Changing PV panels

[Marvin]

I want to add some more PV panels to my system. The ones I have all face south with no shade

 

The panels I want to add will face east and west. 

 

What sort of panels can if fit to the two separate rings I already have without losing power from the existing ones?

 

[JohnMo]

You just put the new one a different inverter or if your existing inverter has spare MPPT do that, then they can be anything you want.

 

East and west can go on one MPPT (but need to be same panel design, same number of panels and same angle) or 2x MPPT if you want. 

 

Do not connect on the same MPPT as your existing South facing, as new panels are very unlikely to match your old ones

Edited 23 hours ago by JohnMo

[Marvin]

Hi @JohnMo

 

6 minutes ago, JohnMo said:

You just put the new one a different inverter or if your existing inverter has spare MPPT do that, then they can be anything you want.

 

East and west can go on one MPPT (but need to be same panel design, same number of panels and same angle) or 2x MPPT if you want. 

 

Do not connect on the same MPPT as your existing South facing, as new panels are very unlikely to match your old ones

I will come back to this if you don't mind.

 

 

I need to change my inverter to one that will allow my system to charge batteries, supply to the mains, and go off grid. Is there such a thing?

[JohnMo]

Hybrid inverter. But they are generally equipped to do limited off grid output.

 

Some makes will do a gateway which will allow the full inverter output in a power cut.

 

Or AC coupled battery with gateway will will allow normal string inverters to work in a power cut. Depends if you already have your battery?

 

All the above depends on what you mean by off grid?

[MikeGrahamT21]

11 minutes ago, Marvin said:

Hi @JohnMo

 

I will come back to this if you don't mind.

 

 

I need to change my inverter to one that will allow my system to charge batteries, supply to the mains, and go off grid. Is there such a thing?

I believe Tesla powerwalls do this, but it’s a hard thing to achieve in the UK as in the event of a power failure, any generation or potential export should turn off or island, and for that reason most don’t operate the whole fuseboard on backup, rather just a backup socket for emergency loads to be plugged into. Maybe someone else knows more about this, but mine certainly doesn’t as an AC coupled. 

 

Don’t agree with East and West connecting to same MPPT, my east and west panels are both active in differing amounts simultaneously, and in winter east does far better than west.

 

Either use a separate inverter, or get a triple MPPT one to handle all 3 strings, these are widely available as normal and hybrid.

 

A good question, do you get the feed in tariff? If you do then don’t go hybrid, as it will wipe out a lot of your income.

[JohnMo]

2 minutes ago, MikeGrahamT21 said:

Don’t agree with East and West connecting to same MPPT, my east and west panels are both active in differing amounts simultaneously, and in winter east does far better than west.

I didn't until someone here pointed me towards design / install instructions that said you could, so researched further. And indead you can and the output per year is actually better than 2x MPPTs as they run longer at best efficiency point. But strings need to be identical, as in number of panels, mounting angle.

[MikeGrahamT21]

9 minutes ago, JohnMo said:

I didn't until someone here pointed me towards design / install instructions that said you could, so researched further. And indead you can and the output per year is actually better than 2x MPPTs as they run longer at best efficiency point. But strings need to be identical, as in number of panels, mounting angle.

wonder how that comes about? Just can’t imagine it from my own install. Have you done this and observed the output difference?

[JohnMo]

14 minutes ago, MikeGrahamT21 said:

wonder how that comes about? Just can’t imagine it from my own install. Have you done this and observed the output difference?

No, but others have.

 

Here you go something to read 

se-ta-efficient-east-west-orientated-pv-systems-wi.pdf

Edited 22 hours ago by JohnMo

[Dillsue]

Maybe Im missing something but the Fronious write up is comparing output of 2 E-W arrays each with different panels, mounted at differing inclinations and facing different directions?? Hard to see how you'd get a meaningful comparison of them wired to a single inverter VS 2 separate inverters??

[MikeGrahamT21]

17 hours ago, JohnMo said:

No, but others have.

 

Here you go something to read 

se-ta-efficient-east-west-orientated-pv-systems-wi.pdf 352.78 kB · 4 downloads

Really interesting that, not what I expected. So essentially there are losses and the sunnier it is the greater they are, but even then it’s minimal and saves buying another inverter. 
 

 

[JohnMo]

49 minutes ago, Dillsue said:

Maybe Im missing something but the Fronious write up is comparing output of 2 E-W arrays each with different panels, mounted at differing inclinations and facing different directions

Think your missing something. One of the rules is the east and west face panels have to be matched. They are comparing essentially 4 systems. One thin film, to one inverter and also 2 inverters, same for Crystalline.