SauRoN's SomeWatt Solar Install

SauRoNZA said:
Sure but are we talking 10% efficiency here or like 90%?
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You can model it, there are many apps / tools available.

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wingnut771 said:
Of the panels, can you post the voltage of your MPPT for the day? Is it not constant?
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No it isn't, and where it is relatively consistent is thanks to Mr MPPT's algorithm designers.

Here is a relatively good day in Gauteng:
1657055231291.png

Here is a cloudy day with not much load in kabookie:

1657055408362.png
 
RonSwanson said:
the lower voltage on either string (before and after 12H00) will pull the overall MPPT down
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You are wrong, swanson. Given that the strings will be in parallel, the string with the highest voltage will lift the rest - a PV cell is essentially a diode (actually a light emitting diode, or LED), so if you apply a voltage below that at which it starts emitting it looks like an open circuit. The sunsynk MPPT does not do a deep scan, so it will only find the peak nearest the open circuit voltage.
 
P924 said:
You are wrong, swanson. Given that the strings will be in parallel, the string with the highest voltage will lift the rest - a PV cell is essentially a diode (actually a light emitting diode, or LED), so if you apply a voltage below that at which it starts emitting it looks like an open circuit. The sunsynk MPPT does not do a deep scan, so it will only find the peak nearest the open circuit voltage.
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Yeah yeah the diodes....
So no loss? Nothing at all?
In theory yes, in practice no.
 
wingnut771 said:
How much loss? 50%?
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I'm on leave in the bush at the moment but will post my string production data once I'm back in the city. There's a clear difference between my two strings due to differences in shading. My 6kWp panels have been producing about 24kWh per day and a rough eyeball of the graph says it could be about 30kWh if there was no shading. So loss for me is at about 25% for the system.
 
Speedster said:
I'm on leave in the bush at the moment but will post my string production data once I'm back in the city. There's a clear difference between my two strings due to differences in shading. My 6kWp panels have been producing about 24kWh per day and a rough eyeball of the graph says it could be about 30kWh if there was no shading. So loss for me is at about 25% for the system.
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You’re talking about shading on one string, I’m talking about 2 strings in parallel on east west roof were the east string is in shade and the west is in full sun.
 
Speedster said:
I'm on leave in the bush at the moment but will post my string production data once I'm back in the city. There's a clear difference between my two strings due to differences in shading. My 6kWp panels have been producing about 24kWh per day and a rough eyeball of the graph says it could be about 30kWh if there was no shading. So loss for me is at about 25% for the system.
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Yes but that can simply be the shade itself, not necessarily the one string affecting the other string.

I mean unless they are identical in size and in the exact same place it’s always going to be different from one to another.
 
Everything I've read and tested with design tools says that if I connect East + West with the exact same number of identical panels in parallel I should be golden with 99% the efficiency I would have had of installing another MPPT or Inverter because the orientation of my house is almost perfectly square.

So the plan then is to move 4 panels off the of the 9 panel string and then balance it as out as the below.

MPPT 1
1 x 5-panel String North in series.
1 x 5-panel String North in series.

MPPT 2
1 x 5-panel string East in parallel with 1 x 5-panel string West.

9000 kWp total with pretty much full day coverage.

If I really wanted to get fancy I could do the North-facing with 6-panels each, but the one would be very offset and part of the other group which just seems messy and probably with little benefit.

Anyway this is only a potential for next year.
 
@SauRoNZA and @Mike Hoxbig - when your batteries are discharging - do they both go down at the sametime or does one say go from 5 to 4 bars (SOC lights) then the other?
 
Mzezman said:
@SauRoNZA and @Mike Hoxbig - when your batteries are discharging - do they both go down at the sametime or does one say go from 5 to 4 bars (SOC lights) then the other?
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All three go together more or less, but not exactly at the same time if that’s what you mean.

Sometimes I’ll have two on 1 LED and the third will be on 2 LED and drop off last.

But it’s not like 1 gets drained and then the next and then the last.
 
SauRoNZA said:
All three go together more or less, but not exactly at the same time if that’s what you mean.

Sometimes I’ll have two on 1 LED and the third will be on 2 LED and drop off last.

But it’s not like 1 gets drained and then the next and then the last.
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ok great - thanks for this. mine do the same as well
 
Mzezman said:
ok great - thanks for this. mine do the same as well
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My ZTEs do that, sometimes one will be flashing 3 bars the other 2,but ten minutes later they'll both be on 2.
 
SauRoNZA said:
Man summer is going to be something else.

9am and already sitting at 2.5kW.
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I'm at 10% more production than at the same time yesterday. With my excess PV currently set to go to the irrigation, my garden is going to be glorious if this keeps up.
 
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SauRoNZA said:
Man summer is going to be something else.

9am and already sitting at 2.5kW.
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The issue in summer is finding load to use the power on.

You'll typically use cooler water so the geyser will draw less, no heaters etc. If you have aircons you could use them but they're a lot more efficient than heating devices.

I'll probably run the pool pump longer but that's still only 750W...
 
Mike Hoxbig said:
The issue in summer is finding load to use the power on.

You'll typically use cooler water so the geyser will draw less, no heaters etc. If you have aircons you could use them but they're a lot more efficient than heating devices.

I'll probably run the pool pump longer but that's still only 750W...
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Yeah the borehole pump and the aircons will do a pretty good job I reckon.

Time to get that pool.
 
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