Flywheel Energy Storage

[svetz]

Ran across this article where Purdue achieved 300 Billion RPM. They did it with nanoparticles, so not quite ready for industrial applications.
Celeroton has a commercial 25mm diameter motor that spins at 1,000,000 rpm (don't get too excited, doesn't look like you can just buy them on eBay).

Are flywheels more practical as small, light, and super fast?
How much power would a 25mm radius flywheel spinning at 500,000 rpm store?

• Let's assume the rotor is a flat disk 1 mm wide with a k = 0.606.
• A 1mm thick disk of with a 25mm radius would have a volume of nearly 2cc and if made of steel would weigh 15.7g, about 3g if carbon fiber. Let's knock it down a bit more to 2g.
• With a radius of 25mm, the circumference is 157mm, at 500,000 rpm that's ω = 3,140,000 r/m or 328,653 radians/s
• I = k m r^2, 0.606 x 0.002 x (.025)^2 = 6.25e-6 kg m2
• Ef = 1/2 I ω^2, 0.5 x 6.25e-6 x (328,653)^2 = 337540 Joules = 93.7 Wh.

UPDATE to correct Math error I = k m r^2, 0.606 x 0.002 x (.025)^2 = 7.575e-7 kg m2 Ef = 1/2 I ω^2, 0.5 x 7.575e-7 x (328,653)^2 = 40909 Joules = 11.3 Wh

So small, light, and uber-fast might be the way to go!

Not sure that it would be practical for mobile devices, cars, or boats due to the gyroscopic effect (mounted in a 3d gimbal)? But 10 of these would probably weigh less than 1 kWh Battleborn and should store the same amount of energy. Probably need some voltage conversion equipment on top of that (A Flywheel Management System (FMS) ;-).

So, what about something a DIYer could do? A Dremel cutting wheel can spin to 35,000 rpm with 1.5" dimeter (0.0381m). What sort of energy storage with 2g worth of disks on a spindle?

• At 35,000 rpm that's ω = 3,140,000 r/m or 328,653 radians/s or 3663.3 rps
• I = k m r^2, 0.606 x 0.002 x (.0381)^2 = 1.75935132e-6 kg m2
• Ef = 1/2 I ω^2, 0.5 x 1.75935132e-6 x (3663.3 )^2 = 11 Joules = 0.003 Wh.

So, not ready for home DIY... but if Celeroton is the real deal and the motors are less than Lithium for $/kWh I could see the technology coming to market fairly quickly.

 

[svetz]

... it was ...comical watching the grunts ...try to turn corners ...

So in the post above I said that these micro flywheels (a little wider than a d cell, but only a few mm high) wouldn't be practical in mobile devices as there would still be some gyroscopic effect, or rather the Conservation of angular momentum. I'm probably wrong on that. Here's why....

The equation for that is L=mvr, where L is the angular momentum, m the mass, v the velocity, and r the radius. So even though m and r are tiny, v is big ... but not a square as it for the power, it's only linear. So going lighter and smaller does vastly reduce the gyroscopic effect. But it would still have some.

By stacking two and keeping the power balanced it seems that it would cancel the outer system's: torque, force of precession, and angular momentum.

So, perhaps the rotos could be stacked up where each is spinning opposite to the other?
From the previous post we'd need ten 1 mm tall rotors for a kWh. If we left 1mm between each rotor, then for a kWh the assembly would be 28mm x 20mm?
Update: due to the math error above, ten rotors would only provide .1 kWh.

The first thing that comes to mind on such a small assembly of counter-rotating rotors, is the interference of the magnetic fields to exchange power to each rotor would be very hard to do.

But... each rotor doesn't need to exchange power. Every other rotor can power exchange and the fields for them would be aligned without interference. The non-powered rotors might be able to be driven in an opposite direction by an assembly of inner magnets... something similar to this:

Probably cheaper/easier to just build them with all the rotors in a single flywheel spinning in one direction, but let them be assembled modularly with jumpers to reverse polarity so they can be stacked in any orientation.

I could see these being assembled, then sealed in ballistic glass wile under vacuum as "cells". The cells are then assembled in series/parallel with an FMS into banks.

 

[svetz]

Yet another mistake.... Celeroton 's motor is 25mm in diameter, not radius. So, that decreases both r and m:

How much power would a 23 mm diameter flywheel spinning at 500,000 rpm store?

