AURORA BASICS

BASICS OF MODELING:

Draw the outline of the home.
- When you're working with roof sections that are all sharing an attic space, most of the time, you can draw it as one shape and the smart roof function is pretty good at resolving all of the contours correctly.
Adjust the height of the Eave to the apparent height of the eave from the Lidar map.
- Don't worry about the height of the ridge. This will be corrected when you set the pitch for each roof.
Adjust the pitch:
- Use the surveyed pitch. If it is drastically different from what it looks like on Lidar, choose which ever pitch is less steep as this will assume less area for PV.
- Note that on most homes, each roof section will have the same pitch. Make sure to apply to the same pitch to all roof sections unless there is clear evidence otherwise (i.e. multiple roof pitch measurements, a clear pitch change on a roof, or contours that make it apparent that there are multiple pitches.)

1 | INTRODUCTION TO PV ARRAY DESIGN

THE BASICS:

The main items to keep in mind for production are:

Azimuth
Shade
Obstructions
TSRF

Be sure to also keep in mind:

We are responsible for creating a quality design for the customer
We are responsible for designing a quality installation for the install crew

AZIMUTH

Azimuth is the direction that the roof mounting plane is facing in precise degrees.

A pitched roof with an azimuth of 180° (South) will have the best overall production. Put most mods here.
Azimuths of 90° (East) and 270° (West) are the next preferred roofs after South.
An Azimuth of 360°/0° (North) is the least preferred orientation. Avoid putting mods here

SHADE

Another factor to consider when designing your layout is shading.

Choose roofs with less tree shading or shade from nearby structures.
This can have a dramatic effect at times. It can even cause a south facing roof to be less preferential for production than a west or east facing roof.

OBSTRUCTIONS

When designing a layout, it is important to consider the placement of roof obstructions:

Obstructions can limit the array area on the roof mounting plane.

Obstructions can cast their own shading.
Be sure to thoroughly review roof photos to avoid missing any obstructions not visible in the aerial imagery.

TSRF

TSRF is the principal factor that affects production.

TSRF is a measure of the available solar energy in a particular location.
TSRF is affected by many factors such as:
- Roof tilt
- Azimuth
- Shading

OVERHEAD SERVICES

Working clearance for overhead service lines is not mentioned in the IFC, however, it does pertain to the roof layout and is extremely important for the safety of our crews.

Must maintain a 3’ working clearance around the service drop.
Can still mount behind the service drop, just avoid mounting directly under or too close to the power lines themselves.

2 | INTRODUCTION TO AURORA

VISUAL LAYOUT GUIDE

AURORA SETBACKS

Aurora will allow you to set your defaults for fire setbacks.

Clearance of 6” from obstructions and roof edges are always required even when no fire setbacks are required.
Note that aurora does not know any fire code. It only knows how to do default setbacks. You still need to make educated decisions on fire setbacks.

AURORA MEASURING TOOLS

Aurora will also allow you to represent the location of electrical equipment and measure in 2D as well as 3D.

The ruler is useful for:

Rafter max span measurement
Home Run distance from the roof to the combiner equipment

3 | ACCURATE MODELING

It takes a little bit of practice and intuition to spot inaccuracies with imagery. Be mindful of the following:

Accurate placement of buildings, trees, and obstructions
Accounting for image skewing utilizing the best aerial imagery possible.

LIDAR

Lidar is one of the most useful tools in aurora when available. What is Lidar?

A remote sensing method used to examine the surface of the Earth
Data is collected via airborne pulse lasers. This creates an elevation map of the terrain.
We can use Lidar data to create accurate tree dimensions, correct roof pitches and building heights.

Basically, Lidar can paint a picture of the landscape for you so that you don't have to guess what the roof/obstructions/trees should look like. Note that Lidar scans could be from a decade ago or more for some areas, so you still need to use surveyed data as much as possible.

Lidar is a tool used to aid your design only, it is not to be fully relied upon.

Sometimes, the lidar mapping function in aurora will not align with the aerial imagery for the sight. The lidar settings will allow you to adjust:

X-offset
Y-offset
Z-offset

This is the best way to ensure accuracy when utilizing Lidar.

NEARMAPS IMAGERY

Nearmaps imagery can help determine the following:

Location of roof obstructions and trees relative to what was captured during site survey
A detailed timeline of the property:
- Can show if trees present on lidar have since been removed.
- Can also help determine when new structures were built or identify new roof obstructions.

