External Inputs
Weather Data
| Variable | Symbol | Units | Destination(s) |
|---|---|---|---|
| UTC Date-Time | — | datetime | • Solar Position • Extraterrestrial Irradiance • Sunrise/Sunset Model |
| Global Horizontal Irradiance | W/m² | • Irradiance Quality Check • Decomposition • Transposition • Ground-Reflected Shading | |
| Direct Normal Irradiance | W/m² | • Irradiance Quality Check • Transposition • Ground-Reflected Shading | |
| Diffuse Horizontal Irradiance | W/m² | • Irradiance Quality Check • Transposition • Ground-Reflected Shading | |
| Ambient Air Temperature | °C | • Solar Position (refraction) • Module Temperature • Inverter Derating • Decomposition (Reindl) • Spectral Models | |
| Wind Speed | m/s | Module Temperature | |
| Atmospheric Pressure | hPa | • Solar Position (refraction) • Air Mass • Decomposition (DIRINT) • Bird Clear Sky | |
| Relative Humidity | % | • Decomposition (Reindl) • Spectral Models | |
| Wind Gust Speed | m/s | Wind Stow | |
| Dewpoint Temperature | °C | Spectral Models | |
| Plane-of-Array Irradiance | W/m² | POAI Decomposition (when Frontside POAI enabled) |
Site Configuration
| Variable | Symbol | Units | Destination(s) |
|---|---|---|---|
| Latitude | degrees | Solar Position | |
| Longitude | degrees | Solar Position | |
| Altitude | m | • Solar Position () • Pressure calculation • Inverter Derating | |
| Albedo | — | • Transposition • Bifacial Model • Bird Clear Sky | |
| Standard UTC Offset | hours | Sunrise/Sunset Model | |
| Horizon Profile | degrees | Horizon Shading |
Other Time Series Inputs (Optional)
| Input | Units | Used In | |
|---|---|---|---|
| Monthly Albedo Factors | — | Transposition | |
| Monthly Soiling Factors | % | Soiling Model | |
| Module Temperature Time Series | °C | Override calculated temperature | |
| Tracking Angle Time Series | degrees | User-defined tracking | |
| Vmpp Time-Series Adjustment | % | Operating Region (V7+) | |
| Impp Time-Series Adjustment | % | Operating Region (V7+) | |
| Inverter Derate Time Series | — | Power derating schedule | |
| Inverter Set Point Time Series | W | Power limiting schedule | |
| LGIA Limit Time Series | MW | POI power clipping |
Model Parameters
Module Parameters (Single Diode Model)
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| Reference Short-Circuit Current | A | Parameter Translation → Single Diode Model | |
| Reference Power | W | Parameter Translation / DC Wiring Resistance | |
| Number of Cells in Series | — | • Parameter Translation • Single Diode Model | |
| Temperature Coefficient of Isc | %/°C | Parameter Translation → Single Diode Model | |
| Diode Ideality Factor | — | Parameter Translation | |
| Temp. Coeff. of Ideality Factor | 1/°C | Parameter Translation | |
| Ideality Factor Polynomial Coefficients | various | Parameter Translation | |
| Reference Series Resistance | Ω | Parameter Translation → Single Diode Model | |
| Reference Shunt Resistance | Ω | Parameter Translation → Single Diode Model | |
| Reference Saturation Current | A | Parameter Translation → Single Diode Model | |
| Dark Shunt Resistance | Ω | Parameter Translation (irradiance) → Single Diode Model | |
| Shunt Resistance Exponent | — | Parameter Translation (irradiance) → Single Diode Model | |
| Bandgap Energy | eV | Parameter Translation (temperature) → Single Diode Model | |
| Recombination Parameter | V | Single Diode Model (7-parameter) | |
| Built-in Voltage | V | Single Diode Model (7-parameter) | |
| Reference Irradiance | W/m² | • Parameter Translation • Temperature Models • DC Wiring Resistance | |
| Reference Temperature | °C | • Parameter Translation • DC Wiring Resistance |
Module Temperature Parameters
| Parameter | Symbol | Units | Model |
|---|---|---|---|
| Conductive Heat Transfer Coefficient | W/m²·K | Heat Balance | |
| Convective Heat Transfer Coefficient | W/m²·K per m/s | Heat Balance | |
| Cell-to-Module Temperature Difference | °C | All temperature models | |
| Absorption Coefficient | — | Heat Balance | |
