Solar Install Confustion, East West Split

ashok.198311

Hi,

I am based in Cheltenham and I am getting Solar Installed Soon, Quote is as below.

16 JPSOLAR 395w Full black Panels. (East West Split 8 East, 8 west)
Giv energy 3.68 KWH Hybrid Inverter.
Giv Energy 5.2kwh battery.
Zappi Charger

My usage comes about 8-9 kwh per day. The Install total cost is about £10,400.

Do you think the inverter is Sufficient as this is a East West split I guess it will not be generating full powert at any point of time in the day? I am also in confusion should I be looking for bigger battery 8.2kwh for @800 extra.

Any Suggestions on this please? What you guys think about the price?

Magnitio

For a few hours on a sunny day the panels may generate more than 3.68kW. The spec sheet for the inverter shows a max DC power of 4500W which your setup exceeds. Certainly worth considering the 5kW inverter and the larger battery. I had a quote for a similar system, with 5kW inverter and 8.2kWh battery at £10,200 in November last year.

ashok.198311

Magnitio said:

For a few hours on a sunny day the panels may generate more than 3.68kW. The spec sheet for the inverter shows a max DC power of 4500W which your setup exceeds. Certainly worth considering the 5kW inverter and the larger battery. I had a quote for a similar system, with 5kW inverter and 8.2kWh battery at £10,200 in November last year.

Thanks, it looks like this is the best price I can get at the moment.. yes the inverter spec sheet says 4500dc max. When I asked for 5kw inverter they are saying 3.6 would be better as the load will be distributed evenly. Would you mind letting me know what's your east panel generation in the afternoon please..?

With all the prices gone up this is the best quote I can get..

Petriix

Inverter undersizing is normal, and (counterintuitively) leads to better overall yields when correctly matched with your panels.

Unfortunately the 8.2kWh batteries are in short supply and, in general, prices have gone up by ~30% recently. I'd consider the 9.5kWh battery. 

ashok.198311

Petriix said:

Inverter undersizing is normal, and (counterintuitively) leads to better overall yields when correctly matched with your panels.

Unfortunately the 8.2kWh batteries are in short supply and, in general, prices have gone up by ~30% recently. I'd consider the 9.5kWh battery. 

Thanks, i can understand some clipping may happen, but I don't want it to be too high or continued issues.. I was thinking on a ideal day I may have 2.8 kw from the 3.2 on east facing and as the sun passes to west the east will not produce as much and takes over by west. So the 3.6 or the DC rating 4.5 should be sufficient.. 

Martyn1981

Hiya, I think it looks a bit too undersized. I've got 5.58kWp across E/W (see my auto-sig), they are on separate inverters and can spike to about 4.9kW, which isn't that important, but can sustain 4.2kW in ideal conditions, when the sun is very high (Jun and July) and can 'see' both sets of panels at the same time. Pro-rata, you'd be around 4.76kW.

That's a bit too high of a waste, I think, but not the end of the world if the max permission you can get is 3.68kW, but as others have said, it's also a lot for the inverter. A bigger inverter, perhaps 5kW, even if capped to 3.68kW export would seem better.

I suppose it gets more complicated as it's a hybrid inverter, so perhaps it could be set to export 3.68kW, whilst putting some excess into the batts, but even if the batts started low, they might fill up quick, capping generation again. But if the batts are set to fill first, then on a sunny day, they will be full, long before generation starts to approach the peak around 1pm (BST).

ashok.198311

Martyn1981 said:

Hiya, I think it looks a bit too undersized. I've got 5.58kWp across E/W (see my auto-sig), they are on separate inverters and can spike to about 4.9kW, which isn't that important, but can sustain 4.2kW in ideal conditions, when the sun is very high (Jun and July) and can 'see' both sets of panels at the same time. Pro-rata, you'd be around 4.76kW.

That's a bit too high of a waste, I think, but not the end of the world if the max permission you can get is 3.68kW, but as others have said, it's also a lot for the inverter. A bigger inverter, perhaps 5kW, even if capped to 3.68kW export would seem better.

