====== Solar calculator - Astronomical clock  ======

{{:en:mervis-ide:35-help:t40.png}}

===== Function name =====

T40_SOLARCALCULATOR

===== ST call =====

<code st-iec>
PROGRAM TEST_T40
   VAR 
        DT1,DT2,DT3: DT;
        REAL1,REAL2,REAL3,REAL4: REAL;
          BOOL1: BOOL;
        FB: LIB.HVAC.V1_0.T40_SOLARCALCULATOR;
  END_VAR
 FB(DATETIME:= DT1, LATITUDE:= REAL1, LONGITUDE:= REAL2, SUNSHINE=> BOOL1, AZIMUTH=> REAL3, ALTITUDE=> REAL4, SUNRISE=> DT2, SUNSET=> DT3);   
END_PROGRAM
</code>

===== Library =====

LIB\HVAC

===== Version =====

V1.0

===== Description =====

The function calculates the position of the Sun for given geographical coordinates and time. It provides information on the position of the Sun against the horizon, and time of sunrise and sunset for a particular day. It is used to control blinds, and in photovoltaic plants monitoring systems.\\


===== Inputs =====

|Input    |Type|Description                                                  |Default value      |
|DATETIME |DT  |Time and date for which the Sun position has to be calculated|0001-01-01-00:00:00|
|LATITUDE |REAL|Latitude in degrees (°) as a decimal number                  |50                 |
|LONGITUDE|REAL|Longitude in degrees (°) as a decimal number                 |14,3999996185303   |

===== Outputs =====

|Output  |Type|Description                                                                |
|SUNSHINE|BOOL|True, if the Sun is above the horizon                                      |
|AZIMUTH |REAL|Horizontal angle (in degrees) which the Sun shows according to the observer|
|ALTITUDE|REAL|Vertical angle (in degrees) which the Sun shows according to the observer  |
|SUNRISE |DT  |Date and time of sunrise in the given day                                  |
|SUNSET  |DT  |Date and time of sunset in the given day                                   |

===== Function =====

The Solar calculator uses equations for description of relative movement of the Sun against the Earth. The lattitude and longitude will most probably be constants: the calculation is performed for the place where the PLC is installed.\\


===== Application example =====

{{:en:mervis-ide:35-help:t40_example.png}}

The //ALARMS_ENABLED// variable is used to unblock all performance-based alarms of a photovoltaic plant. The alarms may be active only if they are enabled by a global variable  //ENABLE_ALARMS//, if the Sun is above the horizon (the output //SUNSHINE// of the block T40 is //TRUE//), and the irradiance sensor shows value higher than approximately 300 W/m2.