Green Building Forum - Solar PV extension

Solar PV extension

williamd — Wed, 13 Jan 2021 19:16:56 +0000

A relative purchased an old house about 2 years ago and has renovated it including extensively insulating it and fitting an air source heat pump.
The previous owner had fitted solar PV panels with eligibility for feed in tariff commencing in May 2013.
My relative intends to build on an extension and wonders whether fitting further solar PV panels to this extension would be worthwhile financially. I assume that FIT will not apply to the new panels so is there any alternative subsidy available and how will this work in practical terms as it would presumably make sense if the existing panels are to remain on FIT.
Thank you for your guidance...

Solar PV extension

tony — Wed, 13 Jan 2021 19:33:13 +0000

you may find that the fit evaporates if the system is changed

Solar PV extension

djh — Wed, 13 Jan 2021 20:19:05 +0000

Posted By: williamdThe previous owner had fitted solar PV panels with eligibility for feed in tariff commencing in May 2013.
My relative intends to build on an extension and wonders whether fitting further solar PV panels to this extension would be worthwhile financially. I assume that FIT will not apply to the new panels so is there any alternative subsidy available and how will this work in practical terms as it would presumably make sense if the existing panels are to remain on FIT.

I take it the rights to the FIT payments have transferred to your relative? I believe it is possible for the ownership of the FITs to belong to somebody other than the owner of the property.

Any new panels will need to be connected separately to the grid, so that the metered capacity of the original installation is not affected. So separate inverter and metering. Also the total size of the system will need to remain within the 16A (3.68 kW) limit otherwise a G59 application must be made. An installer will be able to explain the details.

Solar PV extension

philedge — Thu, 14 Jan 2021 08:53:53 +0000

Im pretty sure the inverter limits its output to 16A on standard domestic installs so adding panels cant add anything to the maximum system output. Adding panels will increase overall generation but stay limited at 4kw/16A. When we got ours installed there was never any mention of panel output being limited, only a system limit managed by the inverter.

Given the original install needed to be installed by an MCS accreditted installer to get FIT payments, I assume youd need an MCS installer to add any panels.

Solar PV extension

djh — Thu, 14 Jan 2021 11:09:43 +0000

Posted By: philedgeIm pretty sure the inverter limits its output to 16A on standard domestic installs so adding panels cant add anything to the maximum system output.

You can't add panels to the current inverter without losing FIT.

Solar PV extension

revor — Thu, 14 Jan 2021 11:35:08 +0000

The way I understand it, but could vary with DNO is that if you want to export more than 3.6 kw you need their permission fill in forms (think the form has now changed) and maybe pay a fee. You can generate more than 3.6 Kw but obviously you would need an inverter for the size of panels and you can get a device which limits what you can send to the grid to 3.6 kw. So if DNO won't allow you to export more than you 3.6 kw I suppose you could use the extra generation yourself and maybe store it in a battery. I do not know what your FIT arrangement is but it could be that there will be no monetary benefit to you. There have been changes in the last year or so in that it was not possible to add extra panels or batteries without loosing your FIT however I understand that new generation of inverters get you the best of both worlds. Have a look at what Powervault
have to offer I also think that Sola X have something as well, there may be others also.

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Peter_in_Hungary — Thu, 14 Jan 2021 13:03:18 +0000

Posted By: revorYou can generate more than 3.6 Kw but obviously you would need an inverter for the size of panels and you can get a device which limits what you can send to the grid to 3.6 kw. So if DNO won't allow you to export more than you 3.6 kw I suppose you could use the extra generation yourself and maybe store it in a battery.

One advantage of having the capacity to generate more than 3.6kW but capped at 3.6 is that you will get more time when you are generating 3.6 (on dull days) than if your max output is 3.6kW. Of course you would have to do the sums to see how much extra PV is worth the expense.

Solar PV extension

Ed Davies — Thu, 14 Jan 2021 13:46:16 +0000

Posted By: djh: â€œâ€¦a G59 application must be madeâ€¦â€

Slight update: AIUI, G83 has been replaced by G98 and G59 by G99 from April 2019:

https://www.ssen.co.uk/G99G98Requirements/

Solar PV extension

jamesingram — Thu, 14 Jan 2021 16:56:09 +0000

Ive a fits system and a non fits systems.
the no fits systems doesnt require MCS registration so can be fitted by a compedent roofer and a electrician rather than a specialist company , this may save on cost. if going over 16A potential export a G99 is required prior to connection , this may have a cost implcation.

