Yield simulation options

The Yield simulation options control how SunSolve performs optical ray tracing and electrical simulations to calculate system performance. These settings affect simulation accuracy, computational requirements, and the level of electrical detail in your results.

Solve type

The solve type determines the electrical configuration level at which the simulation calculates output power.

Module DC

DC output of each module within the unit system. This mode assumes:

Modules operate at their individual maximum power points
Modules are not electrically interconnected
No inverter or string-level losses

Use this mode for:

Module-level performance analysis
When solving PVsyst factors

String DC

DC output of strings of series-connected modules. This mode includes:

Module-to-module electrical mismatch within strings
String-level voltage and current calculations
String definitions configured on the Fields tab

Use this mode for:

String-level performance analysis
Quantifying electrical mismatch losses
DC system design validation

Array AC

AC output of multiple parallel strings connected to an inverter. This mode includes:

All String DC features
String-to-string mismatch
Inverter efficiency modeling and losses
Array and inverter configuration defined on the Fields tab

Use this mode for:

Complete system AC performance predictions
Inverter sizing and selection analysis
Energy yield forecasting

Ray settings

Ray settings control the computational parameters for optical ray tracing, balancing simulation accuracy with solve time.

Ray determination method

Choose how the number of rays per solar angle is determined:

Automatically determine (Default)

SunSolve calculates optimal ray count based on your system size
Minimum enforced: 500,000 rays
Maximum limits enforced to prevent timeout (see module limits)
Shows the Fidelity level control

Rays per solar angle are calculated as:

R = ⌊ N_{modules} \times 2,000,000 ⌋ \times f

where:

$R$ = rays per solar angle
$N_{modules}$ = number of modules in the unit system
$f$ = fidelity multiplier (0.5, 1.0, 2.0, 4.0, or 8.0)
$⌊ ⌋$ = floor function (rounds down to nearest integer)

Custom value (Advanced users only)

Manually specify exact ray count
Allows expert users to override automatic calculations
Shows editable “Rays per solar angle” field
Use with caution: too few rays increase stochastic error, too many cause timeouts

Fidelity level

Multiplier for automatically-determined ray count. Available levels: 0.5×, 1× (default), 2×, 4×, 8×.

Higher fidelity increases the number of rays proportionally, improving accuracy at the cost of longer computation time. For example, 2× fidelity doubles the ray count and approximately doubles solve time.

When to adjust fidelity:

Increase (2×-8×): Complex optical structures, high-precision studies, validation work
Decrease (0.5×): Initial design exploration, geometry testing, large parameter sweeps
Keep at 1×: Most production simulations (default provides good accuracy/time balance)

Note: Higher fidelity levels reduce the maximum number of modules you can include in your unit system. See technical constraints for details.

For more information on the relationship between ray count and accuracy, see Stochastic error.

Transposition of diffuse light

Selects the mathematical model for sky distribution of diffuse light. For detailed description of the models see sky distribution of diffuse light

For most yield simulations use either Hay-Davies or Perez (1990). Reserve Perez (PVsyst) for direct comparison with PVSyst results.

Isotropic

Assumes diffuse light is uniformly distributed across the sky hemisphere.

Hay-Davies

Accounts for circumsolar brightening (concentration of diffuse light around the sun’s position).

Perez models

Advanced anisotropic models accounting for both circumsolar and horizon brightening.

Available algorithms:

Perez (1987): Original formulation
Perez (1990): Updated with refined coefficients
Perez (SAM): System Advisor Model implementation
Perez (PVsyst): PVsyst software implementation (Advanced users only)

Advanced analysis

Special analysis options for isolating specific optical or electrical effects. Primarily used for extraction of PVsyst factors (when using the manual method). These inputs manipulate the 3D unit-system scene.

Block vertical gap

Adds a light-blocking barrier to vertical gaps between panels while maintaining tip-to-tip module group length.

Purpose: Used in extraction of bifacial loss factors. Prevents light passing through gaps to better isolate edge effects.

Omit rear current

Adds a light-blocking barrier to the rear side of every module in the unit-system.

Purpose: Allows calculation of bifacial gain by comparing front-only to bifacial configurations.

Transparent module frame

Makes module frame transparent to light while maintaining its geometry.

Purpose: Isolates frame shading effects.

Note: Removing the frame will often result in more transmission between modules.

Set all structure to transparent/solid

Batch operations to control transparency of all structural components (posts, rafters, purlins, torque tubes, clamps, ballasts, rails, custom objects).

Set all structure to transparent:

Makes all structure transparent while maintaining geometry
Isolates structural shading losses

Set all structure to solid:

Restores normal optical properties
Returns to realistic shading analysis

Definition of system dimensions

Determines the coordinate system convention used to define module orientation within the system.

For detailed explanation of these conventions and when to use each, see System dimensions: XY axis and landscape/portrait.

XY axes (as used to define module)

Uses the same XY coordinate system as module definition. X and Y directions match those in module layout.

Landscape/portrait

Uses landscape/portrait terminology independent of module XY definition.

Output options

Include cell-to-cell mismatch

Whether to include electrical mismatch losses in module output calculations.

