Upgrading a FIT/MCS PV+ST system to PV only + battery

[sharpener]

Just to say I have a very similar setup with the second set of panels DC coupled, am glad I went that way as with the inverter being bidirectional I can have all my PV go to AC or mostly to DC depending on immediate objective. And on-grid the Victron inverter can throttle them simply unlike a third-party AC inverter.

My 2011 Steca inverters work fine in freq control off-grid. So I imagine yr Fronius would too even if you don't/can't implement the proprietary Fronius/Victron link.

Victron web functionality is useful but the Remote Console can run in a browser on any PC on yr LAN. Also don't buy the (expensive) dongle, you can configure everything over VRM.

I have the entire house behind the inverter but with the 50A pass-through it has not been a problem. Cooking on AGA in winter helps with max demand(!) Not sure you can use Power Assist if you are running in ESS mode.

Have automated the HP so it is tripped off on grid fail giving me time to put it in Noise Reduction 50% power mode. Also have a changeover switch for garage for when I want to charge the car and another for the house so I am not in the dark if the inverter fails, recommend that. If doing it again I would automate with a changeover contactor pulled in by mains from the inverter ACOut.

[wookey]

Is there any reason why you can't/don't have the 7 FIT panels all in a row and the 7 new panels in another row either above or below the FIT panels? Could 7 of the Longi 530s go in the second row?

Hmm. not really, no.

I also realised today that I could use 6 480W panels instead of 7 410W ones and that gives me much better packing on the roof and another kWp (7.12 kWp total) as I can fit 8 530W ones:

This scheme would be perfect except that there don't actually seem to be any 480W panels left in the world. This one would be ideal: https://midsummerwholesale.co.uk/buy/eurener/mepv-480w
but I can't find anyone that has any left. Anyone know different?
The only 480W panels the right size (~1900mmx1134mm) I can find that are actually in stock are in Germany and £156 each plus £220 delivery, (https://www.ebay.co.uk/itm/166979621653) which is awfully expensive. Although in total I'd be paying an extra £750 to get about £142/yr more electricity so still covers itself in 5 years so it's not completely mad.

It seems that 480W was never a common size.

This is what your suggested layout looks like, and it does seem like a better plan.

That gives 6.58kWp using panels that are actually available. The 7th 530W panel means a 2nd DC/DC MPPT device for £350, (another 5 year payback, but also better shading performance). Annoying but still worth doing.

I feel a more thorough spreadsheet coming on... :-)

[robl]

As Wookey’s-neighbour with a sunsynk+Seplos battery, i thought I’d add a comment about efficiency here.
When I first installed this system, it had no PV attached for a month, and it had a mid certified bi directional meter on the AC feed line. I’d definitely recommend a meter, for anyone installing this sort of thing. The battery charged up in the ‘go’ period at 4kW, then ‘home matched’ during the day, in winter. On average, over the month, we used around 10kWh/day at 76% efficiency. That 76% sounds dreadful, nowhere near the efficiencies that you see in data sheets - but I note that victron do give better data (they are a better choice if you want full inverter control), and if you use their inverter as I used ours, the charge efficiency at 3kW would be 87%. Output home loads during the day are likely to be low with occasional highs, neither giving peak efficiency (you really cannot just call it 500W average out!) - I’d say 92%. If you assume a 95% round trip battery efficiency into account you end up with 0.867*0.92*0.95 = 0.76.

Since then we’re now on IOG, it’s a longer time window, and I charge the battery at a lower current which clearly improves efficiency as the fan doesn’t kick in. I can’t easily measure it now though, as we have PV on the system confusing things.

[wookey]

It turns out that there _are_ some 480W panels left in the UK.
https://infinite-solar.co.uk/jinko-tige ... -v-bf-jk03

And even having to pay an extra £149 delivery for mixing suppliers, the extra capacity this lets me fit on the roof, combined with matching the letter of the FIT 'agreed capacity' law, _and_ only needing one DC MPPT converter for the new half means that it's well worth spending an extra £470 to get another kWp. The payback on the marginal cost is ~3.1 years. Total capacity 7.1kWp.

I learned from a whole day of dicking about with spreadsheets that electricity is sufficiently valuable that capacity dominates and there isn't any point cheaping out to save capital cost if that reduces capacity (and, if DC-coupling with expensive Victron kit, it is well worth optimising the number of MPPTs needed).

So I've bought those panels before the last ones evaporate. And another decision is made :-)

My sums are a bit simplisitic because I've not properly modelling clipping due to export and inverter limits (which means I won't see _all_ of the capacity increase, but I've ben reasonably conservative about value (just assuming the current SEG holds up for a few more years)) so I'm reasonably happy with the plan, which is now 6x480W Jinkos for the FIT half and 8x530W Longis for the new half. Probably fitted in yet another layout:

[wookey]

I'm trying to work out what to do about export limiting.

