Solar for Beginners [ask your questions here]

allinthehead

https://www.boards.ie/discussion/comment/121366306#Comment_121366306

Ya, they want the limitation to be in the hardware for the NC6, ie. inverter limited.

Markus Antonius

https://www.boards.ie/discussion/comment/121365757#Comment_121365757

Thanks, those do look like a better option, not sure why they are practically same price as the clearance stock.

Surely there is a good second hand market now for panels and other equipment? I would imagine people would want newer or more efficient panels at this stage... I really just want the most bog standard setup and keep the cost below 5000 if at all possible. The reason I want microinverters is so I can use different Wattage/brand/efficiency panels and not need to worry about shading. Also you can get nice quad microinverters and string panels to each outlet as needed i.e. one quad inverter could have 4-6 panels attached and I could monitor the performance of each quad/ change panels out as needed etc.

bullit_dodger

https://www.boards.ie/discussion/comment/121369810#Comment_121369810

Big fan of micro-inverters myself. Just be aware that many quad micro-inverters only have 2x mppt, so if your planning on using a LOT of different panels, you should make sure that you have 2x of the same type on each mppt (or close enough)

dual microinverters are probably the way to go if that's your goal.

10-10-20

https://www.boards.ie/discussion/comment/121369810#Comment_121369810

Yes, I'm a big proponent of microinverters. Look out for the MPPT count on quads through, some only have two MPPT's, so it just means that you need to be slightly more careful with the choice of panel, etc. There is a second-hand market alright, but with the pricing for new panels so competitive and the technical improvements in efficiency, it's making it hard to resell old panels.

Markus Antonius

https://www.boards.ie/discussion/comment/121369863#Comment_121369863

https://www.boards.ie/discussion/comment/121369867#Comment_121369867

Excellent tips, didn't know this re. the MPPTs. To be honest, I might pull the trigger on those 420W longi panels. At 135 a piece, I wouldn't be busting the bank if I get 16 of them. I can get 4x of of these BPE quad inverters for €1250. So that's €3414 so far. Lets say 700 for mounting/wiring/ducting and 300 for electrician work. So that's around €4500 for a 6.7KWp system, which isn't bad going at all. 500 cushion on my 5000 budget.

10-10-20

https://www.boards.ie/discussion/comment/121369863#Comment_121369863

That's hilarious, same response. :)

bullit_dodger

https://www.boards.ie/discussion/comment/121369882#Comment_121369882

Funny that, we were both typing at the same time. If only I'd mentioned the 2nd hand market. Must try harder next time :-)

graememk

https://www.boards.ie/discussion/comment/121369905#Comment_121369905

And some only have 1 mppt tracker.

The one I took apart held the same voltage across all 4 ports but could vary the amount of current on each port.

So shading isn't an issue but I wouldn't mix and match panels.

AmpMan

https://www.donedeal.ie/tools-for-sale/brand-new-jinko-455w-bifacial-panels/35554751

This lad is better value than midsummer if thats the all in price.

Check out his other ads

micks_address

question on immersion heating on night rates.. i have my immersion set at 55 on the tank as any higher its to hot.. but since im heating the water betweeen 2am and 5am on night rates using the eddi, should i consider upping this back to its original setting of 65? obviously once 5am comes around the tank starts to cool - its pre insulated and stays warm for most of the day but does cool by evening time.. its a 120 litre tank so not massive. I don't let the eddi top up during the day.. as there's not much surplus this time of year anyway

Gusser09

Anyone know if it's possible to retrofit panels to an existing system? I'd plan on adding another 4 after the grant is paid.

Dozz

https://www.boards.ie/discussion/comment/121370816#Comment_121370816

@micks_address I would do whatever suits you or your family best. I heat mine to 70 once a week for Legionella purposes but I do find that the water coming from the hot tap is far too hot on those days. Kids also have baths on that day so we have plenty of hot water (300 litre tank).

For the rest of the time I have it set to 50 and it suits us fine so far. (House of 4 with a 300 litre insulated tank).

