Flywheels

[VicParticipant @vic]

I found this interesting. I knew they used giant flywheels many years ago to smooth out the power from steam engines in factories. I didn’t realise they’ve made a comeback.

 

https://youtu.be/Z95t-f-0IjI?si=N4d7QqjPEHhaSGLy

[BazyleParticipant @bazyle]

We have a flywheel store to keep some computers running in the minute or so while the diesel generators run up to speed. First time it was needed in earnest it only lasted seconds as some twerp had wired in the entire building, central heating etc to the same circuit.

[Neil AParticipant @neila]

In the 1960’s they used to produce what were called “No Break Generator Sets”. I think they were mainly used in conjunction with the old style CRT radar systems which did not like any interruptions to the power supply.

The set consisted of an electric motor connected to the mains supply driving a generator and a very large flywheel. On the other side of the flywheel was a magnetic clutch and a diesel engine. The complete set was brought up to speed with the diesel engine by initially repeatedly engaging and disengaging the magnetic clutch, so as not to overheat the clutch, until it had reached the idling speed of the engine, the clutch could then be fully engaged and the speed increased to mains frequency, either 1200 or 1500 rpm. The motor then took over and the engine shut down.

In the event of a mains failure the flywheel, which weighed about 5 tons, would maintain the voltage and frequency until the diesel engine had started and run up to speed at which point the magnetic clutch engaged and power was then supplied by the diesel for as long as was needed.

All very exciting to watch in action. Just think how fast the flywheel would exit the building it ever broke free!

Neil

[duncan webster 1Participant @duncanwebster1]

Bullied electric locos had a similar motor/flywheel/generator setup to maintain power over breaks in the third rail, and I seem to remember a proposal for busses where a short section of power pickup at bus stops was used to accelerate a pair of contra rotating flywheel which stored enough power to get to the next stop. The flywheels ran in a vacuum chamber to reduce windage losses, and there were 2 rotating in opposite directions to eliminate gyroscope effect

[Nigel Graham 2Participant @nigelgraham2]

Much more recently, the Parry People Mover is a light tram using a flywheel spun up to speed by a motor plugged in at suitable stops along the route. Its intended use was on short, urban lines not fitted with overhead or third-rail electrification.

One was tried in Weymouth, on the branch railway along two streets to link the main line to the ferry terminal. No-one thought to clear the soil that had compacted into the rail grooves through some years of disuse, and the PPM was too light for the flanges to displace it.

The experiment was never repeated, and the line itself has now been removed… leaving a forlorn colour-light signal still permanently on against any train that finds itself coming along the road towards the stub of branch-line, now used as an engineering-train siding.

 

There appear to be a few PPMs in use, or at least preservation; but the company was liquidated in 2023, a few months after proprietor John Parry died.

I suppose the idea is ripe for development, perhaps with battery power. A battery EV PPM-phoenix would likely need less woof to propel it with full load along a few miles of rails, than, say, a Nissan ‘Leaf’ for a comparable trip

…..

I can see a potential flaw with putting the flywheels in a vacuum-chamber, as Duncan describes. This is whether the shaft glands and the vacuum-maintaining pump would take more power than absorbed by windage on open wheels.

 

 

[duncan webster 1Participant @duncanwebster1]

Either put the motor/generator inside the vacuum chamber, or use a magnetic coupling. I suspect the development of modern batteries has eclipsed flywheel storage.

[PeteParticipant @pete41194]

While I’ve never gone looking for the information, there’s been bits and pieces about the more modern use of heavy and high rpm flywheels for automotive, power balancing, as a mechanical battery etc since at least the mid 1970’s. A bit less high tech back then of course. But that video didn’t really get into the difficulty and expense to produce almost perfectly true running flywheels for there outer rim, faces and bores with an almost a mirror surface finish since there’s no easy or cheap method to produce an almost perfect vacuum environment for them to operate in. Plus how almost perfectly balanced they need to be. All that helps to further increase efficiency and reduce power requirements to maintain the high rpm. Or at least enough that it apparently matters.

It’s a video mostly about large to very large stationary steam engine flywheels and what happens when things go wrong. https://www.youtube.com/watch?v=khzOQDBU2KY But I think it’s might be AI generated narration. It makes the exact same points over and over with only slightly different wording. Most of the same pictures are also cycled through multiple times. So the video is quite repetitive. I’d watch it if interested with the sound off and maybe with the closed captioning on since anyone here most likely knows more about flywheels than the little it really mentions. Some of those old pictures showing the massive amount of damage caused are quite interesting though.

