[Chugalug] OT: Solar Panels

Dan Lyke danlyke at flutterby.com
Fri Mar 14 16:43:47 UTC 2014

On Fri, Mar 14, 2014 at 8:58 AM, Joe Freeman <joe at netbyjoe.com> wrote:
> a little more than 10 years ago, we looked hard at putting three flywheel
> generators in at the CenturyTel data center. The ones we looked at would
> have been buried in the ground, but they were huge and took like a week to
> spin up, but would have given us enough backup power to run the dc for
> several days without running the NG or diesel gensets. I don't remember why
> we didn't do it for sure, but it was probably cost.

The thing about storing a lot of energy as kinetic energy is that
you're sitting on a system that contains a lot of energy. We know how
to handle fuels, chemical potential energy, we've got quite a bit of
experience in dealing with that, but if you think about a gallon of
gasoline as enough energy to propel two tons of steel twenty five
miles, then you have to think about a flywheel with equivalent energy
as capable of doing the same thing.

There. In your basement. Just waiting for a bearing to go bad and go
screaming through your foundation and bouncing off whatever other
critical equipment you may be running in your basement.

A few years ago I was thinking about energy storage technologies for
Burning Man. Most people brought a car or even a big SUV, parked it
for the week. What if we had a simple vehicle lift, use photovoltaics
to lift that big weight into the air, let it down slowly and generate
power from it at night.

Call an SUV 2,000 kilograms. In earth gravity that's 19600 newtons,
lifted two meters that's 39200 joules. Release that over an hour, you
get whopping ten or eleven watts back out. So a hundred watts means
you've got to be lifting that SUV 20 meters into the air, or lifting
10 SUVs over your head. Running a data center means you have to start
lifting and lowering your building.

Storing that as kinetic energy means that rather than lifting those
SUVs up into the air, you're storing that in a way that's susceptible
to bearing failure or materials flaws in your flywheel (as it breaks
apart and throws chunks everywhere), and all of a sudden keeping large
gasoline or diesel fuel stores on your roof for your genset seems a
hell of a lot less scary.


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