The Solar Thread

Footflaps- I don’t have an I boost or similar so immersion just runs at full tilt when on

doing that manually will get boring very fast

Yes having done a quick google, lighting doesn’t run at 13 amp so a high current rheostat is needed and it needs a heat sink too.

Normally dimmers just chop the 230v using triacs so the on period is less than 100% (or at least the ones I used to build). I assume someone would make a 13A version…

A rheostat sounds like a very old school solution.

might it be easier to run two small immersion heaters off two plug switches?

Footflaps- I don’t have an I boost or similar so immersion just runs at full tilt when on

You could automate it – I have a system [that uses a Pi, IFTTT and a Warmup wireless thermostat] to switch the electric underfloor heating on and off when there’s enough generation which works pretty well.
But that’s ‘only 800w so if there’s an overlap of a few minutes when the generation has dropped but the floor is still on then it’s not the end of the world, but 3kW is another matter. And the times when your panels are producing more than 3kW + your house background usage are going to be fairly limited.

You’re much better off stumping up for a diverter – it’s the best solution for water heating.

might it be easier to run two small immersion heaters off two plug switches

That assumes two immersions in the tank – and still a PITA.

You’re much better off stumping up for a diverter – it’s the best system for water heating.

Or not worrying about drawing off the grid for 30 secs when you boil the kettle….

Although I realise it becomes quite obsessive. I worry about sequencing kettle, microwave and grill when cooking, so as to never exceed our 3.8 kW inverter limit. Totally pointless in the grand scheme of things, but I do ‘get it’!

We’ve just signed up to Octopus’ dynamic export rate, although not yet seen the prices they offer.

Not sure if it’s the same as their “Agile” tariff, where the unit price varies every 30 mins.

Been on the agile since install, just moved onto the 15p tariff as we were consistently below this threshold very rarely above 15p.

what you are doing would not be possible without the ability to control when the export happens

Not really. My batteries dont allow me to choose. Excess solar goes to my batteries, then my solar diverter then back to the grid. It happens sporadically during the day when none of the others have any demand.

Anyway I am looking to extend the PV I have from 5.6kW (5kW inverter) to around 8kW to provide for the increased draw that my future EV will demand. If I didnt export to the grid (at around 15p per kW) then each kW would provide around 3 miles (dependent on several factors of course) of range (of course I give up the export benefit so its not free) but in Feb alone I have estimate around 180 miles so far. Thats roughly half our car monthly mileage.
If I add 2.8kW (assuming I can) then should I add another inverter or feed into the current one??? Tempted to add another as even in Feb I have seen bursts of >5kW so I would be giving quite a lot of free energy away…

Been on the agile since install, just moved onto the 15p tariff as we were consistently below this threshold very rarely above 15p.

Do they use the same value for import and export on Agile?

Or does the export have a lower dynamic value?

True!

As you said, doing it manually is going to get old very quickly – you could switch it on then go out and it cloud over leaving the immersion on, or just forget to switch it off!

If I add 2.8kW (assuming I can) then should I add another inverter or feed into the current one???

I have wondered how this works, I assume they talk to each other (I think the Huawei ones do anyway). Otherwise the whole backing off thing might be a bit random as each thinks it is the only inverter in the system. Or maybe they co-exist fine. Pretty sure with Huawei all the inverters link via Ethernet so act as one.

That assumes two immersions in the tank – and still a PITA.

you can (I think) get dual element immersion heaters for exactly this purpose – the original purpose was one of them run off the economy 7 timer and one for boosting. No idea if they’d be too powerful when both run together

https://www.backerelectric.com/shop/product/27-685-mm-copper-dual-immersion-heater-09432vc-type-627.asp

its worth noting that immersion heaters should be run off dual pole switches, which I doubt any remote control plug hack would achieve.

I assume they talk to each other

I’m pretty sure the Foxess ones work alongside each other and have seen screenshots of the software supporting that. Quite pleased with the vendor so far (battery and inverter) so no need to change I suppose but as the roof is low it is borderline DIY…. Obvs with an expert to make the final connections.

export is way lower than import for obvious reasons orherwise many would just load shift back to grid when prices above import. i was on the dynamic agile export averaged 10-13p, so a flat 15p is better for me. Im still on E7 for import, want to move onto tracker but there is now a 6 month wait as they are only doing 50 applications a day. Flat rate will have to do meantime

http://mysmartenergy.uk/  gives you the details

If I add 2.8kW (assuming I can) then should I add another inverter or feed into the current one???

This is what I want to do and I’m going to add another inverter for a couple of reasons:
1) Existing array is on two strings and the inverter accepts two strings, so there’s no room for a third string [extra panels would be ground mounted]

2) My existing FIT does not allow any alterations to the equipment and I’m not going to risk the [substantial] income that provides!

Two questions….. will your existing inverter take the potential generation from a combined 8kW array and will your DNO allow an increased generation (or are you not going to tell them?

Not really. My batteries dont allow me to choose.

I think your misunderstanding.

With batteries you have a choice.

Without you have no choice

@sharkbait Good questions I will have to check the spec in detail of the inverter. My setup also already has 2 strings. I am waiting for a call from my installer and happy to be open with them and see what they suggest.

Solis numberjumbler app

Ah – fellow tea leaf readers.

I think your misunderstanding.

How so?

I think your misunderstanding.

How so?

I have absolutely no idea.

If you are upping generation (and the new inverter is linked to the grid) You will still need to advise your dno with a gn99 or whatever the form is.. might be worth checking they view this as “not a change”

Two questions….. will your existing inverter take the potential generation from a combined 8kW array and will your DNO allow an increased generation (or are you not going to tell them?

I’m pretty sure that risking the payments on the FIT scheme is the least of your concerns, as OFGEM monitor individual trends and can not only demand a full repayment of anything paid to you under the scheme, but then cheerfully pass the entire case over to the police.

