Solar for Dummies.

A thread here https://www.boards.ie/discussion/2058288583/esbn-new-regulations-on-nc6-form-on-6kw-25amp-inverters-may-31-2023#latest

Looking for some advice from the Solar experts on here...

Our electricity consumption is ~50units ea day, probably split almost evenly (50:50) between day and night units.

I have been playing around with PGIS; in order to try and maximise generation from the panels it would be best to have them on 3 separate roofs - I can only fit a maximum of 6 panels on the south-facing roof & so was looking to try and get panels that are as powerful as possible, e.g. Jinko Tiger Neo N-type 60HL4-(V) rated at 470WP.

To avoid mismatches I would probably get all the same panels but what options are there for connecting 3 strings to an inverter? I was thinking of trying to install 6 south-facing panels, 6 west-facing panels and 12 east-facing panels (according to PGIS, at my location east-facing panels are slightly more productive over the entire 12 month period)

I would get a hybrid inverter but might hold off on battery storage initially - there are 2 EVs so fortunately I can drive one whilst the other is charging.

Is it easy to add a DIY battery afterwards? Is there anything I have to ensure the installer does so that I can add a battery later (apart from making sure a hybrid inverter is fitted)?

Anything I've forgotten??

Thanks in advance

Some inverters have dual inputs per MPPT and can handle double the current. Like the Sunsynk 8.8kW. You could then have the 12 E on MPPT1 and the 6 W and 6 S on the dual input on MPPT2

A non hybrid inverter like a SMA Sunny Boy has 4 pairs of inputs for strings. This could also work for the three orientations mentioned above.

There are probably other brands offering similar that would be also under the NC6 application limit.

Then add a Sofar or similar later when adding a battery.

So with three roofs, you are unusual - but a good few people have dealt with this. Typically the "easiest" way is to get a 2x string inverter and put optimizers on the panels on your south (6) and west (6) facing roofs. Then the 12 east facing panels would go in on the other string (without optimizers). The use of optimizers is debatable. Some people couldn't be bothered, fearing that if one fails they'll have to go up onto the roof to replace it. There's some merit to that, but I think the failure rates are so low that it's like 1/100 (or there abouts) with 12 optimizers that you'll get a failure in 10 years. Those odds are fine in my book.

Going the 3 or 4 input string inverters would be the ideal solution as unkel mentions above, but those puppies are hard to get and (probably) beyond what a supplier will install for you, even if you supply the kit.

I'm also a big battery proponent, but with 2x EV's I'd be slow in your case. Your EV's will be able to soak up a lot of excess, assuming that one is present in the driveway when the sun is shining of course. Another option is to simply get a "normal" (non-hybrid) inverter and get down the road a ME3000.

If money was less than an issue though, with your consumption. Go big. 10Kwh battery along with 8-9Kwp in panel, hybrid inverter.

Aside: 50-50 split on consumption with day/night? You not charge the EV's at night?

Don't think so... Others will confirm

@alfa_aficionado - be careful with the high wattage panels. They are a con. In the way that they are not producing materially more electricity per sq meter of panel, the panels themselves are simply bigger. So fewer of them will fit on your roof. So take proper measurements of your roof and of how many panels of a certain make / model would fit, before you buy anything...

unkel's 100% spot on there. If it was made in the last 1-2 years, virtually all the panels are with 1% efficiency of each other. E.g

Longi 410w panels = 1722 x 1134 x 30mm = 1.95m^2. So watts per sq mq = 410w/1.95 = 210.25 watts/m^2

Longi 450 panels = 2094 x 1038 x 35mm = 2.17m^2. So watts per sq mq = 450w/2.17 = 207.37 watts/m^2

The initial thinking is that the 450w would be better, but as you can see above it only produces more because it's a bigger panel. In terms of actual efficiency the 410w panel is actually more efficient, although it should be noted that 3-4watts difference in a sq meter is nothing.

Ultimately, it depends on the size of your roof and how many of each you can fit. You might be able to fit more of the smaller panels giving you a higher overall output, or it may work out that the larger ones maximises your available space.

Sizes of a fair few panels can be gotten at midsummer e.g. Longi 450w Silver Framed Split Cell Mono (White Backsheet) (midsummer.ie)

What roof height/space do you have to work with for the install. Could you get two rows landscape instead of one row portrait?

If you can only get one row landscape what maximum height could the panels be?

yeah its an interesting balancing act. During the winter i see max 2.5/3 kwh generation for december/jan.. but last week i was over 5 for periods of the day.. ive a 7kwp array split over 2 aspects/strings - south east/north west.. 4kwp/3kwp - my inverter is 5kw

Switching to landscape doesn't really get me any more panels - the roof has a depth of <2.5m

What @bullit_dodger said. In fact a standard size PV panel is just 165*99cm. All the bigger wattage ones we have seen in the last few years are massive cons. Be very aware, buy what fits while making sure your € per wattage is kept to a minimum.

Apologises. I didn't know you were going for the grant, I thought this was a self-build and missed that in the thread. I think it's 30cm to the apex of the roof, but yeah, 50cm to the sides. Might be close to get 2x landscape in, but I think you could do it. Might have to go with smaller panels. I went for these guys myself for 2x panels I put on the shed.

Q Cells G9 350w Black Gappless mono module (midsummer.ie)

1.67m x 1.03m

No I think you are right Redlim. I thought it was 30cm, but I was working off memory. In that case you should be good alfa.

I guess the biggest hurdle redmagic with that is getting a Wifi controlled relay which can take 16A - but yeah in theory it should be doable. It'd be an all or nothing though, an EDDI will detect (say) you have 400w excess going to the grid and then pump that into the element. You'd probably have to wait until you had say 2Kw being exported and then flick the switch. Should be automatable though easy enough assuming you have access to the Inverter telemetry letting you know what you are exporting at a specific time. Or a shelly etc.