Designing Carports/Canopies in HelioScope

Designing Carports/Canopies in HelioScope

Application Note
Designing Carports/Canopies in HelioScope
Introduction
When designing solar canopies in
HelioScope, care must be taken in order to
properly reflect the physical module layout
and thermal properties. This application note
describes the design techniques that can be
used to model carports in HelioScope.
HelioScope Racking Overview
It is best to start with a brief review of the racking assumptions in HelioScope. There are two types
of racking: “fixed-tilt” and “flush-mount”. Fixed-tilt modules are tilted up, along a flat plane (e.g. a
flat commercial roof or a ground-mounted array). Flush-mount modules are flush along a single
plane (e.g. an array on the side of a barn, or a residential array). Flush-mount modules will never
shade each other, since they are all modeled in the same orientation. An example of both can be
seen in Figure 1.
Fixed Tilt
Racking
=
epth
les
odu
4m
kD
Ban
Row
Spacing
θ
Tilt = 20º
Flush Mount
Racking
k
Ban
4
th =
Dep
ules
mod
Row
Spacing
θ
Tilt = 20º
Figure 1: Racking Types in HelioScope: Fixed Tilt and Flush Mount
The racking design also drives the module temperature. Specifically, fixed-tilt modules run cooler
because they have open space behind them. Flush-mount modules, on the other hand, have less
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Application Note
ventilation, and so run hotter. These coefficients can be viewed and modified in the Edit Model
Coefficients section of a Condition Set.
Figure 2: Fixed-tilt and Flush-Mount Thermal Coefficients
Frame Width
In addition to the racking type, it also helps to understand the Frame Width. The default Frame
Width in HelioScope is 1 module wide, which requires that each column of modules be complete.
On the other hand, that assumption can be changed to “0 wide”, which allows partial banks of
modules (see Figure 3). This will be useful in some carport applications.
Frame Width = 1
Frame Width = 0
Figure 3: Module Layout with Frame Width of 1 versus Frame Width of 0
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Application Note
Designing Carports in HelioScope
There are three options for designing
carports in HelioScope. The choice is
driven by two factors: the canopy back
(whether open or closed, which determines
airflow), and whether the size of the canopy
is based on the module count or the area.
When the canopy has a precise module
width, a “Defined-Height Fixed Tilt” is best.
When the canopy size is based on the
area, an “Area-based Fixed Tilt” works best. For closed carports, a “Flush-Mount” racking
technique is likely best.
Method 1: Defined-Height Fixed Tilt
If a specific rack size is known (e.g., the carport is exactly twelve modules wide), then the carport
layout becomes a straightforward application of the Fixed-Tilt racking design. Draw the Field
Segment larger than the target carport area, and enter the bank size as the “up” value of the
Frame Size.
Figure 4: 12-module-high Carport Structure
It is likely that the modules will not be aligned correctly at first, so plan to use the “Align Modules to
Click” to align the carport above the right location.
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Application Note
Method 2: Area-based Fixed Tilt
If the exact size of the module bank is not known, then an area-based approach can be used. In
this case, Define the Field Segment at the exact carport area desired, and set the Frame Size to 50
up and 0 wide. A Frame size of “50 up” is the maximum size of a bank of modules in HelioScope,
ensuring that the entire canopy can be generated in the same bank. With “0 wide”, HelioScope
does not require all 50 modules in a column to be possible in order to place the modules. For
example, if the carport area can fit 11 modules high, HelioScope will draw 11 modules. This gives
a flexible Field Segment design, while also maintaining the airflow of a fixed-tilt array.
Figure 5: Designer View of Area-Based Fixed Tilt
Important: Make sure the row spacing is greater than 0. This enables you to verify that the modules
in the carport are all part of the same module bank (see the green box in Figure 6), and not
straddling the front of one section with the back of another (the red box).
Figure 6: Potential Sub-array Sections with Area-based Field Segment
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Application Note
Method 3: Flush-Mount
For carport canopies that have a closed back (with
reduced air flow and hotter temperatures, the
HelioScope design is a straightforward application
of the Flush-Mount racking.
Draw the Field Segment where the carport will be
built, with a frame size of 1 x 1 and minimal row
spacing. The Field Segment will fill up with modules based on the tilt and dimensions.
Figure 7: Flush-Mount Racking Carport
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