Specification for a Solar System

Grumpy_chap

I am not opposed to obtaining planning permission if it is required.  It will add a small delay in time and cost a few pence, but I'd expect an application to be viewed favourably and design mods can always be made to achieve better visual amenity.

QrizB

Grumpy_chap said:

The first of the companies I sent the enquiry to called and made contact this morning - it was one of the companies identified from an internet search engine.  I thought that was quite good response time given that it is a Bank Holiday.  This particular company has said they cannot offer a quote because I have a rear-dormer loft conversion with flat roof and solar cannot be installed to a flat roof.

I assume that is just this company that cannot offer a flat-rood installation, not that solar is not viable at all with flat roof.  There must be many people seeking to install solar on a flat roof.

One of the limitations for Permitted Devlopment is that the panels don't project above the ridgeline or more than 200mm from the roof surface:https://www.planningportal.co.uk/info/200130/common_projects/51/solar_panels/2

You might be able to install them flat (which will lose you some output, about 16% averaged over the year for a system at my location per PVGIS) or apply for PP and see whether the anyone objects.

Grumpy_chap

Thanks.  I am sure the flat-roof can be overcome if even the first company did not offer that product. 

There are some houses I have seen that have panels at an angle on the flat roof.  They are positioned so that the projection cannot be seen from street level at the front.  In some ways, this type of installation is less visible than panels on an inclined roof.

Being installed flat might lose some output, but being on the former roof will also mean that there is never any loss from shading, so that must compensate to some amount.  I did wonder whether panels can be installed on the vertical face of the dormer as well - directly south facing so would be quite good from a solar gain I would have thought.

Once I have a proposal, I am sure that a planning application will not be sufficiently straightforward and the company providing the system provide the drawings etc.  It must be something they are familiar with.  I have not had issues with other planning applications at my property.

Martyn1981

Grumpy_chap said:

Thanks.  I am sure the flat-roof can be overcome if even the first company did not offer that product. 

There are some houses I have seen that have panels at an angle on the flat roof.  They are positioned so that the projection cannot be seen from street level at the front.  In some ways, this type of installation is less visible than panels on an inclined roof.

Being installed flat might lose some output, but being on the former roof will also mean that there is never any loss from shading, so that must compensate to some amount.  I did wonder whether panels can be installed on the vertical face of the dormer as well - directly south facing so would be quite good from a solar gain I would have thought.

Once I have a proposal, I am sure that a planning application will not be sufficiently straightforward and the company providing the system provide the drawings etc.  It must be something they are familiar with.  I have not had issues with other planning applications at my property.

Hiya. Unless things have changed, you also need PP for wall mounted PV. I think you need it for flat roofs because PP is required where you visually alter the roof pitch, and most panels on flat roofs are, as you say, mounted on angled frames. Might be worth asking your local planning department if flat mounted panels require PP, but I'm scratching my head over the issue of dirt and debris build up. It is far less likely to wash away on a flat panel. In fact, in the UK, cleaning isn't really needed on 30d+ roofs, but might be on shallower pitches, and I have to wash off / remove moss/lichen from my 20d pitch lower panels every couple of years.

Flat panels will not only generate less, but will have a massive summer bias. Check out PVGIS, I've just done side by side comparisons for my location, but south facing (not that that's particularly relevant to 'flat'), and as QrizB suggests got a ~16% reduction, but it kills winter gen. Both (flat and 35d) suggested 125kWh/kWp for June, but all other months fell, with Dec dropping from 32kWh/kWp to just 13kWh/kWp. This is important because you tend to have more generation than you need in the summer, but can consume almost all in the winter, so you lose the most important generation.

Vertical mounted, will have the opposite effect, and whilst losses are greater at around 30%, I get a reasonably flat 60-80kWh/kWp from Mch to Oct, and a low of 38kWh/kWp in Dec and Jan (beating 35d).

Slap up 3 PVGIS's and flick between them, as this will help to give you some ideas on what might, or might not work for you.

Grumpy_chap

Thanks @QrizB and @Martyn1981
I'm happy to go for planning permission, but need to wait until I have a specific system in place first to prepare the application against.

I tried to look at the PVGIS website the other day but simply found it to be a load of confusing gobbledygook to be honest.  It is not for the faint hearted. 

EricMears

Martyn1981 said:

 I have to wash off / remove moss/lichen from my 20d pitch lower panels every couple of years.

