

Spinning wheels [Storing energy using flywheels, not batteries] - igravious
http://www.economist.com/node/21008109
Take home paragraph: Back on the road, flywheel hybrids that cut both fuel consumption and greenhouse-gas emissions by 30% or more appear to be only three or four years away. When they arrive, today’s coal-fired electric cars will look decidedly dirty by comparison. Roll on the day.
======
wanderr
"the electricity delivered during off-peak periods comes from dirty coal-fired
power stations--rather negating the point of having a zero-emission vehicle in
the first place."

Except these so-called dirty coal plants are still far cleaner than car
exhausts, and more efficient especially if you consider the extraction and
refinement processes required for gasoline. Finally, it's much easier to
upgrade or replace a power plant on the grid to make it cleaner in the future
than it is to get thousands of people to replace their vehicles with ones that
are more efficient, cleaner, etc. Nevermind the logistics involved if we
wanted to do carbon sequestration.

~~~
electromagnetic
Off-peak power production depends on where you live. In my region we only have
hydro and nuclear, my energy is (relatively) clean 24/7.

------
thefool
Yeah, the main problem with them is that if anything happens the "stored
energy" is already kinetic energy and the flywheel can do some pretty serious
damage.

The other problem is that they act like gyroscopes. Which means that depending
on how you mount them, will either constantly exert a precessional force on
your vehical, or really protest you making sharp turns at high speeds.

~~~
jacquesm
The second one can be mitigated for the most part by using two flywheels that
rotate in opposite directions.

~~~
pkulak
And the first is a problem with anything that stores energy. Gas can explode.
Batteries can explode. Etc.

~~~
MichaelApproved
I think an accident causes gasoline to burn more often than explode. Even when
the tank explodes I don't think it would be as dangerous as a fly wheel
shattering with shrapnel flying everywhere.

~~~
jacquesm
Flywheels running at high speed are not made of cast iron or other things that
turn in to 'shrapnel', they're made of wound filaments of carbon fibre bound
with resin, usually they are designed with failure in mind. The bigger problem
is dealing with the conversion of the energy in the wheel in to heat.

~~~
jules
If we have a flywheel falling on a movable object on the floor I imagine this
movable object can attain quite high speeds.

------
MichaelApproved
Such an interesting concept but some key data is missing.

How much energy is lost by using a wheel vs battery? Meaning, how much energy
can be extracted from the amount of energy put in? How does that compare to a
battery?

How long would a charge on a wheel last (eventually it would spin down on its
own) compared with a charge on a battery?

~~~
jws
For lead acid batteries, figure 70% of the energy you put in will come back
out. Wikipedia tells me that lithium ion batteries are 99.8% efficient, but
has no citation and the temperature of my phone charging heavily make me
suspicious of that number. Perhaps that is a theoretical maximum.

Motor efficiency is proving elusive on the web. But let's say 90%-95% for
brushless DC motors. (square that for in and out)

The trick about batteries is that if you only want to use them for intense
bursts you will need a huge energy capacity. You don't normally want to charge
at a rate faster than say, 1 hour to get full. If you need to store a 3 second
brake stomp and give it back 5 seconds later then you are going to have about
1200 times more batteries than you needed just to store the energy (to support
the current).

------
escoz
Here's another post with a picture of what it looks like:
[http://www.gizmag.com/torotrak-mechanical-kers-system-for-
bu...](http://www.gizmag.com/torotrak-mechanical-kers-system-for-buses/13023/)

I can't find any links now, but after Williams created the flywheel kers
system, they started talking to the London train system, who was interested in
adding it to a trains in the city. Not sure who that ended up.

It's worthy noting, however, that none of the two companies ended up running
the flywheel kers in real races last year or this year. KERS was only one of
the rule changes for those years, and those teams decided it was best to focus
on the other changes instead.

Not related to the post itself, but I think most people here would really love
F1. F1 is much more about technology than anything else. I love it.

------
superk
Flywheels come up every once in a while (I remember seeing them for the first
time about 20 years ago).... but I wager they'll never become mainstream. The
problem is the more energy they store, the more explosive they become.

[http://en.wikipedia.org/wiki/Flywheel_energy_storage#Advanta...](http://en.wikipedia.org/wiki/Flywheel_energy_storage#Advantages_and_disadvantages)

Same kind of thing with the Dymaxion car (1930) - a 3 wheeled car that could
transport 11 passengers @ 30mpg, reach speeds of 120mph and do a U-turn in
it's own length. Sounds brilliant.. except what happens when something happens
to one of the tires.

<http://en.wikipedia.org/wiki/Dymaxion_car>

~~~
jacquesm
Why do you state that when the article linked clearly says: "The cause of the
accident was not determined, although Buckminster Fuller reported that the
accident was due to the actions of another vehicle that had been following the
Dymaxion closely.".