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philedge — Thu, 14 Jan 2021 18:26:03 +0000

Posted By: djh
You can't add panels to the current inverter without losing FIT.

Have you got a reference for that?

Practically speaking, with our 4kw solaredge inverter that is limited to 16A output, the max recommended panel input is 5kw.

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nigel — Fri, 15 Jan 2021 11:14:38 +0000

Posted By: jamesingramIve a fits system and a non fits systems.
the no fits systems doesnt require MCS registration so can be fitted by a compedent roofer and a electrician rather than a specialist company , this may save on cost. if going over 16A potential export a G99 is required prior to connection , this may have a cost implcation.

I have two PV systems one fit eligible and the other not. I have signed up to Agile outgoing where they pay for exported energy, they will only accept this if both the systems are Mcse installed. So long term unless you will never export I would try and get an MCSE installed system.

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djh — Fri, 15 Jan 2021 12:45:47 +0000

Posted By: philedgeHave you got a reference for that?

Sorry, I'm now not convinced I understand current regs.

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revor — Fri, 15 Jan 2021 14:23:57 +0000

This gives some info on FIT and batteries.
https://www.solarguide.co.uk/solar-battery-with-smart-meter-will-not-stop-fit-payments#/

So looks like you could add a battery and not loose your FIT you get to have your cake and eat it. Might be better option than another PV set up as you can buy back at cheap rate at night and use during the day.

Solar PV extension

philedge — Sun, 17 Jan 2021 10:26:17 +0000

Had a bit of a search round and found the following on the Ofgem site

https://www.ofgem.gov.uk/publications-and-updates/feed-tariffs-guidance-renewable-installations-version-15

The section on modification refers to not exceeding the Total Installed Capacity which is defined as

â€œthe maximum capacity at which an Eligible Installation could be operated for a
sustained period without causing damage to it (assuming the Eligible Low-carbon Energy
Source was available to it without interruption), a declaration of which is submitted as
part of the processes of ROO-FIT Accreditation and MCS certified Registration.â€

The way I read this is that if an inverter has a restricted output of 16 amp, the installations maximum operating capacity is the 16 amp limit regardless of the PV panels input capacity. Anyone read that differently???

Solar PV extension

jamesingram — Sun, 17 Jan 2021 11:45:38 +0000

Posted By: nigel
Posted By: jamesingramIve a fits system and a non fits systems.
the no fits systems doesnt require MCS registration so can be fitted by a compedent roofer and a electrician rather than a specialist company , this may save on cost. if going over 16A potential export a G99 is required prior to connection , this may have a cost implcation.

I have two PV systems one fit eligible and the other not. I have signed up to Agile outgoing where they pay for exported energy, they will only accept this if both the systems are Mcse installed. So long term unless you will never export I would try and get an MCSE installed system.

A good point Nigel , one I hadnt consider.ed
Personally I get a high rate of FITs with my initial system and the 50/50 export payment, so just see the 2nd systems as adding additonal capacity using that funding to pay for it and other improvements so havent really considered the export from the 2nd system.

50% of the 2nd system faces NW giving us some generation until sunset which usually get used. the majority of our 2 systems faces SE

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jamesingram — Sun, 17 Jan 2021 11:51:50 +0000

Posted By: philedgeHad a bit of a search round and found the following on the Ofgem site

https://www.ofgem.gov.uk/publications-and-updates/feed-tariffs-guidance-renewable-installations-version-15

The section on modification refers to not exceeding the Total Installed Capacity which is defined as

â€œthe maximum capacity at which an Eligible Installation could be operated for a
sustained period without causing damage to it (assuming the Eligible Low-carbon Energy
Source was available to it without interruption), a declaration of which is submitted as
part of the processes of ROO-FIT Accreditation and MCS certified Registration.â€

The way I read this is that if an inverter has a restricted output of 16 amp, the installations maximum operating capacity is the 16 amp limit regardless of the PV panels input capacity. Anyone read that differently???

My understanding is your reading is correct.

From memory the issue with expanding and existing system that receives FITs is it then requires an update to its registration which then in turn results in it being classified under the current FITs band.
The result of this when FITs rates were dropping regularly was you would end up on a lower tariff after registering.
Now FITs has stopped to new installs Im not sure what the situation is.

