# pvl_kingdiffuse

Determine the total diffuse irradiance on a tilted surface using the King model.

## Contents

- Syntax
- Description
- Inputs
- Outputs
- Example
- References
- See Also

## Syntax

`POADiffuse = pvl_kingdiffuse(SurfTilt, DHI, GHI, SunZen)`

## Description

This model (developed by David L. King at Sandia National Laboratories) determines the total diffuse irradiance (sky diffuse and ground reflected irradiance) on a tilted surface using the surface tilt angle, diffuse horizontal irradiance, global horizontal irradiance, and sun zenith angle. The model combines the isotropic sky diffuse model with an empirical formula for the albedo for the ground-reflected irradiance.

## Inputs

- `SurfTilt` - a scalar or vector of surface tilt angles in decimal degrees. If `SurfTilt` is a vector it must be of the same size as all other vector inputs. `SurfTilt` must be >=0 and <=180. The tilt angle is defined as degrees from horizontal (e.g. surface facing up = 0, surface facing horizon = 90).
- `DHI` - a scalar or vector of diffuse horizontal irradiance in W/m^2. If `DHI` is a vector it must be of the same size as all other vector inputs. `DHI` must be >=0.
- `GHI` - a scalar or vector of global horizontal irradiance in W/m^2. If `GHI` is a vector it must be of the same size as all other vector inputs. `GHI` must be >=0.
- `SunZen` - a scalar or vector of apparent (refraction-corrected) zenith angles in decimal degrees. If `SunZen` is a vector it must be of the same size as all other vector inputs. `SunZen` must be >=0 and <=180.

## Outputs

- `POADiffuse` - the total diffuse irradiance on a tilted surface.

## Example

    SurfTilt = 30;
    SurfAz = 180;
    DHI = 47;
    GHI = 473;
    SunZen = 60;
    POADiffuse = pvl_kingdiffuse(SurfTilt, DHI, GHI, SunZen)

    POADiffuse =

       65.3974

## References

[1] Lave, M., Hayes, W., Pohl, A., Hansen, C., 2015. Evaluation of Global Horizontal Irradiance to Plane-of-Array Irradiance Models at Locations Across the United States, J. of Photovoltaics v5(2), pp. 597-606.

## See Also

`pvl_perez`, `pvl_reindl1990`, `pvl_klucher1979`, `pvl_haydavies1980`, `pvl_grounddiffuse`, `pvl_ephemeris`

Copyright 2014 Sandia National Laboratories