Only use GHI as input to do irradiance simulation

Hello everyone

I have data on monitored Global Horizontal Irradiance, but no data on Direct Normal Irradiance and Diffuse Horizontal Irradiance. I would like to ask if I can perform the irradiance simulation based only on the monitored GHI data. Does ladybug have a GHI separation model to simulate DNI and DHI?


Hi @yusen, gendaylit has an option for -E that should do what you need to generate the sky.

Usage: gendaylit      month day hour [-y year]  [...]
   or: gendaylit -ang altitude azimuth          [...]
                followed by:      -P          epsilon delta [options]
                         or:      [-W|-L|-G]  direct_value diffuse_value [options]
                         or:      -E          global_irradiance [options]

        -P epsilon delta  (these are the Perez parameters)
        -W direct-normal-irradiance diffuse-horizontal-irradiance (W/m^2)
        -L direct-normal-illuminance diffuse-horizontal-illuminance (lux)
        -G direct-horizontal-irradiance diffuse-horizontal-irradiance (W/m^2)
        -E global-horizontal-irradiance (W/m^2)

        Output specification with option:
        -O [0|1|2]  (0=output in W/m^2/sr visible, 1=output in W/m^2/sr solar, 2=output in candela/m^2), default is 0
        gendaylit version 2.5 (2018/04/18)

I don’t think we have a component that exposes this option but you should be able to modify the existing one to use the -E option.