5
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
3 Inputs and Default Values
SAM requires input data to describe the performance characteristics of physical equipment in the
system, and project costs and financial assumptions. The desktop application comes with default
input values and tools for downloading some inputs from online data services. For SDK users,
when you run SSC via the API, you must assign values to the inputs in your code. (You can use the
code generator described in Section 2.2 above.)
SAM requires a weather data file as input to describe the renewable energy resource and weather
conditions at a project location. In the desktop application, you either choose a weather data file
from a list, download one from the internet, or create the file using your own data.
The desktop application comes with several libraries of performance data and coefficients that
describe the characteristics of commercially available system components such as photovoltaic
modules and inverters, parabolic trough receivers and collectors, wind turbines, and biopower
combustion systems. For those components, you simply choose an option from a list, and SAM
applies values from the library to the input variables.
The desktop application comes with a set of component libraries that store input parameters for the
photovoltaic, solar water heating, wind and parabolic trough performance models:
• Module parameters from the California Energy Commission
• Inverter parameters from the California Energy Commission
• Solar hot water collector parameters from the SRCC
• Trough receiver parameters from NREL
• Trough collector parameters from NREL
• Wind turbine power curves from NREL
The desktop application can also automatically download data and populate input variable values
from the following online databases:
• OpenEI Utility Rate Database for retail electricity rate structures for U.S. utilities.
• NREL National Solar Radiation Database for solar resource data and ambient weather
conditions.
• NREL Wind Integration Datasets for wind resource data.
• NREL Biofuels Atlas and DOE Billion Ton Update for biomass resource data.
For the remaining input variables, you either use the default value or change its value. Some
examples of input variables are:
• Installation costs including equipment purchases, labor, engineering and other project costs,
land costs, and operation and maintenance costs.
• Numbers of modules and inverters, tracking type, and derating factors for photovoltaic
systems.
• Collector and receiver type, solar multiple, storage capacity, and power block capacity for
parabolic trough systems.
• Analysis period, real discount rate, inflation rate, tax rates, internal rate of return target or
power purchase price for utility financing models.
• Building load and time-of-use retail rates for commercial and residential financing models.
• Tax and cash incentive amounts and rates.