Best angle for solar panels

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Best angle for solar panels

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creeper

Joined: 06 Feb 2006
Posts: 83
Location: Vale of Belvoir - Leicestershire

Posted: Sat Jun 24, 06 7:36 am Post subject: Best angle for solar panels

Morning all, I have just bought two 2nd hand solar panel (both tested and working 18v 15w) to use in a shipping container I have on the smallholding as a store/workshop.
As I store petrol mowers/stimmer/genny/hedgetrimmer etc the container can get a bit smelly of petrol on hot days so I am going to put four 12-24v fans to ventilate it, I will have 2 at one end "sucking" and the other 2 at the other end "blowing" with louvres on the outside.
So I need to mount the solar panels on the container - the container is positioned north/south and has nothing casting shadows on it - do I mount the panels flat on the roof on the side of the containers or angled on the roof?
One panel will power the fans directly so will run faster as it gets sunnier and the other will charge a car battery to provide lighting.
Cheers for any advice.

mrutty

Joined: 28 Oct 2004
Posts: 1578

Posted: Sat Jun 24, 06 7:41 am Post subject:
Are they 'bumpy' panels which are lenses which means the angle isn't that important or flat panels. In the middle of summer the angle isn't that important as long as they look roughly south.

dougal

Joined: 15 Jan 2005
Posts: 7184
Location: South Kent

Posted: Sat Jun 24, 06 9:22 am Post subject:

The first thing that leapt out of the question at me was - petrol vapour!
1/ Its explosive.
2/ DC electricity, and DC motors in particular, are a great source of sparks, just tiny little ones, but plenty to ignite petrol vapour.
3/ Hence petrol vapour + DC is not a good combination. At all.

Because petrol is expensive, a scarce fossil resource, and explosive. It'd be a *very* good thing to discover where its escaping from. A smell of petrol isn't inevitable, and usually indicates a leak that could be fixed.

If you want to ventillate the container, I'd suggest that you consider passive ventillation. Low inlets, protected with flyscreens and louvres, combined with a weathercocking cowl on top of a drainpipe chimney as an extractor should do the job for you.

Now then, these panels.
They should produce the greatest output when the sun strikes them square on. For that reason, such panels are sometimes mounted on "trackers", so that they are motor-driven to follow the sun...
If you point the panel due South that's as good as you can do for direction with a fixed mount.
But what angle should it be sloped at?
Well, if you were at the Equator (Oº Latitude), the sun would be exactly overhead at noon, so you'd lie the panel down flat (0º to the horizontal). At the north pole (90º Latitude), you'd stand it upright, 90º to the horizontal. But you are in Lincolnshire (about 53º Latitude), so you'd angle it at 53º to the horizontal...
But wait! At mid-summer, the sun is 22º higher in the sky, and at mid-winter its 22º lower. So, summer ideal, in Lincs, would be about 30º to the horizontal, winter 75º. And yes, that means that a variable mount is ideal.
For a fixed mount, it probably makes sense to bias it to work most efficiently in winter, when there's very little energy available. In summer, you have more energy, more hours of daylight and clearer weather, so you can probably live with lower efficiency, so maybe something like 60º to the horizontal? Mind you, if you were wanting it to be working well in the summer, and never mind the winter, you'd bias it towards the summer angle by laying it down a bit more than the 53º average, maybe just 45º to the horizontal. Which is what you might have done anyway!

creeper

Joined: 06 Feb 2006
Posts: 83
Location: Vale of Belvoir - Leicestershire

Posted: Sat Jun 24, 06 6:58 pm Post subject:

I think the smell of petrol is due to the fact the shipping container is insulated - I wanted this so it didn't get too cold in the winter - in the summer the heat really builds up and if I have filled the genny or mower too full after last using it I think the expansion due to the heat make the filler caps seap a bit - it is not a huge amount of fumes - I still use my petrol stove 5 mins after opening up but I would rather have some ventilation anyway.
I think the 53º will be best angle as I need the ventilation when it is sunny and the container is hot inside in the winter the heat build up is less important.

Cheers for the advice

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