
Using Flywheel Batteries to Charge Electric Vehicles in Ten Minutes - orrhirschauge
https://www.calcalistech.com/ctech/articles/0,7340,L-3738031,00.html
======
eigenvector
Former flywheel energy storage startup engineer here.

The economics of flywheels for this kind of application versus just using
another battery tend to rest on the purported "unlimited cycle life" of the
flywheel system compared to, say, Li-ion batteries that have a very well
documented finite cycle capacity that degrades even further when doing sub-
optimal cycling. To a lesser extent you can also bank on lower parasitic loads
during standby as the environmental requirements for a flywheel aren't as
stringent as batteries that need to be either heated or cooled almost all the
time in many climates.

The problem is that, by and large, "unlimited cycles" is not true. You still
have huge, very high speed bearings. Motors that require routine electrical
testing and can fail. And now all this stuff is sitting below ground under a
massive concrete lid for containment so it's not as easy to do maintenance on
compared with a similarly-sized battery system. You also need uninterruptible
power supply to maintain safety and control systems when grid power is
unavailable since you've still gotten a huge spinning mass that you can't slow
down without somewhere to send the energy (it's possible to use braking
resistors, but it's another cost).

Batteries also benefit from massive economics of scale (both on the actual
cells and the power electronics) that are getting better with time and driving
costs down, while flywheels have been "1 year from commercialization" for the
last 25 years.

I remain skeptical of the commercial benefits vs. increasingly commoditized
and readily available battery systems.

~~~
drumttocs8
Power utility engineer here. I keep imagining a giant flywheel located at
every substation- could be very useful for load balancing, voltage regulation,
even frequency control. I guess what I mean is, a large spinning mass could
potentially have other benefits than just storage, right? Any research into
substation application at that startup?

~~~
sgentle
I was recently reading about power factor correction and found out that
"synchronous condensers", basically just large synchronous motors with no
load, are sometimes used at utility scale for PFC and frequency stabilisation.
Eg, here: [http://www.think-grid.org/synchronous-condensers-better-
grid...](http://www.think-grid.org/synchronous-condensers-better-grid-
stability)

Since it seems like the main source of stability in that system is the inertia
in the rotor, would it be fair to describe it as a kind of flywheel? I didn't
see anything about connecting an actual wheel to such a system, but it seems
like it would be the same thing with more inertia, right?

~~~
eigenvector
Where "flywheels" in common parlance differ from synchronous condensers is
that condensers run at zero torque - so they provide no active power to the
system. They provide reactive power, which is needed to regulate and maintain
the stability of the power system, but not active power which is used to match
generation and demand or shift load. There's no actual source of energy being
fed into a synchronous condenser. In a flywheel, you're drawing energy from
the grid to spin up a really big mass and then storing it in rotational
inertia so you can output it later very quickly. Flywheels can provide
reactive power too, through their DC/AC power converters, but since you don't
actually need any rotating mass to do that (recall, reactive power requires no
torque), you can use a STATCOM - which is functionally like a synchronous
condenser just without any moving parts.

------
joshe
The article isn't very clear.

The car still has a battery, this goes in the stationary charging system. It's
used to increase the current when charging electric batteries. Most electric
batteries can accept much more current than commercial electricity drops can
provide. This system stores the current in stationary flywheels and then
discharges it quickly when a car pulls up and plugs in.

So this provides something like a Tesla super charger, without having to call
up the power company to rewire your gas station. They call it a "Kinetic
Battery". In the video below, the CEO makes the claim that flywheels are much
better for this because you can get many more discharge/charge cycles out of
flywheels than with chemical batteries.

You can imagine that rewiring electric infrastructure all over the country
would be quite a bit more expensive than just plugging in their system. You
could also imagine a solar powered system (off the grid even) slowly being
charged and then recharging a car in 10 minutes.

Cool idea!

Interview with CEO
[https://www.youtube.com/watch?v=YxRfPtYmTDE](https://www.youtube.com/watch?v=YxRfPtYmTDE)

~~~
_bxg1
Is it conceivable that the same type of battery could be used in cars as well,
or would the capacity/falloff/external forces be too limiting?

~~~
XorNot
Gyroscopic forces are a big problem as is trying to get enough mass.

