Effectively Creating Array Areas

An "Array Area" is a two dimensional area on a given project site where you might want to install a PV array. A single project site may have multiple array areas, and may have different types of array areas. You define each array area by drawing a polygon on an aerial or custom image.

There are three different types of Array Areas:

1. Sloped Roofs 
2. Flat Roofs
3. Ground Areas

By defining array areas, you are freed to create multiple customer solution proposals that each conform to the site's given constraints, without having to re-draw anything for each solution. 

Defining Sloped Roofs

For residential cases, sloped roofs are the most common type of area.

The shape must conform to a single roof face. Each face has its own azimuth and slope (any arrays placed on the area will inherit the orientation of the sloped roof). Each edge has a specific roof edge type that SolarNexus can automatically determine based on the identification of a single eave or ridge as the baseline edge.

In case you need help identifying the parts of a roof, see this pictorial glossary.

When defining a sloped roof in the Array Area editor, its best to first assess the image and see if you can clearly identify all edges of the roof faces you wish to potentially use. Before moving to the next step, use the view tilt, rotate, and street views to provide alternate angles that can identify each edge.

SolarNexus will automatically name each array area.  If you wish to override this, provide a good descriptive name for each area. Sloped roofs, for example, can be named using compass directions, sides of the house, and level of the house. Examples might be "SE-front," SW-side upper", etc.

Always take your time drawing the roof face as accurately as possible.  More recommendations for specific scenarios are below.

Defining Flat Roofs

Flat roofs can be any shape. All the edges have the same type (flat roof edge). The area has no azimuth, nor slope. However, you may choose to specify an edge to align the array with. When you define the array for the flat roof area on the PV Array Configuration screen, you will input desired installation type (ballasted tilt, tilt-up roof), and the azimuth and slope of the array.

Defining Ground Areas

Ground areas can be any shape. The edges have no defined types. The area has no azimuth, nor slope. When you define the array for that area on the PV Array Configuration screen, you will input desired installation type (ground rack, pole mount), and the azimuth and slope of the array.  The measurement tool (right click - Show Measurements) can be especially useful when creating ground areas.

 

Example 1

The image below shows a poorly drawn sloped roof. Why? Because it does not represent single roof faces. Instead, the user simply outlined the entire roof, not considering all the different facets.

  

The image below shows the same roof with two properly drawn sloped roof array areas.

Example 2

The image below shows a poorly drawn sloped roof. Why? Because it consists of the entirety of the two desired roof faces into a single area. These two roof surfaces are actually at different slopes, but because they are modeled as a single area, only one slope can be specified. 

See the image below showing each of the faces drawn as individual array areas - each with its own slope specified correctly.

Example 3 - skewed roof images

The image below shows an aerial house image taken from a fairly significant angle to the east. In this case, the West and East roof faces appear to be different sizes, however we can tell from the design of the roof that the ridge is centered between the eaves and the two roofs are in reality the same size. The west and east areas are drawn pretty well tracing the roof edges, but because of the skewed image the east is sized much larger than the west. Furthermore, in effort to trace exactly over the image, the user has overridden the line direction guides, and created hip lines that are not at 45 degree angles to the eaves. 

This will cause different layouts with different numbers of modules to be populated on the east and west sides, as shown in the subsequent image.  Because the hips of the south triangular roof are not drawn 45 degrees to the eave, the array generated there is not symmetrical.

The image below shows array areas created using the provided drawing tools which allows the ridge line to be perfectly centered between the east and west eaves.  All lines are drawn parallel to or at a 45 degree angle from the drawing axis.  This results in equal areas for the east and west arrays, as well as an equilateral triangle for the south roof.  These array areas represent the actual roof much more accurately than blindly tracing over the skewed aerial imagery.

The auto-generated module layout feature now produces the same systems on the east and west roofs.  This is a better representation of what can actually be installed, leading to more accurate proposals, less change orders and happier customers.

 

Use a Mouse and Your Browser's Zoom Feature

Using a mouse is far superior to using a track-pad or touchscreen for accuracy in drawing array areas.

When the customer's roof is too small, even in Google's maximum zoom, you can zoom further using your browser's zoom feature to enlarge the image. In Chrome and Firefox, simply click on the triple bar icon to the right of the address bar to access the zoom.

 

Using Keep-Outs (Restricted Areas)

Keep-Outs provide a means to restrict the placement of modules in the defined area of the keep-out. Keep-Outs should be used for dormers, skylights, chimneys, AC units, and known shaded areas. Keep-Outs may be any shape, and may span over more than one array area.  There are no direction or point guidelines provided when you are drawing a keep-out.

 

Handling Dormers

Many roofs have small dormers. Most of the time the dormer intersects with the eave of the roof face. From the sky, they appear as triangular cut outs to the desired roof face. In most cases they are too small to mount modules on. But when it is desirable to mount an array on the roof face with the dormers, you need to work around them.

One option is to draw around the dormers. Another option is to draw a straight line for the eave across all dormers, then go back and draw restricted areas for the dormers.

 

Handling Chimneys

Chimneys are another routine type of restriction. Because they can be tall enough to throw significant shade, we recommend considering the creation of a restricted area that extends around the likely shaded area caused by the chimney. Of course, if you are using micro-inverters or DC optimizers, this may not be necessary.

 

Handling Vents

In general, you should not attempt to draw vents as restricted areas. They are too small and numerous to draw. One exception may be a grouping of vents in close proximity, or a series of vents in a line. After the modules are laid out in your arrays, you will be able to selectively pick out modules that interfere with vents.