PV array layout

Effects · 09-02-2016 5:21pm #1

Hi, I'm looking for a bit of feedback on a PV array.
It's been a few months since I've last looked into it so I've forgotten a lot in that space.
I've attached an image of a similar layout that I'm looking at. Can anyone point out any issues with it?

One thing I'm concerned about is losing efficacy due to them being flat rather than angled. Will this be a big issue?

I've attached a layout for my own roof, is there any issues there? I think I might be concerned with shadow cast from the upstand of the rooflight section.
I'll have a parapet wall similar to the one in the attached image. The upstand will be a bit higher that this.

We are trying to keep them low to please a neighbour but we don't want to be wasting/not utilising energy at the same time.

Any help/opinions would be much appreciated.

quentingargan · 10-02-2016 12:26am

They won't be self-cleaning if you leave them flat. Also, any shadow from an upstand will block the bottom third of the panel (if they are in landscape format) . Horizontal, according to SEAI give 963KwHrs/m2 compared to 1074 at 30 degree pitch facing south, so the actual loss isn't huge.

You don't want too much pitch as the wind loading increases with pitch. Most ballasted systems stick to a pitch of 10 to 15 degrees for that reason. I guess if you are making a frame, you could raise the ones that are further back as they would be less visible from below, unless the neighbour is a the same height as yourself.

quentingargan · 10-02-2016 12:26am

They won't be self-cleaning if you leave them flat. Also, any shadow from an upstand will block the bottom third of the panel (if they are in landscape format) . Horizontal, according to SEAI give 963KwHrs/m2 compared to 1074 at 30 degree pitch facing south, so the actual loss isn't huge.

You don't want too much pitch as the wind loading increases with pitch. Most ballasted systems stick to a pitch of 10 to 15 degrees for that reason. I guess if you are making a frame, you could raise the ones that are further back as they would be less visible from below, unless the neighbour is a the same height as yourself.

10-02-2016 12:46am

Linear actuators activated by a PIR facing the neighbours window?

If you ask me they look way better than concrete. :rolleyes:

Effects · 10-02-2016 9:18am

The neighbours look directly over the roof. The original reason we went with the flat roof was so as to not block their view.
They also don't like the concrete either so that side of the building will be clad with timber.
I guess I'll have to figure out placement to avoid overcast from the upstand. We also can't have them higher than the parapet due to planning restrictions.

freddyuk · 10-02-2016 11:07am

Why can't you put them on your pitched roof under the permitted development rules? Then nobody is "overlooking" them and they will perform almost to 100%.

Effects · 10-02-2016 11:48am

There won't be a pitched roof, the entire roof area is flat and surrounded by parapet. As panels are shown below the parapet on the plans they have to stay below the parapet.

freddyuk · 10-02-2016 9:27pm

I seem to remember this being posted some time ago. You will not lose a huge amount of generation having them horizontal however if there is any shading along the short side you will switch the whole panel (s) off but if you shade across the long side you will lose a proportion of the output for that whole row of cells. If you trace the silver connections you can see how it is wired in series and cutting off across all the connections the panel is shut down even shading the bottom inch. If you check one panel with a multi meter and a piece of card you can see the effect dramatically. So design accordingly.

Conor20 · 18-02-2016 11:45am

quentingargan wrote: »

They won't be self-cleaning if you leave them flat

How much cleaning would be involved on flat panels?

quentingargan wrote: »

You don't want too much pitch as the wind loading increases with pitch. Most ballasted systems stick to a pitch of 10 to 15 degrees for that reason. I guess if you are making a frame, you could raise the ones that are further back as they would be less visible from below, unless the neighbor is a the same height as yourself.

This is very useful advice. I'm also interested in building a stand for Solar PV. Has anyone here built a stand for PV panels? I am looking into putting a few PV panels on a flat shed roof as a project pre-curser to a bigger pitched roof system. Wind is my biggest concern, as this shed is on high ground and very wind exposed. I'd be interested to hear any designs used and the experience in terms of how they stood up to the wind.

quentingargan · 19-02-2016 8:23am

Conor20 wrote: »

How much cleaning would be involved on flat panels?

This is very useful advice. I'm also interested in building a stand for Solar PV. Has anyone here built a stand for PV panels? I am looking into putting a few PV panels on a flat shed roof as a project pre-curser to a bigger pitched roof system. Wind is my biggest concern, as this shed is on high ground and very wind exposed. I'd be interested to hear any designs used and the experience in terms of how they stood up to the wind.

In terms of cleaning, one seagull emptying its bowels could knock out most of a panels production, but this would get cleaned in the next downpour. In Spain they usually clean solar parks twice a year for dust, but in Ireland, domestic roofs don't need cleaning. Just if they're totally flat, you could suffer a loss of production.

Most flat roofs have a membrane that cannot be penetrated, so you are dependent on ballasted mountings. Is the shed roof completely flat, or just shallow pitch, and what is the roof surface?

BryanF · 26-02-2016 11:07pm

If the panel were simply positioned 'down the garden' what would the cable cost &/or kW/loss be, can this be calculated per additional m ?

27-02-2016 12:41am

Down the garden is far more likely to have shading issues than on the roof. Also then you lose useful land/ vegetation.

In any case there's a few factors involved. Size of the array output, Array Vmp, distance in cable length, acceptable losses, nominal cable temperature, cable gauge and cable cost.