~~~
_bxg1
I could see it being used as a "quick-charge" portion of the capacity. i.e.
you have a full-sized battery, but also a small flywheel so that if you're
really in a pinch you can rapidly charge enough to get somewhere without
waiting for an hour. It'd be like having a small SSD paired with a large HDD.

~~~
Filligree
You'd get better results using the same weight for more batteries.

------
beat
Safety concerns raised... since the maximum amount of power the flywheel can
be expected to store is a known quantity, and the amount of kinetic energy
that can be stopped by concrete or metal shielding is a known quantity, it's
just a matter of burying the flywheel underground, with enough concrete/metal
around it (particularly above it) to prevent shrapnel from penetrating to the
surface. Easy peasy. It's just a cost problem.

We keep those levels of potential energy in underground gas tanks at every gas
station, and no one freaks out about _that_.

edit: For perspective, a typical gas station has 12,000 to 24,000 gallons of
gasoline storage underground. A gallon of gas is about 120 megajoules of
potential energy. So there are _billions_ of joules sitting there - much more
than these flywheels. Of course, without air, gasoline isn't dangerous. But a
90% empty tank has a lot of air in it, a lot of potential boom.

~~~
bluGill
NO, an empty gas tank has a lot of gasoline vapors mixed in that air - the
concentration is high enough that the vapors will not burn. One of the
advantages of gasoline is it will only burn in a fairly narrow window of
concentration (IIRC 5-30%, but since I don't feel like looking it up you will
have to if you care)

~~~
beat
Still, if containment is violated somehow, it's a LOT of power for
fire/explosion. These flywheels are much smaller, by comparison.

The tank of gas in a car probably has over 400kwh of energy. How much will
these flywheels contain, considering a full charge for an electric car is on
the order of 100kwh (electric cars are more efficient than internal
combustion)? The energy of two or three tanks of gasoline is enough to get
several charges out before needing to spin up the flywheel again.

~~~
e12e
But a nearly "empty" flywheel is a lot less dangerous than a "full" one. While
a full gas tank, even if cracked open and lit on fire, would probably burn,
not explode.

I imagine seeing a flywheel leap out of the ground and short through the
foundations of a skyscraper...

~~~
beat
That gets back to my original point, though - we know from the start the
maximum power of the flywheel. Putting enough reinforced concrete above it to
keep it from penetrating in case of catastrophic failure is a straight-up
engineering problem.

------
devindotcom
Boy, flywheel batteries. At the Ford Museum (in Ann Arbor I think?) they have
some of the earliest versions of these, for steam generators I believe. Maybe
30 feet in diameter, must weigh a couple tons at least? The idea of one
spinning even at 20 or 30 RPM was a scary demonstration of potential energy.
If it got loose it seemed like it would blast through the wall and roll
halfway across the country. But they were beautiful, well made, and
instructive.

That said, it's an interesting way to store energy and I hope it can be
deployed safely and beneficially.

