Looking for a Solar array angle comparision site?

Photowhit

So I use to have the site tabbed, many computers ago, that let you plug in the direction and angle of your array and compare monthly output. I can't find the site now. Anyone have this in their tabbed solar sites?

I finally installed my East, South East array to catch morning sun and would like to compare angles and output, Right now it's leaning against my porch, which is fine but I need to finish and put bracing to the back of the frame. It can and will, somewhat lean over the porch, if I won't lose much I might make the top in line with the porch. About a 20 degree difference from 55 to 75 degrees.

Horsefly

PVwatts (http://pvwatts.nrel.gov/pvwatts.php) does let you put in an azimuth as well as a tilt. That seems like what you are wanting, but maybe I'm misunderstanding.

Steve

Photowhit

Thank you, not the one I was looking for, but it'll work.

BB.

The older (and more simple) PV Watts program was taken down (a couple years ago?) and replaced by the link Horsefly gave you.

This one is pretty simple and has lots of international locations... Although at times, it mixes up the state of Georgia and the Eastern Europe Georgia...

http://www.solarelectricityhandbook.com/solar-irradiance.html

Anything specific from a solar calculator you are looking for?

-Bill

Photowhit

Thanks Bill, nothing specific, guess I would really like an hour by hour breakdown, but seeing that 55 and 75 degree angles are very close in production (at 120 ESE), I can interpolate that I'll not be sacrificing much with a higher angle. The lower angle would accept more charge later in the morning, but my main array will be producing by then. The array hangs over the porch right now, at 70-75 degrees it will be about flush with the porch. I didn't want the base to go farther out into the yard past my steps. I'll grab a photo later.

BB.

The new PV Watts site does have hourly data too on the last page:

"PVWatts: Hourly PV Performance Data"
"Requested Location:","san mateo ca"
"Location:","SAN FRANCISCO, CA"
"Lat (deg N):","37.62"
"Long (deg W):","122.38"
"Elev (m):","5"
"DC System Size (kW):","3.5"
"Module Type:","Standard"
"Array Type:","Fixed (open rack)"
"Array Tilt (deg):","20"
"Array Azimuth (deg):","180"
"System Losses:","14"
"Invert Efficiency:","96"
"DC to AC Size Ratio:","1.1"
"Average Cost of Electricity Purchased from Utility ($/kWh):","0.16"
"Capacity Factor (%)","17.7"   

"Month","Day","Hour","Beam Irradiance (W/m^2)","Diffuse Irradiance (W/m^2)","Ambient Temperature (C)","Wind Speed (m/s)","Plane of Array Irradiance (W/m^2)","Cell Temperature (C)","DC Array Output (W)","AC System Output (W)"
"1","1","0","0","0","3.9","2.1","0","3.9","0","0"
"1","1","1","0","0","4.4","3.6","0","4.4","0","0"
"1","1","2","0","0","2.8","2.1","0","2.8","0","0"
"1","1","3","0","0","3.9","0","0","3.9","0","0"
"1","1","4","0","0","1.7","1.5","0","1.7","0","0"
"1","1","5","0","0","1.7","1.5","0","1.7","0","0"
"1","1","6","0","0","1.7","1.5","0","1.7","0","0"
"1","1","7","32","14","2.2","0","22.629","-1.012","69.804","49.045"
"1","1","8","363","49","2.8","0","206.482","8.825","617.984","585.53"
"1","1","9","590","73","5.6","0","423.381","21.962","1253.362","1203.692"
"1","1","10","701","90","6.1","1.5","594.559","23.144","1782.286","1715.285"
"1","1","11","749","100","6.7","2.1","694.045","25.297","2071.674","1994.039"
"1","1","12","750","103","7.2","2.1","708.536","26.464","2105.07","2026.154"
"1","1","13","711","101","7.2","1.5","642.563","26.639","1901.646","1830.357"
"1","1","14","650","81","7.8","0","506.732","30.192","1457.836","1401.79"
"1","1","15","483","60","7.2","1.5","304.39","16.229","904.945","865.203"
"1","1","16","137","28","6.7","1","81.172","8.542","237.9","213.866"
"1","1","17","0","0","6.1","1.5","0","6.1","0","0"
"1","1","18","0","0","4.4","2.1","0","4.4","0","0"
"1","1","19","0","0","3.9","1.5","0","3.9","0","

-Bill

mcgivor

Non scientific method: Drive a nail or screw into a board at 90°, place the board at the angle of tilt/direction and watch  the length of the shadow. Perform during the solstice, winter or summer depending on what season you want the most production, or adjust 11.5° for average throughout the year. Takes care of directional  orientation without the need of a compass, simple but effective.

Photowhit

Haha, not sure I want to wait until next year and chart the length of a shadow for 3 months over 3 hours during the morning.  Not even sure that would be very accurate since the angle into the panels will vary the reflective and absorbed energy...

I'm actually capable of doing the math, but it would take some time for me to setup. I'm much too lazy for that...

I think I have my answer and will check Bills hourly, and see how it works.

westbranch

Crewzer, one of the Mods about 7 years ago clewed me in....  it's called a GNOMON

mcgivor

westbranch said:

Crewzer, one of the Mods about 7 years ago clewed me in....  it's called a GNOMON

Yes, a sundial, however in this case you want to minimize the shadow.

littleharbor2

I thought this was a pretty ingenious little item. It clips onto the back of the frame.

mcgivor

With the nail method, I used a marker to plot where the shadow went during the day, when all the dots were closest to the nail that is the position chosen, same idea as the fancy set up above, but whoever came up with that probably is making money, kind of hard to sell a board and nail for $29.99 plus shipping 

marissadsilva

Hello, I think there would be no need to comparison Solar array angle. solar-electric.com is the best site to buy all kind of Solar instruments.

mcgivor

Some interesting reading on angle of tilt.
http://www.solarpaneltilt.com/

Horsefly

mcgivor said:

Some interesting reading on angle of tilt.
http://www.solarpaneltilt.com/

Yeah, I bookmarked that page last year when  I was looking for anything and everything that might help me.  It really has some good data.  I wish the guy showed more of the math of how he got these angles (he does a little in one paragraph), but I also see that he's offering some consulting service, so it's OK that he doesn't give away all the secret sauce.  Anyway, I'm planning on using some of his data to position our panels up at the cabin.

Unfortunately, for @Photowhit the site provides info on tilt, but not azimuth. 

Steve

westbranch

In theory the max power should be at solar noon, the tables should get you close but you need to 'localize' the azimuth for your site and for that the gnomone can come in handy, an 8 inch  Carpenters square works great laid on the panel and watching for the peak