- Electrical Engineering
- Civil Engineering
Spectrum Solar is a 30 megawatt ground-mounted solar project that was installed over 310 acres. Westwood was brought onto the project as it was entering the permitting phase and soon identified challenges with the project design that needed to be addressed. Overcoming these challenges would be critical to ensuring the project’s contractor could meet their guaranteed production from the PV plant.
Managing Unpredictable Soils
The original civil grading plan, which was produced by another consultant, accounted for a projected amount of “material shrinkage”. However, once work began, the soil did not behave as expected due to the varying soil properties encountered on site, requiring significant changes to the design and construction plans. Westwood made the necessary design adjustments and submitted the plans to the County for plan approval. Following plan approval, the physical grading in the field was revised in a timely manner. Thorough communication and a rapid response were imperative to solving this challenge keeping the project on schedule.
The site was designed to convey stormwater runoff through shallow channels running the length of the project. Erosion became a serious concern because of the soil types and the lack of natural vegetation. In response, additional sediment control devices were designed and installed throughout the channels and a liquid soil stabilizer was applied to the final graded surface for stabilization and dust mitigation. These measures significantly reduced the soil loss usually experienced through wind and rain on similar sites.
Adjusting for Varying Wattages
Solar projects are contracted to guarantee production of a certain amount of power and are commonly designed around a single wattage PV module. However, the PV modules for Spectrum Solar came in a range of five different wattages. Modules of different voltages connected on the same string or even the same inverter cause a decrease in the efficiency of the system as a whole. The original consultant’s design was for a single wattage module. A redesign was necessary to assign specific modules to specific inverters to still meet the guaranteed power output. Westwood used PVsyst to create scenarios that grouped modules of similar wattages together. By doing so, Westwood was able to ensure the project design would meet the production values guaranteed by the contractor. It was an unforeseen challenge that required creative thinking to solve as the trackers were already purchased and installation had begun.
Teaming for Problem Solving
Once the project was commissioned, one transformer within the PV array failed catastrophically twice. Westwood was part of a team of technical experts assembled to identify the source of the problem and develop a solution. Westwood suggested the type of failure seen was usually related to a switching transient or similar event in the electrical system. This theory was explored further by Westwood and other members of the team. Ultimately this led to the successful implementation of a “snubber” circuit in the project substation to eliminate switching transients and resolved the situation allowing the plant to be placed back in safe operation.