Renewable Energy: spec for new solar installation

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- CommentAuthorjhsigma
- CommentTimeFeb 24th 2022
I am about to install solar panels and wonder if anyone can advise on best gear to achive my objecticves .
Requirements for 18 panel system with Battery storage (awaiting permission applied for)
18 solar panels ground mounted 35 deg south facing no shade
String inverters or optimisers ?
Invertor
Controller sending power to
1. Power to Zappi car charger
2. Then to Immersion in heating accumulator
3 . Then to a battery pack (size ?)
And if there is any left to the grid or maybe not
I would also like an isolator to allow me to use my EV to power the house during power cuts .
Is it possible ? will it work
- CommentAuthorRobL
- CommentTimeFeb 24th 2022
That's a great list of stuff! We have PV, a nissan leaf EV with V2G, and I used to use a solic 200 (cheap & simple diverter), so I know about those items.

As you're unshaded, I would advise against individual inverters or optimisers, just more things to go wrong. Often positioned behind the PV panel, so hard to replace if faulty. It sounds like you're after 4kWp, and there's no shortage of inverters at that rating.

You mention batteries - I think they can be "DC" or "AC". DC would be cheaper, combined with a "hybrid" inverter that connects to the PV and the battery. DC wasn't popular in the past, as it reduced the old "feed in tarrif". There's relatively few units I think that provide islanding however - most PV/inverters/battery systems are grid tied only, and switch off in the event of a power cut. I think the (AC) Tesla powerwall can do islanding, I'm sure there are others. I think there will be a significant changeover time gap between mains and battery by the way. Whatever you get, make sure the control can do what you want!

You also mention EV to power the house in a powercut? Did you mean elec car? There are a few V2G / V2H units now, I think that only work with Nissan cars (leaf and maybe a van?). The Wallbox Quasar is the only one that you can buy at present, but there's a few Indra units 2nd hand post OVO trial (that I am on). I doubt any of them would allow islanding though, I think the best use would be V2H (car charges at night on a cheap tarrif, soaks up demand from the house during the day). It's early days, but there are a few people doing this with Octopus.
- CommentAuthorphiledge
- CommentTimeFeb 24th 2022
When considering optimisers remember that shading is more than just a nearby tree/chimney. A dollop of seagul s**t will put a film over a fair bit of a panel and any reduction in that single panels output could bring the whole strings output down. Same with a bit of saharan dust over part of the array. Same with passing clouds- as soon a part of the array is shadowed output drops off until the cloud has fully cleared the other side of the array. All small drops in output in their own right but collectively have a bit more of an impact.

The other big consideration with optimisers and micro inverters is that you get individual panel monitoring so if a fault develops its easy to pin point. Some of the monitoring systems will even alert you to a fault. In a conventionally wired system you might be a year or more before you notice a drop in output and any fault finding is going to mean lifting each panel in turn to test.

Theres no arguing that optimisers can add a fair wedge to the cost of an install but they do offer quite a few advantages over just helping with obvious shading.
- CommentAuthorJeff B
- CommentTimeFeb 24th 2022
Posted By: philedgeWhen considering optimisers remember that shading is more than just a nearby tree/chimney. A dollop of seagul s**t will put a film over a fair bit of a panel and any reduction in that single panels output could bring the whole strings output down. Same with a bit of saharan dust over part of the array. Same with passing clouds- as soon a part of the array is shadowed output drops off until the cloud has fully cleared the other side of the array. All small drops in output in their own right but collectively have a bit more of an impact.

The other big consideration with optimisers and micro inverters is that you get individual panel monitoring so if a fault develops its easy to pin point. Some of the monitoring systems will even alert you to a fault. In a conventionally wired system you might be a year or more before you notice a drop in output and any fault finding is going to mean lifting each panel in turn to test.

Theres no arguing that optimisers can add a fair wedge to the cost of an install but they do offer quite a few advantages over just helping with obvious shading.

