Solar PV Hints, Tips & Troubleshooting

championc

thebackbar wrote: »

Hello,
I have a 1 kWp pv panel kit mounted on my roof, however the system was never commissioned, I didn't get the inverter installed, and now the company that supplied the qcell pv panels are gone out of business. Will I need to get a company that specialises in pv panels to install a inverter or could I buy a inverter and ask my electrician to install it ? How much money would i be looking at for this ?

My gut feeling is that, for the cost of the inverter and the cost of the sparks, you'll be looking at a very long payback time.

However, if payback time is not your focus, you could look to buy about a 3kw inverter. The cables from your roof are likely to already have male and female MC4 connectors, which will connect straight into an inverter. So a sparks only needs to terminate an AC cable coming from the AC of the inverter, to inside your consumer unit, on it's own RCBO.

You can check if the panels are connected to the cable by measuring the voltage, using DC voltmeter, one prong in each of the two MC4's

graememk

Akabusi wrote: »

I currently have solar tubes on my main south facing roof, happy with them they've been doing their job for a number of years now. I am toying with either moving them to another south facing roof on another part of the house or getting rid of them altogether. The reason being is that they are planted bang in the middle of the roof (house is a bungalow) and if they weren't there I'd be able to accommodate 8 PV panels in one row along the length of roof. I can also fit 2 more panels above this row and 2 more on an east facing roof. Finally there is space for 4 more on a west facing roof (front of house) but i'm not to keen on this.
So assuming there are 12 PV panels, is there any need for the solar tubes? Moving them to the other roof would take a day's work, I'd be actually moving them closer to the hot water tank so they should be more efficient.
Other thing to note is we have one EV with a second on the way.
Appreciate any thoughts you guys who are more knowledgeable on this have. Thanks.

Solar tubes are far more efficient in heating water that using solar panels.
They also heat the coldest water, so on a sunny day the whole tank is hot.

Immersions are usually near the top of the tank, although some have dual immersions, for sink/bath.

its a lot easier to just bring electrical cable places than try and move the tubes + pipes. - could be talking what about 500 to move them, maybe more.
Why not put what you can beside the tubes, and then the solar on the other roof?

East/west panels are good in the summer, but they would need optimisers on them.

Ie one string has the south panels and the second has the East west(with optimisers)

mp3guy

championc wrote: »

My gut feeling is that, for the cost of the inverter and the cost of the sparks, you'll be looking at a very long payback time.

However, if payback time is not your focus, you could look to buy about a 3kw inverter. The cables from your roof are likely to already have male and female MC4 connectors, which will connect straight into an inverter. So a sparks only needs to terminate an AC cable coming from the AC of the inverter, to inside your consumer unit, on it's own RCBO.

You can check if the panels are connected to the cable by measuring the voltage, using DC voltmeter, one prong in each of the two MC4's

Does this account for anti-islanding in powercuts?

Akabusi

graememk wrote: »

Solar tubes are far more efficient in heating water that using solar panels.
They also heat the coldest water, so on a sunny day the whole tank is hot.

Immersions are usually near the top of the tank, although some have dual immersions, for sink/bath.

its a lot easier to just bring electrical cable places than try and move the tubes + pipes. - could be talking what about 500 to move them, maybe more.
Why not put what you can beside the tubes, and then the solar on the other roof?

East/west panels are good in the summer, but they would need optimisers on them.

Ie one string has the south panels and the second has the East west(with optimisers)

Thanks

If I don't move the solar tubes I can then only fit 4 PV panels on that main south facing roof. I could fit 2 more on the other south facing roof where I'm proposing to to move the solar tubes.
In theory then I could have a 10 PV panel system on three strings, probably easier than moving the tubes alright but on the other hand I'm down 2 PV panels. The distance the two south facing roofs are apart shouldn't really matter should it, except for a longer cabling run?

graememk

mp3guy wrote: »

Does this account for anti-islanding in powercuts?

Thats built into grid tied inverters... unless im missing a joke/pun here -

1kw, is only 4 panels, maybe a microinverter... plug it into a socket..

Akabusi wrote: »

Thanks

If I don't move the solar tubes I can then only fit 4 PV panels on that main south facing roof. I could fit 2 more on the other south facing roof where I'm proposing to to move the solar tubes.
In theory then I could have a 10 PV panel system on three strings, probably easier than moving the tubes alright but on the other hand I'm down 2 PV panels. The distance the two south facing roofs are apart shouldn't really matter should it, except for a longer cabling run?

Yeah solar pv panels dont really care about distance, mine are 60+m away from my inverter. - i do have a 6mm2 cable running to them though.

Also solar PV doesnt have to be all in one line, you have one here, one there, one on its side (landscape) - only extra cost is mounting hardware.

Do price how much it would be to move the tubes and them make a decision youself.

I dont know of any 3 string single phase inverters on the market, so thats why I mentioned optimisers.

