Solar PV

Solar PV#

The solar PV modules use the PySAM package for the National Renewable Energy Laboratory’s System Advisor Model (SAM) to predict the power output of the solar PV plant.

Presently only one solar simulator is available

  1. SolarPySAMPVWatts - Uses the PVWatts model in Pvwattsv8, which calculates estimated PV electrical output with configurable efficiency and loss parameters. This model is less detailed but more time-efficient, making it suitable for longer duration simulations (approximately 1 year). Set component_type = SolarPySAMPVWatts in the input dictionary (.yaml file).

Inputs#

Both models require an input weather file:

  1. A CSV file that specifies the weather conditions (e.g. NonAnnualSimulation-sample_data-interpolated-daytime.csv). This file should include:

    • timestamp (see timing for time format requirements)

    • direct normal irradiance (DNI)

    • diffuse horizontal irradiance (DHI)

    • global horizontal irradiance (GHI)

    • wind speed

    • air temperature (dry bulb temperature)

The system location (latitude, longitude, and elevation) is specified in the input yaml file.

Outputs#

The solar module output is the DC power (power) in kW of the PV plant at each timestep. Using DC power makes the parameters inv_eff and dc_to_ac_ratio irrelevant. The system_capacity parameter represents the DC system capacity under Standard Test Conditions.

The PVWatts model is configured with the following hardcoded parameters for utility-scale installations:

  • Module type: Standard crystalline silicon (module_type = 0)

  • Array type: Single-axis tracking with backtracking (array_type = 3)

  • Azimuth: 180° (due south)

  • DC/AC ratio: 1.0

The array tilt angle must be specified in the input configuration file.

When log_extra_outputs is set to True in the input .yaml file, the solar modules also output plane-of-array irradiance (poa) in W/m^2, direct normal irradiance (dni) in W/m^2, and the angle of incidence (aoi) in degrees.

Efficiency and Loss Parameters#

ALthough the pysam model SolarPySAMPVWatts model, technically includes efficiency terms:

  • inv_eff - Inverter efficiency as a percentage (0-99.5). (No longer used in Hercules)

  • losses - System losses as a percentage (0-100). Default recommended value: 0 (no losses). This parameter affects the DC power generated by the PV panels, before any conversion to AC by the inverter.

The example folder 03_wind_and_solar specifies:

  • use of the SolarPySAMPVWatts model with component_type: "SolarPySAMPVWatts"

  • weather conditions on May 10, 2018 measured at NREL’s Flatirons Campus

  • latitude, longitude, and elevation of Golden, CO

  • system design information for a 100 MW single-axis PV tracking system (with backtracking)

  • inverter efficiency of 99.5% and system losses of 0%

The system capacity can be changed in the .yaml file, but the DC/AC ratio is fixed at 1.0.

For examples using the detailed SolarPySAMPVSam model, see the test files in the tests/ directory.

References#

PySAM. National Renewable Energy Laboratory. Golden, CO. nrel/pysam

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