Flexible PV solar panels on a single-ply membrane roof

[tpdubya]

Hi,

I'm a newbie here and would love some advice about something I didn't spot at the time.

We've built a single-storey extension and it has a 15-degree pitch south-facing, cold-deck roof with a single-ply (Sarnafil) membrane. We always planned to install a small PV array on it to run the heat battery (DHW). Turns out, most solar installers are (a) run off their feet, (b) have never installed anything on a similar roof and (c) will void the warranty on the membrane if they use any fixings that penetrate it (plus also probably causing it to leak).

So - after many months of back and forth, I wondered if there was any reason why we shouldn't use flexible panels - such as those used on motorhome / narrowboat roofs (e.g. 200 Watt 12 Volt Flexible Monocrystalline Solar Panel - Renogy United Kingdom)? I know they don't produce as much output per sq m, but we have plenty of room for what we need (around 3.5kWh). I can get a suitable adhesive, I can get on / work on the roof easily and safely. I can ask a local electrician to connect into the CU. The Eddi (solar diverter) was installed alongside the heat battery so is already in and working.

I understand it wouldn't be notifiable to the DNO - if under 4kW, but I'm not sure if there are other regulations I need to consider? Or practical details?

Any advice gratefully received.

Thanks,
Tim

[SteamyTea]

Work out the price difference, then look at how much electricity that will buy in.

Also, at 15⁰ off horizontal, you are limiting the production quite a bit. Will be good around noon, in the summer.

[ProDave]

Post a picture of the roof for suggestions.

 

And it DOES need notifying to the DNO if grid tied.

 

Gluing them to the roof seems a bad idea it anything goes wrong with a panel or if the roof needs maintenance. 

[Wumpus]

Take a look at the rooftrak IFP300 fixings. They use the same membrane as your roof covering and do not invalidate the warranty. At least that’s what they told me, and we plan to use with Hertalan. You supply the company with your membrane and they make them up.

 

my notes from a discussion with Nicholson’s technical department:

 

We will provide them with Hertlan EPDM to make the patches over the plates so that the whole system is compatible

They will warranty the connection between the EPDM patch and the fixing collar

They will provide the same 20 year warranty as Hertlan.

The fixings will be thermally broken and are compatible with the 18mm OSB T&G roof deck

Edited November 12, 2022 by Wumpus
Additional detail

[tpdubya]

On 11/11/2022 at 15:33, SteamyTea said:

Work out the price difference, then look at how much electricity that will buy in.

Also, at 15⁰ off horizontal, you are limiting the production quite a bit. Will be good around noon, in the summer.

Thanks @SteamyTea - it seems (from the European Commission's PV GIS online tool) that 8- 10 panels if the type I'm looking at would provide more than enough to recharge my heat battery most of the year. Dec and Jan will be borderline...and I have no idea how realistic their data is.

On 11/11/2022 at 15:38, ProDave said:

Post a picture of the roof for suggestions.

 

And it DOES need notifying to the DNO if grid tied.

 

Gluing them to the roof seems a bad idea it anything goes wrong with a panel or if the roof needs maintenance. 

Thanks for the advice @ProDave - I don't have any pictures available on this machine - will find some later. 

On 12/11/2022 at 08:26, Wumpus said:

Take a look at the rooftrak IFP300 fixings. They use the same membrane as your roof covering and do not invalidate the warranty. At least that’s what they told me, and we plan to use with Hertalan. You supply the company with your membrane and they make them up.

 

my notes from a discussion with Nicholson’s technical department:

 

We will provide them with Hertlan EPDM to make the patches over the plates so that the whole system is compatible

They will warranty the connection between the EPDM patch and the fixing collar

They will provide the same 20 year warranty as Hertlan.

The fixings will be thermally broken and are compatible with the 18mm OSB T&G roof deck

Interesting! Thanks @wumpus

[tpdubya]

And here's a picture of the project. Cladding was 'finished' last week (as in - it's still not finished...!) - guttering is temporary until I sort it out properly.

This is south-facing, 15 degree pitch, cold deck (on 18mm WBP) covered with Sarnafil SPM. It's approx 3m x 10m

 

[Gone West]

2 hours ago, tpdubya said:

And here's a picture of the project.

We really like the look of your extension and especially the roof. Would you mind sharing how the roof has been constructed, was it a cold or warm roof etc. How did you find the Sarnafil SPM and did you do any of the work yourself.

[joe90]

8 hours ago, tpdubya said:

15 degree pitch, cold deck (on 18mm WBP)

🙄

[Dave Jones]

cant see any ventilation on that 'cold roof' anywhere ?

[tpdubya]

On 14/11/2022 at 17:04, Gone West said:

We really like the look of your extension and especially the roof. Would you mind sharing how the roof has been constructed, was it a cold or warm roof etc. How did you find the Sarnafil SPM and did you do any of the work yourself.

@Gone West my son is a carpenter - so he took care of the joists / deck, then we got an approved Sarna installer to do the SPM

On 15/11/2022 at 08:44, Dave Jones said:

cant see any ventilation on that 'cold roof' anywhere ?

@DaveJones - there's a 20 mm gap between the top of the cladding and the underside of the deck and there are Glidevale vents in the upstands against the parapet wall

[Dave Jones]

5 hours ago, tpdubya said:

@Gone West my son is a carpenter - so he took care of the joists / deck, then we got an approved Sarna installer to do the SPM

@DaveJones - there's a 20 mm gap between the top of the cladding and the underside of the deck and there are Glidevale vents in the upstands against the parapet wall

 

and vents at the eaves ?

[tpdubya]

15 hours ago, Dave Jones said:

 

and vents at the eaves ?

yes