A system diagram is placed on record when the system is installed, so it’ll be immediately obvious if anyone visits to read the meter (or because your generation trend has doubled) if it’s been modified.

It’s honestly not worth fiddling. Any new system needs to be completely independent from the existing install. That’s not to say that you can’t do it, but you need to be very careful about how it’s done.

It’s honestly not worth fiddling.

Agree. Thats why I said this

I am waiting for a call from my installer and happy to be open with them and see what they suggest.

It’s honestly not worth fiddling. Any new system needs to be completely independent from the existing install.

That’s certainly my feeling.

I’m pretty sure that risking the payments on the FIT scheme is the least of your concerns, as OFGEM monitor individual trends and can not only demand a full repayment of anything paid to you under the scheme, but then cheerfully pass the entire case over to the police.

A system diagram is placed on record when the system is installed, so it’ll be immediately obvious if anyone visits to read the meter (or because your generation trend has doubled) if it’s been modified.

It’s honestly not worth fiddling. Any new system needs to be completely independent from the existing install. That’s not to say that you can’t do it, but you need to be very careful about how it’s done.

Fairly sure that surfer doesnt get FIT payments – in which case im not sure why anyone would be handing anything to the police.

as for the system diagram – you over estimate the system — ive seen whats on record for my system at DNO level and it amounts to a piece of paper that says ive installed solar and i wont export more than 3.6.

The MCS which is not a legal requirement has a kit list and a schematic but no one will be chasing based on that

My original question seems lost. Im shocked…

You are right @trail_rat I dont get FIT.

I’d be genuinely amazing if anyone is checking up on installed systems and also amazed if the records were correct for most installed systems….

It’s probably all stored on a access database somewhere.

My G99 cert was far more comprehensive and the paperwork from the DNO arrived back from them with all of my system diagrams, etc embedded into the sign off paperwork.

Another shout out for the accuracy of the PGIS Database. Its not totally clear how many Kw my system would generate in February from the graphic but I read that as being 280kW (28 day Feb) As it stands (its cloudy here so may get another kW or so today) I have reached 279.08kW which seems an incredibly accurate estimate…

Its not totally clear how many Kw my system would generate in February from the graphic

If you hover over the graph in the original web page it tells you the actual value for each bar.

@footflaps Cheers. I never noticed that and the above was a screengrab that I embedded in a Spreadsheet alongside other numbers.

This was our prediction:

Solar PV output by Ben Freeman[/url], on Flickr

But we seem to have done much better (over double)….

Feb 2023 by Ben Freeman[/url], on Flickr

which seems an incredibly accurate estimate…

Pot luck, it will just have numbers in for ‘average cloud cover’ for each month for a given region, but no two years will be the same in reality….

@sharkbait, you mention a few posts up you get FIT payments. Do you have a generation meter fitted between inverter and your mains supply?
Similar musings here to add another system on the E/W garage roof, but would be separate and not connected to the generation meter ony FIT paying setup.

Do you have a generation meter fitted between inverter and your mains supply?

With a smart meter, they can just read your generation on the fly as it measures import and export….

We also have a ‘non smart’ generation meter.

@sharkbait, you mention a few posts up you get FIT payments. Do you have a generation meter fitted between inverter and your mains supply?

Oh yes.  It counts all the 65p’s I get (or whatever it is per kWh generated now)

🙂

If I add more PV the panels will feed another inverter (and meter just ‘cos) and then connect to the existing PV feed after the generation meter and before the consumer it in the stable.

Okay – partially in response to the above posts about location/capacity, February’s figures are in!

5.4kWp array – SSE Facing at an inclination of 30deg. 14x385W panels, no optimisers, little>no shading from late Jan, but some in December, 12kWh battery now expanded to ~19kWh of battery storage.

In February we generated 282kWh of power and used 92% of it. We imported 165kWh from the grid and exported 21kWh to it. This export was largely due to 2-3 sunny days where generation exceeded storage/usage and is one of the reasons I’ve added the second battery. The battery allowed us to store and use ~190kWh we would otherwise have lost. The array has rarely exceeded 3.4kW of generation.

To compare. December was 140kWh, January was 200kWh, Feb was 280kWh.

That’s interesting @daffy and I need to look at those numbers to calculate the addition of another battery module which I suspect will be very helpful. Trouble is they are £2500…

Like many others, I sized our battery on what our average (80-100%) daily usage is/should be. I think this is a mistake. The weather in the UK is rarely consistently sunny, so having more capacity to store on the good days often gets you 1.5>2 days which might just get you through a cloudy day, etc. Also, in winter we tend to use more power as the boiler pumps are running more often laundry is dried inside, we eat more hot meals etc, so average usage might be better planned based on winter usage with a plan to charge the packs off-peak.

I also couldn’t afford the second pack at the time of install as it was £4500 (for just the pack!), but managed to get one for £1600 brand new on ebay and fit it myself with the pairing kit from LG. Total cost was £2150 for the battery, RESU plus, cables, tools, ducting, etc for an additional 6.5kWh. Whether it pays off…that’s another matter, but I thought it might be worth a shot.

Simialr figures to Daffy here in SE Wales

4.8 KW array on south facing 38 degree roof with no shading
1.1 Kw on south facing 5 degree roof with some shading at this time of year.
Run through 2 MPPT controllers in a Victron system with 14 KW Pylontech LiFePo batteries. Grid tied on ESS settings with export not enabled. Running 2 households and a farm workshop and sheds (which are quiet at present)
February figures are:
Consumption 328 kWh
Solar generation 275 kWh
Imported from Grid 88 kWh
Exported 0
For comparison December gave 111 kWhs and January was 203 kWhs