What are the bureaucratic restrictions for PV on a flat roof?

Smallholder
Posts: 17
Joined: Fri May 05, 2023 12:44 pm

Re: What are the bureaucratic restrictions for PV on a flat roof?

#21

Post by Smallholder »

MrPablo wrote: Sun May 28, 2023 10:19 am I know you have 20 panels in that plan, but I wonder if it's worth crunching the numbers to see how many panels could be fitted in a back to back east-west configuration on the top roof section.

That way you could eliminate the gap needed to prevent self-shading, still maintain a pitch sufficient for drainage and probably get more generation over the year.
I did also model an alternative layout with all panels in East/West orientation, and it does mean I can get 10 panels on the upper roof section rather than the 8 shown above. The numbers surprised me a bit... You get 26 panels in total rather than 20, and over the course of a year you do generate more power.
However, (with the East-West config) in the summer when I will surely already have a vast excess, you increase your yield by 20% (compared to all panels facing south). But in winter, you get a fair bit more output with the all facing south option.

There is also the cost of more panels, and associated hardware.
But the install ends up looking so much cleaner, and wind should be less of a concern as the panels are tucked down at the edges of the roof.

December
East / West - 160.74 kWh
South - 202.2 kWh (+25% compared to E/W)

January
East / West - 203.48 kWh
South - 239.75 kWh
MrPablo
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Re: What are the bureaucratic restrictions for PV on a flat roof?

#22

Post by MrPablo »

I guess this is a situation that's very dependent on other factors.

Will this be a DIY installation, resulting no MCS certificate and lack of export payments? If not, could the additional summer generation result in sufficient credit balance to make up for the winter shortfall? It might be quite easy if on something like Octopus Flux.

Is there a south facing and unshaded wall somewhere on the property that could have vertical panels for winter generation?
My 3 vertical panels produced 41% of the total generation in January, so had an outsized contribution.

Still, it's a fun problem to solve, either way it'll look quite smart I think!
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Smallholder
Posts: 17
Joined: Fri May 05, 2023 12:44 pm

Re: What are the bureaucratic restrictions for PV on a flat roof?

#23

Post by Smallholder »

MrPablo wrote: Sun May 28, 2023 1:47 pm I guess this is a situation that's very dependent on other factors.

Will this be a DIY installation, resulting no MCS certificate and lack of export payments? If not, could the additional summer generation result in sufficient credit balance to make up for the winter shortfall? It might be quite easy if on something like Octopus Flux.

Is there a south facing and unshaded wall somewhere on the property that could have vertical panels for winter generation?
My 3 vertical panels produced 41% of the total generation in January, so had an outsized contribution.

Still, it's a fun problem to solve, either way it'll look quite smart I think!
I don't want to count chickens... But it looks like I may be able to get the best of both worlds. I found a sparky that is happy for me to get the bits and do most of the install, then he'll come and do the final connections and sign it off with an MCS cert. There are limitations on the kit I'm able to use, and limits on the amount of work I am able to do, but it does seem to be the lowest cost option for getting a system of this size installed and able to export.
Very much on board with the vertical mounted panels as well, I'll see how many I could get on the side of the house and put that data into the magical PVGIS system.
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nowty
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Re: What are the bureaucratic restrictions for PV on a flat roof?

#24

Post by nowty »

Smallholder wrote: Sun May 28, 2023 2:16 pm
MrPablo wrote: Sun May 28, 2023 1:47 pm I guess this is a situation that's very dependent on other factors.

Will this be a DIY installation, resulting no MCS certificate and lack of export payments? If not, could the additional summer generation result in sufficient credit balance to make up for the winter shortfall? It might be quite easy if on something like Octopus Flux.

Is there a south facing and unshaded wall somewhere on the property that could have vertical panels for winter generation?
My 3 vertical panels produced 41% of the total generation in January, so had an outsized contribution.

Still, it's a fun problem to solve, either way it'll look quite smart I think!
I don't want to count chickens... But it looks like I may be able to get the best of both worlds. I found a sparky that is happy for me to get the bits and do most of the install, then he'll come and do the final connections and sign it off with an MCS cert. There are limitations on the kit I'm able to use, and limits on the amount of work I am able to do, but it does seem to be the lowest cost option for getting a system of this size installed and able to export.
Very much on board with the vertical mounted panels as well, I'll see how many I could get on the side of the house and put that data into the magical PVGIS system.
Thats what I did with my second system, the MCS installer was a friend of mine and the FITs paid for the MCS certificate in 1 year.
18.7kW PV > 109MWh generated
Ripple 6.6kW Wind + 4.5kW PV > 26MWh generated
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105kWh EV storage
60kWh Home battery storage
40kWh Thermal storage
GSHP + A2A HP's
Rain water use > 510 m3
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