• Let's assume the rotor is a flat disk 1 mm wide with a k = 0.606.
• A 1mm thick disk of with a 23mm diameter: V=πr^2h, 3.14 x (23/2)^2 x 1 = 415m^c = .42 cc,
• if made of steel would weigh 3.3g, about .6g if carbon fiber. Let's knock it down a bit more to .5g.
• With a diameter of 23mm, the circumference is 72.2mm, at 500,000 rpm that's ω = 3,140,000 r/m or 328,653 radians/s
• I = k m r^2 = 0.606 x 0.0005 x (.013)^2 = 5.1207e-8 kg m2
• Ef = 1/2 I ω^2 = 0.5 x 5.1207e-8 x (328,653)^2 = 2765 Joules = 0.768 Wh.

So, state of the art tech doesn't seem there yet... sorry about that! Knew it sounded to good to be true!

 

[curiouscarbon]

youtube v=yhu3s1ut3wM Flywheel Battery

Very accessible DIY flywheel ESS tutorial

 

[Rider]

I distinctly remember an article in Popular Mechanics back in the 60s, maybe 70s, using a flywheel to power a car. No electric conversion, just rotational energy to the wheels. Just a massive steel flywheel spun up slowly by a small electric motor over time.

 

[deader]

Centrifugal Flywheels... a dumb idea?

Is there any research on adding centrifugal weights to a flywheel?
Probably a dumb idea, but I'd like to understand the theoretical/practical reasons why.

Imagine a strong-spoked flywheel, with toroidal waights around each spoke, dampened by springs.

As the flywheel starts spinning, the weights move outward, thus limiting the RPMs to some max.
With the right tuning of weights, springs, etc., maybe the flywheel would run at some constant RPM
over a large range of stored energy values. Maybe it could be tuned to some multiple of 60hz,
to turn a magneto to generate AC electricy steadily at 60hz or whatever.


Just curious. Thoughts/links appreciated.

 

[WoodsieLord]

I think it would be hard to balance, and-or the need for more mobile parts that require maintenance inside a vacuum chamber makes it more expensive?

There are very little attempts at DIY. If you search for diy flywheel battery 75% of results at youtube will say "free energy". Even if you exclude the term "free" it still pops up (less). makes me angry..

I have a washing machine universal motor lying around, I would like to make something with it, but I lack lot of knowledge to start

 

[deader]

I think it would be hard to balance, and-or the need for more mobile parts that require maintenance inside a vacuum chamber makes it more expensive?

There are very little attempts at DIY. If you search for diy flywheel battery 75% of results at youtube will say "free energy". Even if you exclude the term "free" it still pops up (less). makes me angry..

I have a washing machine universal motor lying around, I would like to make something with it, but I lack lot of knowledge to start

There are plenty of credible youtube videos for re-purposing electric motors. The Fisher Paykel motor seems to be the favorite for wind/hyrdo, used by professional hydro companies, you can find plenty of working examples on youtube, and sites with the schematics for re-wiring them to lower voltages.

TheBackShed.com - Fisher & Paykel Windmill.

F&P Smartdrive based windmill design.

www.thebackshed.com

Here's a good channel on electric motors more generally:

Yes, the flywheel tends to attract the perpetual motion crowd .

My idea of putting moving parts on a flywheel is a recipe for disaster! Though 100 yo flywheel engines have small centrifugal weights for governing... and some automobiles add moveable pendulums to the flywheel to smooth out vibration.

I could generalize the question to "variable geometry"... and some of the links above talk about hollow flywheels with various fluids.

Probably best to keep the flywheel as simple as possible.

 

[deader]

I distinctly remember an article in Popular Mechanics back in the 60s, maybe 70s, using a flywheel to power a car. No electric conversion, just rotational energy to the wheels. Just a massive steel flywheel spun up slowly by a small electric motor over time.

There was the GyroBus, 1960's, I think in Switzerland. Very limited range (maybe 10 km) and top speed (20-30 km/h).

This video is in German, I've seem some other in English.

 

[Mart Hale]

Reminds me of this video.

I see this as most viable underground ;-)

 

[Mart Hale]

 

[deader]

Pros/Cons of vertical vs. horizontal axis of rotation?

I've seen both. Larger commercial flywheels seem to be mostly (all?) vertically oriented.

I can think of many, many engineering trade-offs, but would like to hear from the experts.

 

[deader]

Watched that video recently. Wish he would build an improved version, with a straighter axle, larger size, etc.

And a PAIR of flywheels, which could ALSO be rotors!

The laminated steel cores of the coils are already heavy, so why not utilize that mass as a flywheel?

 

[deader]

326 NeoDymium magnets on the flywheel of a (repro) Lister hit-and-miss engine.

Imagine the possibilities...

 

[eXodus]

I've seen both. Larger commercial flywheels seem to be mostly (all?) vertically oriented.

I can think of many, many engineering trade-offs, but would like to hear from the experts.

large commercial flywheels have magnetic levitation bearings.

when you spin on the vertical axis you use all the bearings "surface" while in a horizontal bearing - you only "use" the lower half of the circle.