Hope this helps

oaklands

https://www.boards.ie/discussion/comment/121370816#Comment_121370816

see...Thermostatic mixing valve

Look into these, By setting the temperature higher, you effectively get a larger Tank. Probably best with very well insulated tank to avoid needless losses & you should check with the plumber if they are suitable for your HW system design. (I am not a plumber/expert). This could be an interesting approach if you have lots of spare solar PV and/or cheap import rates. I believe they are standard on Solar Thermal systems.

micks_address

https://www.boards.ie/discussion/comment/121371133#Comment_121371133

i did want my plumber to fit one back in the summer while here but he kept avoiding it. I turned the stat up for now anyway - it will have cooled by time we got up and have mixer taps so shouldnt be scald issues.. and no young kids/elderly folks in the house

slave1

https://www.boards.ie/discussion/comment/121369877#Comment_121369877

You're planning on spending a lot more on those micro inverters than a single string inverter. If cost is your concern I'd question the extra payback period as you mentioned earlier little or so shading

slave1

https://www.boards.ie/discussion/comment/121371133#Comment_121371133

This is what I've done, 300l at 85degress into mixer valve, high hot water demand throughout the day...

Markus Antonius

https://www.boards.ie/discussion/comment/121372068#Comment_121372068

I think the extra cost for the microinverters would be worth it as the array will be in a field with livestock and I want to be able to quickly identify a panel if it is degrading in performance (or not have any single panel degrade the whole array). Not sure what conventional string inverters are going for but I think its worth the extra few hundred for this luxury.

unkel

https://www.boards.ie/discussion/comment/121372384#Comment_121372384

Panels won't degrade in performance. Not materially. At least if you have easy access to your microinverters you can change them as they break. But I'm with @slave1 here. Micro inverters are more expensive per watt deployed, so they make your pay back period longer. Also several micro inverters means several points of failure. Versus one string inverter. And of course, the elephant in the room - micro inverters can't charge batteries...

Markus Antonius

https://www.boards.ie/discussion/comment/121372696#Comment_121372696

I would be happy if someone did convince me to go the conventional string inverter route as it likely would be easier for setup and the option of a battery would be good down the line (currently have an old style meter, so no interest in batteries at the moment).

However, there will be cattle and machinery going around the field, so I don't want a damaged panel decimating the output of the array or even the thought of trying to find the underperforming panel is swaying me towards the microinverters. The microinverters have a 12 year warranty and 25 year claimed expected life. However, have no anecdotal evidence of long term performance.

unkel

https://www.boards.ie/discussion/comment/121372878#Comment_121372878

It's the other way around. If you have one or two damaged micro inverters, you might not even notice anyting is wrong for months, even years as your production just goes down by a bit. If a cable is severed in a string setup on the other hand, you have zero production so you know immediately what's up. Should be a matter of a few minutes to see where the problem is

Even if every microinverter lasted 20 years on average (they won't) and you have 20 of them, still means one goes kaput on average once every year...

graememk

https://www.boards.ie/discussion/comment/121372878#Comment_121372878

If a panel does go down, There is bypass diodes in it that would "bypass" that panel

Thats why optimisers arent used as much now, or how shadows dont hurt the string of panels as much as they used to do.

For a handful of panels, microinverters are useful. But for a large array, In a field, you can pick up a string inverter that would run 24 panels for the same price as 4 or 5 microinverters.

(Id fence the cattle out though, they are notorious for eating cables and scratching against anything they see. Sheep, well just keep the cables away from them too.)

idc

https://www.boards.ie/discussion/comment/121373075#Comment_121373075

if your claiming every year one will go kaput surely the same would apply to inverters. So lets say every inverter will last 15 years that means by your logic on average every 15th owner will have an inverter that only lasts one year? And then would the same not apply for panels? If lets say the average lifespan of a panel is 25 years and I own 25, does that mean in year 1 one panel will die and likewise one each year??

With the optimisers on average they last 20 years but some will last 23 and others 15. Averaging all of those values will result in an average of 20 years. But it does not follow that each year an optimiser will fail, if we follow your extreme case and have 1 fail in year 1, 2nd in year 2, etc and the last in year 20 the average lifespan is then actually only 10.5 years.

