Can I mix vertically wall mounted panels with 35 degrees mounted panles on one string? How bad? Scotland UK.

[zanydroid]

2.Anyway my installer was kind enough to replace my growatt sph3600 (120v V min) for another inverter which works from 80V and with working range 100-500V.
And obviously use 2 mppts.
This will hopefully work well with 2 strings of 120V?

Ok so for this, you want to look at the voltage reduction at high temperature and see if those temps are probable in your climate. The effect of this would be loss of production when it is hot.

I believe it is the temperature in the solar panel that determines the voltage adjustment, so it could actually be hotter than ambient.

Yeah vertical panels on south side seem pretty popular in the north. The slightly annoying part seems to be the need to do more DIY design of the mount since it’s not that common to do globally. Vertical really sucks at a lot of latitudes, outside of winter

 

[Guy from Glasgow]

Thanks very much Z.
For voltage reduction I found this paper:
https://www.researchgate.net
It seems to show that cell voltage drops from 0.64V to 0.58v at 45C.
0.58/0.64=0.906
So I guess for my panels with Vmax power=29.7V
I should expect 29.7*0.906=26.9V per panel
4 panels should give me 107.6V at 45 C.
This is more then min working voltage of 100V.
O guess 45C panel temp can happen in Scotland as we get to about 29C in the shade once in 3 years probably.
----
2.Did not realise vertical mounts are not generally available. I guess need to check with particular panels installation manuals. Thanks.

 

[zanydroid]

Thanks very much Z.
For voltage reduction I found this paper:
https://www.researchgate.net
It seems to show that cell voltage drops from 0.64V to 0.58v at 45C.
0.58/0.64=0.906
So I guess for my panels with Vmax power=29.7V
I should expect 29.7*0.906=26.9V per panel
4 panels should give me 107.6V at 45 C.
This is more then min working voltage of 100V.
O guess 45C panel temp can happen in Scotland as we get to about 29C in the shade once in 3 years

No need to find and read a paper to get started, the coefficients are listed on the solar panel spec sheet.

The part where a paper or experiment is needed is how much buffer to add above ambient. Most of the error will be in that direction which also is the wrong direction for correct functioning (but at least it is safe, it just turns off)

The error from heat generated on the roof is in the favorable direction for cold temp compensation.

 

[zanydroid]

2.Did not realise vertical mounts are not generally available. I guess need to check with particular panels installation manuals. Thanks.

The best thing to do is to search this forum for vertical installs. That will find you DIY vertical mounting techniques. Good luck getting structural permits though , I don’t remember that anyone did that but I could have missed it.

The panel manuals will include strength numbers for installation to certain mounting standards but I don’t know how these translate to vertical

 

[SeaGal]

Good luck getting structural permits though , I don’t remember that anyone did that but I could have missed it.

Permit is not an issue as he's in the UK - have seen quite a few vertical installations over here.

The caveat though is that a PV installation has to meeting planning permission requirements, one of which (IIRC) is not protruding more than 150mm from the surface it is mounted to - hence flat roof mounted tilt or mounted at an angle against a vertical wall _may_ planning permission.

 

[Ron-ski]

one of which (IIRC) is not protruding more than 150mm from the surface it is mounted to

It's 200mm - I'm looking at putting 3 panels on my SW wall.

Flat roof installation height has been increased to 600mm as of last year