Installing more PV. Questions on Export Limitation / Inverters

[marshman]

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[nowty]

Background.

Already have a 3.15kW pk system on the original FiT (2010) rate so don't want to upset anything on that front. With the recent hike in electricity prices and abundance of cheap panels on auction sites I am looking to add another chunk of PV and possible battery storage to "smooth" peak consumption.

Looking at adding approximately 5kWpk of panels - 2.5kWpk facing ESE and 2.5kWpk facing WNW - to flatten the generation throughout the day, both at a shallow angle of around 11 deg. No shading.

Question:

1. DNO permission. Local DNO is UK Power Networks, I assume I have to ask their permission before connecting as I will be way over the "allowed" 16A limit? That being the case I doubt I will be allowed as we are "at the end of the line" in a very rural area. So I assume I will have to limit the export to 16A. Anyone any experience of this situation and know what forms to fill in, who to contact?

2. Assuming I do have to export limit then if I got a G100 compliant 5kW dual MPPT inverter with export limit and connected the east facing array to one input and the west facing array to the other will that work OK? Think of something like a Solis 5.0kW 5G Dual MPPT. Would that satisfy the DNO.

3. How would that work with my Apollo Gem solar diverter which I use to divert excess power to my immersion? I ask as both woul dbe monitoring current flow in and out of the house and may interact?

4. (last question) I have an export meter fitted and get paid for actual export rather than deemed. I tried to change back to deemed a couple of years ago after I fitted a heat pump but was told that I couldn't. Do I have to tell my FiT provider that I have added more PV so that they "pro rata" the export payment?


Thinks in advance

Roger

1) Officially yes, unless you go down the connecting PV via a charge controller to a set of batteries like Joeboy did.

2) Probably, but remember your whole system should be G100 compliant, so if you already have a system which wont be changed, you might need to implement a very low export limit on the second system.

3) Maybe, my immersun diverters work but only because they allow me to set a min export value.

4) As long as the second system (and your proposed battery system) does not go through either the generation or export meter, then no need to inform the FIT provider.

[marshman]

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[nowty]

Thanks Nowty.

2 more questions based on your answers.

NO.2 . I would have thought that the export limiting function of an inverter would monitor the export current and just ensure it does not exceed a certain lever, i.e. 16A. If that is the case it shouldn't matter that the FiTs system is providing the lions share of that as the limiting inverter should just throttle back until the criteria is met. OR are you saying the DNO will require a "hard limit" . So FiTs system (3kW) capable of 13A so new add on will have to be limited to 3A - (690W). Not really an issue as I won't get paid for the export anyway.

NO.4. The export meter is the main house meter so everything goes through it. Can see it being a bit of a nightmare getting the FiT provider to pro rata the Export but not the Total Generation. Will have to do some more digging on that one.

Roger

2) My answer was "worst case", your expectation may also be correct, depends on the DNO and how the export limiter will work in practice. With the first unrestricted system, will the second limited system still respond in the 5 second limit ?, for example. You might get lucky and they say you can have a higher export limit or they say that's fine with a second limited system.

4) Ok, your export meter is your Smart Meter ?, in that case that's going to cause a headache with the FIT provider. Yes it might be possible to pro-rata the export, that's usually done on sharing a generation meter, but don't see why they could not do it for export but don't know if its even written into the rules. However, if its a DIY job with no MCS certificate, your FIT provider might just cancel your whole contract or maybe just your export payments. An alternative might be to opt out of FITs export and claim SEG on exports.

Time and time again, similar questions like these have been asked in the past here and elsewhere, and there is no easy answer to folks with an original FIT system and now want more, especially as the FIT scheme is now closed. There is another person on here who had deemed exports, but exported more than 50% so they tried to switch to measured exports (on FIT) but were refused because the FIT scheme is closed. But they were able to opt out of deemed exports and join SEG for exports and still keep the FIT generation payments.

[marshman]

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[nowty]

No it is not a smart meter, I had it installed when I had the system installed as I was exporting around 80% of generation & SSE was installing them at zero cost. Since then I have had a heat pump fitted and also a diverter to heat the water so my export is now minimal. I just read an Ofgem guidance document which says I can opt out of FiT export payments. If I do that then that issue goes away. That may be the simplest thing to do as the export payments are not a lot, probably less than £30 per year. I suspect I would get more as an SEG !

OK but I presume then its locked down (with a lead seal) as in you cannot easily fit a henley block between the export meter and the main import meter (smart or otherwise).

Or, you've got no means of isolating the incoming live without pulling the main fuse.

[marshman]

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[nowty]

It is the main meter! Has Rate 1, Rate 2 and Export, So any Export will be recorded, can't get round it. Pic below - I don't want to get it changed as it will disturb the Spider!

OK, then apart from it not being Smart, it is your main import meter so, nothing can be done, apart from opting out of FIT export without the FIT provider headache.

As when we are on the historic top whack FIT payments we don't want to risk losing those do we.

[Burble61]

Just on changing FITS export payments from actual to deemed.

Its entirely possible, have done it. Although with SSE its not! They never explained why, its not down to regulation or or legislation, I strongly suspect their reluctance down to internal IT / process issues.

[nowty]

Just on changing FITS export payments from actual to deemed.

Its entirely possible, have done it. Although with SSE its not! They never explained why, its not down to regulation or or legislation, I strongly suspect their reluctance down to internal IT / process issues.

And you've done that since the FIT scheme closed ?, or was it a while back ?

Originally the intention was to put us all on actual exports when smart meters were installed and the intention was deemed FIT folk could not opt out of smart meters. But I think the law of "freedom" meant we could not be forced to have a smart meter and then I think it became too complicated as the FIT scheme was coming to an end, so it ended up being a fudge.