After the first year or so,  I decided to wash my (17.5 deg pitch) panels.  It seemed to make no difference at all to their output so I've never bothered since.  After another 8 or 9 years,  I still haven't washed them off again and they're still performing in line with PVGIS predictions - obviously not exactly in line but occasionally a bit better, sometimes not quite so good with no overall downward trend that might have indicated ageing of panels or build-up of contaminants.  I occasionally venture up on roof for a closer inspection (& prepared to wash if necessary) but have seen nothing to worry me.

They're having a really good washdown at moment (thanks rainy weather !) following almost six weeks with no significant rain but last few days have been spectacularly good and I'm not seriously expecting to better that next week.

Martyn1981

EricMears said:

Martyn1981 said:

 I have to wash off / remove moss/lichen from my 20d pitch lower panels every couple of years.

After the first year or so,  I decided to wash my (17.5 deg pitch) panels.  It seemed to make no difference at all to their output so I've never bothered since.  After another 8 or 9 years,  I still haven't washed them off again and they're still performing in line with PVGIS predictions - obviously not exactly in line but occasionally a bit better, sometimes not quite so good with no overall downward trend that might have indicated ageing of panels or build-up of contaminants.  I occasionally venture up on roof for a closer inspection (& prepared to wash if necessary) but have seen nothing to worry me.

They're having a really good washdown at moment (thanks rainy weather !) following almost six weeks with no significant rain but last few days have been spectacularly good and I'm not seriously expecting to better that next week.

Yep, I haven't seen any degradation in performance, as the moss stuff is forming along the bottom seams of the panels, and takes years to build into roughly a one inch high, half inch thick sausage, so won't have yet impacted any of the cells. It may be an issue for me as the shallow panels are to the leeward side of the house, so get less rain and wind, and are further sheltered by the upper storey. It could also be a panel specific issue, depending on models installed, and how small, or large, the seams are.

This article covers the issue, though the last sentence in the para quoted, seems extreme:

Do Solar Panels Need Cleaning & Maintenance? The What, How, How Often, When, & Why

As it turns out, the rain might be part of the problem. With many solar panels, seams and edges can hold just a little bit of water. if they do, plants, mold, and mildew can start to grow in those seams/edges. By itself, that wouldn’t amount to much interruption of photons from the sun creating electricity for your home. However, as nature does, that little bit of material then acts like a sponge and holds a little more water and the stuff moves up the panel. I’ve seen panels so covered that light could surely not penetrate.

QrizB

Martyn1981 said:

This article covers the issue ...

I especially like the photo credit at the very bottom of the article:

Photo of dude cleaning panels in full hazmat gear courtesy of Pixabay. Not sure why he’s wearing all that, since it’s typically just water and a soft brush that is used to clean solar panels. But hey, you get what you pay for when you get free images to use on the web. Also, the OSHA stuff is real. That is really, really unsafe what he’s doing there.

Grumpy_chap

That's a very odd photo that does not stand up to any scrutiny:
 - no hose connecting to the lance-sponge
 - OTT splash protection, though there should be very limited splashing I would have though with that equipment
 - no working at height / fall arrest etc equipment

Anyway, I am finding solar companies are a fickle and selective bunch, my enquiries with responses so far:
 - 1 declined (no reason) but sent a link to a directory site where I can send an enquiry
 - 1 declined on location (fair enough)
 - 1 declined because I have a flat roof loft extension
 - 1 declined because I don't (yet) have a smart meter

I still have other enquiries waiting on responses.

Grumpy_chap

Well, this is odd, I have just spoken to one of the companies I sent the enquiry to (and they have sent me an e-mail).  It was actually a company referenced by another contributor up thread.

The company have said they would not recommend a battery and, if I did want a battery, then not Tesla because Tesla are completely discontinuing their battery products entirely and there are better alternatives.  "Better alternatives" can be subjective but can also be true - I'd be very surprised if Tesla are moving away entirely from the battery products though.  Maybe Tesla are discontinuing the PW2 and launching PW3?  That is product development and progress, not completely discontinuing.

The second reason the company said not to have a battery is because I have a dial meter, so I can simply use the grid as my battery with no cost and getting 100% saving at the unit price I am paying.  Quote "The best part this is legal".  As I understand it, this would mean the meter running backwards and does not seem right.

Are there any others with thoughts on these aspects?

In the mean-time, I said they should go ahead and provide their quote and further details.