Status: Always enabled in current version

For more information, see Sources of electrical mismatch and Stochastic error.

Significant figures

Controls the number of significant figures for output display across all results.

Valid range: Typically 2-6 significant figures Default: 4

This is a display-only setting; all internal calculations use full precision.

Advanced user options

These settings require advanced user privileges. Contact us to request access. Most users do not require control of these settings and should use the defaults.

The “Show advanced options” checkbox (visible only to advanced users) controls visibility of:

Spectral range settings (wavelength min/max/interval)
Polarization tracking
Solar angles matrix configuration
Advanced ray options (rays per packet, max bounces, intensity threshold)
Advanced output options

Spectral range

Controls the wavelength range and number of wavelength bins used in the simulation. By default set to 300 nm to 1200 nm with step size of 20 nm.

Minimum wavelength

Shortest wavelength traced in the simulation.

Valid range: 200-2500 nm Default: 300 nm Units: nm (nanometers) or μm (micrometers)

Maximum wavelength

Longest wavelength traced in the simulation.

Valid range: 200-2500 nm Default: 1200 nm Units: nm (nanometers) or μm (micrometers)

Wavelength interval

Step size between traced wavelengths.

Valid range: 1-500 nm (must be > 1 nm) Default: 20 nm Units: nm (nanometers) or μm (micrometers)

Validation rules

Several constraints ensure valid wavelength configurations:

Minimum < Maximum
```
wlMin < wlMax
```
Error: “Minimum wavelength is greater than the maximum wavelength.”
At least 2 intervals
```
wlMax ≥ wlMin + 2 × wlInterval
```
Error: “There must be at least 2 wavelength intervals between the minimum and maximum wavelength.”
Integer number of intervals
```
(wlMax - wlMin) mod wlInterval = 0
```
Error: “There must be an integer number of wavelength intervals between the minimum and maximum wavelength.”
Maximum 250 wavelengths
```
(wlMax - wlMin) / wlInterval ≤ 250
```
Error: “Cannot solve more than 250 individual wavelength values. This is a temporary limit in place until the server side solver is upgraded.”

Polarization

Controls whether ray tracing tracks the polarization state of light rays.

Assume TM=TE at all interactions (Default)

Faster computation
Assumes no polarization dependence in optical properties
Suitable for most PV systems

Track polarisation

Tracks electric field orientation (s and p polarization) at each interface
More accurate for systems with polarization-dependent optical properties
Slower computation

For technical details on polarization handling, see Ray tracing methodology.

Solar angles matrix

Defines the grid of solar positions for which full ray tracing is performed. SunSolve interpolates results for intermediate solar positions throughout the year.

Number of arcs

Number of elevation arcs spanning from horizon to zenith.

Valid range: 2-20 Default: 5 Units: Dimensionless (count)

Points per arc

Number of azimuth points along each elevation arc.

Valid range: 5-60 Default: 20 Units: Dimensionless (count)

Max zenith

Maximum incident zenith angle for solar position solving. Limits ray tracing to solar elevations above a minimum threshold.

Valid range: 80-90° Default: 89° Units: Degrees (°)

Purpose: Angles very near the horizon contribute little to annual energy and take longer to solve due to extreme incidence angles.

Number of isotropic solves

Number of isotropic sky condition solves to perform for diffuse light calculations.

Valid range: 1-100 Default: 5 Units: Dimensionless (count)

Purpose: Isotropic solves calculate diffuse light absorption from all sky directions without direct beam contribution.

Total solar positions traced

Total = (numberOfArcs × pointsPerArc) + numberOfIsotropicSolves

Default calculation: (5 × 20) + 5 = 105 total solves

When to adjust:

Increase arcs/points: Complex systems with strong angular dependencies, high-precision annual studies
Decrease arcs/points: Quick design iteration, systems with weak angular variation
Increase isotropic solves: Sites with high diffuse fraction, detailed diffuse analysis
Decrease isotropic solves: Sites with predominantly direct irradiance

For more on solar arc interpolation methodology, see Ray tracing methodology.

Advanced ray options

Rays per packet

Number of rays traced in each computational batch before results are tallied.

Valid range: 20 to 500,000 (must be multiple of 20) Default: 500,000

Higher values reduce overhead but require more memory. The default works well for most systems.

Max bounces per ray

Maximum number of optical interactions (reflections/transmissions) allowed per ray before tracing ceases.

Valid range: 1 to 10,000 Default: 1,000

When to increase:

Weakly absorbing materials or wavelengths
Complex multi-bounce optical structures
Systems with many highly reflective surfaces

Trade-off: Higher values improve precision but significantly increase computation time. For more on ray bouncing, see Ray tracing methodology.

Intensity threshold

Minimum light intensity (as percentage of initial) at which ray tracing continues. Rays below this threshold are discarded.

Valid range: 0.001% to 99% Default: 0.01% Units: Percentage (%)

When to adjust:

Lower (0.001-0.005%): Capture very weak light contributions (long simulation time)
Higher (0.05-0.1%): Faster simulations when weak contributions are negligible

Validation rules

The maximum rays setting must be at least as large as rays per packet:

maxRays ≥ numRays

Error: “Maximum number of rays is less than the number of rays per packet.”