Akabusi

graememk wrote: »

Thats built into grid tied inverters... unless im missing a joke/pun here -

1kw, is only 4 panels, maybe a microinverter... plug it into a socket..



Yeah solar pv panels dont really care about distance, mine are 60+m away from my inverter. - i do have a 6mm2 cable running to them though.

Also solar PV doesnt have to be all in one line, you have one here, one there, one on its side (landscape) - only extra cost is mounting hardware.

Do price how much it would be to move the tubes and them make a decision youself.

I dont know of any 3 string single phase inverters on the market, so thats why I mentioned optimisers.

That's very helpful thank you. I had familiarised myself with the intricacies long ago on PV but its now sketchy. I have to go back and do my research again.

championc

mp3guy wrote: »

Does this account for anti-islanding in powercuts?

Yes, the ones I was certainly referring to are ON-GRID, so if the grid is gone, they are dead in the water

https://www.aliexpress.com/item/1005001564966795.html

championc

Akabusi wrote: »

Thanks

If I don't move the solar tubes I can then only fit 4 PV panels on that main south facing roof. I could fit 2 more on the other south facing roof where I'm proposing to to move the solar tubes.
In theory then I could have a 10 PV panel system on three strings, probably easier than moving the tubes alright but on the other hand I'm down 2 PV panels. The distance the two south facing roofs are apart shouldn't really matter should it, except for a longer cabling run?

I would expect that moving the tubes could be expensive. You'll need to have the system drained and then you'll need for the whole rig to be dismantled and moved and basically all re-installed.

Of course, your Solar issue is that with East, South and West, almost all inverters are either 1 or 2 string units, which then complicates things with three. Also, most Inverters only start working above 100v, so two on a string will never work, nor really will 3, so you're (and anyone else) better looking at Micro-Inverters for the 2 panel section - that is the perfect solution for such a situation

unkel

graememk wrote: »

I dont know of any 3 string single phase inverters on the market, so thats why I mentioned optimisers.

championc wrote: »

Of course, your Solar issue is that with East, South and West, almost all inverters are either 1 or 2 string units, which then complicates things with three.

Tesla has just launched an inverter with 4 input strings and 8.6kW power. Probably not yet available though and details are sketchy. I'm looking for a 3 input string inverter myself with minimum 6kW power, but only if I can get one for reasonable money

championc wrote: »

most Inverters only start working above 100v, so two on a string will never work, nor really will 3

3 modern panels is ok in my experience, even if the inverter is specified to take minimum 100V per string, it will not suddenly stop working when the input is 90V. I have 3 panels on my west facing string

mp3guy

unkel wrote: »

Tesla has just launched an inverter with 4 input strings and 8.6kW power. Probably not yet available though and details are sketchy. I'm looking for a 3 input string inverter myself with minimum 6kW power, but only if I can get one for reasonable money

One of these? https://www.solaxpower.com/x-ess-g4/

unkel

I already have a battery and a separate smart battery inverter and I'd say that Solax would cost a bomb

graememk

mp3guy wrote: »

One of these? https://www.solaxpower.com/x-ess-g4/

Still only 2 Mppt strings!

air

I wouldn't lose too much sleep over multi string inverters, if you can pick up single string ones cheaply the efficiency penalty will be negligible and it eliminates having a single point of failure.

Granted it can make for a tidier install.

slave1

air wrote: »

I wouldn't lose too much sleep over multi string inverters, if you can pick up single string ones cheaply the efficiency penalty will be negligible and it eliminates having a single point of failure.

Granted it can make for a tidier install.

Agreed, I have a two string MPPT and have an idea to put up another string at the rear of my back garden as a DIY job, likely just buy a small inverter or go with micro inverters. Going to go with almost vertical panels as it's primarily to top up my poor Winter generation due to shading.
Bit away yet (I don't do cold hands) so I'll do my homework on it later.

unkel

air wrote: »

I wouldn't lose too much sleep over multi string inverters, if you can pick up single string ones cheaply the efficiency penalty will be negligible and it eliminates having a single point of failure.

Granted it can make for a tidier install.

I sure wouldn't want the hassle to find another electrician to hook up another inverter for me that I installed myself. The last one charged me €150 as a nixer (with me providing all the parts) and that was his boss doing me a big favour.

Another cable along the side of the house, into the house, more ducting, another group with it's own RCBO in my consumer unit and of course my smart battery inverter can only sense the output of 1 PV inverter, not multiple ones, so that would screw that system up completely

I'd rather buy a 3 or 4 string inverter and replace the current one myself, which I can then sell on too...

air

Assuming the cable you installed the first time wasn't ridiculously undersized, there's no reason you couldn't install a small sub board at the location of the existing inverter.

This could have a breaker for each inverter in this sub board.

