Advice on PV Array Size and Charge Controller Choice

[danmc]

Apologies in advance for the long winded post, but figure it best to include as much information as possible now rather than waste people's time having to ask questions later. Jump right to the end for the question.

Due solely to the great info in this forum In the space of a week I've gone from knowing absolutely nothing about solar/batteries etc to having the solution/plan below. Being well aware a little knowledge is a dangerous thing I was hoping that someone would be good enough to cast their eyes over it to make sure I am on the right track, before I pull the trigger and actually order something that may later prove to be a costly mistake. I've tried to include as much relevant info as I can think of below in advance.

PV Location
Roof 1: SE facing - 10.00m x 7.40m (74 SQM) - No shade
Roof 2: NW facing - 10.20m x 6.20m (63.24 SQM) - No shade
Yearly Average Sun Hours: 2.4 UK (Northern England)
Distance from house to array: 55m.

Electricity Usage
Summer avg daily usage: 8KWH
Autumn/Winter avg daily usage: 11KWH

Solar Spec
PV 60 x (JAM60S20 -380/MR/1000V) - 22800KW (Available, not to be fully used)
PMAX: 380W
VOC: 41.62V
LSC: 11.47A
PV Full Spec: https://www.jasolar.com//uploadfile/2020/1013/20201013031958494.pdf



Background

Last week I was chatting to a local farmer about wanting to go almost entirely off grid, but complaining that I did not have the roof space to do so. Surprisingly he very kindly offered to let me use his barn roof for a PV array or two completely free of charge.

Knowing absolutely nothing I naively jumped straight in with both feet and bought some PV. I stumbled across a good deal locally, but to get a good price I had to buy in bulk, meaning (I know now) I ended up with way more than I would need. I now have 60 x 380W JA Solar panels, just under 23KW. Massively overkill, but I figure it will give me the flexibility to size my array correctly and I can sell what I don't use individually for a small profit which will help fund the rest of the build.

For storage I have decided to go with a Seplos Mason DIY Box and 16 280AH EVE 14.3KWh 200A. Given my usage I hope that will be more than enough (please tell me if you don't think it will be). I'm planning to couple that with a Victron Energy MultiPlus-II 48V 5000VA 70A 50A.

The goal is to be off grid to an extent but still have the grid there to fall back on should I need it.


Question background

I would massively appreciate some guidance on the size of my PV array (or arrays), it's configuration and my MPPT controller (controllers) choice.

As my home is just under 55 metres away from the panels I'm aware I'll need to up the voltage to minimise losses. I'll also need to lay at minimum 16mm, preferably 25mm armoured cable. I'm planning to use 4 core to give me some flexibility.

Also being in a part of the UK which is not particularly sunny I figure I will need to over-panel, missing out on the peak energy created in summer but generating an adequate supply all year around.

My naive calculations have led me to believe that with 2.4 hours avg direct sunlight a day I'll need 9-12KW of solar panels to charge the battery and utilise while during daylight hours, as I work from home, and am in pretty much 24/7.

With this in mind I'm contemplating the following -:

6S4P
9120W
249.72V
45.88A
1 x Victron SmartSolar MPPT 250/100 - Cost (£900/$1072)

6S2P X 2
4560W (9120W Total)
249.72V
22.94A
2 x Victron SmartSolar MPPT 250/100 - Cost (£1800/$2150)

6S3P X 2
6840W (13680W Total)
249.72V
34.41A
2 x Victron SmartSolar MPPT 250/100 - Cost (£1800/ $2150)

or

8S3P
9120W
332.96V
34.41A
1 x Victron SmartSolar MPPT 450/200 (£2000/ $2375)

9S3P
10260W
374.58V
34.41A
1 x Victron SmartSolar MPPT 450/200 (£2000/ $2375)

10S3P
11400W
416.2V
34.41A
1 x Victron SmartSolar MPPT 450/200 (£2000/ $2375)


Finally my question

My question is firstly are my calculations correct regarding the amps and volts in my configurations, what size of an array would you recommend and based on that recommendation which MPPT controller(s) would you suggest I use?

I'm not tied to Victron, nor am I made of money. To be honest before I started I assumed it would be the panels that would make up the biggest cost. My budget was initially £5000/$6000, that's now doubled, so I'm more than open to any suggestions that can bring the costs down, regardless of the manufacturer.

Thanks very much in advance.

 

[Samsonite801]

I really like my 2x Victron SmartSolar 250|100 controllers just fine. I like the Victron Connect management app, I like that I can sync the controllers together (on a bluetooth network) to a BMV-712 shunt so they operate together (read voltage, current, and temp from a common point) and they can be on same charge cycle together, and I like that they support up to 70a Isc (and will self-limit current up to max watts), which means I can overpanel up to 70a with confidence.

Are you against all-in-one inverter/charger options? Did you already buy the Multiplus inverters? I like all-in-one inverter/chargers which are stackable, because they help support scalability in the future...

 

[LywWyr]

I would never invest the time and money to install panels on someone else's property.
Just my 2 cents...

 

[danmc]

I really like my 2x Victron SmartSolar 250|100 controllers just fine. I like the Victron Connect management app, I like that I can sync the controllers together (on a bluetooth network) to a BMV-712 shunt so they operate together (read voltage, current, and temp from a common point) and they can be on same charge cycle together, and I like that they support up to 70a Isc (and will self-limit current up to max watts), which means I can overpanel up to 70a with confidence.

Are you against all-in-one inverter/charger options? Did you already buy the Multiplus inverters? I like all-in-one inverter/chargers which are stackable, because they help support scalability in the future...

