Step by Step Commercial Design

Introduction

HelioScope makes it easy for non-experts to generate high-quality layouts for commercial PV arrays. For designers new to commercial system design, we have prepared guidelines for designing commercial solar arrays based on typical design approaches:

Steps for designing commercial arrays:
  1. Trace rooftop & choose module
  2. Set azimuth
  3. Define racking
  4. Set row spacing 
  5. Set building setback 
  6. Trace Keepouts
  7. Remove/restore shaded modules
  8. Optimize shaded modules
  9. Choose inverter (microinverter or string inverter)
  10. Adjust conductors to maintain voltage drop

  1. Trace rooftop & choose module: In the Mechanical Tab, create a Field Segment by clicking points to outline the rooftop. Then select the module you plan to use – typically commercial projects use 72-cell modules (nameplate power of between 280Wp-320Wp)
  2. Set azimuth: Set the orientation of the array to be in-line with the building: right-click on the “front” edge of the roof, and select “Set Azimuth to ___”. The modules will automatically align to face that building edge.
  3. Define racking: Set to Fixed tilt racking or East-West racking. Most commercial rooftops use low-tilt and/or ballasted racking designs.
  4. Set row spacing:  There are a number of methods for setting the spacing between rows. The most common approach is to set the row spacing based on a zero-tolerance shading rule from 10am to 2pm on the winter solstice. Do this automatically from the  Time of Day link in the Designer. 
  5. Set building setback: Enter a Setback parameter to define a perimeter setback around the array. Most codes require either a 4 foot or 6 foot setback, depending on the size of the building. In areas with significant snowfall, the perimeter requirements may be as high as 10 feet.
  6. Trace Keepouts: In the Keepout Tab Create Keepout objects for each obstruction on or near the roof. 

    - Define setbacks around the Keepouts. If the obstruction has a height, enter that next to the Keepout in the menu. 

    - Add in walkways across both center-lines of the building as a linear Keepout – or, for larger buildings, draw these every 150’.

  7. Remove/restore shaded modules: Keepouts with heights automatically remove modules on the winter solstice from 10am to 2pm. You can restore modules in the shade by unchecking the Keepout from shade checkbox on the Keepouts tab. 
  8. Optimize shaded modules: click on Advanced, then Shading to access the module shade optimization. This feature estimates the shading on each module throughout the year and enables the removal of shaded modules. 
  9. Choose inverter (microinverter or string inverter): In the Electrical Tab select a string inverter, HelioScope will automatically set an inverter quantity that results in a DC-to-AC ratio of approximately 1.25. Move the inverters to the locations where they will be mounted, and the wire content will be adjusted automatically.

    - For microinverters, simply select them, and HelioScope will automatically configure the AC array accordingly. In this case, move the red icon to the point of grid interconnection.

  10. Adjust conductors to maintain voltage drop: confirm the voltage drop next to the conductors once the inverters and/or grid connection point has been set. Most engineers strive to keep the voltage drop values below 2% for both the DC and AC systems.