solar panel roof layout and string wiring

[Gravelrash]

Hi everyone


So, I am straight in with my first dumb question. I am having roofing works carried out right now, and so I have ordered 18 x Longi Solar 410w panels and mounting kit, which will be delivered today, and which my roofer has agreed to fit for me

UK based, and I am undecided what exactly I will do with the panels, whether to go for an off-grid setup, or do the DNO G99 thing properly. I figure have time to research and plan that out. I'm leaning towards the "kind-of off grid" layout discussed in this thread https://diysolarforum.com/threads/kind-of-off-grid-help-uk.72594/

However, whatever I do eventually, I do need to make a quick decision right now as to the wiring layout of my solar string(s). Once they are wired up, with tails leading in to accessible spaces inside the house, then I can worry about the details later

I think I am planning to go for a 9s 2p configuration. This will provide two strings, each operating at around 260v – 335v, up to 13amps per string

I have tried to illustrate my roof with panel layout below, showing my two intended in-series strings wiring in red

Are there any fundamental issues with this wiring layout? Is there a way to do it better? I am aware that there will be some fairly long cable runs to deal with, but given the 13+ meter length of my roof, I think that will be the case whatever I do at this stage

Thanks in advance

 

[MaikaiLife]

Voltage does drop over distance, and if you're concerned, you can use a voltage drop calculator to determine the exact loss. However, running over 200 DC volts for short distances, such as under 33 meters, to connect your panels to your inverter/charge controller won't result in significant drops that would affect your system's output noticeably.

More importantly, ensure your entire string has minimal shading and that all panels receive as equal sunlight as possible. The performance of a DC string is slightly reduced by the lowest-performing panel. If you have significant shading variations, consider using smaller strings with their own MPPT inputs or adding DC optimizers under the panels to mitigate the impact of irradiance differences.

Additionally, when panels are adjacent to each other, you can daisy chain them using the supplied MC4 connectors without needing extra jumper/whip conductors, except at the ends of the string. This reduces the amount of cable required for your project.