Sustainable Energy and the Return of the Fly(wheel)

January 22nd, 2010 by Tina Casey

The flywheel is an old technology that dates back to Neolithic-era spindles and potter’s wheels. Flywheels made a huge splash during the Industrial Revolution (anyone remember steam engines?) and now they’re ready to take center stage in the new wave of sustainable energy.

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In sustainable energy, flywheels come into play as a means of storing intermittent power. Wind power and solar power are notoriously fickle in many parts of the world, and some means of smoothing out the bumps is required. Vycon is one of several companies exploring the potential of flywheels, and it has come up with some interesting twists.

What a Flywheel Does

If you’ve ever played tether-ball, the idea behind a flywheel is simple. You provide sharp bursts of intermittent energy to send the ball around the pole. The weight of the rope and its course around the pole combine to even out those bursts, creating a relatively constant, steady motion. The rope also stores energy; after it is fully wrapped around the pole, the ball reverses course at a relatively steady pace, without any more help from you. A similar principle applies to potter’s wheels, which can be kept in steady motion with intermittent kicks.

What a Flywheel Is

Companies like Vycon have ramped up this simple principle into sophisticated flywheel energy storage systems. Vycon’s proprietary system consists of a steel hub with magnetic bearings, a dual motor/generator (the motor charges the system, the generator dispenses the energy), high tech system controls, and a converter that transforms the flywheel’s AC power into DC.

Flywheel Applications

Flywheels can be used to store energy from solar and wind installations, and Vycon has come up with a couple of other applications that it calls “energy recycling.” The company has developed a flywheel system for harvesting the energy that normally is dissipated when large shipping cranes are lowered. In a similar vein, Vycon has also developed a flywheel system that can harvest and store the braking energy from commuter and freight trains. Both the crane and rail applications could become an important contribution to the management of carbon emissions from global shipping, especially in sensitive coastal areas.

Flywheels in Action

Flywheel technology could also be used to harvest energy from mining operations, or from elevators in buildings. Compared to sustainable energy storage solutions such as molten salt, flywheels may also be more portable and site-adaptable. They are also highly durable and they are already starting to pop up in some high stress environments. A couple of years ago, Formula 1 cars started to phase in a flywheel/hybrid electric system called Kinetic Energy Recovery, which stores waste energy in a flywheel instead of a battery. The newly online Ross Island Wind Farm in Antarctica is expected to make a huge dent in the base’s carbon footprint with the help of a flywheel storage system.

Image: Flywheel from an old factory by Rajesh Dhawan on wikimedia commons.

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Tags: flywheel, Vycon

About the Author

Tina Casey Tina Casey specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

ChristianHJW

All recent developments about flywheel technology are all going in the same direction : Small, rather lightweight rotors made from CFRP (CFK) compound material, mainly with the goal to achieve a very high energy density, sometimes even much higher than even the best batteries.

While this may be smart for mobile applications, like the aforementioned KERS in Formula 1 (not to forget the PORSCHE 911 Hybrid with mechanical flywheel, which has won the 24 hrs of the Nuerburgring last year), it is at least very questionable for stationary applications, e.g. for grid stability improvement and frequency control.

The lightweight CFRP rotors with a small diameter require high RPMs to store sufficient energy, and as a result of that the bearings and their durability do become the Achilles heel of the flywheel. If you do look at the current market for flywheels, you only find them successfully in UPS applications, using conventional steel rotors, operating at rather low RPMs (ty. 12.000), like BEACON Power, Launchpoint LLC or TEMPORAL Power from Canada, you don’t read so much about them recently ? BEACON had a lot of attraction around their famous Stephentown, NY plant, about two years ago, but now it is almost impossible to get any kind of information how the units do work under 24/7 conditions ?

In fact, personally i am convinced that low weight, high RPM flywheels are the wrong approach for stationary applications. If you do study the formula of the kinetic energy of a flywheel in detail, you will find that there are two parameters which do increase the energy to the power of two :

E kin = ½ x ( ½ x m r ² ) x ( 2π x n ) ²

The RPM, bus also the radius of the rotor ! In our new concept ‘RK-Accumulators’ for stationary use we have been putting the focus on increasing the rotor diameter, while keeping RPMs at a rather low level. Our plan is to design and build a flywheel with an energy storage capacity of 1 MWh, by accelerating a 25 tons heavy rotor with a diameter of 2.5 m, made in a unique compound process from steel and CFRP fibres (resin free), up to 6.000 RPM max. . The unit can output 10 MW power, meaning it can be loaded and unloaded in not more than 6 mins, while being rated for > 1 Mio cycles (0 yrs lifetime).