It's a pity investors bailed on the project, it seems like it was well ahead
of its time, prototype failures are usually experienced behind the scenes, not
in front of an audience that large and I think that they investors probably
were on the money pulling out because of public perception, even if they
blamed the tech, it was not the wheels that had anything to do with this, but
more likely a lack of reinforcement of the main structure of the car.

As for flywheels: <http://afstrinity.com/> that company (a merger of American
Flywheels and Trinity Power) is probably right at the cutting edge.

Anything storing a significant amount of energy is prone to accidents, from
batteries to rocks on the tops of mountains.

Flywheels are one of the few technologies that can store signficant amounts of
energy and can be engineered to fail with relative grace, as opposed to say a
fuel tank blowing up. Another strategy is to use many relatively small
flywheels in parallel, each in their own containment vessel.

This also helps with some other engineering difficulties involving flywheels.
Flywheels are ancient tech, at least 50 years old but probably much older, and
if you count them as storage devices in a purely mechanical context as well
then you can go back in to history quite a bit, about a thousand years.

~~~
superk
> Why do you state that when the article linked clearly says: > "The cause of
> the accident was not determined, although > Buckminster Fuller reported that
> the accident was due to > the actions of another vehicle that had been
> following the > Dymaxion closely.".

For the obvious reason why 3 wheel vehicles have never become mainstream....
If you work with computers you should know about Single Point of Failure. If
you are cruising on the highway and get a flat with 1 of your 4 tires it's no
Big Deal. How do you think that would figure with only 3.

Or another example. Why so many wheels on an 18-wheeler. Wouldn't it be
awesome if a truck could do a u-turn in it's own length? Those things blow out
tires all the time. But it doesn't matter because they have 18. SPOF. 3 wheel
vehicles will never catch on in the mainstream. They'll only ever be the
equivalent of glorified motorcycles - the ultralights on the road.

~~~
jacquesm
You could get all the advantages of a tadpole configuration and mitigate the
risk of blow-out considerably by using two wheels at each spot side-by-side,
that's fairly simple engineering and this is used on plenty of lightweight
fly-over trailers.

The tadpole configuration has stability issues though, rolling it over is
fairly easy if the vehicle has a high center of gravity.

The Reliant Robin solved that for the most part by reversing the arrangement
putting the single wheel in front, but they still tend to overturn quit
easily.

The accident mentioned above during the demonstration probably really was
caused by that other car, but the ease with which a three wheeled
configuration turns over most likely contributed to the severity, and in the
long run would have had to be solved using tricky engineering such as a single
wheel for low speed maneuvering and two wheels for higher speeds.

Here is a Reliant Robin doing what it does best:

<http://www.youtube.com/watch?v=xr8SvdSzs7c>

I think there is a topgear episode where they try to improve the Reliant Robin
by putting training wheels on it.

------
jrockway
_Moreover, supplies of the metal are far from abundant, and are located in
countries not necessarily friendly to America: the biggest reserves are in
Bolivia, China and Russia._

Yeah, it's a good thing countries with all the oil for our gas-powered cars
are so friendly.

~~~
yummyfajitas
Canada, Saudi Arabia and Mexico are unfriendly?

The only unfriendly countries which supply a significant amount of oil to the
US are Venezuela and Russia.

[http://www.eia.doe.gov/pub/oil_gas/petroleum/data_publicatio...](http://www.eia.doe.gov/pub/oil_gas/petroleum/data_publications/company_level_imports/current/import.html)

------
drblast
I read about this about 13 years ago in Discover:

<http://www.mega.nu/ampp/bitterly.html>

Seemed like a fantastic idea at the time, but the problem then was that the
wheel would explode at high speeds. Apparently these are very challenging to
manufacture.

------
bluemoon
This has been done before, there was a bus i read about on boingboing that
used only kinetic energy to power it, if i remember the wheel was some 20tons.

------
noonespecial
I see your spinning wheel in a vacuum and raise you a battery drive and the
dirt road behind my house.

