Weather-conscious equipment selection and design for photovoltaic (PV) systems can result in a longer PV lifetime and improved system durability. This page contains considerations for structural and site-related design, electrical equipment, PV modules, and fasteners, considerations unique to the PV system type (rooftop, ground-mounted, carport), and considerations for commissioning and decommissioning. Many of the considerations listed here are based on preparing for the severe weather events that may exist at the PV system site. Return to the Life Cycle of PV Systems landing page to explore more phases in this process.
ON THIS PAGE:
- Structural Design and Site-Related Considerations
- Considerations for Electrical Equipment
- PV Modules
- Racking
- Fasteners
- Unique Design Considerations
- Commissioning and Decommissioning a PV System
Did you know?
Wind is the most common cause of PV system damage, according to a report analyzing system vulnerabilities. However, severe snow, hurricanes, and storms are reported more often. There may also be trade-offs between weather events; for example, agencies should look for ways to minimize the impact of snow while also accounting for potential high wind considerations.
Footnote:
a. The optimal tilt angle for solar exposure is equal to the local latitude. In the continental United States, a tilt angle between 15°–40° facing south will result in the best production. Lesser tilt angles will reduce wind load and can improve solar production, while steeper tilt angles (up to 60°) are more effective at shedding snow and hail, offering greater protection from winter weather. However, steeper tilt angles also increase wind load on panels. Agencies should weigh these trade-offs when designing systems for areas that experience both high wind and winter weather or hail.
Some tilt angle considerations are unrelated to performance. For example, panels installed flush with the roof are often preferred for appearance and wind load, even if the tilt and azimuth are not optimal for energy production. For more information on tilt angles, refer to the Federal Energy Management Program's (FEMP's) Hail Damage Mitigation webpage and Pacific Northwest National Laboratory’s resource guide on solar panel orientation.
Design With Life Cycle in Mind
According to the U.S. Department of Energy Solar Energy Technologies Office, PV module recycling is not widely adopted due to costliness, even though more than 85% of a PV module is composed of commonly recycled materials such as aluminum and glass.
Approximately 70% of PV systems have been installed since 2017, and best practices to facilitate recycling are still emerging.
Decisions made during system design can reduce the waste associated with PV systems. System owners and agencies should consider:
- Making panels easy to separate
- Eliminating rare, expensive, or hazardous materials
- Extending panel lifespans by selecting reliable materials and adhering to best practices for operations and maintenance (O&M).
Considerations for Electrical Equipment
Structural design actions relevant to electrical equipment and cable management include:
- Ensure proper cable management during and after system installation to avoid safety hazards and performance issues such as power loss, electrical faults, or inverter disconnection.
- Place electrical equipment such as inverters and batteries inside of a weather-resistant container.
- Properly enclose electrical equipment in cabinets to prevent water flow into electrical conduits.
- Select enclosures with the proper National Electrical Manufacturers Association (NEMA) rating for the site’s expected weather conditions.
- Secure fasteners around the entire perimeter of the enclosure door.
- Ensure that equipment incorporates all safety features such as grounding and bonding of grounding system, arc flash detection and interruption, ground fault current interruption, and rapid shutdown as required by system type and codes.
- Avoid plastic wire ties, which are prone to premature failure.
- Use underground wires and conduits, if cost-effective.
PV Modules
It is important to design PV modules to withstand a variety of weather conditions. The table outlines a list of common structural considerations for PV modules that developers and agencies should consider, including stow mode trackers, standards for withstanding wildfires, backsheet width, coloring of panels and its relationship to heat exposure, load and pressure rating, glass casing type, size of modules, framed vs. frameless modules, multi busbar modules, and stress testing.