3% voltage drop is generally the acceptable max.
Here's a voltage drop calculator.

Simple answer is you can make it work for not very much extra expense.

Conor20 · 03-03-2016 9:53am

quentingargan wrote: »

In terms of cleaning, one seagull emptying its bowels could knock out most of a panels production, but this would get cleaned in the next downpour. In Spain they usually clean solar parks twice a year for dust, but in Ireland, domestic roofs don't need cleaning. Just if they're totally flat, you could suffer a loss of production.

Most flat roofs have a membrane that cannot be penetrated, so you are dependent on ballasted mountings. Is the shed roof completely flat, or just shallow pitch, and what is the roof surface?

Interesting, thanks. Yep - it's a fibreglass roof which can't be drilled or screwed through as it would lead to leaks. So As you say, it would either have to be heavy enough to withstand the highest wind speed it will experience, or have some grappling style afixing to the edge of the roof.

Sir Liamalot wrote: »

Down the garden is far more likely to have shading issues than on the roof. Also then you lose useful land/ vegetation.

In any case there's a few factors involved. Size of the array output, Array Vmp, distance in cable length, acceptable losses, nominal cable temperature, cable gauge and cable cost.

3% voltage drop is generally the acceptable max. Here's a voltage drop calculator.

Simple answer is you can make it work for not very much extra expense.

Thanks. Yep - there will definitely be shading issues. If I go with putting PV on the shed roof, it would be more of a pet project than an attempt to attain an optimum yearly kWh/€ setup. The pitched roof of the house, which faces south, will make a lot more sense for that.

ColemanY2K · 11-08-2022 8:54am

apologies for resurrecting an old thread but i have a query or two on this topic.

below is the proposed layout for my DIY solar setup. the array will be looking due south (facing the field access road) with no shading issues.

is there anything obviously wrong with the basic layout below?

Is it OK to have the main fuse board for the house in the garage? iirc ideally the fuse board should be close to the invertors/batteries/switchover switch in times of blackout (on one occasion power in the area was down for 14 days after a recent storm!). i can't put it in the attic as it will be outside the envelope and to cut costs - along with helping to ensure an airtight passive house - there won't be any access to the attic.

another reason for locating the gear in the garage is that i'm concerned about not having enough space in the utility (or at least making the room feel really cramped what with the washing machine, dryer, mvhr, hot water tank & sink in there) as well as minimising fire risk to the house which i know is minimal but still.

slave1 · 11-08-2022 10:12am

All I can add is if that is a ground Mount I'd have it a few meters high and with a tilt so you can maximise PV generation i.e. 14degrees in Dec and 60degrees in June. Fix it at the typical 45degrees like most if you want but just to make you aware in "design" stage

ColemanY2K · 11-08-2022 10:36am

https://www.boards.ie/discussion/comment/119457896#Comment_119457896

cheers slave1

i'm kind of limited to how high off the ground i go as it'll back up onto a neighbours boundary which is divided at the moment by sheepwire. i'll eventually put up a 1.8m high fence but that still won't fully disguise the array (3 rows of 10 panels = 30 panels, i might consider 2 rows of 15 but could be tight for space between the back wall and the far end boundary). adjustable ground mount noted, that's my intention.

slave1 · 11-08-2022 10:49am

look to the new ground mount regulations, you are allowed up to 25m2 of panels up to 4m high without PP, over that then you do have to take a Karen neighbour into account unfortunately (or go for planning to cover your ass)

ColemanY2K · 11-08-2022 11:01am

https://www.boards.ie/discussion/comment/119458089#Comment_119458089

ah sugar! 25m2 is only 12 number 480w panels. i could put another half dozen or so on the south facing garage roof but that's only 18 panels in total which in this case is an 8.6Kw array.

i have had little dealings with the neighbour but what little dealings i have had its safe to assume this guy is certainly in the odd ball category.

slave1 · 11-08-2022 12:29pm

Feel you paid friend, feel your pain

Gerry · 11-08-2022 1:53pm

https://www.boards.ie/discussion/comment/119458089#Comment_119458089

4 metres is really high. has anyone tried this in a housing estate? I don't think the neighbours would be too impressed. I'm considering putting a few in my garden, potentially at the same height as the shed roof, approx 2.5 metres. southeast facing.

slave1 · 12-08-2022 3:07pm

I'm not advocating going 4m high, just pointing out that you do not need to consult the neighbours on any matter where PP is not required.

This legislation is currently moving through the houses, not yet enacted

I welcome the Minister of State to the House. I commend my Green Party colleagues, Senators Pauline O’Reilly, Garvey and Martin, on bringing forward this Bill which will amend Parts 1 to 3, inclusive, of Schedule 2 to the Planning and Development Regulations in order to remove planning restrictions that relate to the installation of solar panels on public buildings, schools, homes, business premises and agricultural buildings.

I would echo much of the comments made by Senator Dooley. What the Bill proposes is a no-brainer. There is no question about that. Under the proposals in Bill before us homes will be able to install a larger array of solar panel. Currently, it is restricted to 12 sq. m or 50% of the roof area. Likewise, industrial buildings, businesses and agricultural buildings, in particular, will be able to install them. This is an area where our rural and agricultural sector can have a positive impact on reducing carbon emissions. I hope when we debate the climate Bill later in the week that sector will be credited for reducing its energy requirements through the installation of these panels. Panels will be able to be installed on the ground up to the 4 m in height.

PV array layout

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