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Feeding solar power back into municipal grid: Issues and finger-pointing - Page 17

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Posted by trader4@optonline.net on April 15, 2011, 12:47 pm
 

Thank you Jim.  I was sitting here wishing I could draw
a simple circuit into the newsgroup that models what we
 are talking about and shows what really happens.
You've gone one better and found a perfect example
from an independent and credible source.  That
circuit is EXACTLY the model for the dual battery
example I brought up.  Each battery is modeled as
an ideal voltage source in series with a resistor.  And
each supplies part of the current flowing through
the load.  One never charges the other, nor does
one need to have a higher voltage to "push" current.

I suspect we'll be hearing soon from Homeguy
about how this isn't a valid way two batteries connected
 in parallel to a load can be modeled.

Posted by Home Guy on April 15, 2011, 1:18 pm
 
"trader4@optonline.net" wrote:


You dumbass.

Look more closely at the current flow in battery 1.  It's NEGATIVE.

===================
The negative sign for I1 means that the direction of current flow
initially chosen was wrong, but never the less still valid. In fact, the
20v battery is charging the 10v battery.
==================

Posted by Home Guy on April 15, 2011, 11:44 pm
 Home Guy wrote:
 

Where's trader4?

Where did you go, you coward?

You have no response to what I wrote above?  

You disappeared from this tangent thread pretty fast, didn't you?

You absolutely loved that link posted above, showing Example 1 - where
you thought it was proving me wrong.

Go ahead and substitute 13.33333 volts for Battery 1 in that example and
tell me how much current it's supplying to the load.

Posted by krw@att.bizzzzzzzzzzzz on April 16, 2011, 3:53 am
 wrote:


That's good for a first order approximation.  The fact is that water doesn't
run down hill and electricity does *not* flow from low potential to high.  The
inverter's instantaneous voltage *must* be higher than the grid for current to
flow into the grid.  

Think about turning a bicycle crank, one without a clutch makes the point
better.  You're not doing any work unless you're applying pressure to the
pedals.  If you do nothing it drives you.
 

No, you can't get on the "freeway" unless you're going faster than 60.  If
you're going slower, they're actively pushing you off.


It's OK for a first order, but not for discussing the details people are
trying to get into here.  

Posted by David Nebenzahl on April 17, 2011, 8:35 pm
 On 4/15/2011 8:53 PM krw@att.bizzzzzzzzzzzz spake thus:


Whoa. Where do you get that (using Smitty's analogy)? Sure, you can't be
going slower; that's self-evident. You say you have to be going faster.
But you say nothing about going (approximately) *the same speed*, which
is what Smitty's example was saying. (And is what ever article I've ever
read about inverters, grid interties, etc., has said. (*None* of them
say "the voltage of the contributing system has to be slightly higher
than the grid in order to feed current into it". None of 'em.)

(Which, by the way, is eggs-ackley the same thing I've been saying here ...)


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