Not a week goes by where I don’t receive an announcement about a new photovoltaic racking system. They consistently have the same attributes: ultra-light, ultra-fast and ultra-cheap. Safety, durability and reliability, however, are frequently sacrificed in the rush to bring to market the ultimate low cost, lightweight system.
The systems boast a variety of materials, including composite wood, or plastic, or other flammable or corrosive materials. Typically, their testing and engineering is not through an OSHA certified Nationally Recognized Test Lab (NRTL), but instead by a local provider who has a vested interest in the financial success of the racking company.
Of course, there are a number of well-built, welldesigned, well-engineered and well-tested racking systems over a variety of price points. Some have bonafide certification from an independent NRTL. Some have significant wind tunnel data, including full boundary layer testing on buildings. Some have NRTL listed integrated ground and bonding methods and meet NEC 250 and 690.
Many do not. These systems are like the emperor in the fable: panels dressed up in an “imaginary” rack that everyone pretends is as good as other better designed and engineered options.
Selecting the ideal rack will depend on design, location and roof capacity. A system in the snow belt should have verifiable positive load test data and ballast numbers allowing a factor of safety between the roof capacity and the distributed and point loads. A system in a high-wind zone should have verifiable negative load testing, not only to show resistance to uplift forces, but also to demonstratethat no microfractures are occurring around the attachment areas of the module. Higher angled systems will generate more power per invested dollar than lower angled or flat systems, but generally at a lower total roof capacity and higher ballast weight. If roof capacity is not an issue, higher angles will frequently create an additional 5% to 10% more power and value.
Roof friendliness is another important consideration. Roof drainage, distributed loads, point loads and thermal movement of the system all factor into a proper evaluation of the racking system. The Center for Environmental Innovation in Roofing (CEIR), the research and think-tank arm of the National Roofing Contractors Association (NRCA), has developed criteria for rooftop installation that address the fundamental principles of effective roof system integration. Unfortunately, these are not widely used by EPC contractors.
Until standards are established that require independent certification to electrical, mechanical, wind loading and roofing criteria, there will continue to be difficulty evaluating the actual cost of the mounting system. In the meantime, solar developers, EPCs and solar funds will need to self-determine the value equivalency between established, well-engineered racking and “The Emperor’s New Rack.”
By Ed O’Brien, Partner at SolarDock
Read more about solar racking and mounting reliability in Will Your Solar Racking Hold Up Under Pressure?