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Solar PV Hints, Tips & Troubleshooting

DrPhilG

Well I've reached the point of driving everyone nuts on the PV quotes thread, and since I now have my system installed and running my endless questions no longer belong there.

So I figured I'd ask here, and also provide a home for others in the same boat, with general questions and advice on managing post-install.

My first question (of many) is how do people best manage their production in order to reduce grid export? Despite being overcast and miserable a fair bit of the day, I've produced 24kWh so far today, but ended up exporting 11.

Not too bad when we're home, as the wife did a few loads of washing and drying, put on the dishwasher etc.

But we're both at work tomorrow so other than a timed or remotely activated washer/dryer run we would end up exporting a lot more.

Extra battery capacity or a water diverter would help, but they don't tend to justify their costs in the long term.

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DrPhilG

slave1 wrote: »

Ooooh, charging house batteries via PV to charge an EV later just seems messy.

True, hadn't thought of that.

To be honest in the longer days I could comfortably charge the car on excess when I get home at 4:45pm. And I only need a full charge every 4-5 days.

I just did a very (very) rough calculation based on last year's August generation but adjusted for a 12.5kwp system and 30kWh storage.

*1145kWh generated
*7.6kWh bought from the grid costing €0.61
*380kWh exported for €19

You're right about the best being yet to come. My predicted number for last August was 601kWh, ended up on 572.

My predicted number for June is 741kWh. April mustn't have been too good up this way, my numbers are based on a friend's results last year.

***these are all vague estimates and calculations, not to be taken too seriously!

DrPhilG

KCross wrote: »

Yes, same as it is today assuming you have a 6kW inverter

It's a 5kw Solis hybrid inverter.

KCross wrote: »

Your peaks will be higher (12kW) so you will have more losses.

Peak on August 8th last year was 4.95kw.

KCross wrote: »

You can mitigate that a bit by splitting it across your two orientations but you also need to match the max voltage on each string so you might run into complications there too.... but your rough math is sorta ok.

Yeah it's extremely rough, so "sorta OK" is a good result!

Thats the question, if I go to a system with 2 inverters, which one manages and limits the export? Where does the battery get connected so that both sets of panels can feed it?

I'm veering now into territory I know damn all about, as opposed to the usual level of know very little about...

air

Multiple orientations are the way forward for large systems, it'll increase your self consumption substantially if you have a relatively steady load profile.
I've my panels split over E/W/S and it makes for a really long day of useful production levels from Spring through Autumn.
If you happened to be off grid and winter production was paramount then plenty steeply facing South facing panels are the key ingredient.

MAULBROOK

Just switched off the over night charging of the battery, time to let the longer brighter day take over.
I think it went well. Im now at 80% night 20%day. Last bill was €140 for two months, by far the lowest we have ever had.

slave1

DrPhilG wrote: »

True, hadn't thought of that.

To be honest in the longer days I could comfortably charge the car on excess when I get home at 4:45pm. And I only need a full charge every 4-5 days.

I just did a very (very) rough calculation based on last year's August generation but adjusted for a 12.5kwp system and 30kWh storage.

*1145kWh generated
*7.6kWh bought from the grid costing €0.61
*380kWh exported for €19

You're right about the best being yet to come. My predicted number for last August was 601kWh, ended up on 572.

My predicted number for June is 741kWh. April mustn't have been too good up this way, my numbers are based on a friend's results last year.

***these are all vague estimates and calculations, not to be taken too seriously!

Those are savage monthly generations for that size array, aspect jealousy

DrPhilG

DrPhilG wrote: »

Thats the question, if I go to a system with 2 inverters, which one manages and limits the export? Where does the battery get connected so that both sets of panels can feed it?

Just to expand on this as I was thinking about it overnight...

If I have a second inverter in the garage with an upgraded garage array feeding in, how is the export managed, both to the battery and to the grid?

If the load is covered, how do both sets of panels with separate inverters feed into the battery? Does the battery just act like any other household draw and draw power based on what the CTs tell it is available?

Same query for export. I'm limited to exporting 6kw max rate so if the garage panels have 4kw excess and the house panels 3kw, how is the export managed? Do the inverters speak to each other?

championc

I think you'd need an AC Storage Inverter (like the Sofar ME3000). However, you really more need something which gobbles up power being exported to the grid rather than a device which is monitoring the DC generation (which the ME3000 does)

No matter what, you need a Storage Inverter which is totally independent of either of your inverters.

