in the same way that figure skaters start to spin faster when they draw in their arms and legs.

A one-fiftieth-scale prototype SeaTwirl was tested off the coast of Sweden in August, and it reportedly performed well. The designers claim that in its proposed 430-meter (1,411-foot)-long full-scale incarnation, a commercial SeaTwirl should be able to generate 4.5 megawatts of mean power, or 39,000 megawatt-hours per year. It could reportedly store 25,000 kilowatt-hours worth of power, which they say would be enough to support 8,000 homes for one hour.

Because much of the SeaTwirl system's weight would be supported by the water, it is also claimed that production costs would be lower than those of present offshore wind turbines, as heavier, less expensive materials could be used.

The video below contains some animation that illustrates how the technology would work.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

As the contribution of wind power is such a small percentage, surely there is no need to store electricity? Also the wind blows stronger at the normal height of regular 3 blade turbines, so why is this device so close to the surface?


Very good innovation in Wind Energy Harvesting.

Anumakonda Jagadeesh

under this link can be loked the project of thr best combined turbine.

or on web-site:


energy storage is not needed. Controlled consumption is better. I control mine. Most of my consumption is off-peak

Stewart Mitchell

Great Idea...Vertical Axis Wind Turbines are also an improvement over the horizontal..


Stewart, you have quite a bit to learn about how utilities operate and match output to load. My question, should anyone care to answer...: Besides the manufacturers, has anyone made a profit utilizing wind or solar? It\'s great to \"be green\" but the world goes \'round according to the folding kind. Allow be to qualify my question further, :Has anyone made a profit utilizing wind or solar WITHOUT government subsidies?


Of course the grid needs storage. It is stupid, at least to me, that all power is of the instantaneous \"use it or loose it\". If we had grid storage we wouldn\'t need peaking stations, we wouldn\'t need the above \"local storage\". All the renewable s could simply just work intermittently as they do, but say at times of excess production, in relation to consumption, make say, hydrogen. If we had our entire grid making full power with the excess power making hydrogen then we would soon build up excess hydrogen supplies which could then power say our new hydrogen cars.

and if our base load is met by nuclear (which realistacally is the only technology that can make a dent in our consumption requirements) then a by product of nuclear is, you guessed it hydrogn


Interesting concept. the the \"electric storage \" is in the form of a flywheel system. The same concept would work at home, floated in a rain water tank. hardest part would be the colapsing mechinism and the water proofing of the generator. Though the home versoin could use something like the flex-shaft of a drimel or a speedometer cable and waterproof housing, run through the tank wall, and a dry conventional DC motor as an elrctrical sorce.


Wind genration in the uk made no real dint in the power the goverment claimed it woudl and could provide,Not to mention the eye sores they are the noise to neighbours and the animals they kill.Just what effect will this have on the sea life and birds.We have have as one gentlemen said hydrogen witch now seems to be in compation with more competative electrical cars witch will bring down there charging times puting the worlds so called future enery source in direct compation in terms of cars wise with electrical.Nuclear as one fellow said is the only real sure way to meet our demands.Green is great and yes we are al head for some far out star trek world of the future thats perfect and logical were no life forms die or feel pain.I can see wind turbines being replaced way of in 2070 by turbines in space or solar collectors or 4x more energy.


Windikites, I don\'t know how close to the surface of the ocean is - there\'s nothing relative, like a boat to compare its size. As for downtime - use the power to make hydrogen for the fuel cells we\'re eventually be using.


\"Has anyone made a profit utilizing wind or solar WITHOUT government subsidies.\"

I think the same question could be asked of nuclear power. One source quoted an average cost of ($1998) 320 million to decommission a plant in the USA. To clean up Three Mile Island the cost was estimated at over $800 million. Do the people who made the profits from these plants pay for their safe shutdown and deconstruction 20 or 30 years later?

If I generate excess power renewably (whether solar or wind) and sell it to the local utility, I make a \"profit\" by obtaining that electricity without charge, as well as being paid for that power which the utility immediately resells. There\'s no government subsidies, just market forces.

In many cases government subsidies for renewable power can be viewed as \"seed money investment\" to start a new venture, which in part is recouped by reducing the need to build more non-renewable generation capacity, which indirectly at least, is a \"profit\" to the taxpayer, reducing government spending.

In many parts of Australia, new houses are required to have rainwater catchment tanks, so there may be a large market for a domestic version. (Maybe even something so simple as using excess power to raise water to a height and use the fall to generate power as required.)

Joe Blake


VAWT don\'t need yaw mechanisms, but that\'s their only advantage. They\'re always less efficient than HAWT. There are reasons HAWT designs are used for every utility-scale project.


re; kellory

I would use magnetic levitation/bearings in a vacuum chamber.


