Solar PV on garage roof?

kindandthrifty

We're having a garage built, and as I have an EV I'm interested in having solar panels on the roof & a battery. The garage roof area will be approx 3m x 6m and will be on a 5 degree slope, facing almost due South. We alao have a smaller area of flat roof on the rear of the house (also South-facing) on which I was thinking of adding another couple of panels. [Longer-term I'd be looking to have solar panels or tiles on the main roof, but have been advised not to do that until the roof needs replacing.]
Can anyone advise if this sounds practical? Also, there are so many companies advertising solar & I'm unsure how to find a reputable firm. Any advice on this? I'm in the Brighton area.

Martyn1981

Hiya, just wondering if the roof pitch is decided, as 5d is virtually flat, even a modest slope is about 15d+. My thought being that if you can increase the pitch a bit, you will get better annual generation, and it will be a bit less of a 'summer specialist'. Might give you a bit more space inside, and will slightly increase the size/area of the roof too as 3m will be a tricky size, as it won't allow 3x panels landscape (3m+), nor 2x panels portrait (3.2m+). A mix of the two at around 2.6m might fit, but hard to get them to look nice.

But, putting aside such issues, great idea to PV the roof, and if you could find a way to fit 9 panels, that alone would be a mighty 3kWp(ish).

NigeWick

If you can afford it, I'd go for a 40 degree pitch with a vertical at the North side. This would mean a little less peak generation but more when the sun is lower in the sky. Having that large slope would also mean you could get a little more collection on it, and as Mart said, give you more space to put junk (sorry, I mean collectibles) in.

Martyn1981

PS - Totally forgot to say that 5d pitch will mean they probably won't wash clean in the rain, so you may have to get the extendy pole out. My 20d pitch panels get a light wash down every couple of years, (just steps and the extendy pole) not too bad, but the 30d panels on the main roof are fine, so I'm just extrapolating from there, and 5d could require some cleaning.
But not the end of the World, of course.

kindandthrifty

Thanks @NigeWick and @Martyn1981, that's really helpful. Unfortunately the building control drawings have just been submitted, but I can ask the architect what flexibility there is. When I explored solar PV for another property about 10 yrs ago I was told panels on a flat roof could be mounted on a support to be at the correct angle. Is that still the case? Not as neat as having them directly on the roof of course, and I imagine there are other drawbacks (eg need to protect from birds nesting underneath), but might enable us to fit the larger array?

Martyn1981

Hiya, you can mount panels on an angle, but you might need planning permission, which kicks in if the panels don't follow the roof pitch and/or part of them is higher than the roof ridgeline.
Also, due to shading from the panels in front, you may have to space out the panels, and possibly end up with less.
Have a play with PVGIS and see what the impact of pitch will have, don't just focus on the annual total, also see what impact shallow panels might have on the yearly distribution, such as raising summer gen (when you'll have too much) and lowering winter gen, when you can use it all.
But again, not the end of the world, just ideas and suggestions for maxing out the benefits.

Pile_o_stone

we have 1.8kW of solar panels on our woodshed roof (attached to our garage roof). Although it has a low pitch and faces east, it performs well, and as we are in the South Pennines, we get a lot of rain to keep them clean. The panels are sitting on a simple aluminium rail and I built up the roof around them and added recycled plastic roof tiles to make them look roof-integrated. The solar panels and roof tiles help prevent damage to the real roof underneath that I covered lavishly with pitch before fitting the panels.