At the time I personally thought it wise just to leave any eixisting system receiving funding alone and to not rock the boat and risk loss of tariff

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revor — Sun, 17 Jan 2021 12:41:09 +0000

I need to get my head around these regs as well. My proposed installation is gathering pace now and my inverter is G98 G 99 and G 100 compliant It seems that the G100 bit is about export limitation. The inverter can be programmed to not export or export what you want. However my system will be 6Kw and the proposal I think from the installer is to limit the output to 3.6 so don't need to make a G99 application although I would like to export everything I cannot use. Think that historically in our area everyone with SPV has been limited because of grid capacity.

Solar PV extension

philedge — Sun, 17 Jan 2021 13:02:25 +0000

Posted By: jamesingram

From memory the issue with expanding and existing system that receives FITs is it then requires an update to its registration which then in turn results in it being classified under the current FITs band.
The result of this when FITs rates were dropping regularly was you would end up on a lower tariff after registering.
Now FITs has stopped to new installs Im not sure what the situation is.

At the time I personally thought it wise just to leave any eixisting system receiving funding alone and to not rock the boat and risk loss of tariff

Ive emailed Ofgem to see if they can clarify, if they even answer!!

I can see your concern over jeopardizing payments but for me and maybe others there appears to be a spare 1.5kw capacity in my inverter which would be good to utilise if it doesnt affect the existing FIT payments

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philedge — Sun, 17 Jan 2021 14:06:48 +0000

Posted By: revorI need to get my head around these regs as well. My proposed installation is gathering pace now and my inverter is G98 G 99 and G 100 compliant It seems that the G100 bit is about export limitation. The inverter can be programmed to not export or export what you want. However my system will be 6Kw and the proposal I think from the installer is to limit the output to 3.6 so don't need to make a G99 application although I would like to export everything I cannot use. Think that historically in our area everyone with SPV has been limited because of grid capacity.

If you are set on 6kw then you probably need a battery pack/diverter or to make the Gxx application to your DNO... local capacity may have changed since the last neighbours application?? Another option is to split the panels over different orientations to generate at a lower rate over a longer period. If you cant utilse the extra generation because of a 3.6kw limit it may not be worth installing the extra panels/larger inverter??

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revor — Sun, 17 Jan 2021 14:44:43 +0000

@ philedge I have already bought the panels (18) and am awaiting some cable and connections to come from Germany before I can install them. Can't alter the arrangement as the support array for the panels is in place and it would not be possible to split now although what you propose would be a good idea. The array is in my garden and had to get PP for it so if I did change now would have to go back to planning. A friend has 17 kw worth on his roof built in when he was slating and in different orientations so is producing most of the time there is good conditions. I will be installing a battery (10Kwh) and proposal is to get a small EV and thought would be 6Kw would be a good PV size for it and the EV would be a good storage for the excess. What we need now is to be able to tap into the EV battery to power the house. I have 3 phase on site going to my agri buildings and am kicking myself now for not extending it to the house when we remodelled it. I need to understand this week from the installer (who is basically just doing the connections I am doing everything else) why he thinks we can't get a G99 accepted. It has been a big job sourcing stuff not made in China the inverter is from Italy has auto changeover to battery in event of power cut built in, battery is German made cells from Korea panels also Korean. So should be good when finished.

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jamesingram — Sun, 17 Jan 2021 14:47:07 +0000

Philedge.
Will be interesting to see if and what they reply.
I remember early on in the FITS history there was debate about what the notional 4Kw tariff band meant.
the DNO ( district network operator) set it at 16A/ 3.68kW max export for simple registration (G83 now G98 ) to protect the network (G53 now G99 for anything above requiring pre-inspection via DNO)

The FITs (Overseen by ofgem ) however had a price band at <4kW
and used the terms,
TIC total installed capacity
DNC declared net capaicity
initially this was defined as
TIC= total DC installed
DNC=inverter AC output

this allowed installers who were aware of this to bump up the DC installed to maximise inverter and system efficiency.
as an example my 1st system is 4.32kW TIC 3.68 DNC and receives the higher tariff.

later on in the FITs scheme they changed their definitions and TIC became DNC stopping the opportunity to do the above.

this is separate from the 'later DC expansion' ideas being discussed here but I think it might be relavant if
TIC=DNC in their definitions still.
Again from memory as its a while since I've read their documents and there's been many changes I think any changes other than like for like are considered a new system in terms of FITs

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jamesingram — Sun, 17 Jan 2021 14:59:49 +0000

revor shame about the 3phase , Ive done a few job with <3.68kW down each phase with an AB(PVI) small 3 phase inverter on G83/98
bit late now but would there be a way to send the DC from panels there and have that as your inverter/meter location and run your house off one of the phases or balanced across them if you've little other load?

