Progress Update: Task Group 7
Task Group 7 is focused on snow and wind loading.
The standards for the type approval of PV modules (IEC 61215/61646) contain various tests inducing mechanical loads. Stress from snow, among other factors, is also simulated here. To pass the tests, the modules must withstand a uniform test stress of 2400 N/m2, and even 5400 N/m2 in cases of higher snow load classes. Contrary to the most common and realistic inclined installations, however, these tests are performed on the horizontal plane. In recent years it has become increasingly clear that this test standard is insufficient with respect to the actual snow loads. Inclined installations on roofs, for example, lead to an uneven distribution of the normal force on the top of the module as well as to a transverse force along the direction of the underlying module edge. The additional uneven accumulation of snow has already led in many documented cases to destruction of the bottom frame edge and, therefore, of the glass of the modules. This group also considers wind and hail concerns that are not adequately documented by the current standards.
A New Work Item was proposed to the IEC standards group (Technical Committee 82, Working Group 2) in June defining a new test method for non-uniform snow load simulation. Below are related publications developed by TÜV Rheinland.
- Experimental Testing of PV Modules Under Inhomogeneous Snow Loads
- Experimental Testing of PV Modules under Inhomogeneous Snow Loads
Furthermore, a proposal was made to WG2 to redefine the minimum requirements for resistance to hail impacts. The next draft of IEC 61215 Ed. 3 will be clearer on the definition of minimum requirements.
This task group has completed its current action items and the group will be inactive until new action items are identified. Special thanks to Joerg Althaus for leading the effort to quickly complete this work.
This group is currently inactive. If someone wishes to volunteer, please contact Sarah Kurtz.