Adding more solar

Benny2020

Had my 4kw system since Nov 2015 and making maximum use of it.
Looking at adding more panels and looking for advice from people who have added to an existing system, 
I have 16 x 250w panels and probably have room for another 4 panels horizontally mounted beneath the current ones although you can get higher capacity panels now (400w?).
Also have a south facing conservatory with an east/west facing roof, can you mount panels on a poly carb/plastic conservatory roof?

Verdigris

If you are on a FiT contract, you can't make changes to the system, except for repairs as near as possible to the original spec.

You could opt to end the FiT contract and go on to SEG, but it is probably not as lucrative, even with a higher output. You'd also probably need to get a G99 grid connection, rather than the G98 you get as "standard", which is currently limiting you to 3.68kW output.

Benny2020

Surely I can add more separately to my existing system without affecting my FIT contract?

QrizB

Benny2020 said:

Surely I can add more separately to my existing system without affecting my FIT contract?

Yes, you can add a second (or third, or seventeenth) system, so long as it doesn't modify your existing FIT-qualifying system.

Verdigris

Benny2020 said:

Surely I can add more separately to my existing system without affecting my FIT contract?

As QrizB says, yes if it is a separate system, but my remark about getting a G99 connection applies as you are, almost certainly, at the limit of a G98 connection.

With regard to the conservatory, you can't fit panels to polycarbonate, as far as I'm aware. Planning regulations now allow proper roofs on conservatories, so you'd have to change to some other sort of roofing structure. That may be an advantage, as a south facing conservatory almost certainly overheats in summer. However, assuming it is a two storey dwelling, you will have shading issues at each end of the day, which will limit output significantly.

Martyn1981

Benny2020 said:

Surely I can add more separately to my existing system without affecting my FIT contract?

Separate system is fine. But check with your FiT provider before you change any panels on your existing system. I'm with EDF for my FiT, and they've confirmed (by e-mail) that I can add more panels, or change panels for more powerful ones, but the FiT payments will be apportioned based on the old and new kWp. For example if I went from 3kWp to 4kWp, then FiT payments would be based on 3/4 of the generation.

Also need to consider any generation capping if the inverter is limited. Same example, say 4kWp PV but capping meant generation only went up (proportionately) from 3 to 3.5, then payments are apportioned 3/4, then FiT would actually go down. Hope that makes sense.

ispookie666

You would definitely need DNO approval to add more panels for G99. I doubt any installer would consider conservatory roof.  
Also if installing battery - the inverter would be considered a separate generator if its an AC coupled system.  

Heedtheadvice

In a similar aim to the OP (so worth adding to this thread)

Accepting DNO approval would be required if additional generation that exceeds G98  levels....

I too am considering adding second hand panels (purely on a cost basis) that probably would not exceed 300Wp each thus enabling two each East and West facing to be added. No shading issues except depths of winter.

Does anybody have suggestions for low power inverter(s) , grid tie, to use with these two strings?

I do not have details of the panels performance yet but obviously they would only have low generation voltage possibly in the order of 30 volts. Any heads up would give me guidance as to which inverters to research once I have more details.

Efficiency is desired but I would put more emphasis on reliability.

QrizB

Heedtheadvice said:

I too am considering adding second hand panels (purely on a cost basis) that probably would not exceed 300Wp each thus enabling two each East and West facing to be added. No shading issues except depths of winter.

Does anybody have suggestions for low power inverter(s) , grid tie, to use with these two strings?

I'm sure one of the regulars did something similar, and used microinverters. They're designed to work with one or two panels.

Exiled_Tyke

QrizB said:

Heedtheadvice said:

I too am considering adding second hand panels (purely on a cost basis) that probably would not exceed 300Wp each thus enabling two each East and West facing to be added. No shading issues except depths of winter.

Does anybody have suggestions for low power inverter(s) , grid tie, to use with these two strings?

I'm sure one of the regulars did something similar, and used microinverters. They're designed to work with one or two panels.

That could be me. I added two 300w panels linked to a 600w micro inverter which then feeds a separate meter (just so that I can check all is working ok).  It's completely separate from my FiT system.  

Benny2020

That could be me. I added two 300w panels linked to a 600w micro inverter which then feeds a separate meter (just so that I can check all is working ok).  It's completely separate from my FiT system.  

Is that off grid?