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Comments 8
  1. — Justin    Jan 25, 2007 17:45 PM    #

    Even if this one does fall through, there’s always the carbon nano-tube ultra capacitors (nanotubes on the plate increases the surface area). While nowhere near the the touted barium-titanate powder specs, the developers believe they’ll be capable of exceeding battery energy densities by about 5-10% (can’t recall my source on that, so don’t quote me). They’re talking 6-8 years before they’re on the market though.

    Still, if the “barium-titanate powder” guys can pull off even a quarter of what they say, then I’ll be doing the happy dance.

  2. jerry Halstead    Jan 25, 2007 23:50 PM    #

    Gotta get me some of them nanotubes: ALL of the cool scientists have ‘em!

    It’s great to see all of these new ideas and with the renewed emphasis (i.e. research money) around saving energy, maybe some of them will pan out?

    Anyone heard much about flywheel’s lately? A few years back there were a couple of companies on the verge of releasing new flywheel tech, using carbon composite wheels for safety and so forth. Safe enough to use in buses, maybe cars, but it’s been quiet since then.

  3. — Justin    Jan 28, 2007 03:28 AM    #

    The last I head about flywheels was a backup electrical system that used a magnetically levitated flywheel in a vacuum that spun at almost a million RPM. In the event of a power failure, the flywheel converted its rotational energy back into electricity (a small amount of which was used to keep the maglev system going). I can’t recall the exact figure, but it was capable of running the whole hospital for a significant time.

    As far as small vehicle use, I’m not sure there has been much success given the risk of massive energy release in an accident, and the huge gyroscopic forces involved when trying to turn the vehicle.

  4. — Dan    Jan 29, 2007 23:26 PM    #

    Justin – if you used 2 counter-rotating flywheels, they would cancel each other’s gyroscopic forces.

  5. — Justin    Jan 30, 2007 00:28 AM    #

    Dan, although the net forces would cancel out, you’d still be dealing with some crazy stresses on the bearings. That said, as long as the rotational speeds were kept on the lower end of things, it could work as temporary storage for regenerative braking, similar to the pneumatic systems in some buses.

    The safety factor would still be an issue. Take a look at what sort of damage can be done by a lightweight flywheel (racing vehicles) when they explode. Now imagine a heavier/faster version with enough energy storage to power a vehicle for 100 miles. Now imagine releasing it all in a few 100ths of a second.

    I must admit that the same rapid energy release could be a problem in Ultra capacitor technology if physical impact or vibration broke down the dielectric. Chemical batteries have a naturally limited capability to release/absorb energy, which is why they take so long to charge. Even then, they can blow under heavy load in a shower of molten lead, but at least it’s relatively easy to contain (as well as being a good reason to keep unshielded batteries out of the passenger compartment).

    One idea that just popped into my head is that perhaps you could use an array of smaller flywheels (physically shielded from each other) to reduce the energy density and keep the potential damage down to containable levels. It would push the vehicle weight up, but batteries aren’t exactly light either. Any thoughts?

  6. — Justin    Jan 30, 2007 00:39 AM    #

    Just found this site on flywheel energy storage.
    They suggest using composite rings as flywheels, as they can be designed to explode gracefully by shattering into tiny pieces (less energy than big shards of flying steel). I must admit, my previous thoughts were all based on metal flywheels.

  7. — James May    Jan 30, 2007 19:55 PM    #

    Aircraft have a kind of kevlar mesh around the engines which can absorb some of the shards of turbine blades should they come apart. Maybe these can be used to guard flywheels. Like Justin, I am naturally scared of flywheels and also high speed shafts.

  8. — Justin    Jan 30, 2007 21:58 PM    #

    After a bit of research, it seems that the ideal flywheel design is a high speed/high tensile strength arrangement. The weight is not as important, because the increases in speed store far more energy than a heavier flywheel at slower speeds.

    The construction of most units I’ve found are either a carbon/epoxy composite (carbon fiber and similar), or a thread/epoxy construction that is essentially wound like a giant spool. In the event of failure, you end up with a flywheel housing full of hot sand or a mess of fibers.

    There was one other approach that a soviet engineer had in the 1980’s where the flywheels were made of tightly wound metal tape. Instead of exploding, the tape would unravel and brake itself against the flywheel housing. It could apparently be rewound and put back into operation.