Yes maybe one will die much earlier than the others but it does not mean 1 will fail every year, same way 1 panel does not die every year if you have 25 with a lifespan average of 25.

Markus Antonius

The string inverters I see (that can handle up to 7kW) are going for 1000eur+. I'm clearly looking in the wrong places tho.

unkel

https://www.boards.ie/discussion/comment/121373255#Comment_121373255

Yes of course you won't have one failing every year, more likely none will fail for the first 5 years. But my point is that if you have 1 bit of equipment (string inverter) or 10 bits of equipment (micro inverters), what is the chance that within 10 years anything will go wrong? Anwser is of course if you have 10 bits, it is more likely

And PV panels simply never go wrong. Unless you sever a cable

But go on if you are so set on the micro inverters go for it. I'm just sharing from my own experience and from simple logic 😂

unkel

https://www.boards.ie/discussion/comment/121373257#Comment_121373257

I bought a 6kW Solis in excellent condition, second hand but as new, for €200 at the start of summer on adverts.ie

Markus Antonius

https://www.boards.ie/discussion/comment/121373565#Comment_121373565

Thanks I'll have a look and see what I can find. Do the string inverters have overload protection in them, as in, if I hookup 16x 420W panels to a 6KW inverter, it's not going to melt it during our scorching summers? Would this be a waste of a panel doing this or would a 16x420W array struggle to get up 6KW anyway?

Just a quick look online and anything over 6KW and you are getting into big $$$$$.

unkel

https://www.boards.ie/discussion/comment/121374892#Comment_121374892

You are only allowed a 5.5kW inverter now as per the NC6 form anyway

And yes most inverters can handle a good bit more in panel wp than their rated output (think 8kwp panels on a 6kW inverter), but best follow the spec sheet of the inverter. Most can NOT handle 16 panels in one big string as it would exceed maximum voltage, but split the string into 2 strings of 8 panels and it should be fine

Make no mistake about panel output in Ireland though, south facing panels in many areas of Ireland can produce at least their full rated output. Ireland is actually very good for PV! 😎

graememk

https://www.boards.ie/discussion/comment/121374892#Comment_121374892

What you need to get your head around, is that solar panels can't "overload" an inverter like a turbine can.

When oversized, and the inverter is at its max generating power, that is all that it is generated, anything excess just isn't generated.

But what you do need to watch is the total open circuit voltage (VOC) of the string, and not to exceed the limits of the inverter, with the solis it's usually 10-12 panels depending on the inverter.

ColemanY2K

https://www.boards.ie/discussion/comment/121374995#Comment_121374995

"But what you do need to watch is the total open circuit voltage (VOC) of the string, and not to exceed the limits of the inverter, with the solis it's usually 10-12 panels depending on the inverter".

I just want to double check something.

First question. My panels are 42.2v. my Solis 5kw Hybrid inverter total voc per string is 6000v. If I put 14 panels on one mppt it totals 5,740v. You mention 10-12 panels but in my case I have 14 X 410w panels. Should I be concerned and reduce the number of panels or am I ok because I'm still under the 6000v limit?

Second question. The other mppt only has 5 panels with a total of 2,050v. Would I be correct in saying having an uneven number of panels on each string is ok?

graememk

https://www.boards.ie/discussion/comment/121375406#Comment_121375406

Your out by a factor of 10, 600v ! 😆

But uneven voltages is fine.

As for the 14 panel string, it is pushing it a bit, 42.2* 14 is 590.8v, in my opinion it's too much.

Got this calculation a while back, as panels get colder the voc rises. So a worst case at minus 20.. (with a voc of 40.8 on a longi panel. I've worked out the temp coeff before but mislaid my workings, but it's based off the spec sheet, it will say how much the voltage rises and falls due to temperature )

Worst scenario at -20 degrees is 40.8 x 12 panel x 1.1215 temp coeff x 1.03 tolerance = 565.55V

We'll not get -20 but depending on what part of the country your in -10 has been reached.

I have seen people's inverters error out, without harm buuuut. It's running very close to the line for me.

(And its 5.8kw on a 3.6kw mppt)