| Module STC Efficiency | — | Heat Balance / NOCT-SAM | |
| Conductive Coefficient | — | Sandia | |
| Convective Coefficient | s/m | Sandia | |
| Transmittance-Absorptance | — | NOCT-SAM | |
| NOCT | °C | NOCT-SAM |
Inverter Parameters
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| Minimum MPP Voltage | V | Operating Region | |
| Maximum MPP Voltage | V | Operating Region | |
| Maximum Absolute Voltage | V | Operating Region | |
| Minimum DC Power | W | Operating Region | |
| AC Rated Power | kVA | Power Limiting | |
| Efficiency Curves | kW, % | Efficiency Model | |
| Temperature-kVA Curves | °C, kVA | Temperature Derating | |
| AC Power Setpoint | kVA | Temperature Derating / Power Limiting |
DC Field & Loss Parameters
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| Module Mismatch Coefficient | % | DC Power Reduction | |
| Light-Induced Degradation | % | DC Power Reduction | |
| Module Quality Factor | % | DC Power Reduction | |
| DC Health Factor | % | DC Power Reduction | |
| DC Wiring Loss Percentage | % | DC Wiring Resistance | |
| DC Wiring Resistance | Ω | Added to Series Resistance | |
| Degradation Rate (Linear) | %/year | Annual Degradation | |
| Nonlinear Degradation Rates | %/year | Nonlinear Degradation | |
| LeTID Annual Rates | %/year | LeTID Degradation | |
| Bifaciality Factor | — | Rear-Side Weighting | |
| Structure Shading Factor | % | Rear-Side Losses | |
| Backside Mismatch Factor | % | Rear-Side Losses | |
| Transmission Factor | — | Rear Irradiance (bifacial) | |
| Field-Level Wiring Resistance | Ω | Loss Reporting | |
| Energization Date | datetime | DC Degradation Model |
Transformer Parameters
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| MV Transformer No-Load Loss | % | MV Transformer Model (quadratic) | |
| MV Transformer Full-Load Loss | % | MV Transformer Model (quadratic) | |
| MV Transformer Rated Power | kVA | Transformer Model (quadratic) | |
| HV Transformer No-Load Loss | % | HV Transformer Model (quadratic) | |
| HV Transformer Full-Load Loss | % | HV Transformer Model (quadratic) | |
| HV Transformer Rated Power | MVA | HV Transformer Model (quadratic) |
AC System Parameters
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| AC Collection Loss | % | Array-Level Losses | |
| Transmission Line Resistance | Ω/1000 ft | Transmission Loss | |
| Transmission Line Length | km | Transmission Loss | |
| Transformer High-Side Voltage | kV | Transmission Loss | |
| Conductors per Phase | — | Transmission Loss | |
| Inverter Design Derate | — | Power Factor / Transmission Loss | |
| Cooling Load | W | Auxiliary Load | |
| Tracker Motor Load | W | Auxiliary Load | |
| DAS Load | W | Auxiliary Load | |
| Availability Loss Factor | % | • Availability Loss • Power Flow (ESS re-run) | |
| Grid Limit (LGIA) | MW | POI Power Clipping |
DC Field Geometry
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| Fixed Tilt Angle | degrees | Surface Orientation | |
| Fixed Azimuth Angle | degrees | Surface Orientation | |
| Tracker Axis Azimuth | degrees | Tracking Algorithm | |
| Tracker Axis Tilt | degrees | Tracking Algorithm | |
| Minimum Rotation Limit | degrees | Tracking Algorithm | |
| Maximum Rotation Limit | degrees | Tracking Algorithm | |
| Nighttime Stow Angle | degrees | Tracking Algorithm | |
| Wind Stow Angle | degrees | Wind Stow | |
| Ground Slope | degrees | • Backtracking • Shading Models | |
| Ground Slope Azimuth | degrees | • Backtracking • Shading Models | |
| Ground Coverage Ratio | — | • Backtracking • Shading Models • Bifacial Model | |
| Post Height | m | Bifacial Model | |
| Row-to-Row Pitch | m | • Shading Models • Backtracking • Bifacial Model • GCR calculation | |
| Collector Width | m | • Shading Models • Backtracking • Bifacial Model • GCR calculation | |
| Row Length | m | Row-to-Row Beam Shading | |
| Bay Pile Heights | m | Terrain-Aware Backtracking | |
| East Neighbor Pile Heights | m | Terrain-Aware Backtracking | |
