North facing Panels

[J.P.M.]

At 7 deg tilt, the penalty for north facing isn't as much as for steeper installations. It is possible that the numbers still come out good enough to justify the choice.

Looks closer to 45 deg. tilt to me. Maybe 7 deg. Az. ? Bet the trees aren't helping much either.

[rsilvers]

7 degrees was the heading. Angle is 40 degrees.

PVWatts says that the south side will make 2.1x as much power as this side.

That makes a $4.50 per watt system act like a $9.45 per watt system that faces south.

But yeah on angle. My west-facing panels are going to be at 15 degree angle, so I am going to lose about 18% vs a south face. Had they been at a 40 degree angle, I would lose 25%.

The western orientation is going to make my 315 watt panels act as if they are 260 watt facing south.

[jflorey2]

I just saw this today. It is facing North at 7 degrees. They also have panels on the south of this shed and of their house. The installer put conduit over and around their gutter. I am going to guess this is not free solar PPA as I don't think any installer would have put panels on the north as it would eat into their profits.

On the plus side, all the shade from the trees above the array won't matter as much.

[sensij]

At 7 deg tilt, the penalty for north facing isn't as much as for steeper installations. It is possible that the numbers still come out good enough to justify the choice.

[SunEagle]

I wonder if that person would be interested in buying a bridge?

[rsilvers]

I just saw this today. It is facing North at 7 degrees. They also have panels on the south of this shed and of their house. The installer put conduit over and around their gutter. I am going to guess this is not free solar PPA as I don't think any installer would have put panels on the north as it would eat into their profits.

[J.P.M.]

There are a lot of good things said so far but I have a little different feeling about this.
Given that ROI on PV is kind of low at best when you degrade the output ROI goes way up.
Ask your self if the North facing panels were your only project would you do it.
If you have tiered billing the South array will really cut into your bill and should keep you in the cheep electric rates.

To pay for the North array after your bill is lowered by your South array seems like a real looser.

On the other hand is this a PPA?
If the north array does not produce any electricity what happens to your billing?
Unless your condition is artificially enhanced by the contract I would make them take the North array out of the deal.
They may not even want to come back, remove the array and redo your roof. Get the contract rewritten for just the South array and see how that looks.
Then you may consider a West array but you should evaluate it on its own merritt.

What is the panel name plate rating. You are only getting about 150 watts / panel Something seem really wrong even for your best array. Your inverter seems way over sized.
Seems like you have 260 watt panels producing 150 with great sun. What is you slope? Latitude? Is it getting any better with sun angel change?
What happens if you buy a 11KW system and it works like a 4 KW system?

While folks who peddle PPA's may use people's solar ignorance to make money, I doubt their all so stupid as to get themselves in a situation where their property - the array - would produce poor revenue by peddling an array to a homeowner with a lousy orientation. Double/accelerated depreciation and other tax breaks homeowners don't get are nice but there are other suckers with better orientations for their equipment that will produce more revenue for the array owners. If the PPA needs a higher price/kWh to make up for a poor orientation, that will decrease the competitiveness of the product.

[john phillips]

There are a lot of good things said so far but I have a little different feeling about this.
Given that ROI on PV is kind of low at best when you degrade the output ROI goes way up.
Ask your self if the North facing panels were your only project would you do it.
If you have tiered billing the South array will really cut into your bill and should keep you in the cheep electric rates.

To pay for the North array after your bill is lowered by your South array seems like a real looser.

On the other hand is this a PPA?
If the north array does not produce any electricity what happens to your billing?
Unless your condition is artificially enhanced by the contract I would make them take the North array out of the deal.
They may not even want to come back, remove the array and redo your roof. Get the contract rewritten for just the South array and see how that looks.
Then you may consider a West array but you should evaluate it on its own merritt.

What is the panel name plate rating. You are only getting about 150 watts / panel Something seem really wrong even for your best array. Your inverter seems way over sized.
Seems like you have 260 watt panels producing 150 with great sun. What is you slope? Latitude? Is it getting any better with sun angel change?
What happens if you buy a 11KW system and it works like a 4 KW system?

[J.P.M.]

Sun out all day in S. Calif. You can see te peak is about 6.8 around 1 pm. This is with one south facing 6 KW system and one north facing 5 KW system. About 5 KW system is from the southern facing panels and 2 KW from the north facing panels.

Based on today's output at this time of year what might I expect in June?

Run PVWatts with the hourly output option and 10 % system losses. Look for a high output symmetric clear day around this date. You'll get a reasonable SWAG.

[compchat]

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Picture should go with prior message.

[compchat]

Sun out all day in S. Calif. You can see te peak is about 6.8 around 1 pm. This is with one south facing 6 KW system and one north facing 5 KW system. About 5 KW system is from the southern facing panels and 2 KW from the north facing panels.

Based on today's output at this time of year what might I expect in June?

[JFinch57]

I would have a Suneye analysis done to find out which has the least shading, east or west. No matter how perfect it looks one will be better. The north panels should be moved ASAP!

[J.P.M.]

Good point. I just related "clouds" as being a heavy overcast and not something that will allow any significant light through.

Adjuncts to Murphy's law, particularly with research or reality: Constants aren't, variables won't and absolutes never happen.

[SunEagle]

That depends to a large degree on the nature of the cloudiness. Solid, heavy overcast will produce what is mostly isotropic GHI at a flux rate that might be ~ 5-10+ % or so of a clear sky value (say a GHI value of ~ 50 - 100 W/m^2 or so). If the cloud cover is not quite as solid, say with a GHI of ~ 200 W/m^2 or so, the area of the sky around the sun may, depending on the atmospheric conditions, be the source of more of the irradiance. In those situations, often in the morning before the A.M. haze burns off, but other times as well, equator facing arrays may see increased output that could be measurably higher than output from arrays facing away from the equator, particularly if the panels have somewhat better low irradiance performance - some of which BTW and sort of off topic, will be the result of lower operating temps due to lower irradiance.

Good point. I just related "clouds" as being a heavy overcast and not something that will allow any significant light through.

[J.P.M.]

When it is cloudy I would expect the South facing would not produce much of anything.

So if the North is 50% of the South then IMO 1/2 of "a little bit" is next to nothing and might not have been worth the extra expense for those North panels.

That depends to a large degree on the nature of the cloudiness. Solid, heavy overcast will produce what is mostly isotropic GHI at a flux rate that might be ~ 5-10+ % or so of a clear sky value (say a GHI value of ~ 50 - 100 W/m^2 or so). If the cloud cover is not quite as solid, say with a GHI of ~ 200 W/m^2 or so, the area of the sky around the sun may, depending on the atmospheric conditions, be the source of more of the irradiance. In those situations, often in the morning before the A.M. haze burns off, but other times as well, equator facing arrays may see increased output that could be measurably higher than output from arrays facing away from the equator, particularly if the panels have somewhat better low irradiance performance - some of which BTW and sort of off topic, will be the result of lower operating temps due to lower irradiance.