Examples

There are a few example python scripts using PySAM in the Examples directory of the github repository.

Accessing Variables

All variables in a PySAM class are organized into subclasses called Groups. There are several ways to access a variable. The subclass and variable names and descriptions are given in the Modules documentation.

Variables may be accessed directly as <class>.<subclass>.<variable>. For example, the solar_resource_file which is part of the subclass SolarResource group in Pvwattsv7:

import PySAM.Pvwattsv8 as pv

system_model = pv.new()
system_model.SolarResource.solar_resource_file

Groups and variables can also be accessed using getattr. Variables can be set with setattr:

getattr(getattr(system_model, 'SolarResource'), 'solar_resource_file')
setattr(getattr(system_model, 'SolarResource'), 'solar_resource_file', filename)

If the group name isn’t known, a variable can be accessed using value:

system_model.value('solar_resource_file')

filename = 'My_TMY_or_TYA_File'
# This is how you would assign the variable, solar_resource_file to your own file name.
system_model.value('solar_resource_file', filename)

The assign and export functions can be used to work with groups of variables in dictionaries:

systemDesign = {'azimuth':100, 'gcr': .5}   # ground coverage ratio
system_model.SystemDesign.assign(systemDesign)
system_model.SystemDesign.export()

Creating a Simulation from Multiple Modules

Suppose you wish to create a PV Power Purchase Agreement (PPA) single owner plant simulation. First you go to SAM Simulation Configurations, where you find the modules you need for this simulation are Pvwattsv7, and Singleowner in that order. In this simple example the values are loaded from the set of default parameters in the configuration “PVWattsSingleOwner”. The docs listing possible configurations of the modules are found in the documentation for those Modules; for example, for Pvwattsv7 they are found in Pvwattsv7. There is a configuration for each of the types of simulations listed in SAM Simulation Configurations.

The Singleowner model is created using the from_existing function so that it shares the same underlying data as the PVwattsv7 model. This means when the Pvwattsv7 model is executed, the data for the financial Singleowner model is loaded from its outputs. The execute functions for each model are called sequentially to do the simulation.:

import PySAM.Pvwattsv8 as pv
import PySAM.Singleowner as so

system_model = pv.default('PVWattsSingleOwner')
financial_model = so.from_existing(system_model, 'PVWattsSingleOwner')

filename = 'My_TMY_or_TYA_File'
system_model.SolarResource.solar_resource_file = filename

system_model.execute()
financial_model.execute()

print(system_model.Outputs.ac_annual, financial_model.Outputs.ppa)

Importing a SAM GUI Case

Entering or changing all the data describing your simulation from default values can be tedious, and make your python script less readable. An alternative is to use the SAM GUI to enter the data, and then to save the inputs as a JSON file. This file can then be imported into PySAM, making for less tedium. For an example of how to import the modules and variables from a SAM GUI Case, see To import a case from the SAM GUI.

Sizing a PV + Battery system with ReOpt

Pvwattsv8 and Pvsamv1 have the option to size and dispatch a StandAloneBattery or Battwatts model from ReOpt Lite’s optimization. The Utilityrate5 model is also required to provide electric tariff info, and other financial models such as Cashloan may also be linked to provide financial parameters. The Reopt_size_battery_post function returns a properly-formatted dictionary of ReOpt inputs that can then be posted to the ReOpt Lite’s API as a json string:

import PySAM.Utilityrate5 as ur
import PySAM.Pvsamv1 as pvsam
import PySAM.StandAloneBattery as stbt

system_model = pvsam.default("FlatPlatePVCommercial")
financial_model = ur.from_existing(system_model, "FlatPlatePVCommercial")
battery_model = stbt.from_existing(system_model, "BatteryNone")

# ReOpt requires lat/lon for downloading a weather file internally; custom weather files cannot be provided
# so instead lat lon can be read from a weather file
system_model.SolarResource.solar_resource_file = filename

battery_model.Load.crit_load = [0] * 8760
post = system_model.Reopt_size_battery_post()