Very nice concept. But I think it might work better over a tank or reservoir , rather than open water. This is because seawater would quickly block the mechanisms. Also it would appear that ocean swell would soon damage the structure since it is so close to the surface. I might be wrong... But I hope the developers of this concept keep it up and get it started.

Simon Drozdowski

Wait a second. Can this actually work? Generating and storing energy at the same time? Isn\'t it using all the energy to draw the water up? And why would it go faster when you let the water drain back down?

They say they don\'t need any gear box or transmission ... so is it going to move fast enough to generate electricity?

I get the flywheel on a water bearing thing. The rest of it sounds like free energy.

I could be wrong ... no physics aptitude here.

Albert Sudonim

BurnerJack, you ask: \"Besides the manufacturers, has anyone made a profit utilizing wind or solar?\" As it turns out, the gross cost of solar vs fossil fuel power is about the same. However, the enormous government subsidies received by fossil fuel industries cause the consumer cost of power production from fossil fuel to seem artificially lower than solar power. The consumer doesn\'t realize that the true costs of fossil fuel power production are subsidized by taxes he pays. Just google the phrase \"subsidized coal vs solar\" to discover more information about this. Given equivalent government subsidies, the solar power industry could be every bit as profitable as the fossil fuel power industry.

Having said that, please know that I don\'t think either industry should be receiving subsidies or at least no subsidies beyond the startup phase or R&D phase.


Interesting! How can we find out more about the technology, storm handling including water funnels, tornadoes, hurricanes and tsunami, barnacle and other bioform degradation, effective storage in hours of output at a given power level.


the drawing up of the water is just to give the flywheel more weight, this only happens when the wind is really blowing ..... such that there is way more energy available than what could be stored by the empty flywheel. The thing with a flywheel, the heavier it is, the more energy it will require to get up to speed, but also, the more energy you will be able to tap from it, at a later stage.

for those that think storing energy is a waist of time and not needed, It\'s actually the other way around. Our inability to store energy effectively is the only thing that\'s keeping us in the middle ages, up to now.

Michiel Mitchell

Genuine genious inside! So simple, yet so sense!

Ariel Dahan

re; Albert Sudonim

If you take a car out on a parking lot and drive at 10 feet per second around a light pole at a distance of 50 feet it will take you 15.70795 seconds to make each lap. But if you reduce the distance to the pole to 20 feet and maintain a velocity of 10 feet per second each lap will now only take 6.28318 seconds, While your speed remains constant the number of laps per minute over doubles.

The water retains the same velocity but the size of the circle shrinks dramatically giving a higher RPM but the energy remains the same.


\"In many parts of Australia, new houses are required to have rainwater catchment tanks, so there may be a large market for a domestic version. (Maybe even something so simple as using excess power to raise water to a height and use the fall to generate power as required.) \"...............Rain water tanks are also very common in dry locations like California, where it is forbidden to water plants with tap water(gray water only) I did not understand the eariler comment about magnetic bearing and vac. chambers, (seems more work and more cost than it is worth) But Magnets mounted on the lower end of the shaft could pass rotative power through the floor of the tank with matching magnets under the floor. Inside rotation would draw outside rotation to match. And the exterior magnets would spin the generator shaft. No need to waterproof anything,


Fair comment BurnerJack but these have to be seen as tomorrows technology addressing tomorrows economy; we soon will not be able to afford the money & security costs of oil.The top structure looks too frail and complex to be in the line of fire- why not keep it as a fixed, stronger structure and use the rotation to push a float down into the water (helical track?) which can then rise to assist rotation?


This is a very clever idea: it is simple with relatively few moving parts and exploits a variety of basic principles to accomplish something very sophisticated. The vertical axis of rotation means no machinery of any sort is needed to cope with changes of wind direction. By scaling up, the turbine blades and fluid flywheel can be held well above storm wave height. The slender and very long central column means that the centre of boancy will not rise and fall much relative to its height so vertical forces should not vary too much and the narrow cross section at the surface should minimise lateral force from the waves. The concept of storing rotational energy farmed from the wind as the angular momentum of water in the hollow fly wheel is brilliant! Because the flywheel and its water are turning together there is little loss of energy through turbulence. I think somebody else pointed out that this could be done anywhere, so things like this could be built on dry land, on windy hill tops or on the edge of the desert. Of course that would require some fairly robust bearings which would add to the cost. This does suggest a potential use for one or two abandoned mine shafts though! Or it might be possible also to have the bearing as a very wide, flat and thin disc floating of compressed air.


re; xodarap

Magnetic bearings can be passive, compressed air bearings always require power.


Vertical Wind Turbines should replace Horizontal Turbines in almost all cases...


The problem with this design is the incurred losses from uncaptured wind and drag during the ramping up and down of centrifugal forces. To put another way, the video shows the blades compressing into a disc to store wind. However, any winds that blow during the compression stage cannot be captured to it's fullest capacity. Additionally, if wind capture is desired during high rpm capture, some losses will result from slowing down.

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