Flywheel Battery

I too remember reading flywheel energy storage article or 2 back in the day and I had thought that a vertically mounted in ground fly wheel composed largely of steel and possibly some sort of the heavy mortar for additional mass at lower cost connected via drive shaft to a ground level generator would be a nice setup.

I think the idea of bearing failure and catastrophic failure are a couple reasons companies keep from developing too much? but I could be way off.

Anyhow.. that's why I would want mine underground and away from the house.

As far a the donut shaped wheel.

Look at a bike wheel? I'd say you are correct. Nice subject.

The larger the radius for the same RPM and mass,the greater the energy storage capability.With magnetic bearings,and a vacuum sealed enclosure the friction is nearly zero,and very little maintenance required.I agree that placing it inside for an underground enclosure would ensure safety in the event of a destructive event. A bore hole like a well would do.It would also allow removal if required for servicing or replacement.Weight would not be a factor,however,alignment with the earth's rotation would be a factor to prevent loss of energy due to precession.The only drawback I see at present time is cost per KWH of storage.

Float it on water.

Think of how hard it is to stop a large moving ship. The momentum is huge as is the available energy. The larger the flywheel, the lower the speed needs to be for the same amount of usable energy.

Minimize the friction between the water and the surface of the flywheel to reduce the creation of a wake. With no actual displacement of water, it should be quite stable.

I really don't see the necessity of electromagnets when in a fixed position,unless in an earthquake zone or in a vehicle.Fixed magnets would probably suffice in most stationary applications.The comparisons above should include number of recharge cycles before replacement is required,and the efficiency of power in compared to power out.If you take the expected lifetimes out far enough the costs should even out.

In a large flywheel MG weight not as important as rpm,which depends on strength of the rotor material.I expect that with stronger materials being developed the rpm can be increased.I am thinking about carbon nanotube strands woven as a rotor with the most mass concentrated in the outer edge,like a doughnut.

If used in vehicles,counter rotating MG would have to be used to prevent the resistance of turning corners,and might even be modulated to help cornering in certain cases.The electromagnetic bearings would have to be capable of handling impacts from normal bumps in the road while driving.

I believe they do...If I remember correctly it was a million charge/recharge cycles and 90+% efficiency....It seems the cost vs improved efficiency in automobiles, does not favor implementation at this time...

There was a proposal to use a flywheel to power a city bus. The bus would be powered by the flywheel from bus stop to bus stop, then spin up the flywheel periodically at charging stations. The flywheel would be horizontal near the bottom of the bus in a vacuum chamber. The flywheel was made of fiber, with the strands radiating outward from the hub. The counter intuitive part of the flywheel design was that the hub was thicker than the rim. Apparently that allowed for higher RPM and more energy storage.

The design process should probably start with a mass and RPM that you could safely contain in an accident. Then determine how many of those units would be required for a reasonable travel range.

The Gyrobus concept came from a desire for an electric trolley to disconnect from one set of overhead power lines to another set of power lines blocks if not miles away. AFAIK Today's improved flywheel storage systems of vacuum containment and magnetic bearings were not utilized in the original Gyrobus of half a century ago.

Kinetic energy recovery systems (KERS) are common in many racing circuits. Not all of these approaches use a flywheel battery but many do.

I don't understand your apprehension for a vehicle with an added flywheel-based angular momentum component. Every ICE already has one spinning flywheel.

I don't understand your apprehension for a vehicle with an added flywheel-based angular momentum component. Every ICE already has one spinning flywheel.

Well, that's a good point. Actually, without knowing any details of a flywheel, you can calculate the angular momentum only from the RPM and the stored energy.

ω = 2π/60 * RPM

E=1/2 I ω²

L=I ω

Solve for L in terms of E and ω. You don't need to know I, it cancels out.

L = 2E/ω = 2E/(.1047*RPM) = (19.1 * E / RPM)

where E is energy, kg m²/s², (Joules)

I is Moment of Inertia, kg m²,

L is Angular Momentum, kg m²/s,

ω is Angular Velocity, radians/s

For the same stored energy, a light flywheel at a higher RPM would have less angular momentum than a heavier flywheel at a lower RPM, because angular momentum is proportional to RPM whereas energy is proportional to RPM squared.

