Solar Panel Guide Discussion

tunnel

Theoretically speaking max capacity is best but that also depends on when you're in to make the most of it. What's the split...E/W? or something else?

michaels

tunnel wrote: »

Theoretically speaking max capacity is best but that also depends on when you're in to make the most of it. What's the split...E/W? or something else?

Max 4 panels SSE and the rermainder WSW, no shading 35 degrees.

tunnel

Which 270Wp panels have you been offered? there is plenty of manufacturers now making 285Wp panels that don't come with a premium(14 x 285- 3.99kWp)
take a look on this site http://www.swithenbanks.co.uk/shop.php?action=index
You can get a rough idea as to what would go

michaels

They have quoted a higher price for 14x285 but perhaps I should push for them for this at the same price as it should be a cheaper install as it can be done with 5x2 panels on the larger aspect rather than needing 3 rows.

Martyn1981

michaels wrote: »

One offers q-cell panels and a SMA TL inverter
The other suntech or suntelite panels and an ABB inverter

Max 4 panels SSE and the rermainder WSW, no shading 35 degrees.

Slight concern, so I've just been looking at the SMA and ABB inverters. I was looking at 3.6kW models.

The minimum DC voltage for the SMA is 125V, and the MPP min is 175V.

The ABB 3.6 looks to be adjustable down to 120V.

The reason I bring this up, is that most PV panels operate at around 30V, which means a string of 4 may struggle with the ABB, and fail to meet the minimum of the SMA.

I may be fussing over nothing, and I'm sure the installers know what their doing, but it might be worth checking the specs of the various panel options and looking at the nominal volts.

If it is a problem, then look for higher voltage panels, such as the 72 cell models, rather than the more common 60 cell panels.

Mart.

PS. There's a good chance I'm talking rubbish, so ask the installers. M.

michaels

Thanks - maybe they are assuming the other panels won't be producing nothing but I am not sure if each aspect is on seperate strings (is that the right term?) so perhaps each array needs to meet the minimum?!

Martyn1981

michaels wrote: »

Thanks - maybe they are assuming the other panels won't be producing nothing but I am not sure if each aspect is on seperate strings (is that the right term?) so perhaps each array needs to meet the minimum?!

If you have different orientations, then the panels have to be on separate strings, and each have their own MPPT. Sorry, should have explained that. So you absolutely have to have a dual MPPT inverter. Otherwise, the panels not generating as well, will drag down the performance of those in the sun.

Mart.

michaels

OK - looking at the quotes at least one mentions using 1 of the panels on the wsw with the 4 sse ones to give the required voltage or getting a much more expensive inverter. The 285w panels mention a higher voltage approx 32 so 4x32 would be enough but I am not sure if this voltage applies all the time they are generating or only when they reach a certain level of power output?

tunnel

You def don't want the 4 linking to one from the other aspect, absolute no no.


There is an alternative, the benQ330W panel, 12 of these is 3.96kWp but again comes at a premium. Not sure if you could use 4 of these on one string and then make up the other string with different panels up to the 4kWp max. Speak to the installers about this as it may be possible.

Martyn1981

michaels wrote: »

OK - looking at the quotes at least one mentions using 1 of the panels on the wsw with the 4 sse ones to give the required voltage or getting a much more expensive inverter.

Oh, no no no no no no! What T says. If that was said seriously, then take a little care with that company. Hopefully it was just a 'shut you up' remark, whilst they find a real fix.

michaels wrote: »

The 285w panels mention a higher voltage approx 32 so 4x32 would be enough but I am not sure if this voltage applies all the time they are generating or only when they reach a certain level of power output?

It might be enough for the ABB, but pretty tight, I'm honestly not too sure, but looks too little for the SMA.

The Panasonic 240's are 43V, and the Panasonic 285's are 52V, so they'd be ok. Also you could put a little more wattage on the SSE, assuming 4x285 or 5x240's as the 240's are 80% of the size of a regular 250Wp panel, but that doesn't necessarily mean 5 will fit, as it'll depend on the layout.

Mart.