I've done some web searches, but I don't see anything very current on how close we are to having a home energy storage flywheel system that's comparable in price and performance to a battery system. Contact online >>
I''ve done some web searches, but I don''t see anything very current on how close we are to having a home energy storage flywheel system that''s comparable in price and performance to a battery system.
Also, as a bonus, what is the current state of a domestic-scale flywheel system in terms of maximum energy storage, power output, and usable energy (maximum energy minus minimum energy -- assuming there''s a minimum speed they must maintain, unless there''s not)?
Lets check the pros and cons on flywheel energy storage and whether those apply to domestic use (source):
Compared with other ways to store electricity, FES systems have long lifetimes (lasting decades with little or no maintenance;[2] full-cycle lifetimes quoted for flywheels range from in excess of 105, up to 107, cycles of use),[5] high specific energy (100–130 W·h/kg, or 360–500 kJ/kg),[5][6] and large maximum power output. The energy efficiency (ratio of energy out per energy in) of flywheels, also known as round-trip efficiency, can be as high as 90%. Typical capacities range from 3 kWh to 133 kWh.[2] Rapid charging of a system occurs in less than 15 minutes.[7] The high specific energies often cited with flywheels can be a little misleading as commercial systems built have much lower specific energy, for example 11 W·h/kg, or 40 kJ/kg.[8]
In conclusion: with all the effort put into development of rechargeable batteries and upscaling of a whole industry to massproduce and market them I would doubt that flywheels are ever going to fly (pun intended) any time soon in a residential setting. I would rather expect to see them as grid energy storage in utility-scale levels that would benefit from the advantage of a high power output and where a higher capacity warrants the complexity of such systems (moving parts, vacuum, mag-lev).
Domestic flywheels are unlikely to happen for 3 reasons:
They must be heavy to store significant energy. If you need a crane to install one at your house it''s never going to be super cheap, even with high volume manufacture.
The risk of the spinning mass fracturing requires special safety precautions - commercial operators put them in the ground but that would be super expensive on a domestic scale.Note that this isn''t the same as failed bearings where it might grind to a noisy halt. We''re talking heavy projectile at great speed.
Now if you''re off the grid, that''s a different story. Storage Batteries have trouble with high power - short duration loads such as when your fridge compressor starts up. A very small flywheel could help here in conjunction with normal batteries. It being very small eliminates the problems of weight, safety and energy loss over time. But the right battery already does the job cheaper - a low capacity, high power battery like the one in your car (wired correctly; don''t try it!).
So for it to be cheaper it''d take a revolution in low cost, high speed bearings in tandem with a stalling in high drain battery development; and it''d still only be a very niche market.
We were looking into flywheel UPSes for my company and I read up on this a bit. Of note in recent developments:
Instead of traditional bearings, they''re using magnetic bearings to mostly eliminate friction.
To be able to suspend the flywheel on magnets, that requires a lower weight/mass.
To counter the lower weight/mass, you have to replace that with increased velocity to maintain the same amount of momentum, which is your energy storage.
Supposedly these magnetically-suspended flywheels allow for a very high efficiency, as the reduced mass also means it doesn''t take as much energy to spin it up. "Mass = Resistance to change in motion."
From what I know of mechanical systems, anything mechanical introduces losses due to friction in the form of heat, sound, and vibration. How would you even begin to use the mechanical energy stored in a flywheel? Simply storing the energy induces massive losses. Transferring the energy to its appliances introduces transfer problems such as losses, torquing rods, etc.
My reading after I wrote my knee-jerk reaction:Article showing state-of-art flywheel progress, with efficiency of 85%. Flywheels operate in vacuum. https://
Big $$ spent by Boeing on specialty-use flywheel:https://
Afterthought: This seems to be something for specialty use. The promising flywheels seem to need uber-clean, highly maintained conditions. This is unlikely to be something for use in the home anytime soon. I expect that it is already in prototype experimentation in some factory.
TL:DR: They extend the life of expensive UPS batteries by absorbing the transients.
Example: Hosptial with an MRIEngery surge on start up with UPS graciously assisting. The MRI fires up 10 times a day = 3650 times a year. This hammering halves the rated life of UPS batteries, rated for say 100 deep discharge cycles.
In a month, you have one power outage and 90 transients- half of them comming from within the building itself. This can vary greatly by each place in the extreme. Some municipalities have thousands of transients.
So, this is where a flywheel which lasts decades can save big money: premature battery replacement. (athought: what about using a supercapacitor as a buffer)
I was only able to find one residential flywheel energy storage system for sale as of right now. It has a low (but manageable) power output and is priced competitively.
Unit Specs:Power: 3kW | Energy: 15kWh | Size: 40"x40"x40" | Weight: 750lbsRound Trip Efficiency: >=80% | Depth of Discharge: 100%Connectivity: 48VDC "Virtual Lead Acid" buss.Price: $6,000
There are a few other companies that are getting close, Energiestro is one that comes to mind.
TL;DR - Because of how flywheel energy storage scales it is unlikely that significant efforts will be made to develop the technology for home use.
This is similar to the case for windmills, where the power output increases as the square of the diameter, and the cube of the wind speed (which itself doubles roughly every 20m of elevation).
From the Engineering Toolbox, the equations governing flywheel kinetic energy are:
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