Help on Solar Panel Setup

Planeteer

Following very helpful guidance from people on here, I'm a bit torn on what set up to go for my E/W facing roof (35° pitch, ridge facing south, 2 storey house). My east facing roof has 0 shading, while my west facing roof is facing a line of trees about 10 meters away. If I put in panels both side of the ridge, I'm thinking whether only half the panels on half the roof will work half the time (am), with second half (pm on the west) will only work for the first half again before tree shadows creep up - thereby quartering the efficiency of my  solar panels in effect.

I'm attaching pictures of my roof from above (midsummer, c. 2 pm by shadows, with the nearest tree pruned since - with proposed panels from one supplier), and a second from street level up (yesterday, 3 pm). 

Grateful again for any guidanceo

Screwdriva

Looks like a line of 5 panels on the West aspect will generate well on the topmost part of the roof till 3pm, maybe later. This will increase as the leaves fall. Definitely invest in a minimum of 5 panels on the East side too, and optimizers.

ABrass

Yes you'll suffer a lot from shading on the West aspect. I wouldn't bother, definitely not if it means cutting down on your east facing panels.

Have a look at your roof every hour after lunch on a sunny day and see when the shade starts to hit it, the ln when it hits half way.

You could look at wall mounted panels, they're really good in the winter.

Planeteer

ABrass said:

Yes you'll suffer a lot from shading on the West aspect. I wouldn't bother, definitely not if it means cutting down on your east facing panels.

Have a look at your roof every hour after lunch on a sunny day and see when the shade starts to hit it, the ln when it hits half way.

You could look at wall mounted panels, they're really good in the winter.

Good idea to check on sunfall - hadn't thought of wallpanels - south gable could be an option perhaps. Will check if providers do it!

2nd_time_buyer

Planeteer said:

Following very helpful guidance from people on here, I'm a bit torn on what set up to go for my E/W facing roof (35° pitch, ridge facing south, 2 storey house). My east facing roof has 0 shading, while my west facing roof is facing a line of trees about 10 meters away. If I put in panels both side of the ridge, I'm thinking whether only half the panels on half the roof will work half the time (am), with second half (pm on the west) will only work for the first half again before tree shadows creep up - thereby quartering the efficiency of my  solar panels in effect.

I'm attaching pictures of my roof from above (midsummer, c. 2 pm by shadows, with the nearest tree pruned since - with proposed panels from one supplier), and a second from street level up (yesterday, 3 pm). 

Grateful again for any guidanceo

I am not sure that photo is taken from directly above. It looks like you might be able to squeeze a row in portrait and a row in landscape. So potentially another 4 panels.

QrizB

Are they your trees?

If they are, have you considered pollarding them?

Planeteer

QrizB said:

Are they your trees?

Nope, not mine - get the council to prune every now and then.

QrizB

Planeteer said:

QrizB said:

Are they your trees?

Nope, not mine - get the council to prune every now and then.

That's a shame!

The east aspect seems a shoo-in. To the west, it looks as though the trees might even overhang your roof and so a row of panels low on the roof will be at least partly shaded pretty much all afternoon and may never pay their way. A row near the ridge might still be worth it, although I'm not convinced in the current market.

Vetical panels on the end of your house are an interesting idea but, in your photo, you can see they're shaded by the trees too.

Planeteer

QrizB said:

. A row near the ridge might still be worth it, although I'm not convinced in the current market.

Could you explain this comment? I thought in the current market, any electricity that I feed in would pay back well?

My current design idea is to have a horizontal row of panels on both side of the ridge/rooftop (2x5), or potentially a vertical row on the east side, and only a horizontal on the west/shady side (6+5). Thinking of getting optimisers for the full string - if that counteracts the shade somewhat, and maximising panels while I am installing them.

I am parking the verticals on the gable, as it'll need planning permission for this I gather.

Getting surveyors in day after tomorrow. Is my thinking above reasonable?

Planeteer

Using the Solar Energy Calculator from the Energy Saving Trust, I think I worked out the yield for my two scenarios (4000 kW capacity split across both roof halves and 4800 kW split across both again) as below (to include shading on west side) and find the payback to be between 18 to 16 years (even without battery). For this I am assuming 1)average Octopus Agile tariffs (22p to sell, 28p to buy, on average; 2) I'm not buying a battery, so therefore assuming half my consumption to be fed from the panel and half from the grid (daytime/nighttime equal split); 3) Assuming no added effect from optimisers (didn't know how much to factor in model below). @Screwdriva does this make sense? Payback at actual yields seems a lot longer than our quick calc the other day?

#	Roof	Capacity	Generation	Consumption	Export	Agile SEG	Ave Unit Cost (p)	Payback (y)
1	East	2000	1525	500	1025	£       226	22	To sell
2	West	2000	1220	0	1220	£       268	22	To sell
	Subtotal					£       494
A	Consumption	1000	0	500	500	£       140	28	To buy
B	Net gain					£       354
C	Investment	4000				£   6,200		18
1	East	2400	1830	500	1330	£       293	22	To sell
2	West	2400	1464	0	1220	£       268	22	To sell
	Subtotal					£       561
A	Consumption	1000	0	500	500	£       140	28	To buy
B	Net gain					£       421
C	Investment	4800				£   6,800		16

QrizB

Planeteer said:

QrizB said:

A row near the ridge might still be worth it, although I'm not convinced in the current market.

Could you explain this comment? I thought in the current market, any electricity that I feed in would pay back well?

Sure.

Your panels need to get enough sum that they generate a worthwhile amount of electricity. Your west aspect has so much shade that this isn't necessarily going to happen.