If the flywheel in a vehicle is brought to a stop in time t, the amount of torque, T, applied to the vehicle is angular momentum, L, divided by the stopping time, t,

T = L/t.

So if we wanted to add 300ft/lbs of torque for 3 seconds and we had 2 flywheel's 15kg ea and a diameter of 20cm what would the rpm's need to be ?

If I understand your question correctly:

300 foot pounds of torque T = 406.75 newton meters = 406.75 kg m²/s²

t = 3 sec, ΔL = T * t

Apply this torque for 3 seconds, change in angular momentum ΔL = 1220.25 kg m²/s

Assume 2-15kg solid cylinder flywheels, I = 1/2 MR², M=30 kg, R=0.1 m, I=0.15 kg m²

ΔL = I Δω or Δω = ΔL/I = (1220.25 kg m²/s) / (0,15 kg m²) = 8135 rad/s

ΔRPM = 8135 (rad/sec) * (1 rev / 2π rad) * (60 sec/min) = 77684 RPM

Applying 300 ft lb of torque to 2 solid cylinder 15 kg flywheels for 3 seconds changes the rotation speed by 77684 RPM

Thank you Rixter...An extremely light vehicle of say 400 lbs with driver, could conceivably be spun up in the garage with electrical energy, and driven for quite some distance, and basically have an extremely long service life....Might be fun to try this for the dragstrip....A car that never wears out, ok almost never...

..."Professionally raced karts typically weigh 165 to 175 lb (75 to 79 kg), complete without driver."...

I would have a lot of respect for something rotating that fast!

We have turbo chargers spinning faster than that...of course the mass pales in comparison, but there can be containment research objectives rendering products that are perhaps both lightweight and robust that could put the mind at ease...

Yeah, but a 15kg mass spinning at 77K rpm? Aren't we asking for trouble in an accident (if it breaks out of the case).

You beat me to it! Yes, this was one of the main concerns when they were considering the use of a flywheel in a bus. There could be huge amounts of damage if the flywheel escaped the housing! And bus accidents happen too often and at times they're in highly populated areas and the bus is badly damaged (enough to break a flywheel housing).

In drag strip cars,a flywheel shield is required.Before this regulation was enacted,drivers had lost legs and life when flywheels exploded.

Tungsten and titanium come to mind to contain an exploding flywheel for other applications of flywheel energy storage.

Those are called scatter shields and have saved many racer's body parts and lives. The problem arises when you dump a clutch to get a good launch (or transbrake for automatics). Think of the intense force that goes through the clutch to get the car moving fast - the only link from the engine to the transmission. Flywheel (or flexplate for automatics), clutch disk and pressure plate (or torque converter) - a few parts that transfer 7,500 lb-ft of torque (some claim a peak of 12,000 kb-ft) from the engine to the transmission!

Oh yeah, transmissions come apart too. They have a blanket type shatter shield they use on them also.

The consequences are the same, whether it's clutch/flywheel/transmission parts breaking apart and flying vs an energy storage flywheel letting loose. Though I think the flywheel will need to spin at much higher RPM's and thus cause more damage than a clutch.

Scatter shield,flywheel shield,either name is the same device and function.

Flywheels get very hot due to clutch slippage when all the hp is dumped on them.

I have seen them with hairline cracks where the clutch plate seats on them.

This is the real weakness in the flywheel,and the rigors of the racetrack will expose every weakness.

I never thought about how many revolutions a 3 second 1/4 miler turns.Good point!

A little water cooler trivia.

A Top Fuel Dragster's engine is an engineering marvel, producing over 10,000 hp. It's rebuilt after each 1000 ft run down the track - done in about 40 minutes! In the time it takes to say ready, on your marks, get set and go, the car is already at the finish line! In those 3.4 seconds, how many times does cylinder #4 have a combustion?

Most people guess 5,000. Some say 10,000. What if I told you it's less than 250.

Here's the math. Use 8,400 rpm as the engine speed. 8,400 rpm / 60 = 140 rps. 140 rps x 3.4 = 476 revolutions in a 1000 ft run. But this is a four cycle engine - intake, compression, combustion, exhaust. So you have to take the 476 revolutions and divide by 2 to get 238 revolutions or < 250.

Some of the smaller 1/4 mile engines turn in excess of 10,000 rpm and take 9,10,or more seconds ET.Of course there are faster ones,but in the long run,they have a shorter duty cycle.