All the above. Also note that the OP says that this will be a ground mounted array, hence replacement of individual microinverters should be a doddle.
- CommentAuthorrevor
- CommentTimeFeb 24th 2022 edited
Looks like good spec. With 18 panels you should manage 6kW I have 18 as a ground array with a 6Kw hybrid inverter and 10kW battery. My choice was dictated in that I did not want anything made in China and that was difficult but managed in the end.
I do not divert to heat hot water as I have solar thermal as well. Any spare from charging the battery goes to export. I have to limit export to 3.68 for DNO limitations but when I get a BEV hope that the export will go to battery instead.
As mentioned there is not much choice in systems that run when grid is down but have a look at Victron I did see an YT video of an installation where such a system was set up.
My kit is a Delios Inverter and BMZ battery and that is meant to do it but have not commissioned it properly yet.

One of the snags is, particularly this time of year with shorter days you struggle to fill the battery Today have managed 100 % and managed to export some been out all day so was not here to manage usage. What is in battery will take me through to tomorrow morning but probably will not do a cooked breakfast. So early evening you may start with 75% full battery use some up cooking lights etc than later on get power cut and very little left in battery. One thing to make sure you get and inverter and battery combo that have been tried and tested together, as the way the battery and inverter talk to one another is very important for battery management reasons. Take a close look at what max power the inverter and battery can deliver as this is useful for driving heavy loads albeit for short periods. If got enough solar and battery available I can run a 10 kw shower if short on any of it then comes from grid. For most Inverters it needs to be cabled to the load so that there is no more than 1% voltage drop. If you are doing a ground array it is best to run the DC from the panels to the inverter that way as the DC is at higher volts the cable cross section area can be less than otherwise would be and gets your inverter nearer the loads. an Installer may try to get away with lower rated cable and that can affect performance.
If you go to here.
https://www.spiritenergy.co.uk/
You can sign up to receive some really good write ups about solar PV
- CommentAuthortony
- CommentTimeFeb 25th 2022
Do you have planning permission for this?
- CommentAuthorrevor
- CommentTimeFeb 25th 2022
Posted By: tonyDo you have planning permission for this?

Presumably you are referring to the OP. If it is directed to me YES I applied some 5 years ago but only completed last May. Given the focus on climate change and renewables I think it will be easier now than it was, as long as it is not in conservation area or AONB. But a lot depends on your planning dept.
A further comment to my previous post if you think you may later add a small wind turbine you need to think about the whole system it is difficult to use turbine on a system that has a BMS Li battery as there is conflict as to what "charger" is driving the battery charging. Much easier I am told with a Lead Acid battery.
- CommentAuthorJamster
- CommentTimeApr 26th 2022
How are you doing with this - I came across it looking for something else but co-incidentally I was talking to our PV installer yesterday about similar, bigger systems he is involved with.

WRT your queries, I would recommend individual optimisers for the same reasons others give;
Have you modelled what those 18 panels will give you at different times of year; can you use that much (maybe 6kW an hour for a few hours, potentially when your usage is low / car is not on the drive)?
Coupled with usage, have you looked at the economics of sizing your invertors to cope with generation at different times of year? There may be a sweet spot of panels / output vs invertors above which you are adding another expensive invertor to deal with only a small proportion of output, or in the same vein, you're loosing too much generation from clipping as you have too many panels for your invertors.

A good installer should take you through all this - you don't say where you are but I am happy to whisper one in the NE to you if it would help.

Good luck!
- CommentAuthorneelpeel
- CommentTimeApr 26th 2022
I was looking into 2nd hand PV panels yesterday and noticed this full 2.5kW system with battery pack, bells and whistles...
https://www.ebay.co.uk/itm/203560707633?hash=item2f6529e631%3Ag%3AirQAAOSwoYZhF3NZ&LH_ItemCondition=3000

Seems a lot of kit for the money and may be of interest to someone.

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