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Solar Calculator - Calculate Sunrise, Sunset, and Maximum Solar Radiation

, 10 Jan 2011 CPOL
A C# assembly for calculating Sunrise, Sunset, and Maximum Solar Radiation
// SunCalculator.cs - Calculator for calculating SunRise, SunSet and
// maximum solar radiation of a specific date and time.
//
// Patrick Kalkman  pkalkie@gmail.com
//
// (C) Patrick Kalkman http://www.semanticarchitecture.net
//
using System;

namespace Astronomy
{
   /// <summary>
   /// This class is responsible for calculating sun related parameters such as
   /// SunRise, SunSet and maximum solar radiation of a specific date and time.
   /// </summary>
   public class SunCalculator
   {
      private readonly double longitude;
      private readonly double latituteInRadians;
      private readonly double longituteTimeZone;
      private readonly bool useSummerTime;

      public SunCalculator()
      {
      }

      public SunCalculator(double longitude, double latitude, double longituteTimeZone, bool useSummerTime)
      {
         this.longitude = longitude;
         latituteInRadians = ConvertDegreeToRadian(latitude);
         this.longituteTimeZone = longituteTimeZone;
         this.useSummerTime = useSummerTime;
      }

      public DateTime CalculateSunRise(DateTime dateTime)
      {
         int dayNumberOfDateTime = ExtractDayNumber(dateTime);
         double differenceSunAndLocalTime = CalculateDifferenceSunAndLocalTime(dayNumberOfDateTime);
         double declanationOfTheSun = CalculateDeclination(dayNumberOfDateTime);
         double tanSunPosition = CalculateTanSunPosition(declanationOfTheSun);
         int sunRiseInMinutes = CalculateSunRiseInternal(tanSunPosition, differenceSunAndLocalTime);
         return CreateDateTime(dateTime, sunRiseInMinutes);
      }

      public DateTime CalculateSunSet(DateTime dateTime)
      {
         int dayNumberOfDateTime = ExtractDayNumber(dateTime);
         double differenceSunAndLocalTime = CalculateDifferenceSunAndLocalTime(dayNumberOfDateTime);
         double declanationOfTheSun = CalculateDeclination(dayNumberOfDateTime);
         double tanSunPosition = CalculateTanSunPosition(declanationOfTheSun);
         int sunSetInMinutes = CalculateSunSetInternal(tanSunPosition, differenceSunAndLocalTime);
         return CreateDateTime(dateTime, sunSetInMinutes);
      }

      public double CalculateMaximumSolarRadiation(DateTime dateTime)
      {
         int dayNumberOfDateTime = ExtractDayNumber(dateTime);
         double differenceSunAndLocalTime = CalculateDifferenceSunAndLocalTime(dayNumberOfDateTime);
         int numberOfMinutesThisDay = GetNumberOfMinutesThisDay(dateTime, differenceSunAndLocalTime);
         double declanationOfTheSun = CalculateDeclination(dayNumberOfDateTime);
         double sinSunPosition = CalculateSinSunPosition(declanationOfTheSun);
         double cosSunPosition = CalculateCosSunPosition(declanationOfTheSun);
         double sinSunHeight = sinSunPosition + cosSunPosition * Math.Cos(2.0 * Math.PI * (numberOfMinutesThisDay + 720.0) / 1440.0) + 0.08;
         double sunConstantePart = Math.Cos(2.0 * Math.PI * dayNumberOfDateTime);
         double sunCorrection = 1370.0 * (1.0 + (0.033 * sunConstantePart));
         return CalculateMaximumSolarRadiationInternal(sinSunHeight, sunCorrection);
      }

      internal double CalculateDeclination(int numberOfDaysSinceFirstOfJanuary)
      {
         return Math.Asin(-0.39795 * Math.Cos(2.0 * Math.PI * (numberOfDaysSinceFirstOfJanuary + 10.0) / 365.0));
      }

      private static int ExtractDayNumber(DateTime dateTime)
      {
         return dateTime.DayOfYear;
      }