They actually turn more revs waiting for the green light than going down the track.

A good friend of mine told me to go to an NHRA drag race. They have one here in Pomona - 20 minutes from me.

He said it's mind boggling to see a car accelerate so fast. And the noise! He told me to wear ear plugs if I go.

I haven't yet, but every time the race is here, I'm tempted.

Back in college, I had a friend who had a hot rod Camaro. It was his daily driver, but he did race too. Not sure if it was at a track or on the street, but he raced. It was a very, very, very fast car. One time we were talking and he told me that VW Beetles could be made fast enough to beat most street built V-8's. I said yeah, right! Only if the VW has a V8 in it. He told me his car could break into the 12's (real 1/4 mile), but the Bugs with the flat 4's were in the 11's and the heavily modified ones were in the 8's!

I hear about the "modern" drag cars like the Acura Integra's and Honda Civic's. When you have a minute, watch this video. It's shocking! https://www.roadandtrack.com/motorsports/a25415422/2000-hp-fwd-civic-drag-car-video/

Yes, you are correct. I read about this a few years ago.

I believe the main concern was in the event of an accident. A spinning mass could do a lot of damage if it escaped (housing damaged from an accident)

Al energy storage devices are potential bombs. so are water reservoirs whether for irrigation or electricity generation.

safest devices for electricity seem to be the time tested lead acid gel batteries that do not carry liquid acid, as against Li-ion, that seem to be very efficient but explode too, quite frequently.

Gravity storage with giant concrete blocks seems to be the safest, since any accident would not involve personnel or people unconnected.

A steam horse - the first version of a non-living carrier- was shunned, before refined automobiles took over. Every technology needs testing time.

There also was the "flywheel" powered bus that Bill Lear (of Learjet fame) was attempting to market...but failed.

OOPS...correction, Lear's bus was 'steam' powered, it was a Swiss bus that used flywheel power.

It seems there's been a development or two.

Grid stabilization

Makes more sense to me than mobile applications.

Being below ground is the only sensible arrangement imo.. above ground the scalability of size (efficiency) is greatly reduced by exponentially rising cost of the enclosure robust enough to ensure safe operation.

In a mobile applications why not take advantage of the gyroscopic action and make it a two wheel balancing car.. or bus.. think about how cool that would be.

Your two-wheel balancing act would be cool only until it got to the first corner.

You could make the seat and tank lean into the turn with a handlebar coupled control system....

IF the MG's are counter rotating they would neutralize each other.

Two flywheels on a bike seems a bit much, and probably wouldn't be configured that way to take advantage of "the gyroscopic effect"....Probably wouldn't be a good idea anyway, it seems to me the gyroscopic effect would require a constant speed, which is not how flywheels work...

https://www.wired.com/2011/08/regenerative-flywheel-powered-bicycle/

https://newatlas.com/flywheel-bicycle-regenerative-braking/19532/

..."The Flywheel Bicycle has a continuously variable transmission in the rear hub. This is linked to a 6.8 kilogram (15 lb) flywheel from a car engine mounted in the middle of the frame. When the cyclist wishes to slow down, such as when they're going down a hill or coming to a stop, they shift the transmission to maximize the flywheel-speed-to-bike-speed ratio. This "charges" the flywheel with kinetic energy - effectively a mechanical version of what happens in an EV where a battery stores the scavenged energy."....

I would not want to be sitting on that bike IF the flywheel exploded,or came loose.

it seems to me the gyroscopic effect would require a constant speed,

You have to be posting a fleeting, incomplete thought there. Rotational inertia (aka the gyroscopic effect) is a purely linear effect. Other non-linear attributes (ie. friction) can mask the effect from an observer but the rotational velocity requires neither a minimum nor invariance in speed for rotational inertia to be present.

I was speaking in reference to the force necessary to keep a motorcycle vertical...

http://genjac.com/BoomerBiker/Gyroscopic%20Precession.htm

http://www.gyroscopes.org/forum/questions.asp?id=790

https://www.technologicvehicles.com/en/green-transportation-news/3141/thrustcycle-gyrocycle-a-self-balanced-electric-motorcycle-in-the-akira-style#.XPKr7IhKiM8

They could both be mounted on the same shaft,using half the weight in each.Varying the speed differential between the two could give the desired gyro effect when needed,in either direction.