I understand your focus on ultimately trying to cover your daily total loads, but I would have thought it's only worthwhile if you were going to do the whole upgrade yourself. Your initial cost was excellent thanks to the grant, but you wouldn't have that luxury second time around.

DrPhilG

championc wrote: »

I think you'd need an AC Storage Inverter (like the Sofar ME3000). However, you really more need something which gobbles up power being exported to the grid rather than a device which is monitoring the DC generation (which the ME3000 does)

No matter what, you need a Storage Inverter which is totally independent of either of your inverters.

I understand your focus on ultimately trying to cover your daily total loads, but I would have thought it's only worthwhile if you were going to do the whole upgrade yourself. Your initial cost was excellent thanks to the grant, but you wouldn't have that luxury second time around.

Sofar 3000 I think I've heard mentioned before alright.

I'm hoping to do a lot of the work myself in terms of the battery and inverter setup, then just get a pro in to finish it off. That's what my friend (who built the battery) has done so I'll have help from him, and access to the same pro he used for the final stage.

As for adding panels, I'll probably source them myself and then get my previous installer back to install. From experience I'm confident he'll not rob me blind.

All still just speculation, but I do have most of the money set aside for both the panel expansion and battery upgrade. Only thing I'd then need to save for is the bump from 9 to 30kWh storage.

mp3guy

championc wrote: »

No matter what, you need a Storage Inverter which is totally independent of either of your inverters.

If you mean he'll need an AC coupled battery on a third inverter to capture energy from both PV inverters this is incorrect. You can have a hybrid inverter that all your batteries and some PV sits behind DC side and another regular string inverter with more panels. Provided both are behind the same modbus meter, the hybrid can pickup the power the string inverter would otherwise export and convert that AC back to DC and charge the batteries as if it were charging from the grid. My inverters are literally doing this as I type.

DrPhilG

Thanks mp3guy

Does that mean that the battery (even a DIY version) could to be DC coupled behind the Solis inverter and then any other inverter used for the second set of panels?

I'm just trying to list all the equipment I would need in the event of going ahead with this.

Most likely I'll get the 9kWh battery initially, and whatever additional inverter is needed and get everything set up with room to expand.

Next would be the additional panels, and finally a further battery expansion.

mp3guy

DrPhilG wrote: »

Thanks mp3guy

Does that mean that the battery (even a DIY version) could to be DC coupled behind the Solis inverter and then any other inverter used for the second set of panels?

I'm just trying to list all the equipment I would need in the event of going ahead with this.

Most likely I'll get the 9kWh battery initially, and whatever additional inverter is needed and get everything set up with room to expand.

Next would be the additional panels, and finally a further battery expansion.

Not sure about Solis's capabilities, and you would need to pick the right inverter that can support this. Provided neither inverter is capable of more than 6kW output, only one of them has to monitor the total export and scale itself down. But one of them has to be capable of export limiting.

irishchris

Was wondering if anyone can help me out here. I am finishing installation of 9x360w longi install and went to order one extra to finish it but suppliers now only have 365w in stock. There is a difference of 0.2 volts and 0.08A between the two modules. Would this be an issue or would it be ok?

slave1

irishchris wrote: »

Was wondering if anyone can help me out here. I am finishing installation of 9x360w longi install and went to order one extra to finish it but suppliers now only have 365w in stock. There is a difference of 0.2 volts and 0.08A between the two modules. Would this be an issue or would it be ok?

Would have thought the extra lad will be pulled down to the vols and amps of the existing lowest common denominator which is immaterial from a total array perspective.
There could be other considerations that those more knowledgeable could add like impact on MPPT functionality

Or, could you not source elsewhere, I have to say I'd be triggered if the extra panel looked different also

irishchris

slave1 wrote: »

Would have thought the extra lad will be pulled down to the vols and amps of the existing lowest common denominator which is immaterial from a total array perspective.
There could be other considerations that those more knowledgeable could add like impact on MPPT functionality

Or, could you not source elsewhere, I have to say I'd be triggered if the extra panel looked different also

Cheers. Same model panels just 5w more. Attached the data sheet of it, appreciate any advice here from anyone. Solartricity advise it should be compatible but just double checking

unkel

If the only difference is the max amps of the 365W panel are higher than the same for the 360W panel, than you just lose the 5W extra of that last panel. Immaterial as slave1 says.

graememk

DrPhilG wrote: »

Thanks mp3guy

Does that mean that the battery (even a DIY version) could to be DC coupled behind the Solis inverter and then any other inverter used for the second set of panels?

I'm just trying to list all the equipment I would need in the event of going ahead with this.