Your battery inverter will sense the output from both inverters just the same as if it was one.

championc

slave1 wrote: »

Going to go with almost vertical panels as it's primarily to top up my poor Winter generation due to shading.
Bit away yet (I don't do cold hands) so I'll do my homework on it later.

If they can be vertical and south facing, then you're on the back of the pig. The sun is so low, the sun will be very vertical to the panel surface.

They might work too on a westerly facing wall but you'd get practically zero generation until the sun would come around, so it could be 4 to 6 hours of almost zero generation from it, and that's a large loss

unkel

air wrote: »

Assuming the cable you installed the first time wasn't ridiculously undersized, there's no reason you couldn't install a small sub board at the location of the existing inverter.

Outdoors? I'd rather not. Replacing the inverter with another one I can do myself in about an hour I'd say (not very handy, not very skilled)

Now where are the details on that quadruple MPPT inverter from Tesla? And who wants to buy a Solis dual MPPT 3.6kW inverter? :pac:

air

Fair enough, an IP rated enclosure would allow you to do it outdoors no problem.
Up to yourself.

MAULBROOK

unkel wrote: »

Outdoors? I'd rather not. Replacing the inverter with another one I can do myself in about an hour I'd say (not very handy, not very skilled)

Now where are the details on that quadruple MPPT inverter from Tesla? And who wants to buy a Solis dual MPPT 3.6kW inverter? :pac:

3 MPPT from Solis ok its 9kw
https://www.ginlong.com/1p_inverter2/1879.html

unkel

Exactly what I need, thanks a million MAULBROOK. Now to see can I actually get that somewhere for reasonable money.

MAULBROOK

unkel wrote: »

Exactly what I need, thanks a million MAULBROOK. Now to see can I actually get that somewhere for reasonable money.

Give me a moment

unkel

The two main wholesalers in Ireland don't have them listed yet, but hopefully they will too. I've sent an email to one of them (my preferred supplier for all things solar PV)

MAULBROOK

unkel wrote: »

Exactly what I need, thanks a million MAULBROOK. Now to see can I actually get that somewhere for reasonable money.

https://solartricity.ie/inverter-solis-range/
Best i can do for now, send them a email.

unkel

That's the place I emailed earlier alright :-)

daughy

MAULBROOK wrote: »

3 MPPT from Solis ok its 9kw
https://www.ginlong.com/1p_inverter2/1879.html

I don't understand the voltage limit and max dc input range of this inverter,
It says it can take up to 10.8kw of solar panels,
But the max dc input voltage is 600 volts.
10/10/10 amps.

Maybe I'm doing this wrong, but if I had 3 strings of
10, 350 watt panels in series to make 3.5kw
For the overall amount of 10.5kwp
And 40 volts open circuit x 30 panels is 1200 volts?

air

The 3 strings of 10 are completely separate from one another, they don't combine in series anywhere.

graememk

Been Poking about the met.ie api.

They give a global radiation (so "sunlight") value and its in w/m^2. (hourly, Im only looking 24hrs in advance at the moment)

I think I might be able to give an estimate if tomorrow will be a good solar day or not.

Currently building it in Node RED. I will need to be constantly comparing it with my actual generation and trying to tweak it. will be happy to share the flow.

For instance at 2pm, today the value was predicted to be 120w/m^2, and i was generating 1.3 kw (generated 4kwh today).

I do not intend to even try and predict a value, more to generate a guide, Keeping it simple maybe try and generate a figure from 0-10 to give an indication that tomorrow going to be a good day, better make sure the dishwasher is ready to go. or in the spring/autumn, not to charge the batteries as much overnight.

Current plan is to try and count the hours thats its high and give a rating from that.

mp3guy

graememk wrote: »

Been Poking about the met.ie api.

They give a global radiation (so "sunlight") value and its in w/m^2. (hourly, Im only looking 24hrs in advance at the moment)

I think I might be able to give an estimate if tomorrow will be a good solar day or not.

Currently building it in Node RED. I will need to be constantly comparing it with my actual generation and trying to tweak it. will be happy to share the flow.

For instance at 2pm, today the value was predicted to be 120w/m^2, and i was generating 1.3 kw (generated 4kwh today).

I do not intend to even try and predict a value, more to generate a guide, Keeping it simple maybe try and generate a figure from 0-10 to give an indication that tomorrow going to be a good day, better make sure the dishwasher is ready to go. or in the spring/autumn, not to charge the batteries as much overnight.

Current plan is to try and count the hours thats its high and give a rating from that.

Solcast.com already does this. Free for enthusiasts. You POST your periodic power values throughout the day, it will self-tune after a few weeks. Gives you power predictions on 30 minute intervals for the next few days.

graememk

Ohh.... Nice, theres a node red flow and everything to feed and pull data from it.

So do you think every 10 seconds is enough to tune it? :P - Automate everything!

I might just use both.

Bit overkill tho, all i really wanted was good, bad or meh.