System dimensions

For Fixed and Single-axis Tracker systems, SunSolve Yield provides two methods for defining system dimensions. Both methods define the same physical layout but use different input parameters to accommodate different user preferences and workflows. Waves systems use a different dimension definition method based on peak and trough separations. See the Waves system layout page for details.

Dimension definition methods

The ‘Options’ tab provides two ways of defining the system dimensions:

1. XY Axis - everything is defined in an XY space which matches the definition of XY from the module. This is the most flexible and generic way to define the system although some users may find it complex at first.

2. Landscape/portrait - a simplified set of dimensions that assume that the module is defined such that the X axis is the shorter side (i.e., the module appears as it would in a datasheet).

For most users, the Landscape/Portrait definition method provides a more intuitive interface, while the XY Axis method offers maximum flexibility for unconventional layouts.

Unit system concept

All system dimensions in SunSolve Yield are based on the concept of a unit system - a representative section of the PV array that is repeated infinitely in all directions. By simulating a unit system rather than an entire array, SunSolve can accurately model the behavior of modules in the interior of large installations while minimizing computational requirements.

The unit system contains:

• One or more modules arranged in a specific pattern
• Spacing between modules (module separation)
• Spacing between groups of modules (unit-system spacing)
• The structural components that support the modules

The unit system is then repeated infinitely in both horizontal directions, creating a representation of a large PV installation without edge effects.

XY Axis definition

Overview

In the XY Axis method, all dimensions are defined using X and Y coordinates that match the module’s coordinate system. This provides maximum flexibility for defining system layouts with any orientation.

Key parameters

The XY Axis method uses the following parameters:

• X_MS and Y_MS: Module separation - the spacing between adjacent modules
• X_S and Y_S: Unit system pitch - the full extent (or pitch) of the unit system
• X_SS and Y_SS: Unit system spacing - the spacing between groups of modules within a unit system

The unit-system spacing (X_SS, Y_SS) is in addition to the module separation (X_MS, Y_MS).

Configuration options

When defining the unit-system dimensions, you have three options:

1. Define the pitch: Specify X_S and Y_S directly
2. Define the spacing: Specify X_SS and Y_SS directly
3. Define row pitch and lateral spacing: If the tilt orientation of the modules is in the X direction, the row pitch is equivalent to X_S and the lateral spacing is equivalent to Y_SS; whereas if the tilt orientation is in the Y direction, the row pitch is Y_S and the lateral spacing is X_SS

Visual explanation

The first figure below defines the dimensions of the ‘unit system’ as well as the spacing between modules X_MS and Y_MS. The dimensions X_S and Y_S define the full extent (or pitch) of the unit system, whereas X_SS and Y_SS define the spacing between groups of modules within a unit system.

The second figure shows the layout of a system when it’s represented by the unit system of the first figure. The system contains infinitely many unit systems – which in this example contains 2 × 4 modules – and therefore it extends infinitely in both X and Y directions.

Landscape/portrait definition

Overview

The Landscape/Portrait method is intended to simplify the inputs for the most common system and module configurations. It assumes that the module cell layout is defined with the X axis as the shorter side (i.e., the module appears as it would in a datasheet).

Key parameters

The Landscape/Portrait method uses simplified terminology:

• Row pitch: The distance between corresponding points on adjacent rows (measured in the tilt direction)
• Lateral spacing: The spacing perpendicular to the rows
• Module separation: The spacing between individual modules

The dimensions of the unit-system are defined by the row pitch and lateral spacing, noting that the lateral module separation is included in the unit-system width.

Visual explanation

The figure below defines the dimensions of the ‘unit system’ as well as the lateral and vertical spacing between modules. The system contains infinitely many unit systems – which in this example contains 2 × 4 modules – and therefore it extends infinitely in both directions.

Simulating a central module

For a large PV system – e.g., a system with hundreds of modules – we’re most interested in the performance of a central module. A central module is a module that’s sufficiently far from all sides of the system that it’s unaffected by edge effects.

Edge effects tend to be significant in:

• The first and last row of a system
• The five modules at either end of a row

Configuration for central module

To simulate a central module:

1. Configure a unit system with a single module
2. Set module spacing to zero
3. Set appropriate unit-system dimensions to represent the surrounding array

The figures below show an example unit system (left) and its equivalent system (right), which extends infinitely in X and Y directions.

This configuration ensures that the simulated module experiences the same shading and reflection patterns as a module deep within a large array, without the computational cost of simulating the entire system.