Flywheels as mechanical batteries
Flywheel Energy Storage (FES) is a relatively new concept that is being used to overcome the limitations of intermittent energy supplies, such as Solar PV or Wind Turbines that do not produce electricity 24/7.
A flywheel energy storage system can be described as a mechanical battery, in that it does not create electricity, it simply converts and stores the energy as kinetic energy until it is needed. In a matter of seconds, the electricity can be created from the spinning flywheel making it the ideal solution to help regulate supply in the electrical grid.
It is based on a really old concept and is very similar to an old-fashioned pottery wheel where the potter moves his feet to make the wheel spin. As the potter works, he removes energy from the system, so to keep the wheel spinning; he needs to keep moving his feet.
So how exactly does it work?
A flywheel is a heavy shaft-mounted rotating disc that speeds up when electrical energy is applied to it. When energy is needed, the flywheel is slowed and the kinetic energy is converted back to electrical energy, where it can be transmitted to where it is required.
The energy a flywheel contains is a function of the speed that it is spinning multiplied by the moment of inertia.
The moment of inertia states that the effective mass of a spinning object is not dependant on how much actual mass the spinning object contains. Instead, it is dependant on where the mass is located in relation to the central point that it is rotating around.
For example, if spinning at the same speed, a solid flywheel will store less energy than a flywheel of the same mass that has spokes and its weight situated around the rim of the wheel.
A high moment of inertia is good, but speed of rotation is better!
The speed that the flywheel rotates has a larger effect on the energy stored within it compared to the moment of inertia. If you have a flywheel with a rim weighing 1kg and replace it with a flywheel with a 2kg rim, it has the potential to store double the energy. If you take the original flywheel and double the speed at which it spins, you quadruple the potential energy that it can store.
Innovation of the flywheel
Historically, flywheels have been huge steel structures with the majority of the weight distributed towards the rim of the wheel. However, over the last 30 years, scientific innovation has meant that flywheels can store more energy in less weight and volume, increasing their potential for energy storage. Newer flywheels are made from very strong composite materials and are operated on a bed of near frictionless magnetic bearings housed in a vacuum enclosure. This allows the flywheels to be spun at incredible speeds helping maximise the energy that they can store. In fact NASA scientists have managed to get flywheels to spin in excess of 60,000 revolutions per minute, which is nearly 2.5 times the speed of sound. The amount of kinetic energy that can be stored at this speed makes them ideal for replacing chemical batteries in the future.
There is also potential to use magnetic levitation as a way of prolonging the life of the flywheel energy storage systems. Since there is no friction on a system that is magnetically levitated there will be no wear on the system, so it is thought that these systems could last fifteen years or more as opposed to a chemical battery that may only last five years.
Flywheel energy storage in action
In June 2011, the Beacon Power Corporation completed the company’s first flywheel energy storage plant in Stephentown, New York at a cost of $60m. The plant utilises 200 flywheels spinning at a maximum speed of 16000 rpm to store excess energy and help regulate the supply to the local grid.
On 7th March 2012, Rockland Capital acquired the assets of the Beacon Power Corporation and put up funding to develop a second 20 MW flywheel regulation plant in Pennsylvania.
Flywheel could be one of the solutions to provide mass scale storage of electricity during excess supply and provide the release of energy during excess demand.
GreenAge – Can you comment on this latest FES development?
Engineering student designs revolutionary energy storage solution
August 2, 2016
http://phys.org/news/2016-08-student-revolutionary-energy-storage-solution.html
Hi Alexandre, this looks great. I think energy storage is going to grow into a huge industry, just look what Tesla are doing out in the states! I know that the main investment is going into battery storage, but the flywheel energy system does look interesting. I think a relatively maintenance free system makes it perfect for homes – how much energy can be stored by this ‘football’ sized design?
I truly believe that flywheel energy storage is the way ahead and I’m directing a university level study into it. We have developed a program to optimise the size of the flywheels for home,, town and wind farm storage. Do you have any thoughts on the field and armature coil arrangements to optimise the efficiency of the motor and generator?
Hello, I will be interested in your findings for a community project in Africa
Hello I am a sixthform student with a passion in this area and live in devon and was wondering if i could please have your email to discuss this topic
Hi James,
I’m a student at the new HS2 college. We’re looking into how we can improve the existing designs with a platform presented by the college to put the ideas forward. Could you utilise the kinetic energy of the train wheels using a flywheel storage system to power the start and stop motions of the train?
Flywheel is a simple machine who’s time has come. Think of a heavy wheel that could run on magnetism and gravity with a simple spring or magnetic method of a restoring force. Look on you tube and google Magnetic Experiment 2. I call it axial harmonic motion.
Whos the author of this article? i would like it to cite my reference for an essay
Why is there no mention about just how long the energy from a flywheel can last for when that energy is actually needed?
Batteries will be much cheaper for the foreseeable future, and flywheels only viable with government subsidy in many cases in the immediate future, but as the cost of entry gets cheaper and the materials/technology better, flywheels will certainly play a valuable role … especially since you don’t have to destroy swaths of Earth to get material like lithium and has a much shorter life. Good luck!
hi!! i saw an clip in a show of an old enigine with a flywheel incorporated into it. add building a house in colorado and finding that hooking up to the grid is as expensive as building a minimal battery bank to run the house (20k+)… and battery banks cost for maintenance and replacement batteries every 5-8 yrs…. i was wondering if a flywheel could be used, or multiple flywheels?? your site appeared right on top of the search…. do you know of anyone who can supply a “home: system?