AltEnergyMag spoke with Juan Suarez, the senior director of engineering and program management at Unirac, which has North America’s largest share of the solar infrastructure market:
1. There currently isn’t an industry standard for applying codes in solar infrastructure. What is Unirac doing to address this issue?
The proliferation of solar has attracted a number of new entrants. As module prices continue to drop, many investors and contractors are pushing for lower costs in the underlying infrastructure. This has led many vendors to cut corners, whether deliberately or unwittingly. In addition, the current codes and standards are lacking the complexity needed to address solar infrastructure. Contractors may take elements of different building codes and apply them at-will. Having an industry-wide standard will benefit everyone, as it will eventually make permitting easier.
Since infrastructure is imperative to the success of an installation, Unirac is working with the International Code Council-Evaluation Service on developing the first ICC-ES approved mounting products. ICC-ES Evaluation Reports provide regulators and construction professionals with clear evidence that products comply with codes and standards. ICC-ES Acceptance Criteria AC428 has been developed through an open hearing process with industry input and expertise as well as oversight by code officials for evaluating solar framing structures in compliance with the international building code. Unirac is the first solar infrastructure company to apply for an ICC ESR under ICC-ES AC428.
2. Can you give a couple of particularly egregious examples of bad practices under the existing regulations for racking and mounting equipment?
There are so many! Several of the worst culprits are: spans that exceed building capacity; leveling screw failures; cantilevers above roof ridges; attaching mechanical fasteners to a plywood deck; and failing to consider loads from multiple directions simultaneously. These mistakes are unfortunately common. In more detail:
Spans that exceed capacity can be highly detrimental to an installation as skipping many rafters can increase the load up to 500 percent or 5 times more than intended, which might keep solar on your roof – but you may lose your roof much sooner than you intended.
A leveling screw should not be counted on for more than a quarter inch of adjustment. Some installers use leveling screws up to six inches, especially on tile roofs. This will cause tiles to crack and, eventually, structural failures.
Extending solar panels beyond the ridge of a roof can cause panels to act as a sail and see tremendous wind forces beyond what typical racking can withstand. The result is akin to driving an Indy car backwards.
When attaching mechanical fasteners to a plywood deck, it may be convenient, but solar panels are then held in place with nails instead of screws. The pullout strength of screws into plywood or OSB decking is well known and — in most cases — adequate. Unfortunately, as you trace that pullout force through the decking into the rafters, the concentrated force can rip the decking right over the heads of the nails.
3. What do you see as the core elements or practices for new solar infrastructure codes?
It can be very difficult for non-engineers to evaluate the quality of analysis and testing of solar structures. Engineering calculations based on (1) thorough classical analysis methods; (2) complete physical testing; and (3) simulation of optimization, are the most common methods. The use of uncommon materials, shapes and connections absolutely requires the first two methods of analysis. However, to design solar infrastructure solutions that perform well over the long term, a manufacturer should possess expert knowledge and experience in simulation as well as testing.
(1) Classical analysis methods: While there are many standards for structural data on common building materials, the beams used in solar — such as extruded aluminum beams and light gauge, roll form beams with complicated cross sections — introduce new levels of complexity that require specialized expertise above and beyond general building design.
(2) Physical testing: Infrastructure manufacturers typically employ friction clips that require physical testing to determine connection strength. The results of common testing can vary by 50 percent or more, which means a connection may fail in the field due to the inherent unreliability of insufficiently tested connections. A good way to check if your solar structure has been designed properly is to ask what factor of safety was applied to the friction clip connections — at least 2.5 is typical, but can vary up to 3 or 4.
The testing equipment used is also a good indication of the sophistication of the testing. Calibrated load cells and computer-controlled hydraulics offer far better accuracy than traditional sandbag testing. A good test plan will specify not only how much force is applied, but how quickly and often.
(3) Computer simulation: While effective, Finite Element Analysis (FEA) must be properly calibrated. Additionally, there are some parts of analysis, such as friction clips, that FEA cannot reliably simulate. All simulations need to be validated with physical testing.
4. How should the new codes acknowledge geographical or climactic impacts on infrastructure such as racking and clamps?
Structural engineering is based on the probability of a record wind gust, snowstorm or earthquake hitting a solar array. When the U.S. solar industry was still characterized by small arrays and infrequent installations, the probability of a catastrophic failure was low. It’s now just a matter of time before we start seeing more field failures, with damage to an entire array, causing significant financial loss. The new codes need to address a variety of climactic and geographic issues, and they need to address them simultaneously. At Unirac, we test for all these impacts on our products and test for them simultaneously. We test for wind and snow loads together, we test for seismic impact, we test for all possible conditions that could exist in different geographic regions. Our on-site wind tunnel helps us to determine the exact impact and force of wind on a mounting system. With these testing capabilities, we are able to engineer the most reliable products on the market today.
5. What will be the impact of these new codes on Unirac? on installers? Will they make installations more difficult or speed things up?
For Unirac, these codes simply validate the standard to which we already hold ourselves. For consumers, these codes will offer a better product value, they will make installations go faster with easier permitting, and offer peace of mind to owners. Installers will appreciate how these codes make installing solar more straightforward and less interpretive. With less downtime waiting for permits, they will be able to get more installations done in shorter periods of time and be able to take on more clients.
6. Do you see a threat to domestic racking posed by overseas manufacturers, the way there is for modules?
No, it’s not as much about the source, but the application of the racking. Local manufacturers are more familiar with the specific racking needed for each site. In California alone, there are more than 200 different racking scenarios. You need to sign on with a company that knows your region, and can specifically engineer the project for your needs. Foreign providers won’t have the insight to provide the most successful racking solution to consumers. Moreover, you need to take cost into consideration when you’re talking about shipping steel or aluminum infrastructure. At Unirac, we partner with manufacturers located in nearly a dozen U.S. states as well as Canada to control project costs by shipping rails from a facility near the installation site.
7. Where do you see the strongest market for solar module racking systems at the current time?
Unirac has traditionally seen the biggest part of our business in the residential market; until about 18 months ago, the residential market accounted for about 80 percent of our business. However, due to our emphasis on growing our share in the large-scale commercial and utility sectors, the equation is now a 60/40 split. We anticipate more and more commercial and utility-scale installations in the coming years.
8. What percentage of the cost of a typical solar installation is racking?
There isn’t really a “typical” installation as there are so many factors involved — not only size, but whether it’s commercial or residential; ground mount or roof; with or without a tracker.
9. What is the most-asked question by installers when comparing solar racking systems? How about the end user?
Unirac offers a diverse set of products, so the question really depends on what the installer will be using at the site. If the installer is looking for a roof mounted product, he probably asks about pounds per square foot. If she’s looking for a tracker, she’ll ask about hydraulics. Installers also ask about our tech support and online tools. Installers and end users alike want to know about installation speeds as everybody wants to get the system operational as quickly as possible. And both groups are interested in knowing about warranties, as they’re looking to ensure their infrastructure investment will stand the test of time, under even the harshest weather conditions. Unirac products have 10- and 20-year warranties and our component strength and capacity testing is the most rigorous in the industry.
Senior Director of Engineering and Program Management, Unirac
Juan Suarez is Unirac’s senior director of engineering and program management. He tripled the company’s patent portfolio in less than two years, and led the engineering and product development process to achieve ISO 9001: 2008 certification. Prior to Unirac, Suarez owned his own construction and development company specializing in green building. Visit www.unirac.com and follow the company on Twitter @Unirac.