I suppose it gets more complicated as it's a hybrid inverter, so perhaps it could be set to export 3.68kW, whilst putting some excess into the batts, but even if the batts started low, they might fill up quick, capping generation again. But if the batts are set to fill first, then on a sunny day, they will be full, long before generation starts to approach the peak around 1pm (BST).

Thanks, for me I raised a question asking if I should be going for 5.. they said I may see clipping on very sunny day but told it can also handle about 4.5kwh.. i don't mind a bit of waste as I have been told having a small inverter is more efficient..

ashok.198311

Martyn1981 said:

Hiya, I think it looks a bit too undersized. I've got 5.58kWp across E/W (see my auto-sig), they are on separate inverters and can spike to about 4.9kW, which isn't that important, but can sustain 4.2kW in ideal conditions, when the sun is very high (Jun and July) and can 'see' both sets of panels at the same time. Pro-rata, you'd be around 4.76kW.

That's a bit too high of a waste, I think, but not the end of the world if the max permission you can get is 3.68kW, but as others have said, it's also a lot for the inverter. A bigger inverter, perhaps 5kW, even if capped to 3.68kW export would seem better.

I suppose it gets more complicated as it's a hybrid inverter, so perhaps it could be set to export 3.68kW, whilst putting some excess into the batts, but even if the batts started low, they might fill up quick, capping generation again. But if the batts are set to fill first, then on a sunny day, they will be full, long before generation starts to approach the peak around 1pm (BST).

My house Is faulty east and west roof.. it is actually facing 85 degrees west.. so the east roof is 95 degrees and west is 85 degrees..

Martyn1981

You've actually got a nice set up, and whilst an E or W roof only generates about 80% of a south facing roof, you get to install twice as much PV, for less than twice the cost of two S facing roofs. Sadly, the bulk of the 20% loss is all in the winter months when gen is pitiful, as the sun rises in the SE, sets in the SW, and doesn't get very high.

I think you should ask the installers to apply to your DNO (District Network Operator) for permission for ~5kW export.

I know very little about batts, but the experts on here may be able to suggest ways to prevent the batts filling before peak generation, to minimise capping, and/or perhaps a bigger batt. Does also depend on how much leccy you use in the evening and night, since even a bigger batt in the summer might only reduce capping for one day, as on day two it'll be half full in the morning, and max out early on day two.

BTW I'm jealous of those panels, my 2011 panels are 235Wp, and my 2012 (WNW) are 250Wp. Pro-rata I'd be close to 9kWp ...... not that the DNO would let me.

Magnitio

Not sure there is a straightforward yes/no answer. It will depend on your finances, future energy prices and how you use it.

If it is a "fit and forget" installation, then you will hardly notice the output clipping and battery size limitations. If you monitor it daily, adjust your lifestyle to maximise the use of solar and battery, and minimise grid usage, then you will probably get frustrated at the lost output, exporting to the grid when the battery is full and importing when the battery is empty. As you may have guessed, I currently fall into the latter category, so am happy with the over-specified solution that I had installed.

JKenH

I would agree with Mart’s comments above. 

I have an E/W set up but in reality it is ENE/WSW. I have 3.6 kw on my East roof and 4.2 on my West both with 3.68 inverters. I have seen peaks of 6.3 kw but not consistently and around 4.7kw sustained in perfect conditions. Pro rata that would work out at a peak of around 5.1 kw and 3.8kw sustained  on your system. 

I do get some clipping on my West roof but none on the East. That 10 degrees difference in orientation between your two roofs will be noticeable. Over its lifetime my ESE roof has generated 7.88MWh and the WSW 11.01MWh but that’s a difference of orientation of 45 degrees. 

I find the difference between my system and a S facing one of the same size would be around 25% annually with the loss most noticeable in winter. For instance I only generated 64kwh this last December compared to795kWh in June. My best December generation of 104 kWh compared to my best May of 1029 kWh. Having said that for around 8 months off the year you will have much more useful generation around breakfast time and around 5-7pm when household demand is quite high.