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Ed Davies — Sun, 17 Jan 2021 15:34:21 +0000

Posted By: revorHowever my system will be 6Kw and the proposal I think from the installer is to limit the output to 3.6 so don't need to make a G99 application although I would like to export everything I cannot use.

Is that limitation on the power output of the inverter or on the export? I.e., is it sensed at the inverter or is there a separate current sensor near the meter?

The not insignificant difference would be that if you were, say, using 1 kW and the panels were generating 5 kW then the inverter could output 4.68 kW (throwing away only 320 W as heat in the panels) for a net export of 3.68 kW. Worse, if you were using 4 kW you could get it all from the panels and still be exporting 1 kW rather than the inverter outputting 3.68 kW and you importing 320 W.

Of course, a lot of the year 6 kW of panels will be producing not a lot more than 3.68 kW so it might be a bit academic depending on your ability to use the extra power. That'd also influence your choice of inverter size.

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revor — Sun, 17 Jan 2021 15:43:23 +0000

I did have a possible installer look at the 3 p possibility but he reckoned that the way the supply is configured it would not work. The 3P comes onto the premises to a pole in the garden and 3 P goes into a big agri building underground and one phase splits off at the pole and goes underground to the house.
The cable to the house would need to be from the distribution board in the agri building then there would have been metering issues I think as commercial and domestic use would be mixed. The only way around it is to have another SPV for the agri bit where I have a workshop and office. It is also too far away from the house to run an extension to my workshop to make use of the generation in there. The proper solution was to have taken the 3 phase to the house. Actually thinking about it now it might be possible as the 1P supply goes there through a ducting so could add to it if duct is big enough. Expect it would be expensive as it cost me Â£800 to move the cable (35m) from overhead to underground and I did the trench and laid trunking.

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djh — Sun, 17 Jan 2021 16:45:31 +0000

Posted By: revorWhat we need now is to be able to tap into the EV battery to power the house.

AIUI, the only EV that is currently legal for V2G operation is the Nissan Leaf 40 kWh and various suppliers are operating trials in various areas.

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revor — Sun, 17 Jan 2021 18:01:50 +0000

Have looked into the leaf trials it will be some time before it is generally available and only then if trials are deemed a success and worthy of a rollout. From what I was told the system cannot power the house in a power cut as the V2G charger which is the "clever" bit needs to have a permanent connection to grid.

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djh — Mon, 18 Jan 2021 12:06:14 +0000

Posted By: revorHave looked into the leaf trials it will be some time before it is generally available and only then if trials are deemed a success and worthy of a rollout. From what I was told the system cannot power the house in a power cut as the V2G charger which is the "clever" bit needs to have a permanent connection to grid.

I can well believe that. I lost interest rapidly once I discovered that the only possible car is one I have no interest in (short range). I suppose you could get a small battery and suitable islanding control unit to keep the 'mains' up and then use the V2G to provide most of the necessary energy. But that's just blue-skying; you'd need to check the reality.

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revor — Fri, 22 Jan 2021 17:09:59 +0000

Good news today that Nissan will be producing EV batteries in the UK instead of importing from Japan or USA I hope they will not be importing cells from China to manufacture them. My G99 G100 application gone in today hope they will allow the 6kw if not will see the cost involved in increasing the size of the battery. This where being able to use a car battery for the house would be great as car is idle most of the time but house always consuming power somewhere. I saw an you tube video the other month an American guy living off grid bought a battery from a Tesla write off to replace lead acid ones. It was quite a task splitting pack into smaller units reassembling for the battery voltage required and programming the battery back to be compatible with his generation system. You had to know what you are doing. That is quite a bit out of my league.

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Peter_in_Hungary — Fri, 22 Jan 2021 19:03:45 +0000

Posted By: revorMy G99 G100 application gone in today hope they will allow the 6kw if not will see the cost involved in increasing the size of the battery. This where being able to use a car battery for the house would be great as car is idle most of the time but house always consuming power somewhere.

With range still a bit short (of what I would expect) on most EVs if you are using the EV battery to run the washing machine etc. how do you ensure that there is enough power for the unplanned trip?

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revor — Sat, 23 Jan 2021 10:26:23 +0000

@PiH. We have another vehicle and it would be a desperate situation to run the washing m/c off the battery. Still we have not got an EV yet anyway. Not much point can't go anywhere