MAP SPLIT/STREET VIEW

Aurora will also allow you to enter split map mode. This feature can be used for:

Spotting vaulted roofs and bonus rooms that weren’t surveyed.
Spotting the location of electrical equipment from the street.
Visual of tricky pitch changes.

BASICS OF MODELING:

Draw the outline of the home.
- When you're working with roof sections that are all sharing an attic space, most of the time, you can draw it as one shape and the smart roof function is pretty good at resolving all of the contours correctly.
Adjust the height of the Eave to the apparent height of the eave from the Lidar map.
- Don't worry about the height of the ridge. This will be corrected when you set the pitch for each roof.
Adjust the pitch:
- Use the surveyed pitch. If it is drastically different from what it looks like on Lidar, choose which ever pitch is less steep as this will assume less area for PV.
- Note that on most homes, each roof section will have the same pitch. Make sure to apply to the same pitch to all roof sections unless there is clear evidence otherwise (i.e. multiple roof pitch measurements, a clear pitch change on a roof, or contours that make it apparent that there are multiple pitches.)

ROOF EDGES

One small factor that can have a profound impact on roof area is accurate modeling of roof edges. When correcting roof edges, it is important to not include roof gutters as part of the roof area. This can add whole feet to some roof planes in some circumstances.

Model just to the "white line" of the gutter.
DO NOT OVERLAP ONTO THE GUTTER OR OVER IT.

IMAGE SKEWING

Image skewing occurs when the aerial image is presenting the home viewed from an angle:

Modeling will need to be adjusted in the opposite direction of image skewing.
Skew may be taking place in the X direction, Y direction or both.
When you see this, focus on modeling to the corners of the roof. Don’t focus on the ridge not aligning with the image. Remember, the ridge isn’t being shown correctly in the image due to skewing.

When modeling on skewed imagery, use the following guidelines:

Make sure to model the eaves parallel. Focus on getting the corners in the right locations along the eaves.
For equilateral roofs, the interior ridges and valleys should be resolved accurately by the smart roof tool even though it will appear that it is not lining up with the image.

Hip roofs will have a less pronounced skew. Look at neighboring structures to rule our image skewing on hip roofs before drawing the home.

First, use the smart roof tool and line up all the corners as shown. In this example, we have roof sections of different pitches:

Worry most about the perimeter lining up with the footprint of the roof.

Next correct the pitches to what was measured during the site survey. Use lidar to corroborate this.

The key with hip roofs is:

Hips line up exactly with the corners
Hip lengths are consistent or uniform

If these factors are inconsistent in your model, revisit and redraw if needed. Avoid moving the ridge/valleys to match as it appears in the image.

Definitions

Familiarize yourself with the terminology below related to irradiance

Irradiance

A measurement of the amount of solar energy that arrives in a particular area over a given period of time.

Aurora measures this in kWh/m2/year

Solar Access Percentage (SAP)

🤓 Technical definition: The ratio of the actual solar energy available (taking into account shading cast by objects in the environment) to the solar energy that would be available in the absence of shading.

☀️ Practical definition: A standardized value from 0%-100% that evaluates the amount of sunlight that hits a defined area.

Tilt and Orientation Factor (TOF)

🤓 Technical definition: The ratio of the amount of solar energy a location receives to the amount it would receive if the orientation of the roof were optimal.

☀️ Practical definition: A standardized value from 0%-100% that evaluates how optimal the direction (azimuth) and tilt of a solar array is for energy production.

Total Solar Resource Fraction (TSRF)

🤓 Technical definition: The percentage of the available solar resource that a location receives as compared to what it would receive with optimal orientation and without shading.

☀️ Practical definition: A standardized value from 0%-100% that evaluates how much solar access an area receives and how optimal it’s azimuth and tilt are for solar energy production.

TSRF = SAP x TOF

Total Solar Resource Fraction = (Solar Access Percentage) x (Tilt and Orientation Factor)

LIDAR

📡 Lidar (Light Detection and Ranging) is one of the most useful tools in aurora when available. What is Lidar?

A remote sensing method used to examine the surface of the Earth
Data is collected via airborne pulse lasers. This creates an elevation map of the terrain.
We can use Lidar data to create accurate tree dimensions, correct roof pitches and building heights.

Lidar is a tool used to aid the designers, it is not to be fully relied upon.

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