| Structural Design Considerations | Wildfire | Flooding | Hailstorm | Hurricane | Severe Winter Weather | Wind |
|---|---|---|---|---|---|---|
| Consider “stow mode” trackers | ✔ | ✔ | ✔ | ✔ | ||
| Consider the National Electric Code and International Building Code’s three module designations for withstanding wildfires.a | ✔ | |||||
| Choose a PV module with a thick backsheet (300 micrometers or thicker) | ✔ Increases wildfire resistance | |||||
| Consider choosing lighter colored PV modules.b | ✔ | |||||
| Consider modules rated to withstand a higher than typical load and pressure. | ✔ Manufacturers can provide proof that module passes a hail test | ✔ | ✔ | |||
| Select modules with at least 3.2 mm front glass (typically monofacial, not bifacial modules). | ✔ | |||||
| Select smaller (60-cell) modules over larger modules. | ✔ | |||||
| Weigh the pros/cons of framed vs. frameless panels.c | ✔ | |||||
| Consider multi busbar panels. | ✔ Prevents microcracking | |||||
| Ensure that modules undergo load testing for stress factors. | ✔ | ✔ | ✔ | ✔ i.e., the “twist test” |
Footnotes:
a. Class A is designed to withstand severe exposure for 10 minutes, Class B is designed for moderate fire exposure, and Class C is for light fire exposure. Require fire classifications in accordance with the UL 1703 Standard for Flat-Plate Photovoltaic Modules and Panels, Table 1505.1.
b. In heavily vegetated areas with arid or semi-arid climates, darker colored panels may increase wildfire risk due to heat absorption during extreme heat and drought.
c. Frameless panels shed snow more efficiently but have lower snow and wind load ratings than framed models. Prioritize load rating when snow shedding is not the primary concern.
General Equipment Selection Consideration
Choose PV modules and inverters tested by independent evaluation laboratories according to standard tests of performance and extreme conditions. These labs publish the results in “scorecards” that compare results among PV modules and inverters to identify the best ones.
Racking
Most considerations for racking have to do with resistance to high wind. These include:
- Use properly rated racking systems that meet wind load standards such as ASCE-7 Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE/SEI 7-22).
- Ensure racking and frame elements are protected from high wind and vibration, made from noncorrosive materials, and avoid bimetallic corrosion between dissimilar metals.
- Install lateral bracing for racking designs with vertical frame members to resist lateral movement.
- Install closed-form structural channels to prevent torsional movement.
Fasteners
Critical fastened joints support the structural integrity of the system. Failure could cause safety hazards. Most considerations for critical fastened joints have to do with severe winter weather, high wind, or storms. Considerations for critical fastened joints include:
- Consider additional attachment and support points to reinforce structural strength.
- Choose properly rated critical fastened joints.
- Ensure critical fastened joints are secured and are not subject to torsional movement or flexing of racking and module.
- Through-bolt modules to the racking system.
- Add hardware to compensate for shorter fasteners.
- Do not assemble critical joints with self-tapping sheet metal screws/clamps.
- Use vibration resistant fasteners.
- Include DIN 25201-part B standard locking mechanisms on threaded fasteners.
Unique Design Considerations
Some design considerations are dependent on the type of PV system being evaluated. The main types of solar projects are rooftop PV, ground-mounted PV, and carport PV. Each of these project types have unique considerations that will help to promote long system life cycles, and the following sections outline a summary of these considerations.
Rooftop PV Systems
Evaluate roof suitability based on compatibility, structural strength, age, and wind exposure.
In high-wind areas, use mechanical attachments instead of full ballast to reduce turbulence risk.
Ground-Mounted PV Systems
Design stormwater mitigation into the site layout (e.g., route runoff into regional stormwater management system).
Use pollinators and native plants, including low-growing grass vegetation, to control erosion.
Carport PV Systems
Carports require additional planning for weather and utility safety:
- Create underlying roof deck and gutter to prevent icicles or snow from falling on vehicles or people.
- Prevent black ice formation:
- Consider using Y-design carport systems in snowy regions.
- Ensure that carport systems have a gutter and externally mounted downspout attached to columns.
- Ensure the system is heated or thermostatically controlled to maintain the ability of the gutter and downspout to drain.
- Install modules at low tilt angles to minimize wind loading.
- Cantilever arrays from columns in center to avoid columns near parking spots.
- Add markings or bollards on the ground to prevent tall trucks from clipping corners of array.