However,I believe that mounting them near the wheel rim would be more efficient due to the larger radius.

The hotel bellhop probably won't see the humor of a gyroscope inside a suitcase...

Add some CAW CAW's and flapping wing sound, and it would make a great video...

Reminds me of an old joke about a truck driver with a load of live chickens. His total load (truck and chickens) exceeded the capacity of a bridge he had to cross, but the weight of the truck alone was under the bridge capacity, so he wasn't worried. When he got to the bridge, he stopped, went back and banged on the chicken cages until all the birds were flying, then quickly got back in the truck and safely crossed the bridge while the chickens were still in the air.

One of the associated links shows a man lifting a 40 pound rotating flywheel on a shaft over his head with very little effort.It appears to be almost weightless,however,when standing on a scale the added weight of the flywheel is detected same as when stationary . The weight is transferred to his feet,so it most move through his muscular system,so why does he not feel the effort?The muscles are supporting the same weight?

Lifting a balanced weight vs an off balance weight, makes a big difference...Lift a book with your outstretched arm, now hold it close to your chest and do it....Imagine trying to lift barbell weights with all the weight on one side....

You nailed it. SAFE OPERATION. Too much KE in the flywheel, so if it's somehow released into the real world ... look out! Pedestrians and bicyclists are no longer safe!

Here's an article from Wired (5 years ago). I remember reading this and thought it was a great idea. Wired article on Gyro Energy for Buses

The system is called KERS (Kinetic Energy Recovery System). The package is just over 100 lbs and about the size of a spare tire.

Apparently, they've used it in a specific type of F1 race car and it's been successful.

How it works: Energy from braking is converted to electricity. The electricity powers a flywheel (stores the energy in kinetic form). When power is needed, the flywheel becomes an electricity source and powers the vehicle. Pretty neat concept.

Volvo is adding KERS to their XC90 in 2020. Impressive! https://thebrakereport.com/volvo-using-kers-on-production-cars-in-2020/

A few years ago, Volvo started the high efficiency trend when they got rid of their V-8, straight 6 and straight 5 engines. Everything is their line up is based on the 2.0L straight 4 with turbocharging, supercharging or both AND hybrid systems.

Here's how far they've come. Their 2.0 T6 supercharged turbo 4 puts out 316 hp. Cut the supercharger and it's now called a T5 that puts out 250 hp. Drop to a low pressure turbo and it's a T4 that still puts out 187 hp. Contrast this to my 960 wagon which has a 2.9L straight six, good for 201 hp (slightly above their T4 2.0L 4). My 850R wagon has a 2.3L turbo straight 5 good for 250 hp (same as their high performance 2.0 turbo). My V70 Cross Country wagon has a 2.4L turbo straight 5 good for 197 hp (just above their T4 engine).

They also build a S60R Polestar T8 - 400 hp and 472 lb-ft of torque out of a 2.0L 4 cyl production engine!

Impressive company. Time will tell if their 2.0's are as reliable as their old engines. My V70 has 243K, my 850R has roughly 230K (odometer broke, so mileage unknown). I had a 2.3L 4 that made it over 350K miles (odo broke twice) - I gave it to a friend in need and I still saw him driving it years later.

This is similar to a synchronous converter as used in open cut coal mines with dragline when the mine is at the end of a long supply line. The flywheel is driven by a synchronous motor and when it is up to speed it can smooth out the fluctuations in line loads when the mine is working.

I saw one back in the early 1970 where the flywheel was over 200 tons and housed in a building like a lean to and it was very effective. Should it come loose then the land clearing effects would be most noticeable.

On a similar vein there was work done on replacing the ballast used in Draglines for stability with batteries. The theory being that on the regenerative part of the cycle the batteries were charged and then supplied power on the work cycle. The batteries needed to be added at time of construction not as a retrofit because of installation constraints.

I wanted to start a DC motor pump directly with a PV panel of suitable wattage. unfortunately, the motor wouldn't start unless the wattage of the PV panels employed was at least four times that of the motor. In that connection, some one suggested an inertia starter as used in older versions of petrol automobiles, and some one else said, why not a fly wheel. Since I wanted the system to be portable, to be carried to the source of water. like a stream, and brought back home, in the evening, it could not even be tried.