~~~
WilliamSt
The spinning wheel has kinetic energy, not potential energy, right?

~~~
bonzini
It's kinetic energy if you consider rotation around the center of the flywheel
(I * omega^2/2), but only potential energy to move around and destroy stuff (m
* v^2/2). If you let the flywheel loose, it becomes just a wheel and it's not
potential energy anymore. :-)

------
SteveJS
I remember a fly wheel battery concept from the early 90's. Spin light weight
tiny flywheels on magnetic bearings in a near vacuum and take advantage of the
fact that energy storage is linear with mass, but the square of velocity. Put
the flywheels in opposing directions and spin them really fast. If I remember
correctly, there still was a bit of a safety problem: my understanding was if
one of the tiny flywheels fell off the magnetic bearing it would rip through 9
feet of steel. Not great for a battery in a vehicle. However I don't see why
you can't tune the amount of energy you decide to store, and the amount of
safety barriers to handle catastrophic failure.

Makes me wonder if there is anyway to do something akin to a MEMS flywheel.

------
zck
I'm assuming what they're doing here (they don't really say) is using a
flywheel in the equipment in the charging station to charge a "regular"
electric car -- a car that stores the electricity in batteries. And the
flywheel is used because the environments they want to deploy these charging
stations have lower quality electric grids, "where upgrading the grid for fast
electric vehicle charging can be prohibitively expensive".

They even say they can "...charge a battery in ten minutes..." This sounds
great! But I'm not sure what cars they'd be charging. Can, for example, you
charge a Tesla that fast? I assume not, or Tesla would be charging them that
quickly.
([https://www.tesla.com/supercharger](https://www.tesla.com/supercharger) says
it takes 30 minutes)

So I'm assuming that they're charging cars with smaller batteries. It sounds
interesting, but not as good as my initial reading ("you can charge your car
way faster") made me think.

~~~
sp332
Maybe, but there is another charging standard that's starting to be rolled out
that provides up to 350kW with a water-cooled cable.
[https://arstechnica.com/cars/2018/04/electrify-america-
will-...](https://arstechnica.com/cars/2018/04/electrify-america-will-
deploy-2000-350kw-fast-chargers-by-the-end-of-2019/) That would take 17
minutes to charge even a 100kWh Tesla battery (if you could maintain that rate
of charge the whole time, which battery packs generally can't).

Edit: fixed units

~~~
tigershark
No, Musk explicitly said that future superchargers for the cars won’t be
350kw. [https://electrek.co/2018/05/03/tesla-
supercharger-v3-charge-...](https://electrek.co/2018/05/03/tesla-
supercharger-v3-charge-rate-porsche-faster-charging/amp/)

~~~
sp332
Ok, but I'm addressing zck's comment "I assume not, or Tesla would be charging
them that quickly."

------
jh
It takes about 1 Mega Joule of energy to bring 2500kg car to a stop from 60
mph. The model s with a 100kwh battery can store 360MJ and weights about
2500kg with passengers.

Is it wrong that I get uncomfortable with the idea of a spinning mass able to
charge a model s that fits within the artists rendering of the charging
station?

~~~
gene-h
Yes, because a flywheel is a very efficient device for producing flying
shrapnel. It's already storing kinetic energy, it's simply a matter of letting
all that kinetic energy loose. Energy storage flywheels have injured people in
the past and even led to some flywheel energy storage startups going out of
business[0]. However, with proper safety standards we can prevent many
disasters. [0][http://www.sandiegouniontribune.com/business/sdut-quantum-
en...](http://www.sandiegouniontribune.com/business/sdut-quantum-energy-
folded-explosion-poway-2016jul28-story.html)

~~~
dmckeon
Would putting a vertical axis flywheel in a deep basement containment be a
good start? Cap with rebar & concrete, or steel like a liquid storage tank -
depends on wheel material and failure modes?

~~~
CydeWeys
By the time you're considering building a concrete bunker, it's clearly better
to give up on flywheels and stick with chemical batteries. A bunker will cost
a lot more to construct than a few Powerwalls.

~~~
dangrossman
Just one Powerwall costs more than the cost of burying an underground gas
tank, and you'd need 10 of them to store enough power to charge one Tesla 100
kWh car. That's $35,000 in batteries alone without the cost of installing
them. $35,000 is much more than it would cost to put down an underground
concrete foundation to drop a flywheel into. House-size basement foundations
can cost 1/8th that.

