Windbreak

[Arne999]

I'm not sure where this fits exactly. I've built a stand for 8 (about 15 sqm) solar panels mounted on an old tractor trailer. The panels are angled at 45 degrees and are situated right by a slope with a similar angle, sheltered from weather in all directions except south/southwest.

If we exaggerate a bit for a worst-case scenario regarding wind resistance and force, I came up with the following after some Googling:

F = 0.5 ρ v ^2 c A
where ρ is the air density (1.3)
A is the area (15)
v is the wind speed
c is the drag coefficient <1

c is tricky, but let's say 1 to be sure.

=>
for example 20m/s
3900N

30m/s
8775N

Are these reasonable numbers for the argument? I understand that it "depends on" a lot of things, but this is a worst-case scenario, and if you consider more factors you reduce the margins and increase the risk of it blowing apart. But is there anything obvious to include that would reduce the force without compromising on uncertainty? I assume c=1 implies a flat dense area completely perpendicular to the wind speed, which is clearly not the case here.

Currently, the stand is on a large old timber wagon that weighs a lot... so the entire setup probably weighs 7-800kg. I was thinking of anchoring it somehow, but I don't want to overdo it too much. Any tips?

 

[scorp1on]

The wind load in design is calculated according to SS-EN 1991-1-4 General actions – Wind actions. Then, the wind load depends on various shape factors and the wind velocity pressure, which in turn depends on the wind speed, terrain, and the height of the structure.

 

[Arne999]

Of course, it depends on a lot, but the question is how to oversize just the right amount. I don't need to optimize the build for mass production exactly.

If I calculate my worst case, it becomes ridiculously exaggerated, but that's how I'll construct since I don't know how to dare to cut corners.

 

[scorp1on]

I understand what you mean, but it becomes difficult not to go overboard when you over-dimension, which is the case when you calculate the way you have done.