Protecting your solar installations from the risk of high winds
The recent wind storm in Jaisalmer has blown off the modules from a 300 MW solar plant of a solar developer. Solar installations across the globe face extreme wind pressures and in the cost optimisation the only aspect to optimise the cost after the solar modules and inverters is the mounting structures. in early days the typical solar mounting weight per MW used to be about 50 ton/MW, which has invariable reduced to the tune of 25-30 ton/MW. The typical purline sizes has been reduced from 2 mm thickness to about 0.5 mm thickness. And the result is that the solar installations are vulnerable to the high winds/ typhons.
In general the solar installations are designed for about 150 kmph wind speeds, however few aspects remain ignored.
- As we can see most of the installations are failing at the mid clamps, or the fasteners connecting the modules with the mounting structures/purlines. Most of the failures are due to undersized bolts. At times the module aluminium frame ruptures. We never check the strength of module aluminium frame to withstand the high wind pressures of 150 kmph wind speeds.
- Loose bolts in the mounting structure is also considered a common defect in the solar mounting installations. The quality check of under torqueing of the bolts leads to the module structure blow offs.
- It is important to specify the uplift wind speed to your module supplier as well to ensure that the module frame also withstand to the high wind uplift forces. Most of the module blow off case are due to the module frame rupture as in this case also can be seen. The site conditions should be provided to the module manufacturers and the module aluminum frame needs to be tested in wind tunnel to ensure that the module frame withstands the high wind uplift forces.
- As the module manufacturers are reducing the glass thickness and laminate thickness, there are also cases of module glass dislogged from the frame. Hence it is important that the module BOQ needs to be checked to withstand the high wind uplift forces.
- Due to lack of detailing while the mounting structure designs, the mounting structure members has mis-alignments and leaves to loose connections and structural instability.
While it is important that the solar installations are safe and robust and should be capable to face harsh wind storms, there is a need to develop solar mounting specific best practices/guidelines which become industry best practice so that such failures can be avoided.