Options when DNO says limit to zero export for a PV install

[Bob Smith]

Background:
I got a 4kWp (16 * 250W PV modules) installed facing south on my main roof with FiT since 2016 on residential.

Today:
I want to install more panels as I have other location (facing west, south and south-west) where 9 panels could fit + I want batteries that can be charged by the new panels AND the existing ones.
I want this new system not to interfere with my FiT.

I understand that I will need a new inverter for the new 9 panels. In order to keep my FiT, the existing panels cannot be connected directly to the battery as this will bypass my generation meter. Therefore it has to go through my existing inverter (conversion from DC to AC) and then be converted again to DC to feed the battery. I appreciate there will be some loss but at least I can keep FiT

Now the original proposal was to have 9 x 395W panels which gives 3555W. However, I could install different panels and reach 4725W which is about 33% more.

My question after this long intro (sorry) is what does that mean in terms of DNO.

I have read that for above 4kW (16A x 230V single), there must be a DNO approval, however, I have also read if there is a second inverter it will not be necessary. This said, if it is correct that if I have a second inverter (which will be the case) I do not need DNO approval, it could be that I must be limited to 4kW max as per a standard household installation.
Obviously, I am keen to get the most of the pace I have and as mentioned, I could go up to 4725W. Would that then mean that I need DNO approval for the new system at 4725W and need to move to 3 phases (4725W + my existing 4kW). If so, how can I find out if it is worth the cost? Should I better stay with a single phase system and having 2 investors allows me not to go through DNO approval.

I have spent days trying to understand who to contact and DNO seems to be an obscure thing. The installer I selected has made a request but he said it will take weeks.

so I am trying to find info to see if we pursue the effort to develop the optimal system for the space available, or we better stick with a 4kWp system (ie having 2 4kWp with 2 inverters (one installed in 2016 and one to be installed).

I hope I have given you enough info and that someone will be able to point me into the right different to find the info I need.

Thank you very much in anticipation

Bob

I have split this post to avoid confusion

 

[Bob Smith]

Is this visible? @binky

 

[binky]

I have read that for above 4kW (16A x 230V single), there must be a DNO approval, however, I have also read if there is a second inverter it will not be necessary.

I have split this post to avoid confusion

Drivel off t'internet!

OK, you are allowed to install PV or AC coupled battery capable of backfeeding 16A (3.67kW) to the grid whether the DNO like it or not, and if they have issues with the grid not being capable of handling that, then it's upto them to fix and pay for any upgrades. You do still legally have to notify them within 3 weeks of installating and commissioning the system.

Now you can install multiple inverters (or inverters over 3.6kW) and AC batteries that exceed 16A but you need to apply for permission from the DNO first, just in case it melts the grid or overloads the local transformer. Now, in my experience, you can normally backfeed something like 5kW in most locations. Why would you want to do this? Well, when we got a nice little payment in the form of the Feed in Tariff, that meant you could earn more money from your PV system. As the FiT is now long dead and buried, this is no longer important, although the Guaranteed Export Schemes offered by some leccy suppliers can make this more desirable if you can get such a tariff. Use a G99 application for over 16A connections.

However, whilst the DNO may object to their system being overloaded and refuse more than 16A (or try to charge for network upgrades), it is also acceptable to install bigger or multiple PV and battery systems that have export limitation devices built in that restrict total export to 16A or whatever the DNO say you can export. Bigger systems are of course good for charging batteries, and reducing winter bills. I have always said, and will continue to do so, "size matters". There are set costs to any solar install, eg a pallet is £125 for 1 panel or 20 panels stacked on it, a days work or 2 days work costs £x in labour, scaffold is typically £600 for an average house whether you put 1 panel on the roof or 20 etc etc. So the more you water down the overheads with a bigger system, the faster your return on investement. The DNO may request proof of setting the gear to whatever export limit they allow (photo of setting screens usually suffices), but they are usually quite happy to accept such a setup. They just like to be notified in advance.

Hope that makes sense

 

[Bob Smith]

HI Binky,
It just happens I am on the internet when you are on it lol

Joke apart. Thank you for the information. It clarifies things.
Yesterday I managed to get my hand on the G99 form. I expected a lot more to fill. This said, certain points I can't answer. So more digging.

Have a good weekend and once again thank you for your response. Much appreciated

 

[binky]

HI Binky,
It just happens I am on the internet when you are on it lol

Joke apart. Thank you for the information. It clarifies things.
Yesterday I managed to get my hand on the G99 form. I expected a lot more to fill. This said, certain points I can't answer. So more digging.

Have a good weekend and once again thank you for your response. Much appreciated

there's some comments on one of the thread about filling the forms. Main thing is a little schematic diagram of the installation, and I like to put info into any email sent to explain exactly what I'm doing, just in case I've filled the form in wrong.

 

[Bob Smith]

there's some comments on one of the thread about filling the forms. Main thing is a little schematic diagram of the installation, and I like to put info into any email sent to explain exactly what I'm doing, just in case I've filled the form in wrong.

This makes perfect sense. I just find the form very, well limited if you stick to it and they don't even tell you what to do for additional information.
eg, they don't ask for a diagram... but that should make sense.

 

[binky]

This makes perfect sense. I just find the form very, well limited if you stick to it and they don't even tell you what to do for additional information.
eg, they don't ask for a diagram... but that should make sense.

you will also need G99 or G98 test cert for the inverter to confirm it complies with UK grid requirements.