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Posted 4 May 2010

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

, 10 Jan 2011
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A C# assembly for calculating Sunrise, Sunset, and Maximum Solar Radiation

## Introduction

I was looking for a .NET library to calculate the time the sun rises and sets. There were some libraries available, including here on The Code Project, but they had some problems. After trying some, I decided to create one myself. I needed the sunrise, sunset, and maximum solar radiation for a WordPress plug-in on my blog. The plug-in shows a map of the Netherlands together with the current weather conditions. The top of this post shows a screenshot of the plug-in. The map shows the real-time temperature including an icon. The icon is a translation of the measured solar radiation against the maximum solar radiation.

## Background

It is possible to calculate the sunrise, sunset, and maximum solar radiation using some known algorithms. For those of you who are interested in these algorithms, take a look at the following pages at Wikipedia: Declination of the Sun, Sunrise, Sunset. If you just want to calculate the sunrise, sunset, and maximum solar radiation, take a look below at how to use the code.

## Using the Code

The code is packed in a Visual Studio 2008 solution. It contains two assemblies: `Astronomy `and `AstronomyTest`. The assembly `Astronomy `contains the `SunCalculator` class which performs the actual calculation. The assembly `AstronomyTest `contains several unit-tests that validate the calculations against external sources.

`SunCalculator` is a single class that does not depend on external classes. Although this somewhat goes against the Single Responsibility Principle, it makes reuse of this class easier. The `SunCalculator` class needs the longitude, latitude, and time-zone of your location. You should also indicate whether to use daylight savings. An instance of the `SolarCalculator` can be created like this:

```const Double Longitute = 5.127869;
const Double Latitude = 52.108192;
const int LongituteTimeZone = 15;
const bool UseSummerTime = true;

SunCalculator sunCalculator = new SunCalculator(Longitute, Latitude,
LongituteTimeZone, UseSummerTime);```

You have to supply the longitude and the latitude from the location that you want to calculate the sunrise and sunset time. These are the two first arguments of the constructor. For locations that use daylight savings, you should set `UseSummerTime` to the actual daylight savings status. For locations that don't use daylight savings, set it to `false`.

The actual calculation of sunrise, sunset, and maximum solar radiation can be seen below:

```DateTime sunRise = sunCalculator.CalculateSunRise(new DateTime(2010, 4, 1));
DateTime sunSet = sunCalculator.CalculateSunSet(new DateTime(2010, 4, 1));
sunCalculator.CalculateMaximumSolarRadiation(new DateTime(2010, 1, 26, 16, 30, 0));```

The `DateTime` that is returned from `CalculateSunRise` and `CalculateSunSet` includes the sunrise and sunset time. For more information, take a look at the unit-tests in the assembly `AstronomyTest`.

## Points of Interest

The code first calculates the declination of the sun, cosine of the sun position, sinus of the sun position, and the difference between the solar and the actual time. All these parameters are used to calculate the sunrise and sunset times.

If you want to see the plug-in live, see my blog www.semanticarchitecture.net. The data that is retrieved and shown on the map comes from LetsGrow.com, the company that I work for.

## History

• v1.0 02/04/2010: Initial and first release
• v1.1 28/05/2010: Added a test case for Los Angeles, and a Console application that demonstrates the library in the source code
• v1.2 08/11/2011: Fixed failing tests

## Share

 Architect http://www.simpletechture.nl 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.

Published Windows 8 apps:

Published Windows Phone apps:

Awards:

Best Mobile article of March 2012
Best Mobile article of June 2012

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 how to determine timezone martkoch6-Sep-10 0:06 martkoch 6-Sep-10 0:06
 Re: how to determine timezone Patrick Kalkman6-Sep-10 1:58 Patrick Kalkman 6-Sep-10 1:58
 Could this be used to calculate the time of day that a given solar angle occurs? [modified] tidyup3-Sep-10 1:11 tidyup 3-Sep-10 1:11
 Could this help the accuracy? henslecd30-May-10 18:46 henslecd 30-May-10 18:46
 Re: Could this help the accuracy? Patrick Kalkman31-May-10 7:51 Patrick Kalkman 31-May-10 7:51
 Re: Could this help the accuracy? henslecd31-May-10 7:59 henslecd 31-May-10 7:59
 Re: Could this help the accuracy? henslecd18-Jun-10 17:44 henslecd 18-Jun-10 17:44
 Incorrect Zamir Farooqi27-May-10 13:08 Zamir Farooqi 27-May-10 13:08
 I think there is something wrong with your algorithm. I have used the coordinates for Los Angeles (using Wikipedia) and result I get is incorrect. Here is the code: Astronomy.SunCalculator sun = new Astronomy.SunCalculator (34 , 118, -7, true ); DateTime date = DateTime.Now;// dateTimePicker1.Value(); textBoxSunRise.Text = sun.CalculateSunRise(date).ToString(); textBoxSunSet.Text = sun.CalculateSunSet(date).ToString(); And I get Sunrise: 7:18:00 AM Sunrise: 1:06:00 PM The actual value (from weather.com) should be: Sunrise: 5:45 AM Sunrise: 7:56 AM
 Re: Incorrect Patrick Kalkman27-May-10 19:47 Patrick Kalkman 27-May-10 19:47
 Re: Incorrect Patrick Kalkman27-May-10 20:52 Patrick Kalkman 27-May-10 20:52
 Re: Incorrect ZamirF28-May-10 8:15 ZamirF 28-May-10 8:15
 Example? t.a berglund27-May-10 10:36 t.a berglund 27-May-10 10:36
 Re: Example? Patrick Kalkman27-May-10 19:49 Patrick Kalkman 27-May-10 19:49
 Re: Example? Patrick Kalkman27-May-10 21:19 Patrick Kalkman 27-May-10 21:19
 Re: Example? t.a berglund28-May-10 6:22 t.a berglund 28-May-10 6:22
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