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DC Performance models calculate electrical power output from PV modules based on effective irradiance and cell temperature. PlantPredict implements the single diode equivalent circuit model with extensions for recombination effects and technology-specific behaviors. DC System Losses (Module Mismatch, Module Quality, LID, DC Health) are applied as reductions to effective irradiance before the single diode model is solved. DC Wiring Resistance is added to the module series resistance within the single diode model. These losses are documented separately in DC System Losses.

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Models in This Section

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Single Diode Model

Five-parameter equivalent circuit model solving for maximum power point using Newton-Raphson iteration. Forms the basis for all DC performance calculations.

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Parameter Translation

Scales the five diode parameters (photocurrent, saturation current, series resistance, shunt resistance, ideality factor) from reference conditions to operating conditions based on irradiance and temperature.

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Recombination Models

Extended diode models for improved low-light performance:
  • Martin & Ruiz Recombination: Seven-parameter model with additional recombination current term
  • Nonlinear Gamma: Polynomial irradiance dependence for ideality factor

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Temperature Coefficients

Application of manufacturer-specified temperature coefficients in parameter scaling for voltage, current, and power.

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Metastability

CdTe-specific transient performance effects based on thermal history. Uses 7-day and 6-hour lagged moving averages of cell temperature.

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Calculation Flow

  1. Apply DC System Losses as combined coefficient to effective irradiance
  2. Calculate module temperature from ambient conditions
  3. Scale diode parameters to operating conditions (with DC wiring resistance added to series resistance)
  4. Solve single diode equation for maximum power point
  5. Apply recombination corrections (if enabled)
  6. Apply metastability adjustment (CdTe only)