Don’t Cut Corners: PV Installation Best Practices
As the number of U.S. solar installations has proliferated in the past decade, solar contractors are under increasing pressure to complete more installations in less time. This is a good problem for the industry as a whole; however, it is crucial that contractors frequently revisit their quality standards for each job. In an effort to keep our installers ahead of the curve, we have worked with leading module manufacturer JinkoSolar and DuPont to put together a “Best Practices” resource that all solar installers should adhere to in order to ensure their systems perform for the long-haul. By following these design recommendations, equipment tips, and installation practices, solar contractors should install quality solar systems and generate more business.
Avoid Early Design Mistakes
CED Greentech Account Managers can help talk through any early challenges to a project such as a unique roof plane, difficult shading, or a hard-to-reach point of interconnection. Furthermore, when designing a PV system, it is important to give special consideration to how it will be maintained. For example, it is critical to avoid maximizing the packing density of the panels, which can lead to operation and maintenance difficulties. Leave enough room between panels to permit easy access and movement around them. It is never acceptable to walk on panels, even if the manufacturer claims that it is. Even if the glass does not break, microcracks may still form, damaging the cells within. The damage may be invisible, but it can lead to serious problems. Lastly, carefully review the project site for shading issues.
To ensure that a system meets your and your client’s long-term performance expectations, it is important to have equipment in place to monitor power production as well as a reliable frame of reference to compare power production. Monitoring systems generally fall into two categories: export meter monitoring (daily/monthly/annually) and more sophisticated remote monitoring systems. The best frame of reference for system performance is an on-site weather station, but this can be cost-prohibitive for small installations. Other options include nearby weather stations (note: margin of error increases with distance), a network of local installations, and satellite data (note: large margin of error). Year-on-year production data can also provide a valuable reference.
Most inverters have a 10-year warranty and will not last as long as a system’s solar panels. When selecting an inverter supplier, consider their after-sales service model, as well as other installers’ experiences with them.
Because inverters will likely need to be changed at least once during the lifetime of the installation, it is important to decide on a design that will allow this operation to be conducted safely and securely. Inverters should be easily accessible, out of direct sunlight, and provided with ample free space around them (at least 0.15m on all sides). Circuit boards, capacitors, and various electronic components also may need to be changed during the course of the system’s lifetime. If potential induced degradation (PID) is a concern, be sure to install system-level prevention measures, that is, ground the negative or the positive according to cell type. Inverters may require resets, so providing for remote resets may be a good idea.
Cables and connectors
To minimize resistive losses, make sure cables are properly dimensioned for the current they will carry. Cables should also be UV and humidity resistant. If rodent damage to the negative pole is a concern, consider encasing connectors, especially on flat roofs. Panels are designed for either portrait or landscape configurations. Do not try to use one for the other or the cables will either be too long or too short. Use the original panel connectors, not copies (despite so-called “compatibility,” after-market connectors have caused problems). Connectors should be clean and dry at the point of connection.
Panels should safely maintain a certain level of power production for a system’s expected lifetime of 25 years. Panel defects can be costly. That said, it is important to do your research on the module manufacturers and their financial reliability. JinkoSolar’s modules have been approved for projects by 85 banks around the world, as these banks view JinkoSolar as a stable, long-term partner. This means that Jinko is sure to be around to service your warranty, should an issue with your module occur.
An International Electric Code (IEC) certification is no guarantee that panels will last for the lifetime of the system. In fact, many IEC-certified panels have failed after just four years of exposure. Quality panels adhere to high module design and manufacturing standards and are made with superior materials. Quality workmanship is often evident from the track record of the module maker. Quality materials may add to modules’ cost but are essential for resisting UV, temperature, thermal amplitude and humidity stresses over time. CED Greentech can help you source panels made with quality, time-tested materials from manufacturers such as JinkoSolar, which uses advanced materials from DuPont in all of their panels boosting efficiency and durability while ensuring the modules live up to their 25-year life expectancy.
Rooftop installations run at higher temperatures, calling for more robust materials with a higher resistance to thermal stress. Be sure to select panels with a low coefficient of thermal expansion (CTE), which is important to surviving the 20+ years of expected outdoor exposure and thermal cycling. Panel back sheets must have high softening and melting resistance to survive the stresses of partial shading and hot spots. Also be sure to specify back sheet and encapsulant materials with proven resistance to UV degradation, which can cause subsequent mechanical degradation.
Installation, Operation, and Maintenance
A PV system’s long-term performance may begin with materials, but it also depends to a great extent on how the system is installed and maintained. The following is an introduction to the effective installation and care of solar arrays.
Installing the system
Always perform installation according to the system’s design specifications. Here are some basic recommendations:
• Follow safe installation procedures (working at heights, working with power tools, carrying weight in constrained situations, working with high currents/voltages)
• Read and follow the panel and inverter manufacturer’s installation recommendations
• Consider the whole of the building (roof strength, cable entry points), not just the array, and how it is used (selective access to inverters and power components—accessible for maintenance, not accessible to children and untrained personnel)
• Never walk on the panels
• Ensure that connectors are kept clean and away from moisture
• Do not leave exposed panels in short circuit (the failsafe of the array should be open circuit)
• Consider measures to prevent animal damage (cable protection from rodents and bird nesting)
• Check your installation on a sunny day with a thermal camera (all connections, panels, inverters)
Maintaining the system:
Systems must be maintained if they are to provide sustained performance. If a system is not performing according to expectations, immediate investigation is required. Here are a few recommended maintenance actions:
• Perform visual checks at least once a year. A panel that changes visually does not change for the better.
• Clean panels if they get excessively dirty to avoid hot spots. Panels should not be exposed to partial shading (bird droppings, leaves, vegetation). A panel with uniform soiling should be cleaned only if this affects the power production. Cleaning should result in a uniform glass surface. Avoid using a water jet, which will leave streaks on the glass surface.
• Re-attach trailing cables, tighten loose fittings.
• Perform regular maintenance on inverters (clean/dust inverter filters, check fan operation).
• Perform thermal imaging once per year (check the panels, the inverters, the connectors).
By following these guidelines, your PV systems are sure to last the test of time and perform at a high level. Feel free to comment below with any “Best Practices” you think we might have missed.