Large solar array 40KW 160 panels, welcomed thoughts!!

[nathanb]

Your thoughts

Designing the module layout on a building.... I see many designs where all modules are clumped together like one big roof sheet. Surely its better to to split the module into string sections with a 200-300mm gap between arrays/strings to allow for maintenance (access to each array) and also help with thermal expansion?

Yes is may not be as pleasing to the eye but 160 modules clumped together would be a nightmare if there were any fault.

the string i'm designing is 6 x 21 mods and 2 x17 via SMA design.
also 1 meter clearence from roof edge gutter (not roof top or edge) on commercial buildings? correct?

last question strings to be as close as possible to the inverter to reduce volts drop?

cheers

 

[SolarCity]

If you have the space then it is always better to leave gaps for maintenance and thermal expansion should be factored in to any install.

 

[nathanb]

Yes, theres nothing in any guidence, i cant find.

 

[SibertSolar]

Min volt drop may be cheaper to achieve on the DC cabling than the AC but there's other factors to take into account too, specific to the nature/requirements of the install

 

[Gavin A]

Your thoughts

Designing the module layout on a building.... I see many designs where all modules are clumped together like one big roof sheet. Surely its better to to split the module into string sections with a 200-300mm gap between arrays/strings to allow for maintenance (access to each array) and also help with thermal expansion?

agree entirely, we always design our systems with 500mm access gaps every few panels to allow for maintenance and cleaning, plus it means we can have multiple install pairs working each block at the same time without worrying about them not meeting in the middle.

Yes is may not be as pleasing to the eye but 160 modules clumped together would be a nightmare if there were any fault.

the string i'm designing is 6 x 21 mods and 2 x17 via SMA design.
also 1 meter clearence from roof edge gutter (not roof top or edge) on commercial buildings? correct?
gutter and edge, but not ridge (main or hipped ridge), though in practice it's not a bad idea to leave something like this as the slope tends to be shallow and you risk going over the ridge height, or at least getting too much wind uplift.
last question strings to be as close as possible to the inverter to reduce volts drop?

cheers

nah, volt drop is usually relatively minor consideration at 800V, and we use 6mm2 on commercial anyway generally. Volt drop on the AC side is much more significant due to potential for overvoltage shut downs, particularly if next door gets a solar system installed as well. IMO

 

[nathanb]

nah, volt drop is usually relatively minor consideration at 800V, and we use 6mm2 on commercial anyway generally. Volt drop on the AC side is much more significant due to potential for overvoltage shut downs, particularly if next door gets a solar system installed as well. IMO

what max quantity of modules do you use before moving to 6mm

 

[Worcester]

Expansion depends upon a number of things including the roofing material. Read the instructions included in the mounting system of your choice.

It is usual to allow expansion every 8 panels, though that only needs to be 20 mm, so in some cases depending upon how the rails are installed, you can end up with a gap of only 40mm between every 8 panels.

Maintenance issues depend also upon mounting system and slope angle.

Nearly all our commercial installations include maintenance contracts where we carry out visual inspections every six months and full Inspections and Condition Reports every 12 months, so we design out layouts with this in mind Including roof access...

 

[Worcester]

We only use 6mm... Save us stocking two sizes.
The SMA design module will give you an idea of the voltage drop / efficiency depending upon lengths.

We aim to keep the TOTAL losses including AC and DC < 1%.

When you think of the output, a 1% drop could be quite a few kWh thrown away, so it's false economy to 'get away' with 4mm

 

[Gavin A]

what max quantity of modules do you use before moving to 6mm

like worcester we pretty much only use 6mm on bigger commercial partly to avoid the potential that we'd accidentally end up with a length of 4mm2 where we should have had 6mm2 eg if it's chucking it down and getting dark you don't want to be trying to remember which string needed 6mm2 and which needed 4mm2 for the sake of a few quid on a £30k job, though we'll sometimes use 4mm2 on small runs of 10kW systems which are just 2 x 5kW strings and relatively short runs.

 

[SolarRoofSols]

agree with the comments above.

You should still check with the local planning officer that the area is not in a conservation area. If it is then permitted development is overruled and you need to apply for full planning. If it is then check with them what type of drawings and illustrations they want of the positioning of the panels as some want proper design drawings which you may need to get someone to do.

 

[Ian-LS]

agree with the comments above.

You should still check with the local planning officer that the area is not in a conservation area. If it is then permitted development is overruled and you need to apply for full planning. If it is then check with them what type of drawings and illustrations they want of the positioning of the panels as some want proper design drawings which you may need to get someone to do.

Not true, planning permission is not required in conservation areas except for wall mounted arrays.

" in the case of land within a conservation area or which is a World Heritage Site, the solar PV or solar thermal equipment would be installed on a wall which fronts a highway; "

The Town and Country Planning (General Permitted Development) (Amendment) (England) Order 2011

Councils can apply for an article 4 to remove permitted development rights

"Permitted Development Rights withdrawn

You should also note that the local planning authority may have removed some of your permitted development rights by issuing an Article 4 direction. This will mean that you have to submit a planning application for work which normally does not need one. " Planning Portal - Permitted Development Rights

So only if an article 4 has been applied to a conservation area would planning permission be needed.

 

[SolarRoofSols]

I didn't know that!! I'm gonna check with my planning officer about permission I submitted before christmas to see about the Article 4 as I was told that I would need permission, but they were a bit vague on a couple of other points surrounding permitted development.

 

[nathanb]

QMS system in quotation makes the owness on the customer, easy mcs f41, but advise the customer, large arrays can look unsightly, unless bunch together, hence my question,

 

[Earthstore]

I didn't know that!! I'm gonna check with my planning officer about permission I submitted before christmas to see about the Article 4 as I was told that I would need permission, but they were a bit vague on a couple of other points surrounding permitted development.

Sad as it is, at times you/us have to tell the planners what the rules are, even though it is their job to tell you, they tend to wonder off, look it up then come back and say "you are right, I did not know the rules had changed"

I had to do the very same with my local authority when that rule changed.

But make sure you know the regs before contacting them, the link in the other post may help.

 

[BruceB]

Planners create work to keep themselves in employment and raise revenue for the Council by telling you that you need planning permission whether you do or not. Same applies to building regulations. Sadly, there is no substitute for reading and understanding the rules yourself.