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Old 20-08-2019, 15:12   #1
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Solar Performance in the Med

Hi all,

I am having issues generating solar power in the Med. it was fine in the Caribbean but please see pictures below.

On a sunny day, in direct sunlight around midday, on 17th July in Sicily, I was only generating 51W from my 2 x 150W solar panels.

How can that be? Anything I should be looking at or checking?

They are fairly cheap panels from Amazon however, they were generating 170-200W in the Caribbean.

Any thoughts or help would be appreciated?

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Old 20-08-2019, 16:50   #2
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Solar Performance in the Med

One obvious answer is that you are further north.
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Old 20-08-2019, 16:56   #3
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Re: Solar Performance in the Med

...And casting shadows across them. This will cut output down dramatically.
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Old 20-08-2019, 22:01   #4
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Re: Solar Performance in the Med

test them each seperatly. are you getting 25w from each, or 50w from one and 0 from the other? a good first question.
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Old 21-08-2019, 00:04   #5
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Re: Solar Performance in the Med

Something is wrong, in the summer you should get much more in the med than in the Caribbean, much more sun hours per day in the med.
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Old 21-08-2019, 00:13   #6
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Re: Solar Performance in the Med

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Originally Posted by smac999 View Post
test them each seperatly. are you getting 25w from each, or 50w from one and 0 from the other? a good first question.


I am getting roughly equal output on both. About 25W each.

And also, obviously the figures I am getting are without shadows, good placement etc. I have tried various setups but even not to be getting over 100W from 300W of solar panels in the midday European summer sun must be pointing to something wrong.
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Old 21-08-2019, 01:21   #7
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Re: Solar Performance in the Med

25w from a 150w solar panel indicates something is very wrong if this is without shaddow and in reasonable sun in the Med this time year.

As it is both panels have low output this suggests the fault lies somewhere else. The solar controller or the connections shared by both panels would be first places to start looking.
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Old 21-08-2019, 01:59   #8
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Re: Solar Performance in the Med

The regulator is shot?
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Old 21-08-2019, 02:25   #9
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Re: Solar Performance in the Med

What state are the batteries when this occurs? Are they discharged enough that they could accept full current from the solar?

If yes, then I'm with Noelex; either the controller or the connections. One connection with even moderate resistance (a tenth of an Ohm or less) could cause the controller to see a higher voltage than the batteries and switch to float mode. If it's hard to get at all the connections, use a voltmeter and measure the voltage at the solar controller (battery side) and again directly at the battery posts. Doesn't even matter if it's a good meter, it should read the same at both locations. If it differs by more than say 0.1 Volt then it's time to check all the wiring. If the voltage is the same then not likely a bad connection on that end, could be the controller or the panel wiring although from the description I would rate that less likely.
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Old 21-08-2019, 04:03   #10
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Re: Solar Performance in the Med

I would swing your boom to port or starboard, to allow for direct sunlight on your solar, to
see how much you harvest on a sunny day, you should be able to determine if its the shadow that's the problem. if so I would consider an arch, to mount your solar on.
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Old 21-08-2019, 04:18   #11
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Re: Solar Performance in the Med

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Originally Posted by Dsanduril View Post
What state are the batteries when this occurs? Are they discharged enough that they could accept full current from the solar?

If yes, then I'm with Noelex; either the controller or the connections. One connection with even moderate resistance (a tenth of an Ohm or less) could cause the controller to see a higher voltage than the batteries and switch to float mode. If it's hard to get at all the connections, use a voltmeter and measure the voltage at the solar controller (battery side) and again directly at the battery posts. Doesn't even matter if it's a good meter, it should read the same at both locations. If it differs by more than say 0.1 Volt then it's time to check all the wiring. If the voltage is the same then not likely a bad connection on that end, could be the controller or the panel wiring although from the description I would rate that less likely.


Great advice, I’ll have a look.

The controller is only 9 months old (VictronConnect Blue Solar) so the current suspect might be the connections.

They are flexible, movable panels so I have been changing position and angle to no improvement.
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Old 21-08-2019, 09:22   #12
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Re: Solar Performance in the Med

Shade is you enemy , your picture shows shawdow on your panels
how are they wired , series or paralell,
Make sure you take your readings on midday no shade
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Old 21-08-2019, 11:08   #13
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Re: Solar Performance in the Med

Firstly you are further north than the Caribbean in general so that will have an impact on performance due to solar incidence angles so take that into account.

While there are slightly more daylight hours during the Med summer over the Caribbean Wet the difference isn't that great as solar performance in the early/late hours is absolutely minimal compared to the core hours of about 9am to 4pm which equates to the same hours in the Caribbean. Besides the number of hours only really comes into play when you are worrying about amp-hrs rather than max power output.

If it helps I have a semi-flex 100w panel tied flat onto the top of my bimini or to the coachroof (when on the hard). At 12v this should give a max output of 8.33amps, at 13.8v it is 7.25amps. However I rarely see more than 5amps even in full Greek sunshine at midday. This is probably due to the panel being flat rather than at the optimum angle, possibly being dusty or dirty (I do clean it regularly) or voltage losses along the very long cable runs (I have increased cable sizes accordingly but it's still nearly 12m). Then add in the connectors, controllers and all the other hardware it probably all adds up to the loss of efficiency.

Then of course no solar panel is 100% efficient even under lab conditions and they do degrade with use. Domestic panels loose a few % every year and after 20 years can be down to 75% of their original rating. Marine panels are probably the same and "cheap panels from Amazon" probably worse as they are unlikely to be constructed for the harsh marine environment. So it could just be wear and tear.

Hope that helps

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Old 22-08-2019, 04:15   #14
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Re: Solar Performance in the Med

You are further north from the equator. In short the sun is less overhead.
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Old 22-08-2019, 04:29   #15
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Re: Solar Performance in the Med

Quote:
Originally Posted by lawrence_craig View Post
I am getting roughly equal output on both. About 25W each.

And also, obviously the figures I am getting are without shadows, good placement etc. I have tried various setups but even not to be getting over 100W from 300W of solar panels in the midday European summer sun must be pointing to something wrong.


I get about 200w at a time max from 4 120w panels and 80-100 from two 110w panels together.

It’s just the nature of the beast. It still adds up to over 2kw a day for me from a total of 620w. So basically panel rating x3.2

Normally x4 or x5 would be expected in ideal conditions
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