Glass//glass modules are more than twice as likely to break than glass//backsheet.
During 50 mm hail testing, 89% of 2.0 mm glass//glass modules experienced broken glass compared to 39% for 3.2 mm glass//backsheet modules. Glass//glass modules suffered breakage on the front glass, rear glass, or both.
Corner impacts were the most damaging.
For both glass//glass and glass//backsheet modules, the first impact directed at a module corner yielded the highest breakage rate. 62% of broken glass//glass modules and 43% of broken glass//backsheet modules cracked with this first shot.
Glass breakage reduced at lower hail diameters, but wasn’t completely eliminated.
Manufacturers can choose to retest at reduced impact energies using 40 or 35 mm hail. The glass//glass breakage rate decreased to 57% with 40 mm hail and 18% with 35 mm hail. The factors contributing to breakage versus non-breakage are under investigation.
Extreme hail is not a concern for many site locations.
While very important for some locations, many regions do not experience extreme hail. As such PVEL is not naming Top Performers in the HSS category or counting these as failures in the Scorecard failure statistics. Site stakeholders in areas with significant hail risk should contact PVEL for introductions to manufacturers who did well in HSS testing.