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Adding pv solar panels to existing? DNO issues?

 
Solar Photovoltaic (PV)
Last Post by Tim441 2 years ago
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 Tim441
(@tim441)
Prominent Member Contributor
Joined: 3 years ago
Posts: 357
Topic starter 28/05/2023 6:56 pm  

I have 20 panels on East facing roof - just 5 or 6 degrees pitch. No FIT. 2 strings. 6.4kw total
With GivEnergy 5kw Gen1 hybrid inverter & 3 x 8.2kw batteries
+
7 panels on south facing roof - 45 degrees pitch
+ 1 panel very shaded (almost irrelevant). In theory 2.2kw total
With Solaredge inverter & FIT

The flat roof has space for 5 more panels. I'm thinking I will try and get the 20 panels on flat roof upgraded to add 4 more. Presumably the existing 2 strings of 10 can become 2 x 12? They're 320w panels currently .. again not sure about compatible panels to add but presumably very doable.

The one heavily shaded Solaredge system panel can also get moved to the flat roof where it will get similar output to the other 7. Should be worth the minor effort - just requires 4 clamps for standing seam and the wiring may need cutting & reconnecting.

DNO has given permission for 5.5kwh max export - which I don't think we would currently exceed very often anyway due to non-optimal angle and orientation.

Not sure if they might allow an increase if we ask? Presumably no downside in asking? I'm not aware they've done any upgrades locally.

Otherwise clipping/limiting to 5.5kwh is likely to be ok considering we have a base load & batteries. So "lost/wasted" output is unlikely to be huge. With an ASHP we use a lot of elec during (say) mid Oct to early May. 6 months at least.

Even if I lose out a bit on some peaks ... I will be adding extra output for longer usable periods.... and more frequently useful etc.

I suppose I could try to do some sort of calcs ...but overall feel that common sense is telling me its worth adding the panels. Payback period may be 5, 10 (or 15) years! If 5 panels add (say) 1500kwh output per annum at 15p (Octopus export fixed tariff) then that's £225... savings increase if we can use the output. Let's see what an installer wants to charge for the job! Hopefully payback in 5 to 10 year range.

My base thoughts are adding the panels without any other changes to inverters or batteries.

Any comments or thoughts on issues, practicalities, DNO etc?


Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
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Topic Tags
Pv solar upgrading DNO
 iancalderbank
(@iancalderbank)
Noble Member Contributor
Joined: 3 years ago
Posts: 643
05/06/2023 11:17 am  

the FIT group you can't touch, presume you know that.

 we're pretty much at peak output right now so you should be able to get a pretty good number for how much you will lose due to clipping, if any, by monitoring your existing setup. think about what is your guarantee situation with the existing setup, if you were to make changes to it? You need to check the inverter specs for how DC-side input (potential oversubscription) it allows. DNO no harm in asking , your batteries may make them more inclined to say yes, but that DNO increase would imply getting a bigger inverter so that becomes more of a job?

you've shown yourself to be capable of getting on your roof and swapping panels and optimisers around in the other thread, so have you thought about adding the extra panels as DIY to reduce the cost? 


My octopus signup link https://share.octopus.energy/ebony-deer-230
210m2 house, Samsung 16kw Gen6 ASHP Self installed: Single circulation loop , PWM modulating pump.
My public ASHP stats: https://heatpumpmonitor.org/system/view?id=45
11.9kWp of PV
41kWh of Battery storage (3x Powerwall 2)
2x BEVs


   
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 Tim441
(@tim441)
Prominent Member Contributor
Joined: 3 years ago
Posts: 357
Topic starter 05/06/2023 2:50 pm  

@iancalderbank yes, for FIT system I am only moving a heavily shaded panel to sunny position. already part of the system. No other changes.

Ideally I will go through installer so that everything tidy with DNO or if future issues. But I agree in theory I should be able to do myself as its a standing seam flat roof with easy access. In which case I will need to look up detail on strings, inverter capacity etc... and consider what to do with DNO!

 


Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4427
05/06/2023 9:11 pm  

Posted by: @tim441
↑

@iancalderbank yes, for FIT system I am only moving a heavily shaded panel to sunny position. already part of the system. No other changes.

Ideally I will go through installer so that everything tidy with DNO or if future issues. But I agree in theory I should be able to do myself as its a standing seam flat roof with easy access. In which case I will need to look up detail on strings, inverter capacity etc... and consider what to do with DNO!

 

Rather than moving your shaded panel you could consider installing reflectors if it is feasible. Wooden panels painted with white gloss paint or covered in kitchen foil should increase the output from the shaded panel.

 



   
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 Tim441
(@tim441)
Prominent Member Contributor
Joined: 3 years ago
Posts: 357
Topic starter 06/06/2023 9:32 am  

@derek-m thanks for the thought. In my case reflection is not an option - but a useful idea that might help others.


Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV


   
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Topic Tags:  Pv solar (2) , upgrading (1) , DNO (1) ,
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