| West Neighbor Pile Heights | m | Terrain-Aware Backtracking | |
| Bay Length | m | Row-to-Row Beam Shading | |
| Bay Spacing | m | Row-to-Row Beam Shading | |
| Bays Per Row | — | Row-to-Row Beam Shading | |
| Number of Rows | — | Row-to-Row Beam Shading | |
| Cross-Axis Slope | degrees | Sky Diffuse Shading | |
| DC Field Repeater Count | — | DC Field Aggregation | |
| Inverter Repeater Count | — | Array-Level Losses | |
| Array Repeater Count | — | • Array-Level Losses • Plant-Level Losses | |
| Block Repeater Count | — | Plant-Level Losses | |
| Strings per Inverter | — | • Current scaling (parallel) • DC wiring resistance | |
| Modules per String | — | • String voltage (Vmp, Voc) • DC wiring resistance |
Tracking Control Parameters
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| Hesitation Factor | — | Irradiance Optimization | |
| Rotation Speed | degrees/s | Irradiance Optimization | |
| Wind Stow Threshold | m/s | Wind Stow | |
| Time Interval | seconds | Irradiance Optimization | |
| Time Interval | minutes | Battery Model |
Spectral Correction Parameters
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| Sandia Polynomial Factors | — | Spectral Correction (Sandia) | |
| Two-Variable Coefficients | — | Spectral Correction (Two-Variable) | |
| Monthly Spectral Loss | % | Spectral Correction (Monthly Override) |
Electrical Shading Parameters
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| Fractional Shading Percent | % | Electrical Shading (Fractional) | |
| Number of Module Rows | — | Electrical Shading (Fractional, pre-V12) | |
| Number of Bay Fractions | — | Electrical Shading (Step-Fractional, V12+) |
IAM Parameters
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| ASHRAE IAM Parameter | — | IAM (ASHRAE) / Ground-Reflected Shading | |
| Sandia IAM Polynomial Factors | degree⁻ⁱ | IAM (Sandia) | |
| Refractive Index | — | IAM (Physical) | |
| ARC Refractive Index | — | IAM (Physical) | |
| Absorption Coefficient (glass) | m⁻¹ | IAM (Physical) | |
| Glass Thickness | m | IAM (Physical) | |
| IAM Factor Pairs | degrees, — | IAM (Tabular) |
ESS Parameters (Optional)
| Parameter | Symbol | Units | Used In |
|---|---|---|---|
| Nameplate Energy Capacity | MWh | State-of-Charge Calculation | |
| Usable Capacity Factor | — | State-of-Charge Calculation | |
| Initial Round-Trip DC Efficiency | % | Round-Trip Efficiency | |
| Capacity Cycle Degradation Rate | %/cycle | Battery Degradation | |
| Capacity Calendar Degradation Rate | %/year | Battery Degradation | |
| RTE Cycle Degradation Rate | %/cycle | Battery Degradation | |
| RTE Calendar Degradation Rate | %/year | Battery Degradation | |
| ESS Inverter Efficiency | % | DC/AC Conversion Efficiency (Charge/Discharge) | |
| ESS Inverter Rated AC Power | MW | Charge & Discharge Limits | |
| ESS MV Transformer No-Load Loss | % | ESS Transformer Model (quadratic) | |
| ESS MV Transformer Full-Load Loss | % | ESS Transformer Model (quadratic) | |
| ESS MV Transformer Rating | MVA | ESS Transformer Model (quadratic) | |
| Custom Inverter Capacity Fraction | — | Charge & Discharge Limits (Custom Dispatch) | |
| Dispatch Table | boolean | Dispatch Algorithms | |
| Custom Dispatch Time Series | — | Dispatch Algorithms |
Stage 1: Irradiance Variables
Solar Position, Extraterrestrial, and Clear-Sky Irradiance
| Variable | Symbol | Units | Origin | Destination(s) |
|---|---|---|---|---|
| Solar | degrees | Solar Position Algorithm | • Air Mass • Decomposition • Transposition • Shading • Bird Clear Sky | |
| Solar Angle | degrees | Solar Position Algorithm | • Tracking • Shading | |
| Sunrise Time | datetime | Sunrise/Sunset Model | • Operational hours • Horizon Shading | |
| Sunset Time | datetime | Sunrise/Sunset Model | • Operational hours • Horizon Shading | |
| Extraterrestrial Direct Normal Irradiance | W/m² | Extraterrestrial Irradiance | • Transposition • Decomposition • Bird Clear Sky | |
| Clear-Sky Global Horizontal Irradiance | W/m² | Bird Clear Sky Model | Decomposition (DIRINT) | |
