Solar PV advice

[Richard77]

Anyone got any experience of Scottish Power in Merseyside and how stingy they are with the G99 approvals? Is there anywhere to search online to get an idea of the capacity of the network in certain areas?

I've dealt with SP Energy for my approval and they were pretty helpful.
I would say you should ring them if you want to get some sort of guidance, they aren't stingy but it's all very dependant on local infrastructure.

Installer is submitting the G99 application to them, so will see what happens with that, might also give them a ring. Thanks

[Richard77]

The installer has come back with a proposal of 30x Aiko 455w panels (40.79 voc).

16 on west facing roof (8 on each string) to 1 MPPT.
14 on east facing roof (7 on each string) to the other MPPT.

No panels on garage or south facing roof.

I assume that is because each MPPT on the inverter can only accept 370V, so wants to keep it below that?

From inverter datasheet:
PV input voltage: 370v (125v-500v)
MPPT range: 150-425v

I wanted to fill garage roof and south facing roof as well, can anyone suggest a way round this?

Would I need a different inverter that has more MPPT/strings? Is there a way to do it with this SunSynk 8.8kw inverter (2 MPPT / 2 strings per MPPT)?

Thanks

[Fueltheburn]

Looking at the download for the Sunsynk 8.8kW the MPPT current has startup voltage of between 125 and 150v but doesn't specifically state it. The voltage on the panels is good for the MPPT.

2 problems.

I see running 2 parallel strings on 1 MPPT is the nominal rating of 22A per MPPT. Most panels I have seen over 400w are >14A. 2 of these panels paralleled if rated at 14A per panel would be 28A and therefore exceed the rating on the inverter.
You need to check the amps given out in those panels.

The inverter also has a max PV input of 10400W.
If you get a sunny day where the sun is overhead in the middle of the roof and hitting both east and west panels simultaneously you will likely exceed the rating of the inverter.

I think you have undersized the inverter based on its maximum inputs.

You can also parallel inverters as well to gain more inputs.

[AGT]

https://cdn.shopify.com/s/files/1/0257/ ... 1707139559

[AGT]

Deleted post

[Countrypaul]

The installer has come back with a proposal of 30x Aiko 455w panels (40.79 voc).

16 on west facing roof (8 on each string) to 1 MPPT.
14 on east facing roof (7 on each string) to the other MPPT.

No panels on garage or south facing roof.

I assume that is because each MPPT on the inverter can only accept 370V, so wants to keep it below that?

From inverter datasheet:
PV input voltage: 370v (125v-500v)
MPPT range: 150-425v

I wanted to fill garage roof and south facing roof as well, can anyone suggest a way round this?

Would I need a different inverter that has more MPPT/strings? Is there a way to do it with this SunSynk 8.8kw inverter (2 MPPT / 2 strings per MPPT)?

Thanks

As was suggested earlier in the thread, for the garage and south facing roofs use charge controllers such as Victron which come in a variety of options so you could use one for each face of the garage roof and one for the south facing roof all linked directly to the batteries. This would also probably be more efficient than DC -> AC -> DC. The DNO would also be unconcerned as they will only worry about how much AC could be exported on their wires.
You could consider another inverter on attached to the batteries that is not grid tied (so does not bother the DNO) for running some loads -possibly with a transfer switch if you needed to run those loads from the grid instead of the inverter.

[Richard77]

Thanks everyone...

I had forgot about the charge controllers, as didn't quite understand how they worked.

The 16kw SunSynk looks a good choice, but can't really justify the extra £2500 over the 8kw one.

[sharpener]

No panels on garage or south facing roof.

I assume that is because each MPPT on the inverter can only accept 370V, so wants to keep it below that?

From inverter datasheet:
PV input voltage: 370v (125v-500v)
MPPT range: 150-425v

I wanted to fill garage roof and south facing roof as well, can anyone suggest a way round this?

I take that to mean 370 is the nominal voltage, 425 is the max that the MPPT will properly track the panels and maximise their output, 500 is the limit above which damage may or will occur. So you could maybe squeeze a few more in, bearing in mind their open circuit voltage at the coldest ambient temp.

I had forgot about the charge controllers, as didn't quite understand how they worked.

Basically they contain the MPPT software to present the optimum dynamic load to the panels to get maximum output and track this at it varies during the day. Only difference is the output is at nom. 48V DC to go straight on to the battery terminals.

A side benefit of this is that they and the connected panels are AIUI not notifiable as the DNO does not care what is on the battery side of the inverter, only anything that can potentially export to the grid and/or electrocute their staff.

Also the efficiency is a bit higher esp if it avoids doing a double conversion DC (panels) - AC - DC (battery)

Victron ones integrate with the Victron ecosystem so are controllable from the main inverter and over the web (as per my setup), if you just want free-standing then they are available for less and certainly well under the £2500 marginal price difference you quote.

[Richard77]

No panels on garage or south facing roof.

I assume that is because each MPPT on the inverter can only accept 370V, so wants to keep it below that?

From inverter datasheet:
PV input voltage: 370v (125v-500v)
MPPT range: 150-425v

I wanted to fill garage roof and south facing roof as well, can anyone suggest a way round this?

I take that to mean 370 is the nominal voltage, 425 is the max that the MPPT will properly track the panels and maximise their output, 500 is the limit above which damage may or will occur. So you could maybe squeeze a few more in, bearing in mind their open circuit voltage at the coldest ambient temp.

I had forgot about the charge controllers, as didn't quite understand how they worked.

Basically they contain the MPPT software to present the optimum dynamic load to the panels to get maximum output and track this at it varies during the day. Only difference is the output is at nom. 48V DC to go straight on to the battery terminals.

A side benefit of this is that they and the connected panels are AIUI not notifiable as the DNO does not care what is on the battery side of the inverter, only anything that can potentially export to the grid and/or electrocute their staff.

Also the efficiency is a bit higher esp if it avoids doing a double conversion DC (panels) - AC - DC (battery)

Victron ones integrate with the Victron ecosystem so are controllable from the main inverter and over the web (as per my setup), if you just want free-standing then they are available for less and certainly well under the £2500 marginal price difference you quote.

Thanks for explaining sharpener. Much appreciated.

So the power generated by the panels connected to the charge controllers would be sent straight to the batteries and not go into the inverter?

The power generated would then not be able to be used directly by the house as it would be independent from the SunSynk inverter?

How do you view how much they are generating, etc if not talking to the SunSynk inverter?

If that's correct, will this have any negative affects on how the SunSynk inverter, batteries work together? Or how they power the house, etc?

Thanks.

[Richard77]

Looking at the download for the Sunsynk 8.8kW the MPPT current has startup voltage of between 125 and 150v but doesn't specifically state it. The voltage on the panels is good for the MPPT.

2 problems.

I see running 2 parallel strings on 1 MPPT is the nominal rating of 22A per MPPT. Most panels I have seen over 400w are >14A. 2 of these panels paralleled if rated at 14A per panel would be 28A and therefore exceed the rating on the inverter.
You need to check the amps given out in those panels.

The inverter also has a max PV input of 10400W.
If you get a sunny day where the sun is overhead in the middle of the roof and hitting both east and west panels simultaneously you will likely exceed the rating of the inverter.

I think you have undersized the inverter based on its maximum inputs.

You can also parallel inverters as well to gain more inputs.

From the panel datasheet "I sc [A] = 14.22" and "I mp [A] = 13.47"

The SunSynk inverter datasheet says:

PV input current = 26A + 26A
Max PV I sc = 34A + 34A

It's starting to go woooooosh over my head!