      private static DateTime CreateDateTime(DateTime dateTime, int timeInMinutes)
      {
         int hour = timeInMinutes / 60;
         int minute = timeInMinutes - (hour * 60);
         return new DateTime(dateTime.Year, dateTime.Month, dateTime.Day, hour, minute, 00);
      }

      private static int CalculateSunRiseInternal(double tanSunPosition, double differenceSunAndLocalTime)
      {
         int sunRise = (int)(720.0 - 720.0 / Math.PI * Math.Acos(-tanSunPosition) - differenceSunAndLocalTime);
         sunRise = LimitSunRise(sunRise);
         return sunRise;
      }


      private static int CalculateSunSetInternal(double tanSunPosition, double differenceSunAndLocalTime)
      {
         int sunSet = (int)(720.0 + 720.0 / Math.PI * Math.Acos(-tanSunPosition) - differenceSunAndLocalTime);
         sunSet = LimitSunSet(sunSet);
         return sunSet;
      }

      private double CalculateTanSunPosition(double declanationOfTheSun)
      {
         double sinSunPosition = CalculateSinSunPosition(declanationOfTheSun);
         double cosSunPosition = CalculateCosSunPosition(declanationOfTheSun);
         double tanSunPosition = sinSunPosition / cosSunPosition;
         tanSunPosition = LimitTanSunPosition(tanSunPosition);
         return tanSunPosition;
      }

      private double CalculateCosSunPosition(double declanationOfTheSun)
      {
         return Math.Cos(latituteInRadians) * Math.Cos(declanationOfTheSun);
      }

      private double CalculateSinSunPosition(double declanationOfTheSun)
      {
         return Math.Sin(latituteInRadians) * Math.Sin(declanationOfTheSun);
      }

      private double CalculateDifferenceSunAndLocalTime(int dayNumberOfDateTime)
      {
         double ellipticalOrbitPart1 = 7.95204 * Math.Sin((0.01768 * dayNumberOfDateTime) + 3.03217);
         double ellipticalOrbitPart2 = 9.98906 * Math.Sin((0.03383 * dayNumberOfDateTime) + 3.46870);

         double differenceSunAndLocalTime = ellipticalOrbitPart1 + ellipticalOrbitPart2 + (longitude - longituteTimeZone) * 4;

         if (useSummerTime)
            differenceSunAndLocalTime -= 60;
         return differenceSunAndLocalTime;
      }

      private static double LimitTanSunPosition(double tanSunPosition)
      {
         if (((int)tanSunPosition) < -1)
         {
            tanSunPosition = -1.0;
         }
         if (((int)tanSunPosition) > 1)
         {
            tanSunPosition = 1.0;
         }
         return tanSunPosition;
      }

      private static int LimitSunSet(int sunSet)
      {
         if (sunSet > 1439)
         {
            sunSet -= 1439;
         }
         return sunSet;
      }

      private static int LimitSunRise(int sunRise)
      {
         if (sunRise < 0)
         {
            sunRise += 1440;
         }
         return sunRise;
      }

      private static double ConvertDegreeToRadian(double degree)
      {
         return degree * Math.PI / 180;
      }

      private static double CalculateMaximumSolarRadiationInternal(double sinSunHeight, double sunCorrection)
      {
         double maximumSolarRadiation;
         if ((sinSunHeight > 0.0) && Math.Abs(0.25 / sinSunHeight) < 50.0)
         {
            maximumSolarRadiation = sunCorrection * sinSunHeight * Math.Exp(-0.25 / sinSunHeight);
         }
         else
         {
            maximumSolarRadiation = 0;
         }
         return maximumSolarRadiation;
      }

      private static int GetNumberOfMinutesThisDay(DateTime dateTime, double differenceSunAndLocalTime)
      {
         return dateTime.Hour*60 + dateTime.Minute + (int) differenceSunAndLocalTime;
      }
   }
}

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About the Author

Patrick Kalkman
Architect http://www.simpletechture.nl
Netherlands Netherlands
Patrick Kalkman is a senior Software Architect with more than 20 years professional development experience. He works for SimpleTechture where he helps teams develop state of the art web applications.

Patrick enjoys writing his blog. It discusses agile software development. Patrick can be reached at patrick@simpletechture.nl.

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