On Feb 4, 5:18*pm, "Ralph Mowery" wrote:
wrote in message

...
On Feb 4, 1:54 pm, wrote:





On Mon, 4 Feb 2013 10:41:50 -0800 (PST), "
The reason is to have more water available to supply more
power during peak times during the day. * Let's say you have
100MW of generating capacity from water flow from the
normal flow of a river. * The generator could supply 130MW if
there were more water flow, but the river is only capable of
100MW. * *At night, the demand is only
60MW. *So, at night you take the extra 40MW that isn't needed
and use it to power pumps to move water to a reservoir
upstream of the generator. *The next day, when you need
more than *100MW, you start releasing that extra water,
boosting the generator output above 100MW.
Nothing there violates thermodynamics and there is a
reason for it. *The power generating company has just
help meet peak demand and gotten paid for electricity
that it would otherwise have not been able to produce.
Feel free to admit you're wrong at any time.

Good idea except it does not work that way. *Even at 100% efficency, only
the ammount of water going down hill can only pump the same ammount back
uphill. *If 100 MW of water is turning the turbins, it will take more than
100 MW to turn the pumps to get the water back to the top.

Follow the example. It doesn't require 100% efficiency. You have a
river
that's flowing at 100MW an hour. During the day, there is a market
for
all that power. At night the demand is only 60MW. So, you could let
that water pass by unused or use the 40MW available to pump water
to a reservoir above the power plant. Then, during the day when you
need more than 100MW, you release some of that water. You now
have more than 100MW of water availble to turn the generator
because you have EXTRA water beyond what the river supplies
during that peak period.
Hence you can produce more than 100MW of power during the
day when you need it.




For the system to work, it starts off like you say. *The the flow of water
going down hill is stopped at night. *The pumps and the other users *are
supplied with power from other sources on the grid such as coal powered
plants that have the excess capacity at night.- Hide quoted text -

- Show quoted text -

That's real nice. Let the river go dry at night. I'm sure the
cities, towns, farmers downstream and all the farmers will be
OK with that.....