Do not allow shadows to fall on your solar panels.

Only needs bit of shade on a small area to seriously cut output. I did a little experiment last year just covering a hand sized area of 40W panel ...IMG_5692.JPGIMG_5691.JPGIMG_5690.JPG


Lowest picture shows short circuit current win full sun. Top two show output with about ten square inches of panel obscured.

Cheers

H
 
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Good demo, Phil.
People don't generally realise that shading such a small amount would wipe out the panel harvest - AND all other panels connected to it in Series.
For a lesser installation with fewer panels, "accepted wisdom" is put them all in series to maximize voltage. But maximizing voltage also mazimizes the impact of shading. Pays yer money ......
 
This is quite amazing really... I wish I understood the science behind why this is the case! How can such a drop happen when just one cell out of so many is shaded?
Surely this is something the manufacturers need to address. It just doesn't make any sense to me brain ha ha.

So would the same drop in power being harvested be seen if say 8 panels of a lower wattage but totalling the same overall output were used?
 
Found this...
"If even one full cell is hard shaded, the voltage of a solar panel drops to half in order to protect itself. ... Partial shading of even one cell on a 36-cell solar panel will reduce its power output. Because all cells are connected in a series string, the weakest cell will bring the others down to its reduced power level."

Now I see. 🌞
 
Apologies for the frivolity, couldn't resist.

Interesting Phil, I am surprised covering one cell makes such a difference. You mention that they are wired in series, what are the reasons for not in parallel ? and what would the impact of shading a cell have then ?

Paul
 
My panels are wired in two parallel strings of two panel in series. The reason for not going totally parallel is that the amps in the cable would be quite high. At 35 amps in 6mm cable, I would lose some power in heat.
 
I have 4 panels, until recently wired up in a series-parallel combination.
I have this chart showing the effect of moving from my normal parking position where I get some tree shading to 4 foot further down the driveway ...
SolarYield by David, on Flickr
Instant jump of solar harvesting by 200%!
 
wildebus said:
I have 4 panels, until recently wired up in a series-parallel combination.
I have this chart showing the effect of moving from my normal parking position where I get some tree shading to 4 foot further down the driveway ...
SolarYield by David, on Flickr
Instant jump of solar harvesting by 200%!
Click to expand...
Well obviously because you just moved out of the shade as you state? But that hardly equates to the difference of just one square being shaded, though it's all quite interesting stuff.
 
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Phantom said:
Well obviously because you just moved out of the shade as you state? But that hardly equates to the difference of just one square being shaded, though it's all quite interesting stuff.
Click to expand...
The point is moving just 4 foot from partial shade to no shade should make such a difference (that is a smaller distance than the size of the panels). And also that if I was all series-connected would likely have had no solar.
It was just a comment on a real-world situation and how such a subtle difference in parking can have such a big effect - for example, there is a comment earlier with someone saying his panels are the highest part of his van - so he won't get shade from roofrails or an aerial - but he may well do from SOMEONE ELSES aerial - or a lamp post, or flagpole, or ......
 
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I did a similar test when I had solar panels. Some of my favourite camping spots have trees and partial shade and I was disappointed by the performance. On my new motorhome I have gone for the more expensive option of an Efoy and here I am in the SW of England, with little prospect of any sun over the next few days, generating a steady a steady current of over 5A. It doesn’t sound a lot but in 24 hours it can push out 140Ah which is 2 or 3 times my daily consumption. At some stage in the night it detected that the battery voltage had dropped and turned itself on silently. I use a CPAP all night and running out of power is not a comfortable option. This morning the battery is showing an at rest voltage of 13.5V.

The downsides are mostly cost. Cost of installation and cost of fuel. It is early days yet but I estimate that I use about £2/3 of fuel a day, which is less than the cost of a hook up but a lot more than free solar power. I also reckon there is a weight advantage with the Efoy, 15Kg with a full fuel container and no need for a second battery.
 
The Efoys can be a pricey way to get power, but that price can be worth paying when it comes to the need of say running a piece of medical kit like a CPAP machine - in which case it is 100% sense to make that investment (y)
 
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