Estimating panel output of flat mounted panels?

[SunEagle]

(Finishing last post) 12 from flat June was best flat

June is when the sun is highest in the sky for North latitudes. My guess is that there was less blockage from clouds and more reflection towards the panel during that month.

[J.P.M.]

Its mostly a matter of how much solar radiation is intercepted. If the suns rays are not perpendicular
to the panel surface, try the cosign of the angle difference. Bruce Roe

Bruce: That works reasonably well under cloudless and very clear skies but still not as good as you might think. Even then, believe it or not, about 15-20 % of the irradiance is diffuse with about half of that diffuse coming from all over the sky dome. Under hazy but sunny skies, about 1/3 to 1/2 of the irradiance might be diffuse. Obviously under cloudy skies, it's all diffuse.

[Ho jo]

My thoughts were the sun rises at 6 am at 60 degrees it's not until 9:45 that it's at 90. 3 1/2 hours morning and afternoon the sun is behind the panels if there tilted south.laying flat even with the sun so low gives 7 more hours of weaker light on the panels. Just trying to learn

[J.P.M.]

My thoughts were the sun rises at 6 am at 60 degrees it's not until 9:45 that it's at 90. 3 1/2 hours morning and afternoon the sun is behind the panels if there tilted south.laying flat even with the sun so low gives 7 more hours of weaker light on the panels. Just trying to learn

If trying to learn, consult a solar textbook such as Duffie & Beckman or similar for details about solar geometry, irradiance on a plane of any arbitrary orientation and attenuation of irradiance by the earth's atmosphere. Doing so will be very instructive and not lead you astray as you seem to be at this time.

[bcroe]

My thoughts were the sun rises at 6 am at 60 degrees it's not until 9:45 that it's at 90. 3 1/2 hours morning and afternoon the sun is behind the panels if there tilted south.laying flat even with the sun so low gives 7 more hours of weaker light on the panels. Just trying to learn

You might try setting up some panels with varying directions and variable angle, and check output
over half a year and over the day. That is what the 3 single panels here are doing, I learned a lot.

Another good tool is a Solar Pathfinder or one of many equivalent tools. Bruce Roe

Test3dir.jpg

Pathf2.jpg

[Ho jo]

Thanks bcroe I was thinking of trying something along that line I'm more about hands on experimenting.

[J.P.M.]

Thanks bcroe I was thinking of trying something along that line I'm more about hands on experimenting.

Me too, but I confirm with experiment after I learn. Makes the experiments more focused and I learn more. Can't have one without the other.

[Ho jo]

Point taken and agree. I usually do things backwards experiment first then try and figure out why last.

[PNW_Steve]

Great discussion....

Unfortunately, I am no closer to an answer to my question.

Perhaps my best option is to go ahead and mount all 1800 watts of panels and use the charge current limiting feature on the Midnite Classic/Whizbang Jr. combo to avoid boiling my batteries.

[Ho jo]

On pv watts for my location in dec 4.7 @62 degrees and 2.51 @0. (53%) But in june horizonal is the best. Check pv watts as jpm recommended with your zip.

[J.P.M.]

OK. Your question was what have folks found about a horizontally oriented array's output vs. the same array's output at some other orientation, right?

As has been described at least a couple of times in this thread, PVWatts or some other reliable model will provide an estimate of what you might be looking for.

Seems to me a lot of what you call great discussion has been pertinent to helping you gain some insight into your question.

Sorry that anything I wrote didn't meet your expectations.