[NatureNS] wind power storage

Date: Thu, 30 Aug 2012 02:21:01 -0300
From: "Stephen R. Shaw" <srshaw@Dal.Ca>
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  electricity.&lt;BR&gt;&lt;BR&gt;&amp;nbsp; A
Hi Chris,
Very interesting, never heard of this before. But how is it supposed  
to work as some sort of "battery"?

Suppose you have a 'perfectly' insulated DC high voltage conductor  
line made of copper (except perfect insulation is not possible), that  
is suspended in air and goes for 1700 km or more but doesn't connect  
to anything.  When you connect this line to a power source, no current  
will flow into it from the power source if there is no external load  
and no leakage.  I don't see how you can store any charge/energy at  
all in a network like this no matter how large. Actually the network  
would lose some charge (DC current) from the source through the small  
amount of inevitable leakage that would occur, especially operating at  
very high voltage.

Something therefore seems to be missing from the argument -- have the  
proponents of this approach found some practical way of making,  
attaching and insulating huge capacitors that can store large amounts  
of charge at high voltages?  Recollecting bygone times with tube  
circuits that operated up to fairly high voltages (say 250 volts DC  
rating before electrolytic breakdown): a practical electrolytic  
capacitor of ~20,000 microfarads capacity (not that much) already had  
reached the size of ~4 inches square by ~1 inch thick. Scaling this up  
to a 100,000 volts DC rating would probably make it have to be  
~400-fold thicker, which sounds impractical.  I thought that this was  
the long-recognized problem with storing electricity, the  
impracticability of constructing capacitors with enough storage at  
non-colossal sizes.

So what's the actual storage mechanism, and is there a useful place to  
look this up on-line?
Steve (Halifax)
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Quoting Christopher Majka <c.majka@ns.sympatico.ca>:
... However, some
> jurisdictions are moving to high-voltage DC (direct current) lines   
> (for a large variety of reasons too lengthy to go into here). The   
> upshot is this: a large DC line (there is already one in Africa that  
>  runs 1,700 km) functions to some degree like a very large battery.  
> One  can (within limits) continue to pump electricity into it,   
> progressively stepping up the voltage. Then when you need power you   
> run it out of the line through a transformer. The more extensive a  
> DC  grid the greater the overall capacity of the "battery."  
> Moreover, with  the development of new high-voltage DC valves and  
> much lighter wires  the costs of DC transmission are dropping  
> sharply and their  environmental impact is less.
>
> Cheers!
>
> Chris


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