# Wind Load Calculator for Dual Axis Solar Tracker

Registered Users Posts: 21
I was unable to locate any threads that addressed the subject of how to calculate wind loading on solar panels. If someone could point me in the right direction, or assist me in calculating the wind load on my four panels, I would be very grateful.

I have four solar panels which are going to be mounted on top of my motorhome which is a converted school bus. The bus has dual steel wall construction (even in the roof), and has a steel roof deck built at the rear of the bus where I am going to mount the panels.A friend is fabricating a dual axis solar tracker for me, and I have purchased the STA1000-HW Dual Axis Tracker Controller electronics from Solar Stalker. The STA1000-HW comes with a high wind parking feature which is user programmable. I want to determine wind loads on my panels so I can know what wind speed threshold to set into the electronic controller to instruct it to flat the panels when the winds reach a pre-specified speed.

My panels are set in a parallel array that will have a surface area of 105" x 58". The angle of incline above horizontal will of course change (it is a dual axis system). I am in Georgia at a latitude of 32.45 degrees, so that might provide some indication of how much of an angle above horizontal my panels will attain at various times of the year.

Thanks!

First, you have to figure out how much wind is in your region... Something like this:

http://www.awc.org/pdf/ASCE7-10WindChanges.pdf

The above also gives you PSF (pounds per square foot of wind loading for various regions/calculations). Figure out the square foot of the array/panel(s) times the PSF -- And that will tell you how much load your frames would need to support.

You will probably be surprised how much that loading is--And if you add safety factors (x2 to x10 safety factor)--It can look like an over kill for the design.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 21
Thanks BB. I think you misunderstood what I was wanting. You wrote, "First, you have to figure out how much wind is in your region."

Actually, it doesn't matter how much wind is in my region, or what region I am in since my solar array has a high wind parking feature. All I have to do is set a threshold for wind speed and if that threshold is reached, the panels are put in the flat position. What I was really hoping to find was a website that has a wind load calculator for solar panels where you can input surface area, angle, and wind velocity and find out what the load is. I have seen websites in the past that have wind load calculators that will provide this information, but I cannot seem to locate them now.

I would also be satisfied with a simple formula to calculate wind load. The document you linked is a bit too advanced for me. I appreciate your efforts though.

Here is a very simple to use calculator for building walls/roof--Assume the panel is roughly vertical (worst case):

http://www.soundcedar.com/calculators/force.wind.php

This explains a little bit more how the above calculator work (I think, I have not verified the numbers):

Is this a little bit more helpful?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 21
Hello BB. That is great. That is much more comprehensible. The first link was more along the line of what I was looking for. To be able to simply plug in the numbers and have it spit out an answer is great. But.... The calculator has no option for inputting the surface angle. It is assuming a 90 degree angle to the wind direction as this specific calculator is for siding on a house. The angle would make a very big difference for solar panels.

As for the second link, I also very much like the very simple explanations of the wind load formula along with the graphics. That makes it very comprehensible. Unfortunately, it too lacks a variable to input the angle of the panels in relation to the wind direction. Once more I appreciate your efforts. I know the wind load calculator I am looking for exists somewhere on the Internet as I saw one some time back. I wish I had bookmarked it. The Internet is a very big place to search.

Thanks again,

Joseph