Shaded Panels- is parallel or series better?
- Thread starter Sage
- Start date
ianganderton
Auckland, NZ
This is quite a good look at the options
www.explorist.life
It all depends on your personal set up and use case
Camper Solar Panels - Series vs Parallel
Series vs Parallel: The great debate. Well... not really a debate as there is a clear choice for 90% of builds:
www.explorist.life
It all depends on your personal set up and use case
ianganderton
Auckland, NZ
Ha ha is it a major concern or just a question ?
Your call, but the question was posed solely in the context of shading and minimal energy loss, I don't see how one could conclude otherwise:
If they didn't have bypass diodes, shading a single cell would chop production by 90%. Different panels are more and less effective at it, but you need a bypass diode on every single cell for maximum benefit. Few (if any) do that.
ianganderton
Auckland, NZ
In the real world I think they help a bit but at the end of the day shade is bad for solar and you are best off avoiding it if you possibly can
Sorry to bring this back from the dead, but I want a clearer answer to this question myself. I'm finding on multiple websites (including here) that in a series configuration, shading one panel drops the output of the other panels as well. In practice, this is not what I am seeing. I have 3x100W solar panels for a 12V system using a Victron MPPT controller. When shading one panel, the MPPT controller reduces the voltage and I am left with full output from the other 2 panels. Would it be any better in a parallel configuration?
sunshine_eggo
Happy Breffast!
What you are seeing is the action of the bypass diodes. For controlled situations like you describe where notable shading takes out a significant portion of the panel, they work very well. Partial and variable shading can yield erratic results. Performance is also a function of the quality of the MPPT algorithm.
Example:
3 100V panels
Panels 1 and 2 can output 6A, but partial shading reduces #3 to 2A.
In the series config, there are two choices:
1) maintain voltage and reduce current to 2A for all three panels
2) cut the underperforming portions of the panel out of the circuit by reducing voltage and allowing 6A to flow from unshaded/partially shaded panels.
In the 3P config, you'd get 6A/Vmp from the two unshaded panels AND 2A/Vmp from the shaded panel.
Awesome thank you! So with your 3 example panels where 1 is shaded and 2 are in full sun, you would get:
In series:
Either 2A * 300V = 600W, or 6A * 200V = 1200W.
In parallel:
(6A * 200V) + (2A * 100V) = 1400W.
Is that correct? That is assuming that partial shading would still result in 1/3 power coming out of the solar panel. From what I've seen with my small 12V 100W panels is that covering just one cell reduces power to 10%.
sunshine_eggo
Happy Breffast!
Looks right. A single cell taking out 90% of the panel is atypical, but your panels may have fewer bypass diodes. I think 36 cell panels have fewer bypass diodes, so I could see it taking out 50% of the panel.
It might be about the MPPT algorithm too. Next time you're experimenting, watch the PV current and PV voltage in TRENDS. Every 10 minutes, a Victron MPPT conducts a MPPT sweep. You may find that after up to 10 minutes, the MPPT has found a better max power point.
