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Choosing a solar panel for the British weather

U

Urge38

New Member
Joined
Mar 18, 2023
Messages
233
Location
London Uk
Its been a long hard journey for me for some reason,
not quite there yet, but I am up and running to a point!!!

Its now time to add a small solar array to my current system (Shneider xw+ and four server rack batteries.

currently charging via a chargeverter and a Gen as I am off grid (not tied to the grid)

I am looking for recommendations for 5 panels to fit a slate pitched roof.

any suggestions plz for panels and the MPPT charger
 

Bimble Solar

Affordable Solar Panels and Solar Equipment in the UK and delivered Worldwide. Solar panels - From 20W to 490W, Off Grid and On Grid Packages. MPPT Charge Controllers, Inverters, Batteries and all accessories.
www.bimblesolar.com www.bimblesolar.com
 
Strange supplier to name, I recently purchased 6 x Longi 425w panels & mounting rails from city plumbing - branches nationwide in UK - website with ordering/ prices.

They where the cheapest I could find incl delivery.

With excellent after sales - 1no. Of the panels had a slight mark on it(perfectly usable), notified them of issue and they simple said we can refund the cost of the one panel if acceptable- which I agreed.
 
1234enough said:
Strange supplier to name, I recently purchased 6 x Longi 425w panels & mounting rails from city plumbing - branches nationwide in UK - website with ordering/ prices.

They where the cheapest I could find incl delivery.

With excellent after sales - 1no. Of the panels had a slight mark on it(perfectly usable), notified them of issue and they simple said we can refund the cost of the one panel if acceptable- which I agreed.
Click to expand...

Are the Longi panels you purchased from city plumbing half cut cells ???
 
Urge38 said:
5 panels
Click to expand...

5 panels can make for a funny array , because there is an odd number of panels they must be wired in series, no possibility of series/parallel configuration

For standard 30vmp/37voc panels you would need at least a 200v mppt , more likely a 250v


Urge38 said:
the MPPT charger
Click to expand...

Assuming five 425w panels

425w X 5 = 2,125w array
2125 ÷ 48v = 45amps*

you need at least a 45a mppt


So looking at 250v max PV voltage & 45a..... pretty much your only option for an MPPT is a victron , 250/60a . It's going to cost !

callidus.shop

Victron MPPT 250/60 – SmartSolar Charge Controller – Tr

Victron SmartSolar MPPT 250/60-Tr – SCC125060221 250V maximum voltage from the solar array. 60A maximum current from the solar array. For use in 12V and 24V systems. MPPT optimised for efficient solar charging. Monitor settings and performance through the VictronConnect app via Bluetooth. Tr...
callidus.shop callidus.shop



That or a cheap Hybrid inverter used just for its mppt ..???
 
Just for my ignorance, are their any technologies that are better suited for overcast skies? I understand the general recommendation is for monocrystaline, and if is cloudy vs overcast half-cut cells help, but anything else that makes a meaningful difference? Does bifacial help at all (if appropriately mounted with a high-albedo background)?
 
SamG340 said:
5 panels can make for a funny array , because there is an odd number of panels they must be wired in series, no possibility of series/parallel configuration

For standard 30vmp/37voc panels you would need at least a 200v mppt , more likely a 250v




Assuming five 425w panels

425w X 5 = 2,125w array
2125 ÷ 48v = 45amps*

you need at least a 45a mppt


So looking at 250v max PV voltage & 45a..... pretty much your only option for an MPPT is a victron , 250/60a . It's going to cost !

callidus.shop

Victron MPPT 250/60 – SmartSolar Charge Controller – Tr

Victron SmartSolar MPPT 250/60-Tr – SCC125060221 250V maximum voltage from the solar array. 60A maximum current from the solar array. For use in 12V and 24V systems. MPPT optimised for efficient solar charging. Monitor settings and performance through the VictronConnect app via Bluetooth. Tr...
callidus.shop callidus.shop



That or a cheap Hybrid inverter used just for its mppt ..???
Click to expand...

had not even given that a thought yet !!!

Many thanks for highlighting the possible problems with odd number of panels
 
Urge38 said:
had not even given that a thought yet !!!

Many thanks for highlighting the possible problems with odd number of panels
Click to expand...

4 or 6 would be better if possible

6x 37voc panels in 3s2p would make 90vmp/111voc

In that case you could plumb for a mppt that's much cheaper (but still reliable), like this EPever:

www.sunshinesolar.co.uk

MPPT Controller 50A - 150V 12/24/36/48V

MPPT Solar controllers (Maximum Power Point Tracking) can intelligently regulate the working voltage of solar panels, letting the solar panels always work at Maximum Power Point of V-A curve. Compared with ordinary solar controller, this MPPT controller can increase the efficiency of PV modules...
www.sunshinesolar.co.uk
 
Last edited:
Be aware, a 2-series solar array made up of 37voc panels may not necessarily produce high enough voltage to charge a 48v battery bank

3 series is more appropriate

Or possibly 2 series with a higher voltage panel
 
SamG340 said:
Be aware, a 2-series solar array made up of 37voc panels may not necessarily produce high enough voltage to charge a 48v battery bank

3 series is more appropriate

Or possibly 2 series with a higher voltage panel
Click to expand...

a mountain off help.
many kind thanks

I think I am sold on a half cut cell, only because of shading.
 
