Sighten‘s solar energy system production model incorporates key aspects of the industry’s most sophisticated models while maintaining simplicity of user inputs.
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Sighten offers several modeling improvements over PVWatts. For example, Sighten's model takes into account shade recovery from optimizers and microinverters, unlike PVWatts. Differences in methodology are listed below.
| Component | Sighten | PVWatts |
|---|---|---|
Weather data | NREL TMY Stations | NREL TMY Stations |
Shading | SAM2 shading model | User input |
Module production | DeSoto 5-parameter | User input |
Inverter efficiency | SAM CEC Efficiency | User input |
Sighten production calculation
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- 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
- Micro invertersMicroinverters: 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
- Find array max power (DC) by calculating unshaded and shaded module voltages as functions of a individually-managed current
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