------
DubiousPusher
I gotta say, flywheels are rad. They have all kinds of cool applications
including moving satelites,
[https://en.wikipedia.org/wiki/Reaction_wheel](https://en.wikipedia.org/wiki/Reaction_wheel).

~~~
anacoluthe
For example, some wind tunnels are powered using flywheels (c.f. high enthalpy
wind tunnel F4 from ONERA in France is using a 15 tons flywheel to get the
necessary power).

------
mechsquirrel
Let me channel my inner Thunderf00t here.

A Tesla Model S has about 85 kilowatt-hours of energy in its batteries at full
charge.

\-
[https://en.wikipedia.org/wiki/Tesla_Model_S#Battery](https://en.wikipedia.org/wiki/Tesla_Model_S#Battery)

That is 85 * 60 * 60 * 1000 = 306 megajoules or 3.06 * 10 ^ 8 joules.

According to Atomic Rockets' Boom Table, This is slightly less than a 54kg
high explosive Iowa battleship main gun shell.

\-
[http://www.projectrho.com/public_html/rocket/usefultables.ph...](http://www.projectrho.com/public_html/rocket/usefultables.php#id
--The_Boom_Table)

\- [https://en.wikipedia.org/wiki/Iowa-
class_battleship](https://en.wikipedia.org/wiki/Iowa-class_battleship)

This matters because with a battery, it's Very Hard(tm) to get the energy to
discharge at a high enough rate to cause catastrophic effects, like for
example why Mike Tyson can punch with ~1600 Joules (uncited, popularly
referenced), about the same as a 5.56mmx45mm round fired from an M16/AR-
pattern rifle. Because the Joules are distributed over space (bigger cross
section) and time (slower impact), Mike Tyson's punch doesn't immediately
shred your tissue and bones.

However, it's Very Easy(tm) to get a flywheel to have a tiny mechanical
failure that causes the entire thing to release all its kinetic energy
rapidly. Additionally, there's no conversion penalty with the flywheel. So the
battery under catastrophe can and generally does shed its energy relatively
slowly as rapidly-dissipating heat (see videos of cell phone batteries on
fire), whereas a rotating wheel that just fell of its drive shaft is...
markedly different.

Conclusion: Even if the flywheel only holds enough energy for a single charge,
it would have to be buried far underground and still might create a crater in
the gas station asphalt it sits underneath when (not if) mechanical failures
happen.

Therefore, this is dumb and won't happen. Please help me understand where I'm
wrong :)

~~~
Dylan16807
You're severely underestimating the ability of concrete to stop shrapnel. And
unlike a bomb exploding there's no expanding gas to contain.

[https://www.youtube.com/watch?v=RZjhxuhTmGk](https://www.youtube.com/watch?v=RZjhxuhTmGk)

20 metric tons at 800km/h is 500 megajoules, and the concrete shrugs it off
like nothing.

------
InclinedPlane
This is half of something. Charging a car battery in 10 minutes dumps a crap-
ton of heat and risks damaging the cells, lowering the useful life of the
battery substantially.

------
ChuckMcM
This is a pretty neat idea, I do worry about the 'one and done' problem where
the spinning flywheel charges a car and then then needs an hour to get up to
speed again (more if its just using solar power). That means you either need a
lot of flywheels to service cars.

It is also an amazing amount of energy to be holding in the box next to the
car (if you can believe the artist's conception in the article). I would be
much happier if they put the flywheel horizontal in a vault under the charging
station, that way if a bearing failed the wheel wouldn't go careening off into
the next county mowing things down.

This problem needs to be solved for electric trucks as well.

~~~
oneiric
A Russian hydroelectric turbine (not too different from a flywheel) stored
horizontally in a "vault" (a dam) killed 75 people.
[https://en.wikipedia.org/wiki/2009_Sayano%E2%80%93Shushenska...](https://en.wikipedia.org/wiki/2009_Sayano%E2%80%93Shushenskaya_power_station_accident)

~~~
8bitsrule
I remember following that amazing accident. But as I recall, the turbine
_jumped up out_ of its vault, and that's what started the whole failure.