Shimmy said:
Just for my ignorance, are their any technologies that are better suited for overcast skies? I understand the general recommendation is for monocrystaline, and if is cloudy vs overcast half-cut cells help, but anything else that makes a meaningful difference? Does bifacial help at all (if appropriately mounted with a high-albedo background)?
Click to expand...
FINALLY someone clicked ! hahaha... I was waiting for that.
The Solar Panel Type is a BIG ISSUE as some are better in pure sun, some better in shade and everything in between. There are a vast number of companies producing solar panels and a fairly broad collection of types as well.

Shingled Solar Panels are by far the best for Shade/Shadows but they do cost a "small amount more" but the payback is quite significant because they will generate far more than standard Poly or Mono panels.

For example, the Trina PERC Split Cell panels get Top Marks for performance in shade & lower light conditions and these are available up to 500W panels.
Trina US: https://www.trinasolar.com/us/product
Trina EU: https://www.trinasolar.com/eu-en/product

A good article discussing the solar panel types for shade applications. There is good info to consider here.
solarpowernation.com.au

Which type of solar panels are best to combat shading issues? - Solar Power Nation

One of the most common hindrances to achieving maximum efficiency from solar panels in Australia is the issue of shading. Shade can occur due to the trees and buildings around the property and can obstruct sunlight to fall directly upon the panels. This reduces the output efficiency of even the...
solarpowernation.com.au solarpowernation.com.au

EDIT - Forgot to mention:
Bi-Facial Solar panels have been mentioned. CAUTION ! They can be quite amazing and do as advertised BUT the conditions for them must be right. They require a minimum clearance space at the back, The surface behind/under the panels must be LIGHT COLOURED (preferably pure white to reflect the full spectrum) to achieve full potential. Put them on a black roof is a money toss !
 
Last edited:
Steve S, would you still consider shingled panels if full sun, no shading?
 
If you have full sun (and by that I mean no shading, clouds are consistent lighting from the perspective of a single panel which is what matters for this discussion) then you don’t need any consideration besides cell efficiency.

If you have unlimited space and the total costs including extra racking make sense cell efficiency can be sacrificed too.
 
Steve_S said:
A good article discussing the solar panel types for shade applications. There is good info to consider here.
Click to expand...
TBH I think this overhypes the half cut gain.

In the end shingle cell and half cut are just ways to get more parallel at a clever minimal incremental cost . No need to have so much marketing. Just give the theory and the example teaching scenarios where it’s good and where it doesn’t matter at all.

Edit: also it doesn’t discuss the potential bad interaction with MPPT a more complex curve would yield. The curve is more complex with half cut, I’m not sure about shingle
 
Johneb said:
Steve S, would you still consider shingled panels if full sun, no shading?
Click to expand...
If the option sis available within a reasonable price difference MOST ABSOLUTELY !
Remember when the Talk About shading starts, that it includes cloud cover & low sun days as well.
When you have a string of 4 panels for example, and a single panel get's shade/shadow on even 1/4 of it, the whole strings output falls drastically. This is easily observable and repeatable... Go out and cover any "part" of a panel in a string and you will see it plain & simple on the power it generates.

Actually Andy @ Andy's Garage YT did a reasonable video showing teh differences and how the perc shingled panels took that without a blink. I think it was 4 months ago or so. People would not believe it till he showed that even covering one segment only reduced generation by the amount of that segment and not the whole panel.

Regardless of where someone is, clouds and other factors are always at play.
But what the hell do I know... I just design, build & install systems and more... now starting an ESS Battery Company (Q1-2024) here in Canada so, I'll just move along....
 
I agree completely on the effects of covering a panel (hard shade or non uniform light across a panel), but I fail to see how that applies to clouds which are much more diffuse.

EDIT: what cell types do better at low uniform light? And why (or a reference to where I can read up on the mechanism).
 
zanydroid said:
I agree completely on the effects of covering a panel (hard shade or non uniform light across a panel), but I fail to see how that applies to clouds which are much more diffuse.

EDIT: what cell types do better at low uniform light? And why (or a reference to where I can read up on the mechanism).
Click to expand...

Living in the uk, and like most, needing more, free eclectic in the winter than the summer, I too Conclude low light levels are the evil. i.e. cloud cover etc

I am NOT winning,
BUT being born with dyslexia AND having a mounting of work ahead off me (how have I complied so much work !!??) can someone please just name a panel for me???

not loads of options, just pick one for low light conditions and link it plz.
I would really appreciate that if you don't mind.
 
You’re going to need to focus on help from domestic forum members if you just want a panel name since that depends on what is available locally. You also need to provide the roof geometry or whatever if there is a constraint.

For the MPPT you need to specify budget and other requirements like future expansion plans, whether you want it to communicate with XW ecosystem.
 
I find lots of information on shingled panels but very few for sale that specifically call out shingled.

Do they call them something different?
 
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