Anyone with WSW array in SoCal

[FFE]

If you are in SoCal with a WSW array I would like to hear how many DC watts (STC) your system is and how much energy you created on Nov 16, 2015.

Please post up your azimuth, roof pitch lattitude and estimated shading. I am trying to compare my system to a similar unshaded array. My estimate is about 3.3 kWh generated/ DC kW.

For example: Mine is 5.3 kW, 14.4 kWh, 240 degrees, 4/12 roof (18.4 degrees), 34 degrees north about 15% shading

The reason I ask is because I would like to make sure I have good information on the video I am working on. It seems that most of the info on the web for string inverters claims that one shaded panel will bring down the entire array or one cell shaded reduces output by 50% etc. I found this to be pretty bad information and made a video to show my real life scenario. I did find one video made by a panel manufacturer to show how much better their panel was in the shade. It showed about 29% loss with a string inverter and 28% loss with micro inverters versus 14% loss on a string inverter for their product on a partially shaded panel. Nowhere near what most other sources claim.

[sensij]

Just look on PVOutput.org, a link is in my signature. You'll find a system close to what you've described if you look at Team San Diego. There are a few west facing systems that were in the 3-4 kWh/kW range today.

My system is south facing, produced 4.787 kWh / kW (yours was 14.2/5.3 = 2.679 kWh/kW). Same tilt as yours, with just a little bit of evening shade at this point in the year. Sounds like your system is getting hammered hard by shade.

[FFE]

Thank you sensij! I was able to search and find someone with a west facing system with a 27 degree tilt nearby with no shade. They had 3.6 ratio today. My system was designed with the shade in mind and I still overproduced $$ wise today. Most of the shade will be eliminated in the summer when I need it most.

Found another with identical specs as mine with a 3.5.

[J.P.M.]

Yesterday (11/16/2015) was about as good a day for solar production as it gets for this date at my location. GHI was recorded as about 99% of a theoretically clear sky. Temps. were less/different than TMY data for the date.

For your size, location (latitude) and orientation, yesterday, with no shading and a clean array, if your location was similar in clearness to mine, your array ought to have produced something like, VERY approx. 21 to 22 kWh of electricity for the day, or about 4.0-4.1 kWh/S.T.C. kW. Shading, dirt or other things would have reduced that #.

Add: Output for my 5.232 kW sys. @ 18.75 tilt, 195.75 az. was 25.79 kWh ~= 4.85 kWh/kW w/ about 2.5% fouling and ~ 3.5% reduction in daily output for late afternoon shade. FWIW, note similarity to Sensij's output/kW even though I've got S.P. and he does not. Orientations are similar. I'm about 15 deg. further west.

[J.P.M.]

If you are in SoCal with a WSW array I would like to hear how many DC watts (STC) your system is and how much energy you created on Nov 16, 2015.

Please post up your azimuth, roof pitch lattitude and estimated shading. I am trying to compare my system to a similar unshaded array. My estimate is about 3.3 kWh generated/ DC kW.

For example: Mine is 5.3 kW, 14.4 kWh, 240 degrees, 4/12 roof (18.4 degrees), 34 degrees north about 15% shading

The reason I ask is because I would like to make sure I have good information on the video I am working on. It seems that most of the info on the web for string inverters claims that one shaded panel will bring down the entire array or one cell shaded reduces output by 50% etc. I found this to be pretty bad information and made a video to show my real life scenario. I did find one video made by a panel manufacturer to show how much better their panel was in the shade. It showed about 29% loss with a string inverter and 28% loss with micro inverters versus 14% loss on a string inverter for their product on a partially shaded panel. Nowhere near what most other sources claim.

Cover 1 or more panels around solar noon on a sunny day and note the change in output.

[FFE]

Cover 1 or more panels around solar noon on a sunny day and note the change in output.

I conveniently have this done for me thanks to the trees. I will try this in late spring when I have full sun on all of my panels at solar noon.

It looks like I live in a solar black hole area. Homes within 20 miles of me that report on PV Out have 3.7-2.9 efficiency. For my video I used 3.5 since the closest I could find with no shade faced 225 degrees with identical slope and no shade.

According to PVWatts I would need a 4.3 kW system if I had a south facing roof with 30 degree tilt and zero shade to produce the same annual output. That is a much smaller difference in system size that I would have expected.

Thank you for providing me with your information.

Anyways, here is the video:

http://vimeo.com/146014068

[J.P.M.]

I conveniently have this done for me thanks to the trees. I will try this in late spring when I have full sun on all of my panels at solar noon.

It looks like I live in a solar black hole area. Homes within 20 miles of me that report on PV Out have 3.7-2.9 efficiency. For my video I used 3.5 since the closest I could find with no shade faced 225 degrees with identical slope and no shade.

According to PVWatts I would need a 4.3 kW system if I had a south facing roof with 30 degree tilt and zero shade to produce the same annual output. That is a much smaller difference in system size that I would have expected.

Thank you for providing me with your information.

Anyways, here is the video:

http://vimeo.com/146014068

I believe my clear sky #'s are pretty representative for your size, orientation and latitude.

