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Re: Some Solar problems ahead?

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http://www.theaustralian.com.au/national-affairs/carbon-plan/rooftop-solar-panels-overloading-electricity-grid/story-fn99tjf2-1226165360822
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Article and quotes by CEOs seem complete rubbish to me as a layman. Here's
my take:  The supply from a normal solar panel is unlikely to exceed what a
home uses unless of course everything if off and the people are away. So
given that usually a user of solar panels will simply be *reducing* the call
on the mains supply, the net power drawn through the gird will be less, so
shortcomings in copper should not be a problem.

True there wll certainly be fluctuation when there is intermittent cloud
cover, but on the whole that should be 'normal demand' punctuated by reduced
demand. Not normal demand punctuated by increased demand!



Re: Some Solar problems ahead?
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On second thought I got a bit of an idea where the problem may come to
surface. I have no experience in grid technology, so correct me if I am
wrong.
First of all I must say, people do try to avoid heavy usage when the sun
is shining, cause they can sell their electricity for about double of
what they would pay. Which means they do feed into the net as much as
they can in day time.

The voltage at a transformer would always be at the higher end to cater
for the copper losses to be expected farther down the line.
If, however, there are a number of powerful solar supplies feeding in
along that transmission line, much of the current goes the other way,
and the voltage drop due to copper losses could even ADD to the grid
voltage. So instead of the usual voltage drop due to copper losses we
would have a gain. The only way to avoid this reversal would be to use
more copper or less solar.

As far as fluctuations are concerned, I think we'd need a lot more solar
power, like a double digit share, to see an impact on the grid voltage
or frequency.


Re: Some Solar problems ahead?

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  Not really, or at least, they don't have any say in that.

  In the following hypothetical, (I'm assuming that ALL homes on a given
isolated grid, also have solar assistance).  It won't happen in real
life, but this is just for the sake of this explanation.

  If ONE home chooses to stop using ALL possible power during a peak
demand interval, AND, no-one else does that, THEN, their system has the
*potential* (owing to light and battery power availability) to supply
its full capability into the grid, and get paid for their bit.
  This is of course assuming the remaining homes have a net negative
generation, that is, even accounting for THEIR own solar systems, they
still use MORE than what they generate themselves.  In other words, they
still draw something from the grid.

  If ALL solar homes had the same idea (power off everything and let
their solar systems pump power into the grid), then, NO-ONE would
pumping power into the grid - their controllers simply will NOT let it.
  There are safety limits built in that prevent over voltage from
happening.  This entirely debunks the "solar overloads the wiring"
statement, as well as the amount of copper.

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  It depends. Although the "grid" operates as a large-scale entity, it
does indeed have some localised effects.  And it NEEDS this, because
even though the "grid" operates with some self-regulation as far as
voltage goes (power stations vary up and down according to demand, and
voltage is a good indicator of what the load is.
  There are quite high variations on the local level, because one suburb
may have no air-cons, and the next door suburb may have them all. And
the larger scale grid feeds them both.
  To ensure YOUR grid voltage stays within "acceptable" limits, there
are local transformers that change taps to offer some control for this.

  In the hypothetical that solar systems feed "too much" power into the
grid (they won't, but let's say they do anyway), the transformer will
switch to account for that, so less comes from the larger scale grid,
and the local solars can supply a chunk of power.

  This will not magically "stress" the copper, because the copper isn't
carrying any more current that it's capable of ANYWAY.

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  Firstly, there is no "other way".  Due to normal losses in copper,
YOUR solar system has MOST effect closest to you, and the LEAST effect
furthest away from you.  The change YOUR solar box has on the whole is
rather local.

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  Again, only locally, AND if the box lets it.  If the grid voltage is
ALREADY high, YOUR system will NOT push bucketloads of power into the grid.

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  :-)  Congratulations, you've just turned a positive into a negative.
What you're saying is a GOOD thing, and does not require "fixing".  It's
also the cheapest and most effective way of addressing load.