Further like discussed, a flywheel is also a gryoscope - it's resisting change in direction. Guess what - our planet is rotating and a flywheel is resisting that change and apparently there is a tiny difference in which direction you angle and turn the flywheel to safe energy

 

[eXodus]

Is there any research on adding centrifugal weights to a flywheel?
Probably a dumb idea, but I'd like to understand the theoretical/practical reasons why.

I was thinking about that the other day.

Back in the day - they used just massive wheels out of steel. Sometimes hundred of tons.
They turned fairly slow - many a few hundred RPMs.

Would be interesting to store a few days worth of energy, speed up with solar during the day - draw down during the night.

If you are only taking some simple but heavy material..... hm

 

[wattmatters]

Australian School Spins Up Flywheel Energy Storage System​

Key Energy has installed four flywheel systems at The Armidale School that have been buried underground. Each unit offers 32 kilowatt-hours capacity for a total of 128kWh. The devices used were manufactured by California-based Amber Kinetics, which describes its Kinetic Energy Storage Solution (KESS) as being:

“..the first commercialized four-hour discharge, long-duration KESS solution powered by advanced technology that stores 32 kWh of energy in a two-ton steel rotor.”

.. so, 8kW of power per unit. That two-ton mention is just the rotor – the entire assembly weighs 10,500 lbs, or around 4.76 tonnes. That’s incredibly heavy for what appears to be a very compact setup. Amber Kinetics claims an >86% round trip efficiency (DC), and a life of 11,000 cycles for its KESS.

 

[deader]

large commercial flywheels have magnetic levitation bearings.

when you spin on the vertical axis you use all the bearings "surface" while in a horizontal bearing - you only "use" the lower half of the circle.

Further like discussed, a flywheel is also a gryoscope - it's resisting change in direction. Guess what - our planet is rotating and a flywheel is resisting that change and apparently there is a tiny difference in which direction you angle and turn the flywheel to safe energy

Was wondering if a flywheel on a vertical axis is less affected by precession, at least near the Earth's equator.
Haven't found much on the topic.

The bearing issue seems very complicated. A horizontal axis affords the opportunity of using many bearings, distributing the weight.

I'm guessing the vertical orientation minimizes precession effects, and also simplifies installation.

Can't help but think that batteries will eventually win, since there's been so much improvement over the last several decades, and more breakthroughs are likely, in chemistry, electronics, etc. And electricity is typically the most desirable form of energy.

Flywheels are so simple, I'm not sure they can be improved as much. Plus.. the shipping costs! ?

Australian School Spins Up Flywheel Energy Storage System​

Australian School Spins Up Flywheel Energy Storage System​

Amber Kinetics is also installing some flywheels in Fresno, CA.

Fresno Project To Store Solar Electricity Using Flywheel

The Fresno City Council has approved a land lease that will make Fresno the site of an innovative new energy project. Kerry Klein reports from…

www.kvpr.org

 

[eXodus]

The bearing issue seems very complicated. A horizontal axis affords the opportunity of using many bearings, distributing the weight.

more bearings more friction.

Can't help but think that batteries will eventually win, since there's been so much improvement over the last several decades, and more breakthroughs are likely, in chemistry, electronics, etc. And electricity is typically the most desirable form of energy.

Flywheels are so simple, I'm not sure they can be improved as much. Plus.. the shipping costs!

Maybe not for home and small grid applications - but for large industry or grids. You can keep a flyweel spinning for very low cost for probably centuries. While a battery needs replacing every 10-20 years.

 

[deader]

more bearings more friction.


Maybe not for home and small grid applications - but for large industry or grids. You can keep a flyweel spinning for very low cost for probably centuries. While a battery needs replacing every 10-20 years.

more bearings more friction.


Maybe not for home and small grid applications - but for large industry or grids. You can keep a flyweel spinning for very low cost for probably centuries. While a battery needs replacing every 10-20 years.

Durability is a plus, though there are Edison batteries 50 years old, and maybe some 100 yo NiFe batteries still exist. A bit strange they went out of fashion, though supposedly some companies are starting to make them again.

Flywheels are great for short-term buffering, to level out daily fluxations, but don't seem to be used much beyond handling peak-demand intervals, and absorbing the energy of decelerating trams (when electric grids can't handle such loads).

Wonder what the round-trip energy loss for a flywheel is, after one week or one month. Can't be great, and at some point it's zero.

As interesting as flywheels are, it seems like some inexpensize battery chemistry breakthru will eventually obviate them.

In fact, googling reveals a new "Iron Air" battery. Let the battery battles continue!

New 'iron-air' battery stores electricity from renewables for days