Looking at your video, I'm a bit surprised your loses are as low as they are, but that's a mostly subjective opinion.

That 4.3 kW system size est. you write of for what's pretty close to ideal orientation for max. yearly production seems about right.

[sensij]

The impact of shade on a string inverter will depend strongly on the string architecture. With 20 panels going into a dual MPPT inverter, presumably split up so that each string has its own MPPT, you've got a more shade robust design than some. If you were at the low end for DC (or MPPT voltage) in any of those strings, or had strings in parallel going into a single tracker, the losses would likely be worse.

[FFE]

I believe my clear sky #'s are pretty representative for your size, orientation and latitude.

Looking at your video, I'm a bit surprised your loses are as low as they are, but that's a mostly subjective opinion.

That 4.3 kW system size est. you write of for what's pretty close to ideal orientation for max. yearly production seems about right.

Even if I estimated 4.1 kWh/S.T.C. kW. like you suggested I would only get 35% loss or if I compared directly to sensij it is only a 43% difference. This is much less than what you read on the internet. Based on most of the horror stories about shading , I should only have produced about 5-6 kWh.

Seems like our systems are very close in size. One way to compare my system to your system in full sun would be if you knew how much you produced yesterday from 8-9 am and 9-10 am. I believe my array has full sun from 8-9 am and produced 500 Wh. My array only has a little shade from 9-10 and produced 1500 Wh. Any chance you know what you produced and are willing to share?

[FFE]

The impact of shade on a string inverter will depend strongly on the string architecture. With 20 panels going into a dual MPPT inverter, presumably split up so that each string has its own MPPT, you've got a more shade robust design than some. If you were at the low end for DC (or MPPT voltage) in any of those strings, or had strings in parallel going into a single tracker, the losses would likely be worse.

1 string of 10 panels in series going into one MPPT and identical to the other MPPT.

[J.P.M.]

Even if I estimated 4.1 kWh/S.T.C. kW. like you suggested I would only get 35% loss or if I compared directly to sensij it is only a 43% difference. This is much less than what you read on the internet. Based on most of the horror stories about shading , I should only have produced about 5-6 kWh.

Seems like our systems are very close in size. One way to compare my system to your system in full sun would be if you knew how much you produced yesterday from 8-9 am and 9-10 am. I believe my array has full sun from 8-9 am and produced 500 Wh. My array only has a little shade from 9-10 and produced 1500 Wh. Any chance you know what you produced and are willing to share?

So much for believing everything you read or hear, or how it's interpreted.

Our arrays are close in size, and mfg., but much different in azimuth. What you suggest is pretty much useless. I can provide estimates of clear sky, unshaded hourly output for your location and orientation given your latitude, long., and your already provided orientation. That's how I got the 21-22 kWh clear sky, daylong est. for your approx. location. #'s will be approx. due to unknown array temp. profile, and unknown array fouling, among other things. Holler back w/ long. and I'll take a SWAG. I'll be out this P.M.

[FFE]

I can provide estimates of clear sky, unshaded hourly output for your location and orientation given your latitude, long., and your already provided orientation. That's how I got the 21-22 kWh clear sky, daylong est. for your approx. location. #'s will be approx. due to unknown array temp. profile, and unknown array fouling, among other things. Holler back w/ long. and I'll take a SWAG. I'll be out this P.M.

I was using actual data since I couldn't find anything easy to calculate full sun output. PVWatts shows 17.6 kWh for November 16, but that uses historical data that probably includes some shady days. I am sure someone has the software to figure it out. If I was motivated enough I could calculate it using a multitude of equations. I would use your SWAG over what is currently on the video and can delete the video it and put it up with better info.

Thank you for your help. I hope at some point if one person that thinks solar is useless at their house because they have one tree shading their roof changes their mind, it would be worth it.

N34.2 W118.9

[J.P.M.]

I was using actual data since I couldn't find anything easy to calculate full sun output. PVWatts shows 17.6 kWh for November 16, but that uses historical data that probably includes some shady days. I am sure someone has the software to figure it out. If I was motivated enough I could calculate it using a multitude of equations. I would use your SWAG over what is currently on the video and can delete the video it and put it up with better info.

Thank you for your help. I hope at some point if one person that thinks solar is useless at their house because they have one tree shading their roof changes their mind, it would be worth it.

N34.2 W118.9

More later, but for now, run PVWatts w/ a 8-10% system loss instead of the 14 % default, get the hourly output option and look for a "clear" day near the date you're seeking. It ain't perfect, but it's not too bad either.

[sunguy]

Thank you sensij! I was able to search and find someone with a west facing system with a 27 degree tilt nearby with no shade. They had 3.6 ratio today. My system was designed with the shade in mind and I still overproduced $$ wise today. Most of the shade will be eliminated in the summer when I need it most.

Found another with identical specs as mine with a 3.5.

I have 4 panels facing West, here in SoCal.

[sensij]

Found another with identical specs as mine with a 3.5.

Which system are you looking at?