Another battery type
 

Green Car Congress: Audi R18 e-tron quattro: diesel hybrid Le Mans racer with electric flywheel energy storage

regards
Mech

Back when i was in CC, I was looking at old back issues of Popular Mechanics, and saw and article about flywheel powered vehicles. I forgot the issue number but it's been around for a long time, but just really hasn't seen common use.

And the wonderful bit is a CF flywheel's failure scenario is that it turns into a giant carbon brush of de-laminated layers.

As opposed to a metal flywheel that separates into 3 approximately equal missiles.

It's definitely not a new idea, but it's interesting to see someone is going to try to make it work again. I remember reading the article in Popular Mechanics or Mechanics Illustrated as well. They fitted a Pinto with a flywheel and drove something like 50miles at 50mph, if memory serves. I always wondered what undisclosed problems kept the concept from going forward. I think that using it in a hybrid makes good sense and the technology is so much better now.

Yeah, use the motor to charge up the flywheel and use the momentum from the flywheel to drive the vehicle. That would REALLY save on the battery packs of an EV or hybrid.

The big issue is friction. Lightweight flywheels need to work at 10s of thousands of RPM to be viable. The friction involved in such rotation in a moving vehicle is difficult to overcome with just bearings and lubricant alone. So you need vacuums and magnets, all the more complicated, all the more expensive.

Yes. A few Formula One cars used the Flybrid system for a while. Added about $100,000 to the cost of the car (and the system stored less energy than the standard Prius battery does). Flywheels have had some success in uninterruptable power supplies, but in vehicles, the weight/energy storage/cost just doesn't work.

In a vehicle, the bearings must be ultra low friction but also ultra strong to withstand the precession forces associated with handling and ride motions.

I'm quite sure that the flywheel in the Pinto was running in a vacuum and had magnetic bearings. I'm sure the up front cost would be very high and I'm also guessing that any hard acceleration would kill it pretty quick. Still, it should virtually last forever with almost no maintenance. There have been many seemingly great ideas that, for whatever reason haven't made it into the hands of the general public. I'm assuming flywheel energy storage is just another one.

It's probably because batteries had more potential, with plenty of room for improvement in energy density.

It was probably felt there was a reasonable limit to how big and how fast you could make a flywheel, and that would quickly be met.

Flywheel storage is, of course, used in every engine (and most dramatically in singles) to carry the engine through the exhaust, intake, and compression strokes. So the idea has not died out, it has just found the niches where it works economically.

The UPS market is one where there could be continued growth in flywheel application. Grid load leveling is another potential market. However, batteries are much more economical as a storage method right now. (I could not possibly consider flywheel storage as a serious competitive technology as part of my plug-in hybrid... it would triple the cost of the car.) Flywheels are already at a very high level of development, so no one is forecasting a large drop in price ($/kilowatt-hour storage). Batteries are, however, expected to drop in price to about 1/3 their current price.

LithiumX batteries in cars can be expected to last about 10 years, which for that market is acceptable life. In a home installation, however, it would be nice to have longer life, so a flywheel system to store solar and wind energy from a home installation (for later use in the home or for use by others via the grid) could have some appeal, even if the system costs twice as much as a battery system.

In vehicles, a flywheel's tendency to maintain its orientation in space is potentially problematic (because the instantaneous bearing loads can be so high over bumps etc.) However, if Lit Motors is successful, they will translate this potential problem into an asset.

...wasn't Bill Lear (of Learjet and 8-track tape player fame) involved with "fly-wheel" powered busses at one time too?

I thought so too, but his bus was apparently steam-powered, and the flywheels were applied to a car. Cool guy -- here's an obit which mentions both bus and car.

There were flywheel-powered buses in Sweden or Switzerland several decades ago. They'd spin them up at stops.

The turbos in a B17 had a vertical axis of rotation and spun at 22,000 RPM. When hit by flack or other projectiles they would disintegrate and cut the ball turret in half. They did help to stabilize the plane.

While I understand the dynamics of gyroscopes to a point, it was one of the factors that changed my direction in favor of hydraulic accumulators.

The real question is how much capacitive storage do you really need beyond a single high speed stop or start? From what I have read the energy lost in a 60-0 stop would propel your car down the road at 60 MPH for .7 mile. If you cycled the engine on for .3 mile, the off for .7 mile, it would be about the same as a typical P&G cycle, without speed variations.

Some like to compare this to battery capacity, but that is not really the point. The battery electric cars weakest performance is regenerative braking, as well as P&G type operation. Both of these states of operation are high losses for electric power. Losses in a decent hydraulic system are much lower by a factor of at least half.

regards
Mech

From this site.

http://ecomodder.com/forum/showthrea...ing-20431.html

regards
Mech

And hydraulic accumulators have the advantage of being less expensive and simpler.

Probably, the energy of two stops from 60 is a reasonable lower limit. This allows for a small amount of assist on long hills, permitting the engine to be smaller than it otherwise would be. The Prius shows that this is not always enough, with a Corolla easily beating a Prius up a long hill.

Although energy density can be a concern. The UPS hydraulic hybrid had, per Eaton, 2000 hp-seconds (.4kWh) capacity. The accumulators and fluid weighed about 900 lbs. The Prius battery weighs about 100 lbs and has more than three times the energy capacity. (The Li batteries in my POC also weight about 100 lbs, and have 8 times the energy capacity of the Eaton accumulators.)

I hope you will sign up for Doug's "Git er done" challenge. Perfect can be the enemy of the good, and these challenges can help you prioritize what really needs to be done.

Regards, Ken