A second array for winter sun

Big Lar · 11-01-2022 5:17pm #1

Would I be mad to do this.

Currently I have a 4.8Kw ground based array facing Southwest, I am considering putting in a second 4Kw array facing south but wondering if I would put it at a 60deg angle to harvest the winter sun a bit better ?

bullit_dodger · 11-01-2022 5:22pm

Not mad at all. Many of us (including myself) have thought the same. If you are thinking of a 2nd array, it would really help if you can adjust the angle of the panels. Even 3 "settings" would be helpful, summer/Autmun & spring/Winter.

If you already have a SW facing one, can you adjust the angle on your current one? You may find that that alone could boost production 30% (depending on the current situation)

slave1 · 11-01-2022 5:23pm

Surely much more vertical for Winter Sun

Big Lar · 11-01-2022 5:28pm

@bullit_dodger: Unfortunately the setup is cheap and cheerful and non adjustable, see below

@slave1: I was playing around with angles on some website and I figure that the gain that I would get from 60deg to around 75-80 deg was 10% or thereabouts in the winter but losses would be greater for the summer months, so 60 was my target

bullit_dodger · 11-01-2022 5:46pm

Big Lar .... I like that a lot!

To be honest, I'd first off have a think about making your existing one adjustable. All you'd need is a hinge down at the bottom which you'd attach your lower rail too, and then some piece of angle iron to "push" the top part away from the wooden beam. Still though, while you would improve things a little, you're azimuth would still be South West facing, so while it would give you some better production, it wouldn't really solve your winter production. Though might be worth considering anyway.

As for the winter problem.....I was thinking of vertically mounting 3x panels to my shed . Yeah, not great in the summer with them vertically mounted.....but in the summer I should have plenty from my main arrays anyway, so those 3x panels specifically tailored for winter might be fine. Similarly for you, even 3-4 4 panels targetted to specifically maximise winter production, angled say at 20 degree away from the vertical at exactly 180 degree facing would be ideal (assuming your existing array is matching your needs for the rest of the year?)

slave1 · 11-01-2022 6:36pm

Nice setup Lar

graememk · 11-01-2022 7:03pm

Yep a south high angle will work well. But I'd not touch your existing array.. them poles aren't going anywhere!

Sure, you'll lose a bit in the summer but you'll be generating plenty anyway. Problem with adjustable, is that it's complex.. it's usually better off just adding a few more panels.

Big Lar · 11-01-2022 8:24pm

@graememk Wont be touching the poles is correct.

Wind would also be a factor where I live, turned out to be a slow evening so see calculations based on 4Kw array facing south.

Used this calculator https://pvwatts.nrel.gov/pvwatts.php

50-60 Deg I'm thinking would be there or thereabouts, perhaps 50 to reduce wind loading

graememk · 11-01-2022 8:40pm

Will have a closer look soon but here's another site that a lot of us use for solar predictions.

Usually beat the pv-gis Sarah prediction https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

bullit_dodger · 11-01-2022 9:29pm

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP%20that's%20the%20calculator%20for%20Europe

I use the europa.eu one too - although both give very similar results in this case.

If it was South facing... being adjustable helps for maybe 5%, although as you say graememk chucking on another panel will achieve the same thing......but for fun I just ran the numbers myself for SW facing array and the benefits are very limited (only 10's of kwhr/year is all, €2-3 basically. So not even the cost of the angle iron!)

If you have a shed and one of the walls faces 180 south, you might get 2-3 panels on that? No wind issues then and you'll get good production for Nov-Feb from that. Crap in summer, but as I mentioned if your existing array covers you well for summer, if you can just solve winter that's a "win", right?

unkel · 12-01-2022 2:12pm

I'm liking that setup a lot, nice work!

You obviously DIY so if you can get a near vertical S facing array added for minimal costs, go for it. Try find the panels as cheaply as you can, that is half the battle of pay back time won before you even start. Keep us updated.

Big Lar · 12-01-2022 2:58pm

Thanks for the info & compliments.

Right so, have obtained permit from "her indoors",it will be another few months before the ground dries up for the job.

I have one or two questions if ye dont mind.

Already have a 4.8Kw array and would I go another 4.8Kw although the inverter is rated for 8Kw, am guessing that will produce full 9.6Kw for certain months over the summer but for the rest of the year it would be adequate. Would doing that break my little inverter ? I think the answer is no but just to be sure..

1st set of panels I got was from a company in Dublin, no complaints the service was good. Just wondering where would one get prices for another 4-5Kw of panels

SD_DRACULA · 12-01-2022 3:07pm

It will not produce more than 8kwh that it is rated for and you need to check the spec of it as you can probably connect 2 strings of 5kwh panels to it.

You also need to be sure the total voltage of the panels does not go over the limit of the inverter as well but if you have one string of 4.8kwh and no issues then adding the same should be ok in theory.

For example I have a 6kwh inverter and it can take 4kwh on each string so 8kwh in total but never goes above 6kwh production.

For panels try the likes of solartricity or midsummer and try to get the same panels if possible.

bullit_dodger · 12-01-2022 3:15pm

Yeah, you can think of it that the inverter will only "suck down" as much as it can handle. So if you have a 6Kw inverter and have 10Kwp in panels, then the inverter will quite happily only suck down 6Kw safely.

The one additional comment I'd make is that if you add another 4.8Kwp in panels, it's unlikely that you'll ever have them both producing full tilt at the same time. By very nature of you putting in another array with different orientation to the one you have, when the sun is to the SW and giving you best production from your current array, it will probably be suboptimal for your new one which is orientated differently.

The next question is what angle/orientation to put your new array !? :-)

Me? I'd probably go SE or SSE me considering you have a SW one, and angle 10 degrees higher than your existing one.....but there are different ways to look at it.

unkel · 12-01-2022 3:22pm

As SD_DRACULA said, check out the spec sheet of the inverter. I would have liked 14 oversize panels (5.25kwp) on one string of my inverter, but the max voltage per string limits me to 12 of these panels per string

Also you are not supposed to be able to export more than 6kW to the grid, in your case be careful if you get a smart meter, or the ESB might find out (not sure if they do anything with that really)

bullit_dodger · 12-01-2022 3:26pm

https://www.boards.ie/discussion/comment/118461686#Comment_118461686

That's a good point, I'd not even considered that as most everyone has a 5Kw or 6Kw inverter, but if you have 8Kw Big Lar, you might have to set the max export on it to 6Kw. There's probably a setting for it.

Big Lar · 12-01-2022 4:11pm

Soz for the confusion. Its actually a Solis RHI-6K-48ES-5G 6Kw inverter but I was referring to the "Recommended max. PV power" on the data sheet of 8Kw. So that was my question really.

On the idea of the SE array, I wonder if that would the way to go as I have a wall and it would be easy enough to make up the angle that I need with a few more poles.

Big Lar · 12-01-2022 4:24pm

Am using around 30Kwh a day here in the house, See the vision is to get the daily bills down as much as we can, with the leccy first of all then an electric car in the next year or so, that's what the end game is here.

Have 10Kw lifep04 batteries on the way and will probs go another 10Kw before the year is out

unkel · 12-01-2022 4:30pm

Depends how many you could fit on the SE I suppose. If enough, then go for that. More effective all year round then vertically mounted S facing

In a way I am similar to you, I have a 6kW inverter with just under 8kwp combined in two S facing strings. So I can never produce more than 6kW, let alone export more than 6kW

A second array for winter sun

Comments