[Charles LamontParticipant @charleslamont71117]

For what it’s worth, two Parry People Movers remain in service on the 0.8 mile Stourbridge Juction Branch. They are designated as class 139 and are running in West Midlands Railway (or whatever it is called today) livery.

[Howard LewisParticipant @howardlewis46836]

IIR correctly, the Oerleiken Gyro Bus was propelled by a 2 ton to flywheel running in a chamber filled with hydrogen, and was powered up at every stop.

Once I had to confirm that turbocharged 8 cylinder gen-set engine could deliver 85% of max power withing 15 seconds of first crank.  It could, but obviously there would be a short hiatus as the engine ran up. (Didn’t like to think what it did to the Turbocharger bearings before oil pressure stabilised!) Being a gen set, it had a heavy flywheel, which increased run up time.

The heavier and larger the radius of gyration, the more energy the flywheel stores. Speed has to be controlled. If a flywheel bursts, a lot of the stored energy reappears as heat in whatever attempts to contain it.

A colleague once watched a 15″ viscous damper detach from an engine, running at 2100 rpm, charge across the test shop, and attempt to climb the mountings on another test bed!

A small turbocharger, although the Compressor and Turbine are small and light, can take a couple of minutes to spool down to stop from 80 – 100,000 rpm.

[Neil AParticipant @neila]

Although a bit off subject, but following on from Howard’s comments about standby gen-sets, quite often they would have the coolant and the oil heated to close to normal running temperatures. The oil would be primed, either continuously or on a timed cycle ready to go at a moments notice. I have a feeling the “Linesman” sets were like this.

Always makes me wince when I see someone start a car for cold and race away at high speed. I wonder if the oil ever reaches the bearings in time to do any good?

Neil

[duncan webster 1]

On duncan webster 1 Said:

Either put the motor/generator inside the vacuum chamber, or use a magnetic coupling. I suspect the development of modern batteries has eclipsed flywheel storage.

The intent of these devices are not primarily storage of energy. They are used to stabilise the grid. This was discussed recntly in a thread on EV’s. “renewable” energy sources like wind, solar and battery storage do not provide the short term (seconds) stabilising effect of rotaing iron generators. Thus these inertial stabilisers are being added to the grid. They can absorb or supply significant amounts of energy in short periods of time.
Modern electronic loads that try to maintain constant power also destabise the network.

Robert.

[duncan webster 1Participant @duncanwebster1]

The company I worked for tinkered with flywheel storage. These ran at tens of thousands of rpm in vacuum, and were intended as UPSs. They spent a fair lot of money on it, but it came to naught

[Bob WorsleyParticipant @bobworsley31976]

An example in one of my engineering books gives the following.

Kinetic energy in a flywheel 9′ in diameter running at 3,600rpm weighing 1 ton is about the same as 1ib of coal, about 1.5E7 J.

Added to the cost of continually driving the flywheel, and a vacuum is essential, and it becomes a joke. The advantage of pumped water, batteries etc is that they consume no energy whilst waiting to be called upon. A battery powered motor will run up to speed in seconds and then be available to take a load, a diesel engine won’t. Even compressed air is better, but like all energy conversions it loses half of the applied energy into the store, similarly with springs and similar.

What material are you going to use to run at tens of thousands of rpm? A 1GW turbo alternator is about on its limit at 1m diameter and 3000 rpm. Strangely, the optimum material for a flywheel is fibreglass, not steel.

 

 

[duncan webster 1Participant @duncanwebster1]

If I told you the material I’d have to kill myself and destroy the ashes, but rest assured, they ran and stored energy, they just weren’t competitive on cost.

[Martin Johnson 1Participant @martinjohnson1]

When I chased the daily dollar, I designed 3 flywheel sets for ensuring that centifugal pumps ran down slowly enough to prevent serious water surge.  They were roughly 10 ” thick by 2′ diameter running at 4 or 6 pole speed.  The details now escape me.

They were balanced in our test bay using a spare motor (that sure grunted during spin up!) Once running we took a vibration reading and then used the trial vector method of balancing using screwed balancing plugs.  Since spin down took well over half an hour without the pump load, it was quite a long job.

The use of flywheels for pressure surge suppression is still done although pressure vessels are a more common solution.

Martin

[Author]

Posts