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Solar Modelling In Sketchup

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#1 Alphonsox


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Posted 03 June 2014 - 07:46 PM

Thought I would share this find, I can't be the only one trying work out these issues.....

I have been trying to decide where to place my Solar PV array. The available choices are either
( A) on the main roof of the house or
( B ) on the roof of the garage behind the house.

( A ) Is "aesthetically challenging" according to both my architect and my wife but is south facing with no overshadowing.
( B ) is visually more acceptable but could be overshadowed by the main house.

( B ) was the preferred option but I needed to asses the extent of the overshadowing during the year.

It turns out that SketchUp allows you to do this very easily.

First tell SketchUp where in the world your house is situated (Window - Model Info - GeoLocation) and enter latitude and longitude.
Secondly enable the shadow tools (Windows - Shadow). Use the sliders to vary the date and time of day

The attached file shows the shadowing at noon in January.

Attached Files

Edited by Alphonsox, 03 June 2014 - 07:48 PM.

#2 ProDave


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Posted 03 June 2014 - 09:27 PM

Good stuff.

Looking at that one snapshot, you are going to have afternoon shading issues in the winter if you put them on the garage.

I would play with that and see how far you need to get into the year before the shading stops being an issue. December and January are poor months for PV anyway, it really falls off a cliff, so loss of afternoon PV for just a short period in winter may not be a big issue, as long as say by the end of February the shading is not too bad.

You could use that model to move the garage to the right a bit and see if it makes much of a difference. It looks like you have the room to move it over.

I agree I don't like solar PV on the front of a house, unless you do an in roof system like Jeremy which looks fantastic.

Edited by ProDave, 03 June 2014 - 09:28 PM.

#3 NeilW


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Posted 03 June 2014 - 09:30 PM

I used Sketchup to get the hard shading on my roof modelled as well. Works very well.

The general theory with solar panels - assuming you actually want it to offset your electricity usage - seems to be to have as many of them as possible as flat as possible.

That's because it's mostly cloudy, and you get far more offset by having a gentle constant trickle of 500Watts coming from the diffuse light than blasting 3.6KW occasionally when the sun deems it appropriate to shine.

So I have a 9.8kWp SolarEdge system designed and in front of the electric board now with the majority of the panels facing North West. Renesola 255W all black to go with my slate effect roof and optimised to handle the different direction and hard shading.

#4 temp


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Posted 05 June 2014 - 05:39 AM

Will you need Planning Permission? It's only permitted development if...



Panels on a building should be sited, so far as is practicable, to minimise the effect on the external appearance of the building and the amenity of the area.

It's possible that if you don't put them on the garage you would need planning permission because of the above. Councils have argued that the "so far as practicable" part means "you must minimise the impact as much as possible" and not "you must minimise the impact as much as possible without effecting the performance of the panels".

Not sure if you can see this link..

Edited by temp, 05 June 2014 - 05:56 AM.

#5 Alphonsox


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Posted 05 June 2014 - 04:04 PM

Thanks for the replies :

@Dave - Good point, optimising for winter sun in Northern Ireland is probably not required. I do have room to move things around a bit, In fact I have moved the garage forward 5-6 meters from where we have it for planning. It may have to go back. If I do put PV on the house it will be in roof (like Jeremy's) rather than on roof. The problem is finding someone in Northern Ireland who can supply such a fitting system, all the ones I have looked at so far just want to do a "standard" on roof installation.

@NeilW - I hadn't considered placement for cloudy days, so another option for me could be to mount them on the East/West roof of the rear annex.

@Temp - Very Interesting, looks like one of those areas where planning regs differ between Northern Ireland and England. As far as I can see there is no such clause in NI.

#6 TheMitchells


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Posted 27 February 2015 - 05:54 PM

Hi - another thing you may consider is when you would be actually using the electricity. While listening to a podcast on Solar PV at http://www.houseplanninghelp.com podcast 82, I was intrigued to hear the 'expert' point out that putting PV on the east and west roof elevations can sometimes be a good idea if that would provide the energy when you would actually be using it. It may suit those families who are out most of the day. the expert does live in Australia and they do not get paid a huge amount for the energy they produce so tend to want to use as much as they can themselves. This idea was not something i had considered, thinking that it was only best on a south facing roof.
Another thing to think about when planning our build.

"With so little being paid for over-production that goes back to the grid, it actually makes sense for your peak levels being generated to be at the peak time that you will need it. For example, north facing panels (in Australia) would have a peak production in the middle of the day, and if you’re not there in the middle of the day then it’s not matching your energy requirements. It might be better to have two strings of panels with an east-west array that will be giving you a peak production closer to your waking up and getting home times of day."

#7 SteamyTea


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Posted 27 February 2015 - 09:06 PM

If you are going to be getting consistent shading then consider micro-inverters, you only 'loose' the panels that are shaded that way without compromising the whole string output. There are other systems that bypass the shaded string but then you may find a mismatch with your inverter.
If you can go for an in-roof design on the south side and all black panels, then do so, you can always divert the energy to your DHW storage. Storing as heat is probably the best offset you can get, and it is cheap and easy to store in water.