The DNO approved my application to add 4.4kW Multiplus II 48/5000 (VICEN/02689/V3/A3 in ENA database) to existing 2.65kW Fronius, (total 7.05kW) with this qualification:

Please note that your generation capacity has been amended as agreed:
Agreed export capacity (including G100 devices): 5.00 kW
G100 export limiting scheme on premises? Yes

What's not clear to me is whether that means they are happy for the Multiplus-II to limit export or if they expect some other device to be added to do this? If so, what?

The Multiplus-II was certified for G100-1, but when G100-2 came out that lapsed and there has not (yet?) been a new one.
This was discussed earlier this year on the old Victron community board: https://communityarchive.victronenergy. ... round.html

Does anyone know whether the Multiplus-II does in fact comply with G100-2 and it's just a matter of time before it gets the right certs again, or if it can't actually do it? I tried asking my supplier about this and they were mostly useless, saying 'go find a competent installer and ask them'.

It seems like it should be fairly simple, and not particularly expensive, to knock up something that sat on an analogue or digital meter and tripped if the output power was too high, but my search-foo is only finding things like the Hark G100 export limiter, which look very expensive (https://harksys.com/solutions/g100-export-limitation/)

Suggestions?

[Stinsy]

I'm trying to work out what to do about export limiting.

The DNO approved my application to add 4.4kW Multiplus II 48/5000 (VICEN/02689/V3/A3 in ENA database) to existing 2.65kW Fronius, (total 7.05kW) with this qualification:

Please note that your generation capacity has been amended as agreed:
Agreed export capacity (including G100 devices): 5.00 kW
G100 export limiting scheme on premises? Yes

What's not clear to me is whether that means they are happy for the Multiplus-II to limit export or if they expect some other device to be added to do this? If so, what?

The Multiplus-II was certified for G100-1, but when G100-2 came out that lapsed and there has not (yet?) been a new one.
This was discussed earlier this year on the old Victron community board: https://communityarchive.victronenergy. ... round.html

Does anyone know whether the Multiplus-II does in fact comply with G100-2 and it's just a matter of time before it gets the right certs again, or if it can't actually do it? I tried asking my supplier about this and they were mostly useless, saying 'go find a competent installer and ask them'.

It seems like it should be fairly simple, and not particularly expensive, to knock up something that sat on an analogue or digital meter and tripped if the output power was too high, but my search-foo is only finding things like the Hark G100 export limiter, which look very expensive (https://harksys.com/solutions/g100-export-limitation/)

Suggestions?

It doesn't specify you must have G100-2, it says you must have G100, the Multiplus is G100, so good-to-go as far as I'm concerned (unless there is some kind of addendum that clarifies that G100 refers to G100-2).

[wookey]

G100-2 became compulsory for installations after 01st May 2023:
from https://www.energynetworks.org/assets/i ... (2023).pdf

This document applies to all in Customers’ Installations connected at any voltage, where
new load or generation equipment is commissioned on or after 01 May 20231, such that
there is an agreed need to restrict the flow of current at the Connection Point

So G100-2 does now apply, but in practice just sending in an undated cert saying 'G100' may well keep them happy.

I found this good page on the new requirements for G100-2:
https://www.alternergy.co.uk/blog/post/ ... compliance

And the relevant new stuff is a much more sophisticated state model for the control system:
G100-1 just said 'bring excursions back to agreed level in <3 seconds' (inferred from other docs - I've not found/read the original yet)

The new one has 4 operating states '1:Normal', '2:Occasional Excursion', '3: Failed' and '4:No CLS,Lockout'.
'2:Occasional Excursion' state:
* Periods of <15 seconds over export or import limit are permitted (but should be occaisional)
* Up to 1 minute is allowed to bring back under limit (unless DNO ask for shorter)
'3:Failed' state is entered if:
* the CLS exceeds the MIL or MEL thresholds for greater than 60 seconds
* the CLS exceeds the MIL or MEL thresholds for more than 15 seconds but less than 60 seconds, three times in a 24 hour period
* there are two 15-seconds-or-more consecutive breaches of the MIL or MEL within a 10-minute window.
'4:Lockout' state is entered if:
* the CLS has entered state 3 more than three times, then the CLS is locked out and normal operation of the devices is not permitted. Unlocking of the CLS can only take place by a qualified professional.

'CLS' is 'Customer import/export Limitation Scheme' and comprises the combined effect of all the control systems and sensors in the installation. Typically the inverter(s), sometimes with external current meters/sensors.
MIL is Maximum Import Limit, MEL is Maximum Export Limit

All of this is just current monitoring and keeping track of times/states. If VenusOS doesn't already do this then it can easily enough be made to do so. So I'm happy that the hardware complies, and that it could be demonstrated.

We already know from the G100-1 doc that the output goes to zero within 5s if comms to the controller or current sensor is cut. What I don't know is if this is true for the internal sensor because that wasn't in the cert, and of course it's harder to test.

So when the approval says "G100 export limiting scheme on premises? Yes"
It means something should be doing the above.