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Electrical Engineering Services for Commercial and Utility Solar Facilities

Detailed solar electrical design sustains long term performance

Commercial and utility scale solar projects bring immense possibilities for clean energy production and cost savings. But full savings won’t happen unless you plan ahead and obtain adequate solar engineering, permitting, and interconnection approvals with the local electric utility and the grid balancing authority. At Blue Oak Energy we apply our advanced electrical engineering expertise to ensure your project obtains proactive and timely permitting and interconnection approvals. We are determined to efficiently move your commercial or utility scale project from initial construction to energy production.

Plugging into the power grid is a detailed step-by-step process requiring knowledge about regulatory compliance requirements, efficient product applications, and latest technological advances. Blue Oak Energy has the modern experience, knowledge, and expertise to get your project connected and built within the confines of limited budgets and schedules. Read on for a more detailed look at how our solar electrical engineering services fit into the larger process.

Site Surveys

Roof survey: As part of the initial preparation for roof-top projects Blue Oak Energy will perform a detailed roof survey as the basis for an as-built roof plan. Our team will locate the exact coordinates of all rooftop obstructions, and identify surrounding objects—such as trees and power lines—that could potentially shade the solar array and impact annual energy production. The process concludes with a complete CAD as-built site plan for the design engineering team.

Electrical site survey: To lay the groundwork for interconnection, Blue Oak Energy will have an arc-flash certified electrician survey the site’s existing electrical system. This includes a switchgear inspection for load-side or line-side taps and documentation of existing switchgear specifications, such as model numbers, BIL ratings and breaker sizes. The electrician will also survey the area for equipment pad locations, wall-mounted equipment locations, and conduit penetrations.

Solar Energy Performance Modeling: To further model the solar project’s viability, Blue Oak Energy will conduct a weather study to determine available sunlight irradiance for the specific location. The resulting information, along with the system design, will factor into the PVSYST energy production model, allowing us to determine appropriate model inputs.

Utility Interconnection Package

Blue Oak Energy continues the utility interconnection process with a series of comprehensive agreements with electrical utilities and power system regulators such as CAISO (California Independent System Operator) and various RTOs (Regional Transmission Operators). Blue Oak Energy has had great success in connecting projects to major utility grids such as those operated by PG&E, SCE, LIPA, NV Energy, APS, National Grid and many others. Fortunately, use of new technology, such as sophisticated programmable reclosers, curtailment systems, and modern utility scale inverters with power factor controls, has made the solar utility interconnection process more advanced, functional, and satisfactory for all parties involved.

Fundamental Documents

BOD Document: Blue Oak Energy will provide a Basis of Design (BOD) template for client review and input. Once approved, the BOD will serve as the defining document for the project going forward, determining the design parameters and standards of all work listed in the Engineering Work Order.

SLD with Interconnection Design: Once we have collected the necessary data, Blue Oak Energy will generate a single line diagram (SLD) that shows the interconnection design. The SLD will clearly illustrate the AC and DC electrical systems, inverters, power/auxiliary transformers, metering, breakers, and disconnects. It will define the overall power collection strategies and outline the plant utility protection scheme.

Array Layout: The final array layout is a culmination of a number of aspects, including topographic and site boundary surveys, and factors laid out in the BOD such as shade analysis, module string size, string-rack configuration, and other efficiency measures which reduce unnecessary costs. At this point we begin populating the solar array with the module layout, honing in on sub-arrays and inverter groups, optimizing inverter loading ratios, establishing preliminary road locations, and other related details.

Low and Medium Voltage Engineering

Solar utility projects are typically a combination of both low voltage DC and medium voltage AC electrical systems. Bridging the design details from DC to AC and creating cohesion throughout the design is one of the unique features of Blue Oak Energy’s design team. There is an exciting trend towards offering solar array wiring of up to 1500 Volts DC on ground-based systems and 1000 Volts DC on rooftop solar systems. We’re enthused to be at the forefront of this transition as solar facilities become more ubiquitous.

Our DC electrical design incorporates solar source circuit and homerun feeder circuit wiring plans, plus the equipment pad layouts with a detailed wire and conduit entry plan. The process also involves developing a conduit routing or trenching plan, creating a more detailed single line diagram, and the final engineering for the interconnection into existing switchgear. We conclude with the final preparation of conductor and conduit sizing schedules, equipment elevations, and our highly detailed electrical and mechanical construction details.

AC electrical design calls for different measures and specifications. Blue Oak engineers will design and configure the solar AC medium voltage switchgear and collector system, as well as the ratings for distribution in step-up transformers. The process also requires designing underground and overhead feeders, medium voltage trenching and boring, switchgears (including breakers), and equipment elevations. During the medium-voltage process, engineers will coordinate with utility engineers, sub-station engineers, and other project stakeholders.

Underground Cable Sizing

As part of its best practices, Blue Oak Energy takes the extra step of determining optimized underground cable sizing when implementing its solar PV projects. Proper sizing of underground cable requires assessing the cable and conduit spacing based on soil conditions, including during worst-case scenarios such as a flood or a drought. Blue Oak engineers use modern software packages to determine the ideal underground conductor sizes based on current flow, soil temperature ranges, soil thermal resistivity, and other factors.

Additional Solar Electrical Engineering Services

In addition to the items above Blue Oak Energy also provides the following services:

  • Performance Monitoring and Reporting System design
  • SCADA engineering and controls
  • Arc flash and load flow studies, energy meter programming
  • Lighting design for solar carports
  • Tracker control system engineering, and
  • Security system design.

We are a high integrity, well-balanced team offering technical engineering services when required and experienced advice at other times.

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