Solar PV advice

[Richard77]

Hi All....

I hope it's ok to start a new thread to ask for advice or any thoughts on my plans to get solar panels and battery storage installed.

We currently use about 12000kwh a year of electricity. We also have an EV charger installed for the EV. All our appliances are electric, only use gas boiler for hot water and heating.

I was hoping to take advantage of the night time rates of a tariff such as Octopus Intelligent Go to charge the EV and to fill the batteries up during the night at the cheaper rate and use the batteries to power the house at all other times.

House is 3 storey semi detached, with no access to the roof space (space was created into rooms and are plasterboarded to the roof). I've got a detached garage that I plan to house the inverter, batteries.

I intend to get a SunSynk 8.8kw ECCO hybrid inverter installed and have purchased 30kwh of battery storage (thanks Colin!) that is due to be delivered in the near future. This will be able to accept 10.4kw of DC input from the panels. I think this is a decent inverter and would be suitable for my plans?

I was thinking of getting a few solar panels installed on the garage roof while I get the inverter/batteries installed. The garage is a low pitched (12°) south/north facing and gets sun on both sides at same time.

Garage:



I have a quote for around £4000 (reasonable?) to supply and install the SunSynk 8.8kw hybrid inverter and 4x Aiko 625W (https://www.pluginsolar.co.uk/?product= ... anel-gen-2) solar panels with 2 horizontal on each side . This would give me a 2.5kw array and using PVGIS calculator would generate me approximately 1950kw a year. I suppose something is better than nothing!

I was going to wait a while before hopefully getting the roof of the house filled with as many solar panels as possible, to possibly generate enough to cover our whole electricity usage. I then started thinking what if I just did it now, see if it could be done and at what cost?

I had a play with opensolar last night and tried to fit as many of the Aiko 625W panels on the roof as possible:



I would lower the chimney stacks to reduce the shading as much as possible. The main roof is East/West facing and the other smaller ones are south facing. The east facing would be a 6.25kw array and generate approximately 4655kwh a year. The west facing would be 9.375kw array and generate approximately 6768kwh a year and the 2 small south facing roof (possible to be on same array so far apart?) would be 2.5kw array generating approximately 2378kwh a year. Any ideas how much to expect this to cost to add panels to the roof? The cables would have to be run down the wall to garage as no roof access from inside.

Total size of arrays, including garage, would be... 20.625kw and total generation would be approximately (calculator time!)... 15751kwh a year. So that's more than our usage, in the summer months , so would then hopefully be able to export the excess after filling the batteries up. Building up £££ to cover the cost of the winter months?

A question to ask the experts out there... Is that many separate arrays possible on the roof and would the SunSynk inverter be able to accept that many arrays? I think it has 2 MPPT and 2 strings on each MPPT (unsure what all that means!)?? I assume the SunSynk wouldn't clip as would never be generating more than 10.4kw at the same time with the orientations of the roof?

Sorry for the long post and thanks if you read until the end. Just hoping for someone with more knowledge than myself can say to me, either that's a load of bollocks and you can't do that... Or sounds a decent idea and go for it!

If anyone can offer any advice or recommendations to these plans that would be better than what I have come up with or any problems that you can envisage with anything I have said, that would be great.

Thanks for your help...

[MrPablo]

Regarding the garage, I would be very tempted to cram as much PV on that as possible.
A lot of panels are 1722mm long, 1134mm wide. You could just fit 5 panels a side, so that's a 4kWp array straight away.

From what I saw on the datasheet for the Sunsynk 8.8kW unit, it has 2 MPPT inputs which would normally result in 1 string per MPPT.
You can play around with parallel wiring, etc, but I don't have any personal experience of that - I think Nowty has details on one of his posts though.

Perhaps for now, it makes sense to cram the max on the garage (wired as 1 string, or perhaps 2 if shading is an issue).
In future, you could take that back to a single string and use the other MPPT for a main roof array.
Additionally, I wonder if using another PV only inverter to handle the additional arrays makes sense. AC coupling is not as efficient, but you'd be able to deal with mega loads in the summer...

[Richard77]

Regarding the garage, I would be very tempted to cram as much PV on that as possible.
A lot of panels are 1722mm long, 1134mm wide. You could just fit 5 panels a side, so that's a 4kWp array straight away.

