Re: [Phys-l] Efficiency problem

[Hugh Haskell <haskellh@verizon.net>]

At 07:56 -0400 05/29/2010, Jeffrey Schnick wrote:
> On a related note:  There is a company near here that sells 
> multi-ton flywheels that further smooth out the demand on a plant 
> even after the day/night disparities have been ironed out.  The 
> devices are designed to contiuously monitor consumption, and provide 
> power to the grid whenever consumption is above a certain level, and 
> store energy from the grid in the form of the kinetic energy of the 
> flywheel whenever the consumption is below a certain level.  See:
> < http://www.beaconpower.com/ >
>
> _
I'm happy to hear that this interesting technology is still around. I 
got interested in it about 35 years ago when I was stationed in the 
Pentagon and saw a write-up on it in Scientific American. At the 
time, they were saying that new technologies were making flywheel 
storage a distinct possibility for transportation use--wheels made of 
Kevlar (heavy and with high tensile strength to withstand the 
centrifugal forces of high spin rates), and magnetic bearings to 
reduce friction, meant that overall efficiency could be over 90%, 
with dynamic braking to recover energy from stops or slowing down. It 
was tried in some busses in San Francisco, IIRC, but nothing much 
came of it.

But stationary applications like this seem to be a pretty good fit, 
and would be really useful for storage at wind or CST sites as well. 
Don't know much about current costs, however.

Hugh

PS. I used conservative efficiency estimates in my hypothetical 
example to allow for other losses in the pumping system and to 
simplify the calculations. The issue is not with conservation of 
energy. This is not a perpetual motion scheme, and whether it can 
work in the scenario that was proposed or not depends entirely on the 
difference between the cost to purchase electricity to pump the water 
up hill and the price that can be realized from the electricity 
generated when the water flows downhill. This is true regardless of 
the efficiency of the overall system.

H^2

--
Hugh Haskell
mailto:hugh@ieer.org
mailto:haskellh@verizon.net

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