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How to Plan for the Unexpected in Solar Design & Engineering


When designing and engineering utility-scale solar projects, being proactive and adaptable is critical to avoid significant unforeseen costs and schedule delays. From supply chain obstacles to changes in utility requirements to equipment modifications, there are a number of challenges that could derail your project. Below we have provided a comprehensive guide on how to navigate these design and engineering uncertainties effectively. 


1. Select a design & engineering firm that has all engineering disciplines in-house


Selecting a design and engineering firm that encompasses all engineering disciplines in-house, including civil and electrical, is crucial for managing unexpected challenges efficiently. When different companies handle separate aspects of the project, discrepancies and communication delays often arise, leading to significant constraints and inefficiencies. For instance, if the civil and electrical components are managed by separate firms, any changes in one area may not be promptly communicated to the other, causing delays as customers take time to review and approve the modifications. This not only disrupts the project timeline, but also results in higher quotes due to the unexpected changes. In contrast, an in-house team can swiftly address adjustments under one roof, maintain a unified project schedule, and streamline communication, ensuring a smoother and more cost-effective process.


2. Demand geotechnical reports and review AHJ requirements during due diligence


During the due diligence phase, it's not uncommon to face the challenge of not having all power studies and geotechnical reports prior to design work commencing, leading to potential drastic design alterations down the line. For example, a cable initially designed to be buried at 36 inches based on code compliance may need to actually be installed deeper, at 45 or 50 inches, per geotechnical findings. To mitigate such issues, design firms should proactively request all necessary reports from the customer in advance, if available. If the reports are not yet available,  the parties responsible for producing these reports should be identified as soon as possible to establish clear lines of communication. This ensures the most efficient flow of information when the details that will be included in the reports first become available, resulting in expedited designs. 


Design firms should also engage directly with the Authority Having Jurisdiction (AHJ) to confirm current NEC codes and specific construction requirements, ensuring the latest standards are applied. Experience plays a crucial role in anticipating varying AHJ requirements, such as medium voltage cable depths, which can differ significantly from the NEC standard - from 24 to 60 inches. 


3. Determine in advance who the independent engineer is that will be reviewing your plan set & prepare accordingly


Knowing who the independent engineer is for your project is critical, as each engineering firm & each engineer have unique requirements, significantly affecting project timelines and design approaches. Review times can vary from one week to three or four months, depending on the engineer, for example. Since there is no single industry standard, each independent engineering firm, such as DNV, may apply its own distinct criteria. For instance, while the standard moisture content for northern states is 10%, DNV might require a more conservative estimate of 2.5%, substantially increasing safety factors. Similarly, circuit designs adhering to a 25% safety factor per NEC might need to adjust to 40% under DNV's guidelines. Therefore, having specific design sets tailored to each reviewing organization is essential. This preparation at the due diligence stage prevents extensive redesigns, saving time and resources, and ensures compliance with the reviewing engineer's standards.


4. Determine what utility is involved in the project & leverage templates accordingly


Understanding the requirements and processes of the utility company you are working with is crucial for efficient project execution. For instance, organizations like National Grid in New York typically offer a more streamlined process with quick turnaround on comments, usually requiring only minor changes. In contrast, PSEG on Long Island has unique requirements such as the 86 lockout relay and therefore specific breaker installation, which can complicate and prolong the design phase. Utility requirements can change annually, as seen in the evolving interconnection standards from 2023 to 2024, which can impact designs even mid-project. To manage these uncertainties, it's essential to prepare multiple design templates in advance. For example, having designs ready for both recloser and vacuum breaker installations ensures that if changes are mandated at the IFC stage, you can quickly adapt without significant delays. This proactive approach, with ready-to-use templates for different scenarios, can reduce potential project setbacks from months to days, ensuring a more efficient and responsive design process.


5. Build design flexibility into plans from the outset 


Building design flexibility into plans from the outset is essential for accommodating unforeseen changes and mitigating risks. For instance, in the case of using a CAB wire management system, initial designs may rely on this system, but lead times can extend from months to 1 to 2 years, necessitating a switch to another system. If the alternative system does not use messenger wire as equipment grounding, additional grounding conductors must be incorporated, increasing the wire configuration in a raceway. This adjustment increases load, possible conduit requirements, and overall design constraints. To prepare for such scenarios, design & engineering firms must leave some room for possible additional wires and larger equipment, i.e. avoid designing everything too tightly; and ensure there is sufficient clearance around cable hangers to accommodate larger sizes if needed. Without this foresight, interference with other structures can cause friction, leading to ground faults and potential equipment damage. By anticipating these changes and designing with flexibility, you prevent safety issues, reduce financial risks, and avoid costly delays and repairs, ensuring a more resilient and adaptable project.


6. Have alternative equipment options ready for common supply chain constraints


To effectively manage supply chain constraints, it's essential to have alternative equipment options ready from the outset. For instance, the lead time for low voltage switchboards frequently fluctuates, necessitating flexibility in equipment choices. When faced with delays, switching to a hard bus connection — eliminating the need for underground wiring between the switchboard and the transformer — is often ideal. However, securing this equipment can also be challenging due to lead times. To address this, design and engineer firms should maintain a comprehensive database of all major low voltage switchboards, enabling them to quickly pivot to a different vendor if necessary. By incorporating this preparedness into the initial design stage, you ensure that alternative equipment options are readily available, minimizing disruptions and keeping the project on track despite supply chain uncertainties.



If you’re looking for ways to de-risk your utility-scale solar projects through adaptable and proactive design and engineering, get in touch with an expert at Castillo Engineering today. 


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