How is production calculated in Sighten?

Sighten‘s production model incorporates key aspects of the industry’s most sophisticated models while maintaining simplicity of user inputs.

Highlights

Simple and non-assumptive user inputs required: module and inverter quantities/models, pitch, azimuth, and shading
Hourly production calculations with granular weather data
Module and inverter-level electrical behavior modeled

User inputs	Irradiation	Module output	Array output
Location Equipment Pitch, azimuth, solar access	Weather data Sun position Solar access	Absorption Cell temps Module current- voltage curves	Aggregate modules Inverter clipping & efficiency

Production output: Production is simulated for each array on an hourly basis (8760 hour profile)

Data inputs: Primary sources of input:

TMY weather data (8760 hours) based on system location
PV module electrical specifications per manufacturer spec sheet
- Includes parameters we calculate to construct IV curve (DeSoto)
Inverter electrical specifications per manufacturer spec sheets
Array details (e.g. the user inputs or defaults for tilt, azimuth, string size, shading, etc)

Calculation description: For each hour of a TMY dataset:

Determine the solar radiation incident on the tilted surface
- "Unshaded" radiation includes beam radiation component
- "Shaded" radiation assumes no beam radiation
Determine solar cell temperature based on PV model specifications in both shaded and unshaded conditions
Construct I-V curve of solar cell based on IV curve parameters calculated as functions of solar cell temperature for both shaded and unshaded conditions (Desoto)
Calculate AC power generation (see next)

AC Power Generation: Determine the AC power generated from the array

Note on Shading: the percentage shading implies the percentage of PV modules IN EACH STRING that receive "unshaded" radiation versus "shaded" radiation
String Inverters: If the array uses a string inverter:
- The string voltage is calculated as a composite of the unshaded and shaded PV modules
- Find array max power (DC) by calculating string voltage as a function of a universally-applied string current
- Find module voltage on the I-V curve for unshaded module
- Find module voltage on the I-V curve for shaded module
- String voltage is the sum of voltages generated by unshaded and shaded modules in their respective proportion
- Iterate until maximum of product of string voltage and array current is found
DC to AC Conversion: Convert array power (DC) into array power (AC) based on inverter efficiency specifications (per spec sheet) and derate assumptions applied to all string inverters:
- wiring_dc = 0.980
- mismatch = 0.980
- diodes = 0.995
- soiling = 0.950
- wiring_ac = 0.990

Microinverters (Enphase): If the array uses microinverters
- Find array max power (DC) by calculating unshaded and shaded module voltages as functions of a individually-managed current
  - Find module max power (DC) on the I-V curve for unshaded module
  - Find module max power (DC) on the I-V curve for shaded module
  - Convert module power (DC) into module power (AC) for unshaded and shaded modules based on inverter efficiency specifications (per spec sheet) and derate assumptions applied to all microinverters:
    - wiring_dc = 0.995
    - mismatch = 1.000
    - diodes = 0.995
    - soiling = 0.950
    - wiring_ac = 0.990
  - Array power (AC) is the sum of power (AC) generated by unshaded and shaded modules in their respective proportion of the array

Optimizers (SolarEdge): If the array uses string inverters with optimizers
- Same methodology as for microinverters, but using the following derate factors:
  - wiring dc = 0.980
  - mismatch = 1.000
  - diodes = 0.995
  - soiling = 0.950
  - wiring ac = 0.990

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