Ronski's Solar & battery DIY build with whole house backup

Journey said:
That is actually not strictly true, you can use 'alternative' certification as MCS isn't a legal requirement, as per the Ofgem rules and SEG licencees are deemed to be able to accept other standards. Check the Ofgem "Guidance_for_seg_licensees_final.pdf" section 4.6, 4.7 and 4.8.

Negotiating with the SEG licensee is easiest done with a G99 system though, as you'll get certification from the DNO which you can argue is acceptable for export if it is acceptable for connecting the equipment to the network, especially as the requirement for a smart meter (for SEG) now means they have a guaranteed correct export figure.

Obviously you need to chose wisely but Octopus have accepted customers without MCS on new systems via their SEG team, and the relevant documentation being provided to show the system is compliant.
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Yup our install is certified through something called flexiorb which allows us to export via SEG.
 
Thanks for the info Ronski.

We're not heavy electric users and use about 2500 - 3000kwh a year so the 16 x 280ah batteries would be overkill unless we moved over some of our gas usage which isn't trivial.

Presumably most systems like to operate using 48V batteries so I'd probably look at some of the smaller batteries that EVE do.

As you've pointed out with the cheaper night time tariffs (assuming they continue to exist and I can get on one) then I'd guess a battery alone would save about 60-75% off the unit cost which would equate to about £600 a year.

At that amount it's not really worthwhile for a commercial system unless eletric kw unit prices go up significantly but it may be viable for a cheaper homebrew system. I also find the whole thing quite interesting too.
 
If you're on a capped rate you could switch to Bulb, they have an EV tariff (doesn't require an EV), I've just switched and I'm paying exactly the same rate, and when the time comes I'll switch to the EV tariff. Bulb may possibly be bought by Octopus. Unless changing to a fixed price contract most suppliers won't take you on.
 
Ron-ski said:
If you're on a capped rate you could switch to Bulb, they have an EV tariff (doesn't require an EV), I've just switched and I'm paying exactly the same rate, and when the time comes I'll switch to the EV tariff. Bulb may possibly be bought by Octopus. Unless changing to a fixed price contract most suppliers won't take you on.
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I'm actually with Bulb at the moment and had seen their EV tariff and that's probably the one I'd go for as it seems no EV is needed.

For me the off peak is about 9.3p so higher than a lot of other areas but still significantly cheaper.

Am I right in thinking that you're going to be looking at about £5k in parts for the battery, inverter and wiring side of things for what will be about a 15kwh system?
 
Including the solar the panels the whole lot is at least £10k mark - I'm really hoping the electrician is kind to me as that's not yet costed.

If you took the panels, mountings and solar charge controllers out then that would save roughly £3.2k, but I am going with an inverter (Quattro 48/10000) that can supply 8kw and its an expensive make, so if you went with a smaller inverter you could reduce that a lot further. The 4kw one (Victron Multiplus II 48/5000) is £1272 inc vat.

Yes the battery will be about 15.5kWh
 
Ron-ski said:
Yes please, I believe I need two Smart Solar MPPT 140/45TR, that's according to data I entered at https://www.victronenergy.com/mppt-calculator

6 panels on each string, likely 405W JA Solar Mono PERC Half-Cell MBB Black Frame solar panel.
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The SS MPPT 150/45 can be had for £358.18 from - here! although you could run a single 150/85 if you ran 3s/4p although that is a fair whack more wiring on the panels, but would mean only buying one controller at £565 from - here! and if you want a bit more headroom, then you can get the 150/100 for £570.92 - here! that would allow a max PV input of 5800w vs 4900w of the 150/85, you still need to do the 3s/4p though.
 
Ron-ski said:
Thanks, I'll have an east / west panel arrangement so need two charge controllers
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The shaded strings that are in parallel do not affect the voltage of the strings that are in full sun, so you have 2x 3 panels for your East strings and 2x 3 panels for your West strings, then use a pair of 4 to 1 solar branch connectors (about £15), plenty of info around that will confirm this for you if you are unsure. :)
 
Ron-ski said:
Including the solar the panels the whole lot is at least £10k mark - I'm really hoping the electrician is kind to me as that's not yet costed.

If you took the panels, mountings and solar charge controllers out then that would save roughly £3.2k, but I am going with an inverter (Quattro 48/10000) that can supply 8kw and its an expensive make, so if you went with a smaller inverter you could reduce that a lot further. The 4kw one (Victron Multiplus II 48/5000) is £1272 inc vat.

Yes the battery will be about 15.5kWh
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Thanks for the info.

Yep a smaller setup with 10kwh battery and 4kw output would be sufficient for us.
 
Journey said:
The shaded strings that are in parallel do not affect the voltage of the strings that are in full sun, so you have 2x 3 panels for your East strings and 2x 3 panels for your West strings, then use a pair of 4 to 1 solar branch connectors (about £15), plenty of info around that will confirm this for you if you are unsure. :)
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I did find this on Victron site, which states two controllers is better

2 strings in parallel with diferent shading - VictronEnergy

community.victronenergy.com community.victronenergy.com

and this which ultimately comes to the same conclusion

Series strings connected in parallel with different shading - VictronEnergy

community.victronenergy.com community.victronenergy.com

Seems another of those situations where there is lots of differing opinions, so difficult to know which is correct, but two MPPT controllers will definitely work OK, just cost a bit more.
 
Ron-ski said:
Seems another of those situations where there is lots of differing opinions, so difficult to know which is correct, but two MPPT controllers will definitely work OK, just cost a bit more.
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Yes, I am having to use two of them, but that is only due to the array size (in max kWp). The cost difference isn't too bad so I'd agree the dual MPPT controllers are a good idea, I was just offering an alternative as the layout and setup you have is slightly different to a standard shading issue, and the typical responses do not cover your configuration, as you don't have shading as such, since all the panels will be pushing the same voltage in each parallel string, non-sun facing, and then sun facing.
 
Ron-ski said:
I will have some shading, but that will be early morning and late afternoon/evening, it will be worse in the winter as the sun's lower. The morning shading is caused by our tree, which needs trimming, evening shading is a neighbors tree.
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So if you are having shading in the morning and evening, how are you going to layout the panels 3s/2p on each controller, as further up you said 6 panels on each string which is too much voltage for a 150/45 with 6 panels of that spec in series? Assuming you used the data from the JA Solar data sheet?
 
Yes., 3S2P. If you refer to the picture in the first post there is four rows of three panels, each row will be a string, the two strings facing east on one CC in parallel, the other two strings facing west on the other CC.

I put the relevant info into the Victron MPPT calculator, and it suggested the 150/45. Hopefully I did it correctly.

Edit. I'll correct the error in the previous post.
 
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