| Clear-Sky Direct Normal Irradiance | W/m² | Bird Clear Sky Model | Decomposition (DIRINT) | |
| Clear-Sky Diffuse Horizontal Irradiance | W/m² | Bird Clear Sky Model | Decomposition (DIRINT) |
Derived Irradiance Parameters
| Variable | Symbol | Units | Origin | Destination(s) |
|---|---|---|---|---|
| Relative | — | Air Mass Model | Transposition (Perez) | |
| Pressure-Corrected | — | Air Mass Model | • Decomposition (DIRINT) • Spectral Models | |
| Precipitable Water | cm | Weather file or calculated from RH/T | Spectral Models | |
| Spectral Correction Factor | — | Spectral Model | POA Irradiance adjustment |
Tracker & Surface Orientation
| Variable | Symbol | Units | Origin | Destination(s) |
|---|---|---|---|---|
| Tracker Rotation Angle | degrees | True Tracking | • Backtracking • Irradiance Optimization | |
| Backtracking Angle | degrees | Standard Backtracking | Terrain-Aware Backtracking | |
| Terrain-Corrected Angle | degrees | Terrain-Aware Backtracking | Surface Orientation | |
| Optimized Tracker Angle | degrees | Irradiance Optimization | Wind Stow / Surface Orientation | |
| Commanded Tracker Angle | degrees | Wind Stow | Surface Orientation | |
| Module Tilt Angle | degrees | • Configuration • Tracking | • Transposition (view factors) • AOI Calculation | |
| Module Azimuth Angle | degrees | • Configuration • Tracking | AOI Calculation | |
| Angle of Incidence | degrees | Geometry Calculation | • Transposition (beam) • IAM • Row-to-row shading |
Plane-of-Array Irradiance Components
| Variable | Symbol | Units | Origin | Destination(s) |
|---|---|---|---|---|
| Transposition Factor (Global) | — | 3D Transposition | POA Irradiance adjustment | |
| Transposition Factor (Beam) | — | 3D Transposition | POA Irradiance adjustment | |
| Transposition Factor (Sky Diffuse) | — | 3D Transposition | POA Irradiance adjustment | |
| Transposition Factor (Ground) | — | 3D Transposition | POA Irradiance adjustment | |
| Pre-Shading POA Irradiance (B/D/G) | — | W/m² | Transposition | Shading Models |
| Shaded POA Irradiance (B/D/G) | — | W/m² | Shading Models | Soiling |
| POA Irradiance After Soiling (B/D/G) | — | W/m² | Soiling Model | IAM |
| POA Irradiance After IAM (B/D/G) | — | W/m² | IAM Model | Effective POA |
| Front POA Irradiance | W/m² | Transposition (sum of B/D/G) | • NOCT-SAM Temperature Model • Irradiance Optimization | |
| Effective Front POA Irradiance (B/D/G) | W/m² | After All Adjustments | Effective POA Irradiance | |
| Back POA Irradiance (B/D/G) | — | W/m² | Bifacial Model | Effective POA Irradiance |
| Effective POA Irradiance | W/m² | Front + Back × Bifaciality | Single Diode Model |
Loss/Adjustment Factors
| Variable | Symbol | Units | Origin | Applied To |
|---|---|---|---|---|
| Horizon Shading Factor | — | Horizon Shading | Beam POA Irradiance | |
| Beam Shading Factor | — | Near Shading Models | Beam POA Irradiance | |
| Sky Diffuse Shading Factor | — | Diffuse Shading (view factors) | Sky Diffuse POA Irradiance | |
| Ground Shading Factor | — | Ground-Reflected Shading | Ground POA Irradiance | |
| Electrical Shading Factor | — | Electrical Shading | Beam POA Irradiance | |
| Soiling Factor | — | Soiling Model | All POA Irradiance Components | |
| Beam IAM Factor | — | IAM Model | Beam POA Irradiance | |
| Sky Diffuse IAM Factor | — | IAM Model | Sky Diffuse POA Irradiance | |
| Ground Diffuse IAM Factor | — | IAM Model | Ground POA Irradiance |
Stage 2: DC Performance Variables
Module Temperature
| Variable | Symbol | Units | Origin | Destination(s) |
|---|---|---|---|---|
| Cell Temperature | °C | Temperature Model | Single Diode Model | |
| Module Surface Temperature | °C | Temperature Model | Output |
DC System Losses & Parameter Translation
| Variable | Symbol | Units | Origin | Destination(s) |
|---|---|---|---|---|
| Scaled Effective Irradiance | W/m² | DC System Losses | Parameter Translation | |
| Series Resistance | Ω | Parameter Translation | Single Diode Model | |
