In the rapidly evolving landscape of utility-scale solar energy projects, effective cable management is a critical component when it comes to optimizing the performance, safety and longevity of your installations. As solar power projects grow in scale and complexity, keeping up with the latest trends and best practices in cable management is essential. This article explores the key factors to consider when designing solar cable management systems - from cutting-edge materials and technologies to streamlined installation techniques.
Types of Cable Management Systems
Over 90% of the time, whether you install an above ground or below ground cable management system will ultimately be determined by the Authority Having Jurisdiction (AHJ)’s specific requirements. For example, some AHJs specifically prohibit above ground cable management systems, which can often be the lower upfront cost option assuming you do not have bedrock. Castillo Engineering operates in 50 states and Puerto Rico and is currently seeing a fairly even, 50-50 split between AHJs that require above or below ground cable management. For this reason, it’s important to understand the pros and cons of both options and the considerations for each type of system.
Underground Cable Management
Methods and Materials:
Trenching Methods:
Excavator: This is generally a more expensive option, especially if bedrock or difficult soil conditions are present.
Trench Digger Machine: This can be cost-effective for certain sites, especially where a traditional excavator would be too costly.
Vibratory Plow: While this is the least expensive option of the three, it can have constraints due to site-specific conditions, such as existing underground infrastructure.
Conduits:
PVC Conduit: Typically installed 18 inches deep, PVC conduit is often preferred due to its cost-effectiveness.
Metallic Conduit: Unlike PVC conduit, metallic conduit can be installed at shallower depths (e.g., 6 inches), which can shorten the distance underground times three, thereby reducing total trenching costs. Metallic conduit is preferred in sites where soil disturbance must be minimized, such as landfills that have sensitive caps that cannot be pierced.
Considerations for Installations:
Thermal Resistivity: The geotechnical report must be analyzed to decide on the trench design and backfill materials to ensure efficient and safe cable operation.
Conduit Selection: PVC is generally preferred due to its lower price, but in some instances, metallic conduit can help to reduce specific types of costs. For example, certain types of metallic conduits may be used to act as the equipment grounding conductor (EGC), which can be beneficial in short runs of large conduits. In these scenarios, one wire is able to be removed since the metallic conduit is also serving as the EGC. This is not possible with PVC conduit installations, which require an additional, separate EGC.
Above Ground Cable Management
System Types:
Messenger Wire-Based Systems:
CAB Solar: This was previously one of the most popular systems, but long lead times and increasing costs have led to the search for alternatives.
Benefits: Messenger wire-based systems can offer a higher current rating for the wires, faster installation times than underground systems, easier fault wire replacement, and the potential use of the messenger wire as an EGC.
Drawbacks: AHJs have varying requirements for installation height. For example, the AHJ may say the system has to be installed higher to avoid water in the event of a flood and to avoid damaging any vegetation beneath the system. If these systems are not properly installed, they may also cause site access issues, such as blowing into pathways.
Cable Tray-Based Systems:
Pros: These are more rigid and stable than messenger wire systems, with similar benefits.
Cons: The downside is that these systems are significantly more expensive and complex to install and engineer, making them less common.
Considerations for Installations:
Height Requirements: Must be installed high enough to meet AHJ requirements and avoid issues such as flooding or vegetation damage.
Accessibility: Ensure that wire management systems do not obstruct site access or maintenance activities.
Key Takeaways
Consult the AHJ Early: Engage with the AHJ during the due diligence phase to understand their specific requirements and recommendations.
Evaluate Site Conditions: Thoroughly analyze geotechnical reports to determine the most suitable cable management method and materials.
Cost and Efficiency: Consider the cost-effectiveness and efficiency of different trenching methods and conduit materials based on site-specific conditions.
Flexibility in Above Ground Systems: Be prepared to explore alternatives to traditional systems due to increasing costs and lead times.
Understanding these trends and best practices ensures that projects are compliant, cost-effective, and efficiently managed, whether cables are installed underground or above ground. Get in touch with a technical expert at Castillo Engineering if you need support in selecting or designing your cable management system.