Most likely I'll get the 9kWh battery initially, and whatever additional inverter is needed and get everything set up with room to expand.

Next would be the additional panels, and finally a further battery expansion.

You need to look at the whole picture now. Questions to ask yourself.

More storage
Are you ditching the pylon techs or getting a second stand alone Storage inverter?

Where are you putting it? All in your attic? Or in the Garage?
If in the Garage, How are you getting the power back to the house/main consumer unit.

Anything in the garage will need CT's run to it at least to measure the main feed from the grid and ideally the solar. Ie it needs to know if there is import/export to either charge or discharge the batteries.

As with the solis hybrids i dont know how they operate, I touched on this before, eg:

does it take the mppt feed and convert all to AC

then monitor the grid I/E and charge/discharge accordingly (from AC).

Or is it on the DC side with DC/DC converters.

- If its AC it would be able to pull power from more than one inverter but if its
DC it can only pull it from panels connected to it. I have a feeling it could be AC.

Charge rates, Take the ME3000 from sofar for example, the max it can charge or discharge at is 3kW.

I think the Solis Hybrid can do 5kW but that is battery dependant too!

Plans for going forward
If you left your current setup alone.
Storage inverter for the extra battery (in garage?)
Panel expansion with inverter in garage, with that one doing the export limitation.

A bit rambley i know but trying to cover most of the bases can be tricky

irishchris

One last question here on my setup. I see a lot of people discussing overpowering their inverters, or more panels than the rated inverter.

I'm in process of installing ground mount system and Solis inverter is a 3kw which states max DC 3.3kw. assuming this means I cannot go over 3.3kw input or is this just at perfect conditions? Have opportunity of extra 365w panel which would bring my new setup to 3.6kw. is this viable? Would be well within voltage limit and within max amps.

graememk

irishchris wrote: »

One last question here on my setup. I see a lot of people discussing overpowering their inverters, or more panels than the rated inverter.

I'm in process of installing ground mount system and Solis inverter is a 3kw which states max DC 3.3kw. assuming this means I cannot go over 3.3kw input or is this just at perfect conditions? Have opportunity of extra 365w panel which would bring my new setup to 3.6kw. is this viable? Would be well within voltage limit and within max amps.

Yep As long as your within the voltage and current limits, you could prob go 2-3 more!

irishchris

graememk wrote: »

Yep As long as your within the voltage and current limits, you could prob go 2-3 more!

Cheers Graememk, That's brilliant and will get that extra panel now.
So what is the idea behind the max DC wattage that they specify on the inverters?

DrPhilG

graememk wrote: »

You need to look at the whole picture now. Questions to ask yourself.

All good questions, and I'll be going through them with my installer before I do anything concrete.

A quick summary, by no means definite or final. Just ramblings as you say.

Basically the plan is to:
*Sell the PylonTech to fund the expansion.
*Buy about 10kWh of storage to replace it.
*Double both arrays, garage from 2.8 to 5.6kwp, house from 3.4 to 6.8kwp.
*one inverter in the house with the 6.8 connected.
*second in the garage with the 5.6 connected, and the battery.
*add additional storage for about 25-30kWh total.

3 stage plan, financially dependant.

1 - replace the PylonTech with either China sourced batteries like championc has, or my friend's 9kWh Leaf pack. Add the second inverter at that stage both to connect the batteries in the garage and to future proof for the panel expansion.

2 - add extra storage. If going Chinese, then I can add 8kWh (usable) packs for €1500 a time. If going Leaf cell, I can add about 20kWh for around €2500.

3 - double the panels. Either DIY or via previous installer depending on price. When I added a few panels on top of my original quote, he charged €200 supplied and fitted. Different story now though I'd imagine.

I have funds for stage 1 and 2 now, stage 3 in a year or so. Obviously no point in doing step 3 before 2, as I'd have no storage to handle all that extra juice.

My friend's Leaf pack, he has connected with a Victron inverter and a Batrium BMS setup. However (to be confirmed) the Leaf pack is connected via canbus which the Solis supports, so in theory (again tbc) I can connect the Leaf pack DC coupled, the same as the current PylonTech ones. Then the Solis inbuilt BMS would manage it.

So I could move the Solis to the garage along with the cells, and put a new 5kw standard inverter in the house.

Now as for the connections back and forth, I'm fairly in the dark and this is where I'd speak to the pros. I currently have 2 x 100m DC solar cables between house and garage which feed the garage panels to the inverter in the house. I also have underground cables connecting the fuse board in the garage (which the Zappi is connected to) back to the house. With a 7kw Zappi attached it's presumably a pretty heavy duty line.