Thanks for the info.

I was surprised at how much the charge controllers were going to eat into my budget, it's the distance that's killing me and the need to keep the volts up to limit losses. The costs of the charge controllers are almost making me question doing it tbh.

No I've bought anything yet other than the panels. I did see the Victron Easy Solar but I think it was my computing background that made me instinctively break it out into separate devices. One element breaking and the whole system being out of action seemed like too much of a risk. Also strangely it actually works out more? I guess due to ease of use?

 

[danmc]

I would never invest the time and money to install panels on someone else's property.
Just my 2 cents...

Yeah I take your point. In an ideal world I wouldn't be, but other than moving house I've literally no other choice. My roof as well as being barely big enough to fit 3KW of panels is about 6 feet from a huge protected oak tree. I get more sun in winter than summer at the front due to the huge amount of shade it casts .

On the plus side i've known the family for decades and I trust them implicitly. Otherwise I wouldn't even consider it. Also I figure with energy prices rocketing and inflation going through the roof what's the point of having it in the bank. And if I buy the equipment at the right price and buy a decent brand like Victron which should hold some value should I be forced to take it all down in 5 years I should be able to recoup a fair proportion of my initial outlay if i need to.

 

[Danke]

You are next to a farm with a barn? Is there open land where you could just ground mount system so as to get optimum orientation and tilt?

 

[danmc]

You are next to a farm with a barn? Is there open land where you could just ground mount system so as to get optimum orientation and tilt?

Not really. I have to run a 50m cable through another farmers field just to get to the barn, he wouldn't go for it unfortunately. He only just about agreed to me putting an armoured cable through his field.

Also we are limited to 9 sqm in the UK, anymore than that and you have to jump through hoops and get permission for such an installation. Existing buildings however we can mount as much as we like without question.

But yeah it's the distance that is killing me. It's making it almost unfeasible.

 

[Samsonite801]

Thanks for the info.

I was surprised at how much the charge controllers were going to eat into my budget, it's the distance that's killing me and the need to keep the volts up to limit losses. The costs of the charge controllers are almost making me question doing it tbh.

No I've bought anything yet other than the panels. I did see the Victron Easy Solar but I think it was my computing background that made me instinctively break it out into separate devices. One element breaking and the whole system being out of action seemed like too much of a risk. Also strangely it actually works out more? I guess due to ease of use?

Yeah the Victron CC's are more expensive, dollar per watt I think... Can you guys in UK get the brand new release EG4 6500EX inverters over there (they have high PV volt limit on them) ? Or maybe Sol-Ark style (sold as Deye in the UK) or something?

Much cheaper and stackable. Or could you locate an equipment shed nearby the solar array, and send over the AC via the long run to your house?

 

[danmc]

Yeah the Victron CC's are more expensive, dollar per watt I think... Can you guys in UK get the brand new release EG4 6500EX inverters over there (they have high PV volt limit on them) ? Or maybe Sol-Ark style (sold as Deye in the UK) or something?

Much cheaper and stackable. Or could you locate an equipment shed nearby the solar array, and send over the AC via the long run to your house?

That does look like it could be an option. I wish i could get my hands on the EG4 stuff over here, but I contacted them about a battery order to the UK and was ignored. I Imagine I'd get the same result regarding the inverter. One concern I have though is not back-feeding into the grid. I know the Multiplus II can be programmed not to do so, so I would not need to get it signed off. I'd have to look to see if the 6500EX can do the same. maybe some zero export setting?

I did look at AC Coupling as well as storing the hardware with the panels initially but dismissed it as I wanted it all in my house fully under my control. Perhaps I need to take another look at it. The savings may make it more appealing now.

 

[Samsonite801]

That does look like it could be an option. I wish i could get my hands on the EG4 stuff over here, but I contacted them about a battery order to the UK and was ignored. I Imagine I'd get the same result regarding the inverter. One concern I have though is not back-feeding into the grid. I know the Multiplus II can be programmed not to do so, so I would not need to get it signed off. I'd have to look to see if the 6500EX can do the same. maybe some zero export setting?

I did look at AC Coupling as well as storing the hardware with the panels initially but dismissed it as I wanted it all in my house fully under my control. Perhaps I need to take another look at it. The savings may make it more appealing now.

I know the Sol-Arks in the US can backfeed to grid, but I think they made a proprietary agreement with Deye to not market the Deye equivalents.. Perhaps there is a Deye model though being sold in UK that can backfeed, or if you could get a Sol-Ark delivered over there. They cost more though. Sol-Arks can handle high PV volts though.

 

[danmc]

I know the Sol-Arks in the US can backfeed to grid, but I think they made a proprietary agreement with Deye to not market the Deye equivalents.. Perhaps there is a Deye model though being sold in UK that can backfeed, or if you could get a Sol-Ark delivered over there. They cost more though. Sol-Arks can handle high PV volts though.

Sorry, I should have been clearer. I don't want to feed back to the grid at all. It's just not worth it in the UK. We're charged 0.41p/$0.49 a KWH and paid around £0.4p/$0.5 feeding back. I'm planning to mine crypto with any excess.

 

[Samsonite801]

Sorry, I should have been clearer. I don't want to feed back to the grid at all. It's just not worth it in the UK. We're charged 0.41p/$0.49 a KWH and paid around £0.4p/$0.5 feeding back. I'm planning to mine crypto with any excess.

Yeah, any of the hybrid inverters that can backfeed don't have to. They can just be used for charging batteries or bypassing inverter. Some of the brands/models can only bypass in order to charge batteries and cannot simultaneously charge batteries (from grid input) while inverter mode is running.