/// <summary>
/// Angle of incidence: The angle between the beam radiation
/// on a surface and the normal to that surface.
/// Equation 1.6.2, page 14
/// </summary>
/// <param name="tiltedSurface">
/// Describes slope (beta) and azimuth (gamma) angles of tilted surfaces
/// </param>
/// <param name="latitude">Latitude in radian (phi)</param>
/// <param name="declinationAngle">Declination angle in radian (delta)</param>
/// <param name="hourAngle">Hour angle in radian (omega)</param>
/// <returns></returns>
public static double GetIncidenceAngle(TiltedSurface tiltedSurface,
double latitude,
double declinationAngle,
double hourAngle)
{
(double slopeAngle, double azimuthAngle) = tiltedSurface.GetAnglesRadian();
// Abbreviations to improve readability
var sinBeta = Math.Sin(slopeAngle);
var cosBeta = Math.Cos(slopeAngle);
var sinDelta = Math.Sin(declinationAngle);
var cosDelta = Math.Cos(declinationAngle);
var sinPhi = Math.Sin(latitude);
var cosPhi = Math.Cos(latitude);
var sinGamma = Math.Sin(azimuthAngle);
var cosGamma = Math.Cos(azimuthAngle);
var sinOmega = Math.Sin(hourAngle);
var cosOmega = Math.Cos(hourAngle);
var cosTheta = sinDelta * sinPhi * cosBeta
- sinDelta * cosPhi * sinBeta * cosGamma
+ cosDelta * cosPhi * cosBeta * cosOmega
+ cosDelta * sinPhi * sinBeta * cosGamma * cosOmega
+ cosDelta * sinBeta * sinGamma * sinOmega;
// Ensure that cos(ThetaZ) is positive, so that ThetaZ is between 0 and pi/2
cosTheta = Math.Max(0, cosTheta);
return(Math.Acos(cosTheta));
}
/// <summary>
/// Constructor for setting location and tilted surface of interest
/// </summary>
/// <param name="location">Location defining latitude and longitude</param>
/// <param name="tiltedSurface">Tilted surface defining slope and azimuth angles</param>
public SolarAngles(Location location, TiltedSurface tiltedSurface)
{
config = Configuration.Config;
calculator = new BaseSolarCalculator();
Location = location;
TiltedSurface = tiltedSurface;
}
/// <summary>
/// Private method to calculate either incidence or zenith angles,
/// depending on passed tiltedSurface
/// </summary>
private double GetIncidenceAngle(DateTime solarTime, TiltedSurface tiltedSurface)
{
var declinationAngle = config.DeclinationAngle.DeclinationAngle(solarTime.DayOfYear);
var hourAngle = HourAngle.GetHourAngle(solarTime);
return(IncidenceAngle.GetIncidenceAngle(tiltedSurface,
Location.Latitude.FromDegreeToRadians(),
declinationAngle,
hourAngle));
}
