Mix portrait and landscape oriented panels in a single string

[solnisse]

Hi there!

I'd like to maximise the usage of my single roof area by mounting as many solar panels as possible on it. I can fit 6 rows with 9 panels mounted in landscape orientation. That gives me three strings with 18 solar panels in each string. Not so bad.

Now, I have the option to fit three more panels in portrait orientation. That is, to each existing string with 18 landscape oriented panels i can attach a single portrait oriented panel giving me 19 solar panels in each string. The additional panels will of course be mounted to the same rectangular roof area (parallell to the roof).

However, lately I have been thinking that it might be a bad idea to go ahead with adding the 19th portrait oriented panel... What if the both panel orientations (portratit vs landscape) doesn't always yield the same voltage/power at any arbitrary solar angle? Another way to put it, can a solar panel be spun like a fortune wheel without varying the power output? If not I guess I should avoid adding the 19th differently oriented panel to the strings.

I might not always be good in explaing things... can my question be understood?

Thanks in advance for any help!

Cheers!
57 paneler layout.jpg

[inetdog]

In the absence of partial shading you should not notice any difference in panel output between landscape and portrait orientation.
If a shadow falls across a panel the way that shaded cells are distributed among bypass diode groups may cause differences in output. (If a shadow hits 15 cells, all in one bypass group, you may lose only 1/3 of the panel output, but if the shadow hits cells in each of the typically three bypass diode groups you will lose the entire output of the panel.

Depending on the racking system you use, it may be physically difficult to mix orientations.

[J.P.M.]

A couple of other considerations unrelated to possible problems caused by panel orientation difference between/among panels if any partial shading exists.

If your sketch shows the entire roof area, you have little area for access.

1.) How will you service any panels that are inaccessible ? Doesn't (hopefuuly) happen too often, but it will. Cleaning can be another consideration. Again, not often, but if not necessary, at least good practice. It's not usually possible or practical to cover every m^2 of a surface with panels. Think ahead.

2.) Depending on any local building codes you may have, you may be required to have some open area(s) on the roof in specific places, often/usually done for for first responder (firefighter) access to your house/roof. I'd check for any local code requirements.

Add: Just saw you are in Sweden. Another consideration: Snow removal.

Valcommen till forumet om farre illusioner !

[ButchDeal]

A few things to consider:

Do you live in a state with required roof setbacks for fire code?
Did you account for the attachment bolts which go between the PV modules to clamp them to the rails?

There is no power issue with the strings mixing orientation, but you need to make sure that the rails line up with the correct area of the landscape modules and the portrait modules.

What inverter are you using for this system?

[solnisse]

In the absence of partial shading you should not notice any difference in panel output between landscape and portrait orientation.
If a shadow falls across a panel the way that shaded cells are distributed among bypass diode groups may cause differences in output. (If a shadow hits 15 cells, all in one bypass group, you may lose only 1/3 of the panel output, but if the shadow hits cells in each of the typically three bypass diode groups you will lose the entire output of the panel.

Thanks! Shadowing won't be a problem.

Depending on the racking system you use, it may be physically difficult to mix orientations.

It's a trapezoidal metal sheet roof. I'm using the K2 multrirail and I can mount them either horizonattly or vertically so it will be easy to solve. Thanks!

[solnisse]

A couple of other considerations unrelated to possible problems caused by panmel orientation difference between/among panels if any partial shading exists.

If your sketch shows the entire roof area, you have little area for access.

1.) How will you service any panels that are inaccessible ? Doesn't (hopefuuly) happen too often, but it will. Cleaning can be another consideration. Again, not often, but if not necessary, at least good practice. It's not usually possible or practical to cover every m^2 of a surface with panels. Think ahead.

2.) Depending on any local building codes you may have, you may be required to have some open area(s) on the roof in specific places, often/usually done for for first responder (firefighter) access to your house/roof. I'd check for any local code requirements.

Add: Just saw you are in Sweden. Another consideration: Snow removal.

Valcommen till forumet om farre illusioner !

Thanks for your reply.

1) The sketch shows the south facing side of the roof only.I believe servicing will be a nightmare with or without the additional 3 portrait panels. I can only access the outer row of panels on 4 sides. I have invested in a decent scaffold though.

2) I haven't considered that but I've never heard about any requirements concerning firefighter access. The do require to have access to both the AC and the DC switch though (FWIW).

We do have snow here occasionally but only a few times per winter and it uses to disappear after a few days. It's much worse up in the north. I live in the south on the west coast where the winters are mild

[solnisse]

A few things to consider:

Do you live in a state with required roof setbacks for fire code?

No and as most people in Sweden, I don't have to apply for a building permit.

Did you account for the attachment bolts which go between the PV modules to clamp them to the rails?

I have. The clamps will take up almost an inch. On the left and right side, there will be about 2 inch spacing between the panels which will allow for good ventilation. That space is determined to fit in well with the tops of the trapezoidal metal sheet.

There is no power issue with the strings mixing orientation, but you need to make sure that the rails line up with the correct area of the landscape modules and the portrait modules.

Sounds great. I will be very careful to fasten the panels in the allowed area specified by the manufacturer (which is Heckert btw)

What inverter are you using for this system?

I will be using a Fronius Symo 15.0-3-M (3 phases) together with a Smart Meter. A have permission to feed max 11 kW to the grid but the inverter can dynamically take local consumption into account and may theoretically produce up to its maximum which is 15 kW. I could change the 3 16A main fuses to something larger value but that would cost me a lot monthly.

[littleharbor]

We do have snow here occasionally but only a few times per winter and it uses to disappear after a few days. It's much worse up in the north. I live in the south on the west coast where the winters are mild

Nice, Is that where all the blonde haired, blue eyed, beach bunnies hang out?

[solnisse]

Nice, Is that where all the blonde haired, blue eyed, beach bunnies hang out?

The topic has been fully answered so I guess I won't violate any rules if I go slightly off topic.
Summer time is amazing here. I've always lived on the seaside. Hoping for lots of sunshine for several reasons the coming season

DSC_1260.jpg

[littleharbor]

Hmmm... Dad and his daughter on the left are wondering why this guy decided to change in the middle of the crowd without a towel wrap. Europe, I guess. That would probably get that guy locked up in the US.

[J.P.M.]

Hmmm... Dad and his daughter on the left are wondering why this guy decided to change in the middle of the crowd without a towel wrap. Europe, I guess. That would probably get that guy locked up in the US.

Yea, they could be scoping out what might be the rest of that light(er) colored protuberance peeking out just left of bottom center of the white rectangle that's masking Nils' junk.