Electronics > Power/Renewable Energy/EV's

Optimisers for solar panel shading

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--- Quote from: Siwastaja on March 16, 2023, 06:30:00 pm ---(Oh I hate intellectual dishonesty and discussions where agenda overrules technical understanding. As end result, problems do not get fixed, but random technical choices are done until the solution works by luck, or someone gives up. Since the false FUD campaigns of SolarEdge and others causing such large damage to collective intellectual understanding, the least we can do is to not spread the same old myths.)

--- End quote ---

Then you won't mind me pointing out the fallacy or misstatement in your critique:

--- Quote ---With the exact same logic, optimizers and microinverters do not work at all if you find a single example where they do not work (and you'll find).

--- End quote ---

I've never said that they don't work at all, nor that one issue with one product condemns them all.   What I am pointing out is that simply because a theoretical solution to a problem exists, even if widely implemented, it doesn't follow that the solution has always been implemented.  I believe you have actually posted that your own string system does not track properly because the inverter is oversized.  The OP clearly has a string system that isn't working ideally.  Shading and DC-arc fires do happen and are almost entirely associated with string systems.  Neither your issue nor the OP's nor most solar system fires would have happened with micros.  Do you deny any of that?

As far as spreading FUD and 'old myths', I pointed out in my very first reply that a properly designed string system and an inverter with global MPPT would likely not have this issue.  Would your 'intellectual honesty' require me to suppress actual facts and examples of real systems that have these problems, however rare you think they are, in service of some mandated truth or forced consensus? 

I think the most you could possibly say and maintain any claim to intellectual honesty, even in response to what you consider false and misleading advertising, is something like this:

First, acknowledge that optimizers and micronverters do fully solve shading issues and further acknowledge that microinverters mitigate DC-arc fire hazards completely or nearly so.  Or, if you disagree, provide evidence to the contrary.  Then you may claim that properly implemented DC string systems with properly sized and operable global MPPT can acheive shading peformance as good or nearlys good as optimizers/micros, provided you don't have extremely heavy shading.  And you may also claim that properly installed DC strings that use properly matching connectors of a type that have not been shown to be defective are fairly unlikely to start a fire. 

But if you are going to be honest, you have to also acknowledge that there are a certain number of DC-string systems that don't meet the stated criteria.  Like yours, the OP's and a whole bunch of commercial installations on WalMart roofs.  Your claim that DC string systems are common and have a good overall record has nothing to do with discussing a particular failure mode or example.  Understanding these issues helps us all avoid them, pretending they don't exist to support a 'correct' narrative does not. 

b/t/w, just as an aside, I've seen a fair number of solar installations that are not working or not working properly.  It's not rare.  To the extent that newer ones might be better, it is because lessons have been learned, some of them along the lines of this discussion. 


Part of the discussion is also price. If I look at the Enphase micro inverters (MQ7 / MQ8) then I notice that 1) they cost almost the same as an entire solarpanel 2) they can't deal with a modern day panel running at full power. Even with the reasonably low prices of the solar panels, the time the system starts to pay itself back is very long  (assuming you have the system installed). I agree DC strings are not the most ideal solution from a technical POV and need attention when being installed but they are about the only choice if you want to have a ROI at all.

All modern string inverters are within 2-3% of microinverters under any shading condition.


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