The clear-sky direct normal irradiance (DNI) profile is sometimes useful for CSP analysis. There are several models available for estimating this value, which is location dependent and can account for certain exogenous factors, such as current humidity, pressure, or seasonal effects. The goal of calculating clear-sky DNI is typically to serve as a comparison to observed DNI, and to assist in determining the fraction of DNI energy lost over each time period due to cloudiness. In this respect, clear-sky models that predict what the DNI would have been had there been no cloudiness during a time period would be most useful.
The SolarPILOT code already contains several clear-sky models, taken from
Kistler, B.L. “A User’s Manual for DELSOL3: A Computer Code for Calculating the Optical Performance and Optimal System Design for Solar Thermal Central Receiver Plants.” Albuquerque, NM: Sandia National Laboratory, 1986.
These include:
All of these models are fairly old, and newer options are available, e.g. the Perez & Ineichen formulation implemented in pvlib.
The clear-sky direct normal irradiance (DNI) profile is sometimes useful for CSP analysis. There are several models available for estimating this value, which is location dependent and can account for certain exogenous factors, such as current humidity, pressure, or seasonal effects. The goal of calculating clear-sky DNI is typically to serve as a comparison to observed DNI, and to assist in determining the fraction of DNI energy lost over each time period due to cloudiness. In this respect, clear-sky models that predict what the DNI would have been had there been no cloudiness during a time period would be most useful.
The SolarPILOT code already contains several clear-sky models, taken from
These include:
All of these models are fairly old, and newer options are available, e.g. the Perez & Ineichen formulation implemented in pvlib.