Advice on PV + Battery config please, you wonderful PV brainiacs

neiljcartwright

I recently had two options proposed with different configurations.  Sorry about the diagrams (my mind works better in pictures).  I would very much welcome your collective thoughts (any advice needs to be couched in terms an idiot can understand).
Option 1. - DC-coupled Hybrid system £9,492.20 (fully installed including scaffolding)

Option 2. AC-coupled system £10,453.70 

Exiled_Tyke

This (or actually the second option) is very similar to what I now have. (Which is 13 panels, 11 through a Solar Edge inverter and therefore with optimisers, the remaining 2 have microinverters).   I'm also very happy with the Solax battery.  My total cost came to about £11k (over two phases) so the prices seem about right.   

I would have thought the key question is whether you need Solar Edge? If there is a significant amount of shading - especially which will affect the panels to differing degrees at different times or day or year (e.g. Chimneys on the property, nearby trees or even other buildings) then SE will maximise production. Otherwise it's a waste of money paying the extra. 

neiljcartwright

We are unlikely to be shaded by the neighbours, perhaps their chimneys (x 3) in Winter on the Eastern elevation.
The pitched roof adjacent to the South elevation may shade slightly as well.  Proposed roof layout is here:-

Is there any research that demonstrates the Solaredge optimisers enhance output by compensating for cloud shading or improve performance significantly?
Do the additional components in the Solaredge scheme lose power between the additional components transferring from DC to AC (then back again for the battery storage) that would negate any additional benefits of the optimisers?
I am hugely tempted by the ability to geek out monitoring the panels individually with the Solaredge solution but if the resultant power output improvement is marginal then it seems likely that this may be an unnecessary nerdy luxury.

Coastalwatch

It's not just nerdy, Solaredge shows the output for each panel so if one goes down you'll soon find out and know which one it is. Plus you only lose that panels output and not the whole string.

Looking at your layout I would suggest there will be shading issues whereby the string output will be limited to that of the lowest performing panel. Couldn't possibly give you any cost benefits but having had a Solaredge system for almost two years now  I've certainly no regrets for having it installed.

Afraid I can't make any suggestions as to which battery systems might provethe most beneficial.

JKenH

Just looking at the photo provided, the East roof could be as much as 30* N of E. My East roof is 15* N of E and is useless in winter - the sun just never hits it a at a decent angle. My best combined result so far this year for my East/West PV array is about 1.6 kwh/kwp, less than half what those with South facing roofs are achieving and I estimate the East roof on its own is about 1kwh/kWp. I think with your East roof it could be even less efficient.

Personally, if you are going to add batteries, I would forget the East roof and squeeze as much on the South roof as you can, perhaps consider using higher efficiency panels. 

Pile_o_stone

I'd always go AC Coupled so that you can charge the batteries in winter from the mains. 

neiljcartwright

Is it not possible to charge the battery from the mains using the DC Coupled Hybrid system?
Looks like you are near me @JKenH in North Lincs, so that eastern elevation may be a little underproductive.

neiljcartwright

Hmmm just read this "Despite being 'DC-coupled' (battery connected on the PV side of the inverter), the Hybrid units are capable of charging from the grid, under 'Force Time Use' mode. The user is able to programme two charging periods over a 24 hour period, to coincide with the low rate tariff periods on a time of use tariff." which looks like the first configuration may be able to charge from the mains.

Exiled_Tyke

Pile_o_stone said:

I'd always go AC Coupled so that you can charge the batteries in winter from the mains. 

I would never charge batteries from the grid. When you look into the cost of even the cheapest off-peak electricity from the grid and then add in the cost per unit of the battery over it's useful life, I've always found that the calculation comes out as more expensive than simply buying standard rate electricity from the grid.   

neiljcartwright

I think I am leaning towards the simpler configuration with the DC hybrid inverter 🤔 : -

• fewer power losses through dc - ac - dc conversions
• fewer parts to go wrong.
• approx £1k cheaper.

I am expecting another proposal early next week from another installer that may add to options.
The benefit of this proposal is that it is interest-free for 3 years meaning I don't have to shell out a large amount in a oner.
Your thoughts are very helpful if you think there is anything else I should consider please shout up.

1961Nick

If there's any chance of you moving house, seriously consider the ac option as it's portable & you can take it with you.