Re: [Phys-l] Efficiency problem

[Bernard Cleyet <bernardcleyet@redshift.com>]

This is rather old hat, as it's a means of saving on investment in additional power stations, by storing power in fallow time for use when needed.

"The first use of pumped storage was in the 1890s in Italy and Switzerland. In the 1930s reversible hydroelectric turbines became available. These turbines could operate as both turbine-generators and in reverse as electric motor driven pumps. The latest in large-scale engineering technology are variable speed machines for greater efficiency. These machines generate in synchronisation with the network frequency, but operate asynchronously (independent of the network frequency) as motor-pumps."

http://en.academic.ru/dic.nsf/enwiki/168432


I first heard about its use in France, fifty? years ago.

http://www.erth.waikato.ac.nz/staff/bardsley/download/pumped_storage_note.pdf


Here's wiki's list:

http://en.wikipedia.org/wiki/List_of_pumped-storage_hydroelectric_power_stations

bc


On 2010, May 28, , at 14:31, Hugh Haskell wrote:

> The advantage of this process is two-fold. First the pumping can be 
> considerably more energy efficient than a thermal process (nuclear, 
> coal, or natural gas turbine) which is limited to usually bout 30-40% 
> thermal efficiency, and second, the process  can be turned on or off 
> quickly, thus responding to short-term changes in demand more easily 
> than a coal or nuclear plant, which typically take hours or days to 
> bring on line, can be.
>
> But the economic analysis has to be carefully done or it can quickly 
> turn into a large money sink for the producer.
>
> Hugh



from:





On 2010, May 28, , at 13:49, Peter Schoch wrote:

> I've had a former student return with a question that I could use some help with...
>
>  In his community, a developer wants to convert an old quarry that is now a man-made lake into a power generation scheme.  The developer would excavate under the quarry.  Then, during the day, they'd let the water run from the "lake" down into the holding tanks underneath, in the process turning a generator and creating electricity.  Then, at night they'd pump the water back up to the "lake" when the electricity was cheaper.  In this way they'd generate electricity and the claim is that this is "green" electricity.
>
> The student came to me because he remembered (yes, I did jump for joy that someone remembered something I had presented them as part of the class!) that no process could have an efficiency of 1, so his thought was that this process is not "green" as advertised.  He thought that due to this loss, this process would ultimately consume more electricity than it would generate and that it was just a "shell game" for making money.
>
> Well, my first inclination is to agree with him.  However, I did tell him that he was trying to apply an efficiency concept from Thermodynamics to electricity generation.  I assured him I'd do a bit of digging and get back to him.  Well, I can't seem to find how I might calculate the efficiency for this process and how to determine if it is truly "green" or not -- thus being a way to make money but not be green.
>
> Any suggestions and/or help would be appreciated,
> Peter
>
>
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