Conventional CFRP rotors can not be built this way, the tensions between the individual CFRP fibres are becoming too high, they tear from each other and the whole rotor will delaminate.

Flywheel can be a wonderful partner to battery storage systems, in so-called ‘Hybrid Storage’. As the flywheels is unbeaten in handling short peaks and reacting to short demand fluctuations, it could act as a kind of ‘damper’ for the battery containers, taking the short cycle variation stress from them (no battery likes switching constantly between loading and unloading). We are convinced that a single of our flywheels can extend the life time of a stack of battery containers significantly, in such a ‘Hybrid Storage’ solution.

Best Regards

Christian Wiesner
ROTOKINETIK, Germany
- Bob_Wallace
  
  Very interesting comment Christian. I hope that when you have some performance data you’ll give us an update. Contact Zach if you’d like to write something up at that point.
  
  Now, I realize that you do “have a dog in this fight” but, what’s your take on flywheel vs. ultra-capacitor for short duration fluctuations?
  - ChristianHJW
    
    Dear Bob, my ‘dog in this fight’ is a puppy still, as our project is not fully funded as of yet. And every time when i do make statements about possible flaws in the concepts of other flywheel vendors, there are two hearts pounding in my breast :
    
    I am a strong supporter of the idea to use flywheels for frequency control and grid stabilisation, and if these guys can succeed, they will prepare ground for our concept (superior concept, of course ).
    
    On the other hand, if they do fail it will be very hard for any other flywheel concept to re-enter the market successfully again. However, as i am the type of guy who doesn’t like depending on others too much, i decided some time ago to name the flaws in their concepts which i can see clearly, and right from the beginning.
    
    If the guys from AMBER and TEMPORAL feel mistreated that way, well, there is not so much out in the wild about the real performance of their units, so yes, maybe i am not being fair with them, we will see. AMBER’s idea to use high performance steels, rather than CFRP compounds, is actually quite smart. However, their units are much too small to really become cost competitive to batteries. The real benefits do come if you do scale these beasts up to a certain size, which will give you a lot more freedom both in design and concept. About TEMPORAL power, nothing substantial is known about their units, except that their designer is a genius and some truly outstanding performance data, plotted on their website. I’d love to get a price idea for such a 50 kWh unit ?
    
    About Ultra-CAPS, i hate to admit that i lost track on recent development. Will use your remark as a reminder that this is unacceptable, you always have to know where competition is and where they are moving to, to create the right strategy for your own venture:-) ….
    - Offgridman
      
      It has been two years now, can you give us any kind of update as to your larger scale flywheels, or how they compare with current battery or supercap technology?
mark

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mark

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Susan Kraemer

Love that Neolithic tech!
Susan Kraemer

Love that Neolithic tech!
http://extremegreenvillage.com Bob Henry

I remember hearing about this a long time ago

It fascinated me as a kid.I think it’s wonderful that it is coming up again.

The same problems exists, but really for me it has incredible possibility for energy storage for a small town, village or community.

The problem is friction. Magnetically levitating the massive flywheel weight seemed to be a way.

The question always is, if you put energy in to it. How much energy is lost every week if you don’t use it?

Is it 1% a week? Is it 2#?

How much energy can be held, how much is lost (% per week) and how much does it cost?

These are the questions.

We need examples and ranges. How does it compare to batteries, compressed air, heat storage and the other competing forms?
http://extremegreenvillage.com Bob Henry

I remember hearing about this a long time ago

It fascinated me as a kid.I think it’s wonderful that it is coming up again.

The same problems exists, but really for me it has incredible possibility for energy storage for a small town, village or community.

The problem is friction. Magnetically levitating the massive flywheel weight seemed to be a way.

The question always is, if you put energy in to it. How much energy is lost every week if you don’t use it?

Is it 1% a week? Is it 2#?

How much energy can be held, how much is lost (% per week) and how much does it cost?

These are the questions.

We need examples and ranges. How does it compare to batteries, compressed air, heat storage and the other competing forms?