- Ensure service access to system components without requiring lifts.
- Consider installing snow guards.
- Integrate water discharge into stormwater management system.
- Obtain local fire marshal approval for fire lanes and ensure that fire lanes meet new codes and standards.
- Ensure that roofs and space available is enough for the types of vehicles required (e.g., large trucks).
- Consider ADA-compliant parking access.
- For underground utility work, there are hazards related to utility strikes, which can result in safety issues, project delays, and unnecessary added costs. These include strikes to water/sewer, storm water, electrical, natural gas, telecommunications, hot and chilled water, fire hydrant, and lab gas lines. Best practices include:
- Use multiple methods to capture metal and plastic pipes and lines.
- Share site utility drawings with a disclaimer stating, “For information purposes only—contractor must verify route, depth, and type of each utility.”
Carport systems offer futureproofing since they can accelerate the addition of EV charging stations or battery energy storage systems at a reduced cost. Much of the work that is required to add additional electrical infrastructure—such as trenching, underground utility survey work, and connection to the main building’s electrical service—are completed during carport system set up. Additionally, the room available is typically enough to house storage and electrical gear for the creation of microgrids. They can also provide protected areas for emergency response activities.
- Severe Weather Resilience in Solar Photovoltaic System Design
- Solar Photovoltaic Hardening for Resilience – Wildfire
- Preventing and Mitigating Flood Damage to Solar Photovoltaic Systems
- Hail Damage Mitigation
- Solar Photovoltaic Hardening for Resilience – Winter Weather
- Successful Deployment of a Solar Power System at Mount Rainier National Park
- Solar Photovoltaic Cable Management: Best Practices for DC-String Cables
- Severe Weather Resilience in Solar Photovoltaic System Design
Commissioning and Decommissioning a PV System
This section discusses the process of commissioning and decommissioning a PV system. Although decommissioning will not take place until the end of the PV system life cycle, agencies should plan and budget for this process early on. For more information on decommissioning best practices, navigate to Phase 4: Prepare for End of PV System Performance Period.
Commissioning Best Practices
A commissioning plan and budget should be in place ahead of project construction. The plan should include the following best practices:
- For commercial, industrial, and utility-scale systems, apply the latest version of IEC 62446: Grid Connected Photovoltaic Systems—Minimum Requirements for System Documentation, Commissioning Tests, and Inspections commissioning guide, which includes:
- System documentation
- Array testing
- Whole-system performance testing.
Note: IEC 62466 lacks detail on fasteners, electrical connectors (MC4), and wire management. The IEC 62446 may be amended to include a torque audit of fasteners.
- Perform commissioning procedures:
- When the system starts operation
- After one full year of operation, at which point full system acceptance will be maintained.
- Obtain third-party verification of the PV system for:
- System concept
- Site selection
- Design and equipment decisions
- Installation
- Commissioning at system start and after one year
- Performance reporting
- Annual certification
- Certification for transfer of ownership or refinancing
- O&M practices
- End-of-performance period procedures.
Decommissioning Best Practices
A decommissioning plan for the end of system life should be in place as a part of the land-use agreement and could be required to construct a new PV system. Include:
- Contact information for all parties (landowner, solar developer, authorities having jurisdiction, recycling services, and emergency service providers).
- Any warranted recycling of PV modules or other components that were provisioned as part of the original procurement; any bonds to take back PV modules or other equipment.
- Conditions that trigger the decommissioning (date certain, end of lease, system inoperative for 12 months, any other).
- Timeframe for decommissioning (e.g., 6 months).
- Scope of work for the decommissioning (equipment removal, grading, land restoration).
- Roles and responsibilities of the landowner, solar developer, and any other parties clearly delineated.
- Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems; 3rd Edition, Technical Report (2018)
- Best Practices at the End of the Photovoltaic System Performance Period, Technical Report (2021)
- Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems; 3rd Edition, Technical Report (2018)
PV System Life Cycle
You're on phase 2 of the PV System Life Cycle. Learn more about each phase and explore key resources: