Planning solar PV... maybe

oldskoo1

You can install after but the additional cost would make it not worth it. You would need scaffolding, installer costs and an additional solar edge control box i believe.

Your quote was for a pricey SMA inverter (a good one), so i think it will be worth asking if you could swap it for a solar edge inverter + panel optimizers.

Typically this will be more expensive than most inverters but as you have been quoted that with an SMA its worth asking to see if it ends up the same. Typically the inverter is about £550 + £350 for the optimisers which is usually only a tiny bit more than an SMA inverter.

The benefits are voltage optimisation of each solar panel for maximum output. For a single roof with no shading it has no advantage, for a roof with minimal shading morning and evening there is also no advantage. For a split array or arrays with shading through peak hours it can be advantageous, with that you get excellent monitoring. It should also give you the flexibility to place panels on the roof face where you think max generation might occur, without being limited to 2 logical and ideally same sized strings.

Generally speaking if you have a split roof and potential shading when the sun is lower and the quote is similar you should consider it.

oldskoo1

Had a look at your suncalc. I assume to you are talking about an install on the SE roof which looks like it has a new set of tiles, and then the SW roof that is adjacent, looks like it has something blurry there like a chimney vent or maybe a small velux?

To me it seems pretty straight forward providing that SW thing doesn't block any light.

I'm relatively new to all of this and there are people here with more knowledge and SW/SE split installs who can advise better.

One of the best things i did was time lapse the roof to see what happened as you will then be able to make a more informed decision of what equipment you need and where to position things.

Martyn1981

Pulpdiction wrote: »

Martyn, thanks for your advice, I discussed shading with him and his advice was that as the SE facing roof is a lot steeper than the SW facing roof - notice the V shape in the roof means the roof doesn't rally cast any shadow over the SE facing roof he seemed to think it was not worth worrying about. Their web site also gives quite a bit of difference in the price for the two as can be seen here:

http://www.tpsolar.co.uk/Solarpv.php

He also said that the panels on the SW facing roof would be mounted as high as possible to minimise any shading in the evening from the SE facing roof.

I get what you're saying, and please don't think I'm trying to push a SolarEdge system, but it's probably worth considering, at the very least.

At the moment, shading will be minimal, but during the GMT months when the sun is lower and rises in the east and sets in the west, and in late December rises SE and sets SW, then both rooves are going to get some shading, covering some panels.

Whether or not that's worth considering is tricky, and the SolarEdge system will mean 16 extra bits of kit where they are hard to access if there's a fault. But consider the numbers carefully:

Firstly, not sure what the company price difference is, and checking retail prices I notice that SMA have lowered their prices. The 4000TL is now £750 + VAT (down from around £1k), whilst the SE4000 is about £550, then you have 16 x £30 (also retail) for the PO's, so approx £300 more for the SE system. But .....

let's assume just a 4%* improvement from shade management, and 1% from higher efficiency inverter, gives the SE system a 5% advantage. If your generation is approx 3,600kWh pa, then that's approx 180kWh extra, which at 15.5p (FiT + export after July cut) = £28pa or £550 over 20 years.

[* I chose 4% purely because it's a very small number, so seems justifiable across the GMT months, and rounds out well with the 1% difference in the euro efficiency ratings of the inverters.]

Also, the SE inverter has a 12 yr warranty compared to the 5yr SMA warranty, and can be extended to 20 years for ~ £200. The 20 year ext on the SMA is £450.

I'm not saying don't go for the SMA set up, it looks ok to me, just pointing out that even a small difference in performance may make the SE kit worth considering, depending on how much more the quote is.

Hope this helps, rather than complicates.

Mart.

Martyn1981

Apologies oldskoo1. I read the new posts to the bottom of the page, but didn't realise there were more on a new page - forum error 101. So sorry for repeating a lot of what you said, but nice to see how similar our numbers are.

Mart.

oldskoo1

i keep getting request timed out - something is defiantly up today!

Pulp thew numbers Mart posted are what i was hoping would be posted!

Martyn1981

Martyn1981 wrote: »

At the moment, shading will be minimal, but during the GMT months when the sun is lower and rises in the east and sets in the west, and in late December rises SE and sets SW, then both rooves are going to get some shading, covering some panels.

I'm starting to think I've got this backwards!

@Pulpdiction - I'm being thrown by your rooves meeting inwards, rather than outwards. Not sure how to explain, but your rooves meet with a lead valley, whereas the SW roof meets the SE triangle roof with ridgetiles.

So, maybe the shading issue is a BST one? When the sun rises in the NE my ESE panels get sun as soon as the sun is high enough to clear any ground obstacles. So, the million dollar question, if you look at your rooves in the early hours now, perhaps 6am or even earlier, when the SE hipped triangle is in the sun, is any of the main SE roof shaded?

If there is shading on the SE roof in the early hours, then logic suggests the exact same will happen on the SW roof (from the SE roof) in the late evening.

How much shading is the question, but going back to my earlier post, just 4% would seem to justify extra expense on a SolarEdge system ....... though the decision is bigger than just the money.

Can someone help me out on this shading issue, as I've totally confused myself now!

@oldskoo1 - I'm getting timed out constantly, have to keep going back and trying again.

Mart.

Pulpdiction

They are quoting me a £600 increase in price, for me that's not possible up front at the moment and to get the FIT now before it drops would be better I think. Thanks for all the great help but I think I am going to go for what they quoted.

Pulpdiction

On the shading part, the SW roof has a shallower pitch so it does not give shading at any point after about 7.00am as far as I can see on the SE roof (the SW roof is a third wider roughly).

oldskoo1

thats good about the shading. I think it is a fairly straightforward install.

If you want to get the price down did you ask about a cheaper inverter like a Samil SolarRiver 4000TL-D ?

If the SMA price has dropped this may not save you much but i'm curious.

Pulpdiction

No didn't ask, they were reluctant to spec anything other than the SMA unless I wanted microinverters - they said SMA is the best as far as they are concerned and they don't go wrong.