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Solar PV Shading, a Shady Tale!


(Dave) #1

Hi all
I thought it would be useful to highlight the detrimental effect even minor shading has on a panel and/or string.
I got my script working again that pulls data from my micro inverter working so I can monitor the output from each panel. I had noticed that one of my panels was producing a reduced output (19%)

Solar

I investigated when I got home and found the following flower covering less than a cell on one panel!
TBH I was gob-smacked on the effect of this minor shading and how much it affects the output of the panel!
The moral of the story is to not underestimate any shading on PV panels…

Regards
Dave


(Robert Wall) #2

Here’s your solution, assuming that it’s allowed by The Management.

(Sorry, I couldn’t resist…)


(Dave) #3

Ive already told my neighbor I’m gonna be trimming her bush!

Regards
Dave


(Bill Thomson) #4

Bet you’re glad you don’t have a series string setup!


(Dave) #5

I put micro inverters on that array because I expected shading as the sun goes round but I would have never expected that much deterioration from that small amount of shading!

Regards
Dave


(Bill Thomson) #6

Given the cells in each module are series connected, it’s the same effect.
Only at the module level, vice the array level.

Shading is one of the reasons I went with micorinverters too. (Scalability was another)


(Jon Murphy) #7

On Monday, Aug 21 at 1:19 PM I’ll get to enjoy a solar eclipse! In Chicago 87% of the sun will be blocked by the moon. I’d like to add to Dave’s Shady post but I don’t have solar panels (yet).

For those of you with solar panels: Are you anywhere near the path of the eclipse?

This notice is appearing on Nest Thermostats:
jpg-mosaic


(dBC) #8

SolarEdge have a technical note that explains shading and why bypass diodes aren’t as effective as people think they are at saving them from shading:


(Bill Thomson) #9

From what the article says, as long as the MPPT is happening at module level, the loss is less than it would be with inverter level MPPT.

Since microinverter based systems have module level MPPT, it sounds as if they too wouldn’t suffer the increased loss.


(dBC) #10

Yep, I think the SolarEdge approach and the microinverter approach both have that in common. The only difference between them is whether you run AC around your roof, or DC and whether you have lots of little inverters, or one big one… each with their own advantages and disadvantages.