From what I saw on the datasheet for the Sunsynk 8.8kW unit, it has 2 MPPT inputs which would normally result in 1 string per MPPT.
You can play around with parallel wiring, etc, but I don't have any personal experience of that - I think Nowty has details on one of his posts though.

Perhaps for now, it makes sense to cram the max on the garage (wired as 1 string, or perhaps 2 if shading is an issue).
In future, you could take that back to a single string and use the other MPPT for a main roof array.
Additionally, I wonder if using another PV only inverter to handle the additional arrays makes sense. AC coupling is not as efficient, but you'd be able to deal with mega loads in the summer...

Thanks MrPablo....

With regards to the panels going in portrait on garage, none of the installers were happy with installing that close to the edge, against regulations or overhang onto gutter. Some went with 3 horizontal each side at 435w each. Then it was a tight fit and close to the edge. 2x 625W offered roughly the same anyways without the space issues.

I wasn't that bothered and as you said would have been happier with getting 5 on each side even with a little overhang!

With regards to the MPPT stuff and strings... Not sure on that stuff mate. I am sure I read somewhere though that the SunSynk 8.8kw can handle 2 strings per MPPT. I will try read up on it all and educate myself a bit more. Thanks.

[Countrypaul]

Have you got permission from your DNO to have an inverter that can output that power? If not, that could result in a big hurdle to overcome.

The DNO is not bothered about the DC side of things, so using charge controllers directly coupled to PV and to the batteries may be somethig to consider.
If you have several different sets of panels, at different orientations etc. then coupling them all to a DC bus with batteries and your inverter is a common approach. It also means you can easily add more panels and another charge controller as time goes by.

I agree wih MrPablo, if you are going to put panels on the garage roof then fit as many as you can - a common feature on the site is those wish they ut more panels on at the start.

[Richard77]

Have you got permission from your DNO to have an inverter that can output that power? If not, that could result in a big hurdle to overcome.

The DNO is not bothered about the DC side of things, so using charge controllers directly coupled to PV and to the batteries may be somethig to consider.
If you have several different sets of panels, at different orientations etc. then coupling them all to a DC bus with batteries and your inverter is a common approach. It also means you can easily add more panels and another charge controller as time goes by.

I agree wih MrPablo, if you are going to put panels on the garage roof then fit as many as you can - a common feature on the site is those wish they ut more panels on at the start.

Thanks Countrypaul....

The installer is submitting the G99 for the 8.8kw inverter this week so haven't heard anything back yet. Fingers crossed!

Yeah I would like more panels on garage, but just don't think can fit them on in portrait and pass regulations with how close/over edge they will be. And 3x horizontal gives basically the same as 2 horizontal 625w ones.

[MrPablo]

Could you get 6 x 435w fitted for now (for the MCS certificate) then rejig it in future to fit 4 more on?
There's rarely a roof as easily accessible and DIY friendly as the garage.

[AGT]

Heck out the inverter instructions it had 4 pairs of PV Input
I like this inverter

[Richard77]

Could you get 6 x 435w fitted for now (for the MCS certificate) then rejig it in future to fit 4 more on?
There's rarely a roof as easily accessible and DIY friendly as the garage.

I can mention it to the installer, so 3 panels in portrait towards the longer sides of the roof? Then DIY the other 2 and squeeze them on and let them overhang a bit (and don't worry about regulations as it's just a garage?)?

Do you need to inform the DNO if you add more panels?

[Richard77]

Heck out the inverter instructions it had 4 pairs of PV Input
I like this inverter

Yeah it looks a good one mate.... Well to me anyway, not like I know what a bad one looks like though!

[Krill]

I was going to have that inverter before my first choice installers backed out on me, it looks sound. If the installer is making the application then I expect the DNO will just sign to off and export problem solved.

The other problem is that if the general load is low most of the time it will not be that efficient and will eat the battery capacity. I've found that having 2 smaller inverters and setting one to zero discharge gives far better discharge efficiency, and I turn it on when I need it. OTOH if wall space is limited...

Would those 4 panels even be enough to get the MPPT working? The start up voltage could be an issue.

I don't see any issue with changing which strings of panels attach to which dc charge controller or hybrid inverter post install, so long as the mcs certificate is in place.