Unusual Generation in the Morning
- Thread starter BaldDave
- Start date
Mixed up thread?
My sorted out system I think will be three strings:
9 west to its own MPPT to be PV1
another 9 west to its own MPPT to be PV2
6 east to its own MPPT to be PV3
My question is about optimising the west strings which will se a chimney shadow some of the year…but no other shadows .
My sorted out system I think will be three strings:
9 west to its own MPPT to be PV1
another 9 west to its own MPPT to be PV2
6 east to its own MPPT to be PV3
My question is about optimising the west strings which will se a chimney shadow some of the year…but no other shadows .
Sergio95050
New Member
Care to elaborate with numbers in hands ? Ohm law ? Kirchhoff's circuit laws?
Sergio95050
New Member
I did experiments with one panel on a ground (for easy access) - dramatically! Power dropped to 10% or less, especially low when the shadow crossed all three internal strings of the panel
Each my panel has three strings separated and combined by three diodes.
Result!Sounds like a sensible plan to keep the optimisers on the string that has potential shadow. If you're not wifi connecting them then, in theory, you only need the optimersers on the panels that experience shadows.
Never a numpty question
Bit off topic, but to answer that (as I triggered the query in the first place).... it depends on how the inverter's MPPT algorithm works.
One would:-
a) need to ensure the strings are equally matched in terms of panel voltage, current and power vs. luminance characteristics (or the inverter won't be able to find the sweet spot).
b) never get more power than the inverter can receive on the one input, so not efficient compared to having 2 strings
c) need fuses on the PV circuit if deploying more than one string
And, IME, the inverter may trigger an error alarm if their MPPT algorithm hasn't been designed to handle a greater possible PV current than it was designed to handle.
timselectric
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Brucey
Solar Wizard
Often the amperage limits per string may relate to reverse polarity protection, I e with a Victron 450/100 you can connect up to 18A in reverse polarity without an issue, you could go higher but that protection won't be there. Assuming you have a multimeter and can check before connecting there shouldnt be an issue exceeding the current rating.
Some don't have reverse polarity protection for pv at all (eg4 18kpv).
Some don't have reverse polarity protection for pv at all (eg4 18kpv).
timselectric
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When solar panels are wired in series, they become one single large panel.
They need to see the same amount of sunshine to produce efficiently.
By putting part of this single unit in a different orientation, you are purposely designing for a poor outcome.
And then trying to correct it with Optimizers is just throwing money at a problem that should have been avoided.
If a "professional" is running this scam, it's a sad situation. But these days, nothing surprises me.
timselectric
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I would keep them.
Optimizers help during temporary shadowing. (Moving shadows)
Rather than go into those, Tigo’s website doesn’t recommend putting East and West panels on the same string. What actually happens is that power generation is restricted across the entire string even in full sun at the start and end of a day.
Thanks. I’m trying to cost how much energy I’d lose across 25 years against the cost of optimisers. It might be they save me £5 a year or £100 a year….I don’t know!
timselectric
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I don't know either. I've never needed them.
I just know that they were invented for shading issues and they do help some.
They help the most in bright sun, when single panels see shading.
Sergio95050
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Not that what we got - the point is using panels with own optimizers.
timselectric
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I'm not sure what you are saying.
The point is that the "instaler" tried to use optimizers to correct their design flaw.
You asked...
For me it would be 'worth' it for not seeing a "dip" in production when the shadow goes across the panels, irrespective of any financial savings... but YMMV.
I’m like that too…so is the installer at heart. Had to look up YMMV. LOL!
Sergio95050
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Well. Not everyone has acres of land in own possession!
My place has available pitched roofs with 17 degrees of inclination in three directions: E, S and W. Only.
No way to run all my 19 panels without 18 optimizers ! Period.
timselectric
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3 directions, 3 strings.
If you have shading issues, then I would understand optimizers.
Sergio95050
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Yes, I have a few, include VERY tall tree at W side, a chimney is there, tall structure holding my two tanks with cold/hot water, water solar heating panels, a couple of 12' sat dishes. Plus, part of walls at an edge between roofs making shades
Sergio95050
New Member
It would force me to run a lot of DC cables to the SE3000 inverter.
One string with OPs is optimal setup. I posted a plot of one day generation - see above.
I found a report that says single strings can work well with inclinations of 15 degrees and less, the single string being East and West. 17 is close to that really. But mine is 35 degrees.
For top performance, mine needs different strings, even with optimisers.
I don’t have acres of land…just the position of my place with others around it, including trees (which are lower than my panels!). Higher obstacles are to my North….which barely affect production.
As we get close to the longest day, my East West split string, fully optimised, ‘wakes up’ earlier….7am today…and less KWh are lost in the ‘sleep’. Whereas in December it takes far far longer to wake up and a bigger % is lost.
So last Sunday, June 1st, sunny all day, my system produced a whopping 58.3 KWh. Looking at the graphs, it lost around 3 or 4 KWh before it woke up (KWh it would have produced with separate strings)
In summer months, I lose more by ‘clipping’. The inverter clips above 6KW…and it could do that for hours each day.
For top performance, mine needs different strings, even with optimisers.
I don’t have acres of land…just the position of my place with others around it, including trees (which are lower than my panels!). Higher obstacles are to my North….which barely affect production.
As we get close to the longest day, my East West split string, fully optimised, ‘wakes up’ earlier….7am today…and less KWh are lost in the ‘sleep’. Whereas in December it takes far far longer to wake up and a bigger % is lost.
So last Sunday, June 1st, sunny all day, my system produced a whopping 58.3 KWh. Looking at the graphs, it lost around 3 or 4 KWh before it woke up (KWh it would have produced with separate strings)
In summer months, I lose more by ‘clipping’. The inverter clips above 6KW…and it could do that for hours each day.
timselectric
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Wow, that's a lot to deal with.Yes, I have a few, include VERY tall tree at W side, a chimney is there, tall structure holding my two tanks with cold/hot water, water solar heating panels, a couple of 12' sat dishes. Plus, part of walls at an edge between roofs making shades
timselectric
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A single string broken up across 3 different directions is never optimal.
It's just bad planning.
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