| Shunt Resistance | Ω | Parameter Translation | Single Diode Model | |
| Diode Ideality Factor | — | Parameter Translation | Single Diode Model | |
| Saturation Current | A | Parameter Translation | Single Diode Model | |
| Photocurrent | A | Parameter Translation | Single Diode Model |
DC Power Outputs
| Variable | Symbol | Units | Origin | Destination(s) |
|---|---|---|---|---|
| Open-Circuit Voltage | V | Single Diode Model | • Inverter Region Model • Output | |
| Short-Circuit Current | A | Parameter Translation | Output | |
| MPP Voltage | V | Single Diode Model | Inverter Region Model | |
| MPP Current | A | Single Diode Model | Inverter Region Model | |
| MPP Power | W | Inverter Region Model |
Stage 3: Inverter Variables
| Variable | Symbol | Units | Origin | Destination(s) |
|---|---|---|---|---|
| DC Open-Circuit Voltage | V | DC Field Aggregation | Inverter Region Model | |
| DC Voltage (after clipping) | V | Inverter Region Model | Inverter Efficiency Model | |
| DC Operating Power | W | Inverter Region Model | Inverter Efficiency Model | |
| Degraded DC Power | W | DC Degradation Model | Inverter Region Model | |
| DC Degradation Loss | W | DC Degradation Model | Output | |
| DC LeTID Loss | W | DC Degradation Model | Output | |
| Temperature-Corrected Max Power | W | Temperature Derating | Inverter Region Model | |
| Inverter Efficiency | — | Inverter Efficiency Model | AC Power | |
| Inverter AC Power | W | Inverter Efficiency Model | Inverter Aggregation |
Stage 4: AC & Plant-Level Variables
Array Level
| Variable | Symbol | Units | Origin | Destination |
|---|---|---|---|---|
| Array AC Power | W | Inverter Aggregation | AC Degradation Model | |
| Degraded AC Power | W | AC Degradation Model | Auxiliary Loads | |
| AC Degradation Loss | W | AC Degradation Model | Output | |
| LeTID Loss | W | LeTID Model | Output | |
| Auxiliary Loads | W | Cooling + Tracker + DAS | MV Transformer Model | |
| MV Transformer Loss | W | MV Transformer Model | Output | |
| Block Power | W | Array-Level Losses | Plant-Level Losses |
Energy Storage (Optional)
| Variable | Symbol | Units | Origin | Destination |
|---|---|---|---|---|
| PV MV Transformer Output | W | Array-Level Losses | • Charge & Discharge Limits • Power Flow | |
| PV Power After Availability | W | Plant-Level Losses (PV-only) | • Charge & Discharge Limits • Dispatch Algorithms | |
| HV Equipment Losses | W | Plant-Level Losses (PV-only) | Charge & Discharge Limits | |
| Charge Flag | boolean | Dispatch Algorithms | Battery Model | |
| Discharge Flag | boolean | Dispatch Algorithms | Battery Model | |
| Available Charge Power | W | Charge & Discharge Limits | Battery Model | |
| Available Discharge Power | W | Charge & Discharge Limits | Battery Model | |
| State of Charge | Wh | Battery Model | Battery Model (feedback) / Output | |
| Battery DC Power | W | Battery Model | Power Flow | |
| DC RTE Loss | W | Battery Model | Output | |
| Combined PV+ESS Power | W | Power Flow | HV Transformer Model (re-run) |
Plant Level
| Variable | Symbol | Units | Origin | Destination |
|---|---|---|---|---|
| Plant Power | W | Block Aggregation (or ) | HV Equipment | |
| HV Transformer Loss | W | HV Transformer Model | Transmission Model | |
| Transmission Line Loss | W | Transmission Model | Availability | |
| Power After HV Equipment | W | HV Equipment Chain | Availability | |
| Power After Availability | W | Availability Model | LGIA Clipping | |
| Grid Limit Clipping | W | LGIA Clipping | Output | |
| Grid Power | W | LGIA Clipping | Output |
Notes:
- B/D/G: Beam, Diffuse, and Ground components are tracked and exported separately.
- V12+: Some variables (e.g., Bay Fractions for electrical shading) are only available in Version 12 and later.
- Aggregation: Power variables aggregate hierarchically: DC Field → Inverter → Array → Block → Plant.
- Timestep Loop: All time-series variables are calculated for each timestep, then aggregated to hourly/daily/monthly/annual summaries.