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Re: Pumped storage etc.



Howdy-

On Thu, 18 Jan 2001, Laurent Hodges wrote:

Also, the point has been made that electric companies charge for energy,
not power. This is generally true for homeowners, but NOT for large
businesses, whose rates are a function not only of the kilowatthours used
but also the peak kilowatts during the month (or whatever period is
involved), sometimes just daytime peak.

At the school where I used to teach in Houston, the electric utility was
paying for the public schools to change their air conditioning systems. I
don't know if they ever finsihed the project as I left town, but here is
the scheme as presented.

The school used a radiator with fan system for cooling, a pretty standard
arrangment for a large building, where water is centrally chilled and then
is pumped to individual room radiators that had fans to blow air over the
radiator fins. The chilling device worked like a normal air conditioner.

They replaced the on demand chiller with a giant freezer. All night long,
the chiller made ice cubes that were stored in an enormous, massively
insulated ice box. Pipes ran through the box to chill the water for use
during the day.

This system then shifted the electric use to the night when demand was low
from the day when it was high. Further, the utility claimed that this kind
of chiller worked more efficiently because the difference in temperature
in trying to remove the waste heat was greater. (That is, the night air
is cooler compared to the exhaust from the compressor than during the
day.)

According to the television show "The Secret Life of Machines", in
England, many people have electric heat, but the cost of the electricity
varies with the time of day. So the heating element is wound around a
large concrete block. The block is heated during cheap hours, and then air
is blown over it when the heat is needed.

---

Marc Kossover
marck9@mail.idt.net