Solar Design

[sparkypenguin]

Hi all,

I am designing a Solar PV / Battery / Export system and I will have panels on 3 different roofs, E, W and N, S not possible.
I have trawled the net and found a couple of calculators and articles about efficiencies and angles etc but non take into consideration all aspects.

This is what I have found:-

Month	Approx. PV production %
JAN	3.0%
FEB	4.5%
MAR	8.8%
APR	11.0%
MAY	12.0%
JUN	13.5%
JUL	14.0%
AUG	11.5%
SEP	9.0%
OCT	6.0%
NOV	4.2%
DEC	2.5%

Month	Optimum Tilt of Solar Panels by Month
JAN	71
FEB	63
MAR	55
APR	47
MAY	39
JUN	32
JUL	39
AUG	47
SEP	55
OCT	63
NOV	71
DEC	78

So these are very broad figures and do not take into account the 3 roof directions which will surely have different PV production / optimum angles due to different sun heights.
Also these angles will change throughout the year.
Hence I am trying to calculate the optimum angle for each roof as I am sure that the 3 should be at different angles.
I want to be able to see how much each roof will produce by day / month and also the effect of changing the angles of the panels.
This is also important as I am planning on having electric heating and therefore will use much more electric during the winter months which may mean that I am better having a higher angle that will produce more during the winter and sacrificing some of the summer production that will just get exported.
I may also consider some form and mechanical device that will allow me to alter the angle if I decide it is worth it.
Therefore I'm hoping someone can point me to a calculator of some sort that takes all of this into account and allows me to mess about with numerous scenarios.

Any help would be much appreciated.
Regards,
Mark.

 

[fourtytwo]

The first problem is you do not seem to have taken into account permitted development rules, these basically prohibit you from mounting your panels at a different angle to that of the roof, even on a flat roof the protrusion of the panel is limited to something like 100mm leaving very little room for any angle. So the first thing to do is measure the angle of each of your roof faces and assume that will be the angle of the panels.

 

[cjcoffin]

The calculator here should help.
In the UK you will not get enough from an array on a N facing roof to make it worth while installing. Even E and W facing roofs are a long way from optimal.

 

[sparkypenguin]

The first problem is you do not seem to have taken into account permitted development rules, these basically prohibit you from mounting your panels at a different angle to that of the roof, even on a flat roof the protrusion of the panel is limited to something like 100mm leaving very little room for any angle. So the first thing to do is measure the angle of each of your roof faces and assume that will be the angle of the panels.

Thanks, I was not aware of that but I need to discuss with planning anyway as my build has had the permitted development rights removed and I only have permission for 2 of the 3 roofs at the moment.

The calculator here should help.
In the UK you will not get enough from an array on a N facing roof to make it worth while installing. Even E and W facing roofs are a long way from optimal.

Thanks, I I've had a quick look at the calculator and it does look like it may do the trick.
I was not planning on any on the N roof but the extra expense of the panels is not that significant as most of the other costs won't increase too much. Plus if export / import electricity prices increase then the payback becomes much shorter.

Has anyone seen any mounting kits that enable the angle to be changed?

 

[fourtytwo]

Has anyone seen any mounting kits that enable the angle to be changed?

You still haven't got it! NO there not made because your NOT allowed to change the angle from that of the roof.

 

[sparkypenguin]

You still haven't got it! NO there not made because your NOT allowed to change the angle from that of the roof.

Thanks but I'm not sure that is correct as I have seen many panel on flat roofs that have been angled. I believe if you involve planning and get permission then you can alter the angle. Not 100% sure but guess I will find out during my investigations....

 

[cjcoffin]

See the Solar page here https://camelot-forum.co.uk (but currently seems to be offline), various home-made tilt schemes discussed at length there.

In the UK the usual angle for a pitched roof (~35 deg) is so close to the year-round optimum that it is not usually worthwhile to fit panels other than parallel to it in view of the extra cost, extra wind loading and hassle with PP. Flat roofs are another matter.

 

[bernardgreen]

as I have seen many panel on flat roofs that have been angled

A flat roof is a totally different matter.

If the panels on a pitched roof are not parallel to the pitch of the roof then they will be at risk of being torn off the roof from wind and/or snow build up. There may also be a problem with one panel shading the panel above it reducing the effective area.

 

[flameport]

For maximum output, install as many panels as possible.
Altering the angle will have very little effect on generation but will create a pile of problems and expense.
Winter output will always be dramatically less that in the summer. Adjusting angles will not change that.

The only viable way to have various angles throughout the year is to have a ground mounted system with tracking installed, and that will cost many multiples of a roof system, and even with that, most of the gains will be in the summer.

 

[StephenStephen]

Bear in mind that time of use tariffs (both import and export) have (or are likely to have) higher rates between 4pm and 7pm. This could make it more worthwhile to mount panels on a west facing roof.
More generally, it's useful to think about producing energy when you need it, rather than just going for max output.
Consider installing batteries, and (as said above) go for the max number of panels, (but with a lower rated inverter for greater efficiency).

 

[SpecialK]

Any garden space for a ground mounted array? Vertical panels on South facing walls? Car port? Sheds?

 

[fourtytwo]

Any garden space for a ground mounted array?

Unfortunately ground mount has to be >5M from any boundary ruling it out for most ordinary mortals. As for roof protrusions the rules state 200mm max (I could not remember exactly). Here it is in government ruleese permitted development At least it's not quite as bad as trying to put a wind turbine up!!

 

[sparkypenguin]

Thanks to everyone for their input , it's very much appreciated .

I now think I have enough opinions and new information to push me towards not having any form of angle changing system, it's just a pity that I could not have a ground based tracked system as they appear to significantly increase the energy produced but not an option for me!

I may still fit the 3 roofs at different angles depending on my findings once I have used some of the suggested websites.

Any garden space for a ground mounted array? Vertical panels on South facing walls? Car port? Sheds?

Ground mount is a no.
However it is on my list to look into vertical south facing panels on some of my garden walls and I do have 2 south facing balconies to build so I am going to investigate some form of PV balustrade, plus I do have a shed that may be able to stick a panel or 2 on.

If anyone has any thoughts about PV on balustrades then I'm all ears!

Thanks again to all!
Mark.