Calculating solar potential

barker77

Hi

is there somewhere I can work out if my roof is suitable for solar and rough potential generation?

i was hoping there might be a tool somewhere to take into account roof shading etc too?

Many thanks! 

2nd_time_buyer

barker77 said:

Hi

is there somewhere I can work out if my roof is suitable for solar and rough potential generation?

i was hoping there might be a tool somewhere to take into account roof shading etc too?

Many thanks! 

The PVGIS software is a good starting point.

https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html#PVP

 If you have more than one roof elevation you will probably need to consider them separately.

If your roof is shaded then it this won't necessarily be taken into account (or the effects of optimisers to mitigate it). However, it should be a good initial estimate.

I am not aware of any free software that takes into account shading. I have used the Solaredge design software a fair bit and that does and so far seems very actuate but it is only available to installers. I don't think many installers use it though as it is a little involved.

Martyn1981

If it helps, both of my roofs have light to moderate shading issues. In fact both have a panel that butts up against the northern side of the large central chimney. Speaking of which, my house is the north half of a semi-detached, so the  central chimney has an impact on all panels through the day.

I have Solaredge systems on both roofs, and my annual generation is roughly on par with the PVGIS estimates, despite the shading, as PVGIS (which is absolutely excellent), does have old and quite high default estimates for losses (14%). So, so long as your shading isn't really bad, and you have shade mitigation (such as Solaredge) then hopefully the PVGIS figures will work for you.

Over the 11yrs we've had PV, our annual production, v's PVGIS estimate, has ranged from 97% to 110%, with 3yrs under 100%, and 8yrs over it.

Of course, take all this with a pinch of salt, as "results will vary", so my info is purely just an example.

barker77

Thanks both - did you just get a company out to give you figure’s vs trying to guess yourself? 

gefnew

No you have to input your details in and all the fields to have some idea of potential generation.

Boffinboy24

PVGIS is pretty good. If you want something more involved you can use the SMA SunnyDesign website, this will model shading etc for you, but unless you have lots then probably not worth the additional effort. 

barker77

I’m trying to do this on my phone but on the PVGIS I can see my street but not individual houses. Am I missing a toggle option or something? 

Martyn1981

barker77 said:

I’m trying to do this on my phone but on the PVGIS I can see my street but not individual houses. Am I missing a toggle option or something? 

I wouldn't worry about being too exact (though, yes you should be able to put a pin on your house).

Rough location will give the necessary solar levels and weather conditions. Then just pop the PV size in the kWp box, put in the orientation*, and approx roof pitch, and hey presto for a very good annual guestimate and monthly breakdown.

*Orientation uses south as the azimuth (point of interest), so due south will be zero degrees, south east is -45d, east is -90d, west +90d etc.

Actually, for simplicity, you might want to just put 1 in the kWp box, and then you will have a generation per kWp figure, say 950kWh/kWp pa. From there you can just multiply it by the size of system being quoted / negotiated, without redoing the figures each time, eg 4kWp = 4x950 = 3,800kWh pa.

EricMears

barker77 said:

I’m trying to do this on my phone but on the PVGIS I can see my street but not individual houses. Am I missing a toggle option or something? 

I don't think marking the individual house would offer any great advantage.  I'm sure the PVGIS organisation aren't aware of e.g. every tree in the world or of how tall your chimney stack is !

barker77

EricMears said:

barker77 said:

I’m trying to do this on my phone but on the PVGIS I can see my street but not individual houses. Am I missing a toggle option or something? 

I don't think marking the individual house would offer any great advantage.  I'm sure the PVGIS organisation aren't aware of e.g. every tree in the world or of how tall your chimney stack is !

Ah - how might I be able to calculate shading? I think one of the houses nearby generates some substantial shading in winter which I was keen to try and work out 

2nd_time_buyer

barker77 said:

EricMears said:

barker77 said:

I’m trying to do this on my phone but on the PVGIS I can see my street but not individual houses. Am I missing a toggle option or something? 

I don't think marking the individual house would offer any great advantage.  I'm sure the PVGIS organisation aren't aware of e.g. every tree in the world or of how tall your chimney stack is !

Ah - how might I be able to calculate shading? I think one of the houses nearby generates some substantial shading in winter which I was keen to try and work out 

I think you will need to use software that does 3D modelling - the SMA SunnyDesign software 

Boffinboy24 linked to looks like it will do the job. 

However keep in mind that you will only generate <20% of your total annual energy between November and February. So shading may not have a big effect on your total generation even if it is has a significant effect in winter...

... although all energy is not created equal. Winter energy is generally more valuable as it is mostly self-consumed.