The snow can significantly affect the performance of PV system by the snow. However, energy simulations indicated that the optimum tilt angle for PV arrays installed on vertical axis trackers in northern latitude is 60° or more. Snow does not stay on a glassy surface at that angle. This has been confirmed by monitoring tests in Kimberley under heavy snow conditions.
The figure above plots the occurrence of snow on PV modules at 56° tilt as measured in Kimberley (on more than 1 million records). Episodes of snow coverage will appear as high radiation level and negative temperatures (the zone in dark blue below the x-axis). In total, there were less than 0.2% of these occurrences, which supports the conclusion that snow is not an issue for a PV system with high tilt.
Using frameless (double glass) modules instead of standard modules with aluminum frame may address the problem, if any, as they have no edge preventing the snow from sliding away. However, The steep tilt angle makes it unlikely that snow is a significant issue in solar farms installed in the north.
An easy way to assess the amount of snow on a tilted module is to use the snow load formula in the Canadian National Building Code. (NBC) . Assuming a PV module is similar to a ‘slippery roof’, the NBC slope factor formula is:
- 1 for slope <=15° (No snow shedding)
- (60 – slope) / 45 for 15° < slope < 70° (partial snow shedding or all the snow stays on the PV module)
- 0 for slope >= 70° (full snow shedding or all the snow slides from the PV Module)
For example, a PV module at 30° tilt has a slope factor of ( 60-30)/45 = 0.66. A PV module at 45 has a slope factor of ( 60-45)/45 = 0.33. Thus it can be assumed that a PV module at 30° will have half of the snow of the same module at 45°