FIT system extension

[bontwoody]

So following on from my previous post regarding adding additional capacity to my existing 2.66kW FIT system, I have now had DNO approval and a quote to install a Solar Edge panel and battery system.

My intention is to leave the existing system well alone and put the new system split equally over a East/West (ish) facing roof.

The installer has said that the DNO will allow an additional 3.68kW of panels with a 10kWh DC battery attached but added the phrase “

The proposed system that we would install would only contribute to the consumption in the home and will also store in the battery.

“

Im happy with the quote for the panels but the battery is beyond my budget. IT does seem to make sense however to install some batteries while the VAT is zero rated.

I had hoped to do something more modular with the battery system, starting at say 2-4kWh and seeing how it goes before adding more.

So my questions are:

• Does the quoted phrase mean that the new system wont export at all, and so I must have a DC battery installed
• Does the DC battery have to be that big? Or could I have a smaller modular battery system and if so what suggestions are there that would be compatible with the solar edge inverter.
• Can I have an AC coupled battery system instead, and would an advantage of that be that I could store the excess from my FIT system as well as my new system.
• Would it be a good idea to oversize the new system substantially and use a smaller than 3.68kW inverter (the quote is for a Solar Edge 3680 HD Wave inverter)

For information, Im just about to have a Mixergy HW cylinder installed with a PV diverter, and intend to switch away from the existing gas combi to a ASHP as soon as I can. I also have an eMonPi monitoring system that I would like to be able to monitor the new PV system with. An EV is on the cards in the future.

Any help would be appreciated.

 

Cheers Mark

[Dillsue]

1 hour ago, bontwoody said:

The installer has said that the DNO will allow an additional 3.68kW of panels

Are you sure they said 3.68kw of panels?? DNO is usually only interested in the inverters max output and does care how many panels you have.

 

Its more usual for DNOs to say you can have an additional 3.68kw of export which is governed by the inverter you choose. If that is the case then an SE3680H can have 5.7kw of panels connected to it, more if they are facing differing directions.

 

Whats the maximum additional kw capacity you could get on your roof in each direction, including the FIT system panels? 

 

 

[bontwoody]

2 minutes ago, Dillsue said:

Are you sure they said 3.68kw of panels?? DNO is usually only interested in the inverters max output and does care how many panels you have.

 

Its more usual for DNOs to say you can have an additional 3.68kw of export which is governed by the inverter you choose. If that is the case then an SE3680H can have 5.7kw of panels connected to it, more if they are facing differing directions.

 

Whats the maximum additional kw capacity you could get on your roof in each direction, including the FIT system panels? 

 

 

Sorry that was my paraphrasing, he actually said:

 

"Western Power (national grid) have done the calculations and would allow an additional 3.68kWp of Solar PV to be installed with a SolarEdge 10kW DC battery attached."

 

By eye I think I could fit 9 panels to the East side and more than that to the West if allowed so probably 5.7 at least. But does he imply that I have to have the DC battery to be allowed them? Thanks

 

 

[Dillsue]

If its a DC coupled battery then the batteries output comes through the inverter and is limited by the inverter. If you go for an SE3680H, the DNOs limit, with an SE battery then the PV and or battery output to the house/grid is limited to 3.68kw.

 

Your DNO wont care if the power is coming from PV or battery, so long as its limited to 3.68kw.  You can have as much PV or battery capacity as you want so long as the inverter limits output

[bontwoody]

15 minutes ago, Dillsue said:

If its a DC coupled battery then the batteries output comes through the inverter and is limited by the inverter. If you go for an SE3680H, the DNOs limit, with an SE battery then the PV and or battery output to the house/grid is limited to 3.68kw.

 

Your DNO wont care if the power is coming from PV or battery, so long as its limited to 3.68kw.  You can have as much PV or battery capacity as you want so long as the inverter limits output

I cant go for the SE Battery though as it only comes in 10kWh size and is too pricey, so I need a modular system that can interface with the SE inverter if I have to go for a DC coupled system. Is there any reason why I cant go down the AC coupled route do you think?

[Dillsue]

If you go for AC coupled then the battery pack adds to your potential max export and youll need DNO approval for new inverter AND batteries!

[bontwoody]

3 hours ago, Dillsue said:

If you go for AC coupled then the battery pack adds to your potential max export and youll need DNO approval for new inverter AND batteries!

 

So is the DNO approval I already have only valid for the DC coupled batteries then? If that so then what I need is another battery system option that is compatible with the SE inverter but modular in nature so I can start small and increase as needed. I assume that I can still have the additional PV panels with no batteries attached.

 

Anyone have any ideas or experience of such a system?

[Dillsue]

Your DNO approval is for the inverter which will limit export to the grid from either or both PV and DC coupled batteries. If you have AC coupled then the inverter can only limit PV export and your batteries are free to do want they want. 

 

SE are quite limited in their DC coupled battery options. I think youve got the recently launched Energybank or the earlier Storedge system using LG batteries. Other than those its AC coupled with an uplift in DNO approved export limit or an export limitation set up