  Take the far southern end of Victoria for instance.  They're at the
end of a long copper line, ant the wrong end of the power generation
side, so there are significant losses. They have increasing peaks loads
due to air cons and huge TV sets.
  Increasing copper would help, but ultimately, no-one is going to pay
millions so a tiny town can have air cons and TV sets.
  What they're doing now, is using wind power to supplement peak power.
  So that droop due to load goes away, because the wind generators are
taking up the slack.  This is a GOOD thing.
  Of course, they want to whine about the noise, and they have every
right to do that.  The easiest way to fix that is to get THEM and THEM
ALONE to pay the millions or billions for the copper upgrades.  As long
as everyone else doesn't have to pay, I'm quite happy to let them have that.

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  That theory would fail, mainly because it's these huge peaks (aircons)
that need LOTS of power generation over short periods.
  Generating this class of power is expensive, but in above example,
it's still cheaper than copper.
  Again, this is for long haul copper, local systems will see no
(worthwhile) gain in copper upgrades.
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Re: Some Solar problems ahead?
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I meant they don't do the washing or run the pool.
With a 2KW system, he fridge and smaller stuff draws 1 or 2 amps.
6  amps will be fed in the grid.

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I don't see the point of the assumption. There will always be a number
of houses with PV producing more than they use, especially on days where
no A/C is needed. The line loss will lift the voltage.
Should the upper voltage limit be reached, some of the inverters will
cut out first and the voltage will not rise above he limit. But,
depending on the hysteresis of the sensing circuits, they will switch on
again. An inverter that switches off turns into a sink what used to be a
source and so not only takes away feeding current but also adds some
load and so amplifyies the effect. Depending on a lot of factors and
inverter design I could imagine some oscillation happening here.
Modelling this situation is difficult and we will wait and see if it can
happen.
In any case, it's not good as a switched off inverted defeats the
purpose of the PV system and oscillations, God knows...
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Never knew that. Are those solid state switches?

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I don't doubt that but I think in the article the assumption was that
too many PVs are feeding. If you got more sources than sinks the net
effect is source, with the above mentioned possible effects.

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Well the downside is, if PVs switch off and assuming nothing else bad
happens, the investment would still be a waste of money (taxpayers money
too). The owners might not even notice, only wonder why the power bill
doesn't go down!

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What I meant was that sudden solar PV changes won't cause problems at
the generator side yet, due to the small scale.

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Re: Some Solar problems ahead?

"TonyS"


** John Tserkezis is a life long, total nut case.

Like the proverbial Zoo Gorilla, he annoys himself.

So, it is a totally superfluous to annoy him with facts or logic.

They are both forever beyond his comprehension.

FFS   -  wise up.




....  Phil








Re: Some Solar problems ahead?

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http://www.theaustralian.com.au/national-affairs/carbon-plan/rooftop-solar-panels-overloading-electricity-grid/story-fn99tjf2-1226165360822
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Wth noting that the two towns cited in the article -  Exmouth and
Carnarvon - are both relatively small and distant from the main state grids.
AFAIAA both would be reliant on relatively small local generating
facilities, their grid may not be all that stiff.



Re: Some Solar problems ahead?

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  It's been a while, but the names ring a bell.

  Either limited local generation, or long distance cables causing
voltage lag will do it.
  I'm thinking it's more likely to be long distance cables.

  Wind is out there to supplement peak power use, and that works well,
if you ignore the constant whining and protesting to get the wind
generators taken out, citing noise and eye-soreness as reasons.

  Quite sensibly, they are all ignored.
  It's easy to leave the wind generators installed and ignore the
whining and protesting
  It's hard to remove the wind generation, and ignore screams of blue
bloody murder when they get to their quiet homes, turn on the lights and
barely get a dim glow.
--
The worst thing about censorship is **************************.

Re: Some Solar problems ahead?
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Or their complete disbelief when the wind generators are left in place,
and the people turn on their lights, but the wind isn't blowing.

Sylvia.

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