On 16/08/2010 16:17, M.L. wrote:
>
> Please be more careful with quoting.. I said nothing about the size of
> the operation. I'm actually not sure why you lumped my efficiency
> question in with the size question, considering that you wrote the
> remark about size.
>
> I was merely stating that pumping (pumps are inefficient) water up
> pipes (inefficient) into a lake (lossy) and running the water back
> down pipes (inefficient) and through a turbine (inefficient) results
> in an inefficient system.
>
You are now stating, what you state. Previously you just said it was=20
inefficient.
I made the assumption you thought it was inefficient because it's large=20
as you didn't make clear your point.

You are making the false assumption that storing electricity by pumping=20
water to convert it to potential energy is inherently "inefficient".

It might be 15% less efficient than a flywheel* (up to 4MW, but not sure=20
of the MWh rating) but it's very scalable. I doubt that rechargeable=20
batteries are as efficient averaged over an economical lifecycle=20
including energy to make replacements compared with 40 years of Pump=20
storage operation. Compared with converting sunlight to electricity=20
directly with PV cell, Pump Storage is very efficient.  It's one of the=20
few methods of storing wind power. Flywheels are another.
http://www.smartplanet.com/business/blog/smart-takes/beacon-power-closes-43=
-million-doe-loan-for-20mw-flywheel-energy-storage-plant/9647/?utm_source=
=3Dtwitterfeed&utm_medium=3Dtwitter


(*or less difference with flywheel  depending how long you store the=20
energy and the efficiency of the motor / generator set).

--=20
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