Real world solar panel results in clouds and rain

[rmaddy]

I've just recently mounted three 330W panels in series (990W total). They are Silfab SIL-330 BL panels. They are mounted flat on the roof of the trailer.

It is 2pm as I type this, 90ºF, and the sky is gray with 99% cloud cover. I'm at 39.75ºN latitude. I just checked and my panels are producing 315W of power. 32% seems pretty good for the cloud cover. Just curious what other people see on cloudy/overcast days.

I was just about to post this when the sun poked out a little and my panels were showing 940W briefly (the first time I've seen it that high). Then it settled around 750 for a bit. Now it's shaded again and down to 350W.

Here's a shot of the sky when I was seeing 315W:



And a view of my trailer while the sun was poking out a bit:

 

[circus]

Sounds about right. My two new Heliene 360's often produced over 200w while raining. As expected, my limiting factor are the batteries. I wanted to avoid what often happens to noob's. They spend a lot of money on small panels just to end up throwing them away to upgrade later.

 

[HRTKD]

I don't know that I see that many watts during cloud cover, but I suppose it depends on the clouds.

@rmaddy, that's a sharp looking trailer. I've had good luck with Haulmark. BTW, your gutters need to be cleaned.

 

[rmaddy]

that's a sharp looking trailer.

Thanks. The inside looks even better.

BTW, your gutters need to be cleaned.

LOL. I was hoping no one would notice that in the picture. The rest are clean but I can't get to that side until the trailer is moved offsite next week.

 

[wattmatters]

Just curious what other people see on cloudy/overcast days.

It depends on the nature of the cloud. Light sparse cloud which diffuses the light can actually be pretty good for production. But solid cloud and rain is lousy for output.

As an example about 4 weeks ago I got 3.7kWh for a day out of my home array. Rainy winter day. Yesterday was sunny and I got 44.6kWh. My peak output is over 70kWh/day.

I was just about to post this when the sun poked out a little and my panels were showing 940W briefly (the first time I've seen it that high). Then it settled around 750 for a bit. Now it's shaded again and down to 350W.

Cloud lensing of the sun's rays sometimes happens when the sun pokes out from behind a cloud and it can actually result in output briefly exceeding the rating of your panels, or at least higher than what is to be expected based on the panel's orientation relative to the sun.

 

[rmaddy]

@wattmatters Good info. Thanks.