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Author Topic: In roof PV sizing and capacity. 5 quick questions  (Read 619 times)
MrK
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« on: March 15, 2020, 12:25:05 PM »

I need to make some progress so I can get on with instructing my roofer. Some questions

1) are PV panels a standard size regardless of manufacturer, output etc - if so, what?
2) What is the highest output per panel typically - what is the best panel for cost v output?
3) roughly what space would be left around the perimeter of the install for slating?
4) Should I over-rate my install in order to generate more power on dull days. Is it worth just installing as many panels as I con fit on that bit of roof and store in battery
5) how easy are these things to install myself and get my electrician to set-up/commission

thanks
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Countrypaul
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« Reply #1 on: March 15, 2020, 12:43:35 PM »

Panel sizes do vary, so the largest size might not be the best fit for your roof. You mention in-roof PV, in whihc case you need to take account of the tray size as well as the panel size we found that we could not get as many panels on the roof as expected due to the tray being just slightly larger than expected.

We left no space for tiling along side our panels but put a trim in place instead, similarly no tiles about the panels other than the ridge tiles.

I think it is now common practice to put as many panels on as you can fit and rely on the inverter to limit the output to the grid. It will depend on the "inverter" whether you can charge batteries directly or not. 
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brackwell
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« Reply #2 on: March 15, 2020, 02:36:59 PM »

1) No, but there are many similar sizes. If tight for space you would choose a size which fits your roof area

2) There are many panels around the 325W.  Higher rated panels will be generally marginally more efficient but slightly more expensive so you get back to (1.  aLL panels are legally rated so they all do what they say.

3) Legally you are supposed to have 300mm around each edge.

4) Absolutely yes and an inverter to either 15% below rating of panels or to whatever the DNO restricts you to.  You are only allowed to fit up to 3.68 KW of panels without applying to the DNO (the supplier of the infrastructure)

5) can be done as you say by a competent DIYer not afraid of working on roofs but you still have to buy the gear and perhaps do some research.
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Countrypaul
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« Reply #3 on: March 15, 2020, 02:49:09 PM »

Ken,

Are you sure about point 3 - I though that only applied to on roof rather than In-roof panels.
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brackwell
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« Reply #4 on: March 15, 2020, 05:30:39 PM »

Paul,
You could be correct - i dont know what applies to in roof PV
Ken
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biff
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« Reply #5 on: March 15, 2020, 07:28:19 PM »

Hi K,
     The panels come in all different sizes and voltages.
  The bigger the panel, the more efficient,  generally.
 You need to look for decent frames and well constructed and strong PV panels. The PC will generate much the same power with either cheap or well made frames but the well constructed frames will be sealed better and not affected by the storms.
 If you buy a pallet of PV panels, say 250watt babies. You will find that they are easy to sell when you have a few left over. I know everybody wants the 325watt+ panels but they are hard to control in the slightest breeze. The 250watt  panels are still a handful for 2 people but nothing as bad as 325watt.
 Buy good pv and then sell the surplus keeping a couple for spares in case of breakage later.
 I cannot advise on inverters  everybody had their own favourites. Paul, might know.
 The lads have been pretty helpful, all you have to do is look up the local regs and get out your A4, ruler and pen.
     Enjoy.
         Biff.
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An unpaid Navitron volunteer,who has been living off-grid,powered by wind and solar,each year better than the last one.
Pile-o-stone
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« Reply #6 on: March 16, 2020, 07:41:45 AM »

I'd fit the most powerful panels that you can afford. You're only going to do this once so make the most of your roof space and future-proof your system (think electric vehicles, heat pump and maximising your winter generation).

Once you've decided on your panels, measure the roof and determine how many you can fit in there, then decide on the fixing mechanism.
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