IIRC, the speed of a water-powered generator is regulated by the load on it.
Take that load away, it spins faster and faster (think that's what happened to
the other generators). So that one guy had to climb up to the top of the dam
to close the gate.

~~~
oneiric
About the "faster and faster" remark, turbines will only get to about double
their nominal speed without load (called runaway).

------
reaperducer
Charging a car in ten minutes is great.

But what will really make you rich is finding a way to charge a set of AA
batteries in ten seconds.

~~~
leggomylibro
You'd need a new sort of AA battery; rechargeable nickel chemistries are a bit
finicky and they are usually not charged faster than 1C, similar to the rate
of lithium chemistries. It is also bad for NiMH batteries to charge them
constantly at those voltages; typical recommendations are to avoid "steady-
state" charging them at rates faster than 1/40 - 1/20C [1]

[1]:
[http://batteryuniversity.com/learn/article/charging_nickel_m...](http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride)

Lithium-hybrid supercapacitors are often rated for 10C charge/discharge
without the low cycle limits or volatility of lithium batteries, but they are
a young technology and it looks like commercial options are currently very
expensive with capacities in the 1-10mAh range @ 2.3-2.8V.

------
recharged93
Check out activepower. They've been in the flywheel biz for awhile for data
center power.

But they've been struggling for a viable business last 10yrs.

Area required and noise are big issues.

~~~
tzahola
Dumb question: couldn’t a vacuum chamber and magnetic bearings overcome those
issues?

~~~
wahern
Active Power's UPS systems do use magnetic bearings:

    
    
      Immediately after the output is transferred from bypass to
      the power stage, the flywheel field is excited which also
      provides magnetic lift to unload the flywheel bearings.
    

Source: [http://www.activepower.com/en-
US/documents/3801/wp108-operat...](http://www.activepower.com/en-
US/documents/3801/wp108-operationups)

------
digi_owl
I seem to recall that the new class of carriers being built use flywheels to
store up the energy used to drive the catapult.

------
_bxg1
I'd never heard of flywheel batteries. They're steampunk as hell.

------
andyidsinga
seeing the diagram - I wonder what the replacement period is for the solar
panels. Also the service costs for the panels relative to batteries.

------
solarkraft
Fly wheels are not new. I wonder why they haven't caught on (seeming like a
pretty good way of stationary energy storage), but using one for an EV charger
doesn't seem very innovative.

~~~
beat
It may not be a huge innovation, but it's an interesting potential business
model. And as an investor, I'd be looking at financial potential, not
"innovation".

------
post_break
This could be a cool low cost option. Imaging if a solar panel could spin up a
fly wheel which you could then pull power from at night. Cheaper than regular
or expensive lithium batteries, and "unlimited" assuming motors don't wear
out. I'd love to see something like this to help power my home. Or maybe have
it run on the grid at night during free power times and then pull from during
the day.

~~~
masklinn
> Cheaper than regular

FES is currently as expensive or more expensive than battery, and while it
could go down faster than batteries that's unlikely considering how old FES
tech is.

If you want to store lots of power in a flywheel, you need big flywheels
spinning very fast without spinning out of control and blowing themselves up
(because then all the power they stored remains kinetic but stops being
contained).

They've got plenty of advantages over battery (inert materials, less affected
by temperature variations, potentially infinite lifespan for magnetic bearings
in vacuum-sealed enclosures) but safe large-scale flywheels are not _cheap_.

Neither Beacon Power nor Amber Kinetics provide any pricing information on
their pages, despite specs in the same range as battery storage: a Powerwall 2
is 13.5kWh/5kW, an Amber Kinetics M32 is 32kWh/8kW. The M32 is also ~4.5 tons.

The M32 _does_ have the advantage of an estimated 30 years lifespan, and no
health danger outside of the rather immediate effects of a containment breach,

