How many PV modules can be fit in one group without creating a sail?

[SouthernSpark]

We currently fit smaller domestic installations, but have done the occasional smaller commercial install. Weve been asked by a customer to design and install a 40kW system, I am happy with the wiring system, enclosures and inverters etc, but im wondering how many panels we can fit in one section on a roof without creating a sail effect? For example, the best solutuion would be 5 rows of 24 panels landscape in one large section, then another 2 rows of 20 panels in another large section. Im looking for information on WWW and other known information sources, but no one can seem to give me any helpful information. Can we fit them in the above format or will they need to be split into smaller 5 x 4 module sections to allow for wind dissipation?

Thanks for any help.

 

[Worcester]

One, even that can create significant uplift if installed in the wrong place.

Follow the rules on wind loading and uplift as defined by the regs and the training courses that you have been on.

If you don't know which rules or regs you shouldn't be doing it, and you should be partnering with one of the professionally qualified PV installers that does this stuff day in, day out.

Whose taking responsibility for the structural design?

 

[SouthernSpark]

The training courses dont cover thermal effects on the panels and wind uplift created by a 23 x 5 panel array, they just point me in the direction of the building regulations and the calculations to assess loading on a flat roof which the array seems to comply with. Were attaching them to the main framework of a steel structure with 200 x 100 wooden rafters. Iv been in contact with the module manufacturer who were happy to help.

I was simply asking for friendly advice, thanks.

 

[SolarCity]

Make sure you get it checked by a structural engineer, that's the best advice I can give. Speak to the mounting equipment manufacturer about expansion joints and other data.

 

[Worcester]

In all seriuosness, the potential financial consequencies of a failure on a 40kWp system are phenominal, and if you don't appreciate those liabilities, you really shouldn't do it. Even just to be covered by your own insurances you will need to have a structural engineer on board who can do the proper calculations. The calulations are NOT simple, they are complicated and important.

There were some photos on here last year showing the consequencies of getting it worng..