We did have a huge Flywheel for our steam engine, that was employed for running a shaft, that ran a couple of expellers for vegetable oils. It worked fine, but later replaced with electric motors.

Here is a link to some old steam engines and flywheels.The largest one was a Corlis 5000 hp.

https://www.practicalmachinist.com/vb/antique-machinery-and-history/steam-engine-flywheels-112618/

I recall rotary vertical UPS being manufactured in the 1980's & 90's. I think they were made by Reliance do Mexico and comprised an AC machine and a flywheel which operated as a motor driving the flywheel until the power failed when the machine then generated to allow for a controlled shutdown of the computer systems fed from the supply. This was technology that suited the times. We tend not to close servers down now that we have the internet and UPS has to last longer and offer a stable frequency. operational longevity and stability were not the inherent strengths of these devices.

There was a car used in the opening of the Sydney Olympics (2000) which had a mixture of Fuel cells (I think) and flywheel energy storage. The flywheels were housed in evacuated spheres and built to withstand flywheel failure, and were gymbal-mounted to overcome precession. These were mounted in the front of the car (not the best place in my view).

As any mechanical engineer should know, drilling a hole in the centre of a spinning disc doubles the stress, so a doughnut shape would not be ideal and is why they are never seen on high speed flywheels.

Scientific American 1973 cover and featured article was on flywheels if I remember correctly.

I do not want to spend the time/money on the reprint since I believe that I recall the main concepts presented:

1. e=1/2 m*v*v for each atom in the wheel means that the outer rim of the flywheel is the fraction of the total mass of the flywheel storing the most significant portion of the energy since energy/atom is proportional to velocity squared.

2. The tension forces on the outer rim stretch it more than each radial increment toward the hub.

3. The SciAm focus at the time was dealing with this radial force gradient.

4. A uniform material flywheel of say, steel, must have a progressively thicker cross section the closer you get to the hub to avoid pulling the outer rim off of the wheel.

So, they had a variety of design variations all oriented toward keeping the outer rim from detaching so that the energy could continue to be supplied and removed from the hub and so the flywheel would not release all of its energy catastrophically. Strength per weight is the first order material choice characteristic so carbon nanotubes or kevlar or such may beat steel. Expansion of the rim will come into play for any material choice due to the extreme dynamic range of tension variations and oscillation of the rim upon power operations will need to be analyzed since the radial thickness of the rim is small.

Your doughnut configuration is a credible approach and I think they did mention a wheel which was only a (radially) thin cylindrical shell but did not spend much time on it because they were concerned about the lower power handling capacity of any means other than a central hub. They rapidly moved on to concentric cylinders with flexible interconnects.

I do not think that we have driven these concepts far enough and been willing to compromise enough. If we use a radially thin flywheel and are able to get most of the energy in and back out(even slowly) then power grid buffering can be improved.

I recommend underground flywheels with an axis parallel to the axis of rotation of the earth to minimize bearing forces and earth rotation interference. Since we are talking power grid energy magnitudes we should even think about possible interference with earth precession over deep time so we may still want counter-rotating wheels within an enclosure.

I accept that permanent magnets may be one way to apply and remove energy but caution that eddy currents may reduce the maximum lifespan of the energy stored. There are other alternatives, each with their own problems.

Automobiles could benefit from flywheel energy storage and I assert that intermittent slurps of power from roadway embedded power sources/sinks means that you are not wasting as much energy as you do now by carrying around a heavy battery with enough storage to go 200 miles or more. Cars would therefore require a fairly large power spurt tolerance for the slurps and be a significantly different design point than power grid buffering. Cross-car dynamic braking could save a lot of energy especially at city traffic control lights. People stopping at a light might sell their braking energy to those accelerating from the light with automated person-to-person microtransactions via wifi or follow-ons. We just need to keep the power companies from skimming too much per transaction for their role in transferring the energy. The timeframe for these energy transfers are ideal for flywheel buffering even with traditional flywheel designs(see flywheel buses in post WWII Britain for acceleration/deceleration feasibility even in a single vehicle).

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thewildotter

I had seen a few years back use of energy from a flywheel being used in no break sets. The generator is driven by a motor and a flywheel is also mounted. When power fails, the flywheel keeps the generator running for a few seconds before the diesel engine starts and takes over.