Now how that would apply to my initial plan, I don't know. Can the power go back via the DC cables that are no longer needed to link the garage panels in? Can it go back via the cable from one fuse box to the other? There are a few ethernet lines from house to garage too already.

The thought did cross my mind to get a single 10kW inverter but those are seemingly as rare as hen's teeth, and also extortionately expensive so no point.

Anyway that's my ramble. Very vague and I'm sure there's a load of things in that plan that make no sense. But that's why you nice folk are here plus my installer will be on hand to make sure I don't blow anything up.

graememk

DrPhilG wrote: »

Now as for the connections back and forth, I'm fairly in the dark and this is where I'd speak to the pros. I currently have 2 x 100m DC solar cables between house and garage which feed the garage panels to the inverter in the house. I also have underground cables connecting the fuse board in the garage (which the Zappi is connected to) back to the house. With a 7kw Zappi attached it's presumably a pretty heavy duty line.

Now how that would apply to my initial plan, I don't know. Can the power go back via the DC cables that are no longer needed to link the garage panels in? Can it go back via the cable from one fuse box to the other? There are a few ethernet lines from house to garage too already.

As you have a zappi connected to the garage consumer unit, it would at least be a 6mm2 feeding it, more likely a 10mm2

(I have a 16mm2 going from my house to the yard, but its a long run)

I can't see any issue connecting the solar(or battery inverter/hybrid inverter) to that consumer unit as the AC power can flow each way as necessary.

Will have to use one of the ethernet cables to carry ct's back to the house consumer unit.

The DC cables would just not be used i think. if house inverter just ran house panels and garage inverter only ran garage panels.

Batteries in garage and just an inverter in the house would be a good way to go. Wouldn't personally feel comfortable with them attic.

DrPhilG

graememk wrote: »

The DC cables would just not be used i think. if house inverter just ran house panels and garage inverter only ran garage panels.

I could even shift both inverters to the garage, keep it all together, and use the DC cables the opposite to how they're used now.

graememk wrote: »

Batteries in garage and just an inverter in the house would be a good way to go. Wouldn't personally feel comfortable with them attic.

That was my thinking too.

Good to see that there are no obvious howlers in my ramble at least!

slave1

Is it worth such an investment in these batteries when ....
a) night rate now so low with Energia EV plan
b) FIT coming in

graememk

slave1 wrote: »

Is it worth such an investment in these batteries when ....
a) night rate now so low with Energia EV plan
b) FIT coming in

More panels yep, battery.. well all you need is enough to peak shave and run out the clock until night rate kicks in.

My base load was nearly covered when the night rate stopped this morning.

DrPhilG

slave1 wrote: »

a) night rate now so low with Energia EV plan

I just changed to a Energia a few months ago, then the buggers bring out that EV plan. Typical.

jprboy

DrPhilG wrote: »

I just changed to a Energia a few months ago, then the buggers bring out that EV plan. Typical.

:eek: Me too, changed to Energia last Nov as best offer at the time

For me I'm seeing 16.64c(day) 4.78c(night) - all inc VAT in this offer.

Currently paying 14.22c day and 6.82 night (inc VAT)

Normally use much more proportionately at night during winter as have heat pump and EV.

However, working nearly full time at home since last March so EV charging costs slashed for now.

Therefore initial estimation is not much advantage for me in this EV plan but cannot give conclusive answer as number crunching function has been impaired due to wine/beer/whiskey consumption............

MAULBROOK

DrPhilG wrote: »

I just changed to a Energia a few months ago, then the buggers bring out that EV plan. Typical.

Give them a call they might change you over if you ask nicely:D:D

slave1

DrPhilG wrote: »

I just changed to a Energia a few months ago, then the buggers bring out that EV plan. Typical.

MAULBROOK wrote: »

Give them a call they might change you over if you ask nicely:D:D

I was going to jump on it but now with an install just a few months in and FIT coming in I'm going to sit back until the end of the Summer generation and FIT "constraints" are known, then decide.
Not a huge saving given I'm currently moving night duties to day, washing machine/dryer/immersion etc

the_amazing_raisin

MAULBROOK wrote: »

Give them a call they might change you over if you ask nicely:D:D

I tried that last year, they said because I'd signed up to a 12 month contract I couldn't change even when I offered to sign up to 12 months again

tsiklon

We're renovating an old house, which will require substantial work on the roof to bring it up to spec. We probably don't have the budget to purchase panels just yet.

What would we need to do now in order to have panels added at a later stage? What type of brackets etc are required?