# SOLAR PATH CALCULATOR

This calculator determines the path of the sun as it traverses the sky.

It can be used to calculate the sunlight hours in a day or year for any location. It also calculates the zenith angle, azimuth angle, and air mass of the sun at any (solar mean) time of day.

# DEFINITIONS AND MODELS

An explanation of the solar path, and definitions of the various angles, are given on the PV CDROM (www.pveducation.org).
A definition of solar mean time can be found on Wikipedia.
We note that until 18-Dec-2018, the calculator incorrectly referred to 'solar mean time' as 'sidereal time'. Thanks to Arne Raaen for correcting us.

There exist several algorithms for determining the solar path. References to the algorithms that are available on the Solar path calculator are given below. We currently recommend using the PSA algorithm [Bla01], which is accurate to within 0.5 minutes of arc for the period 1999–2015.

In this calculator, the zenith and azimuth angles are with respect to the centre of the sun neglecting refraction. Sunrise and sunset are determined to be the second at which the zenith angle is pi/2 and therefore they neglect refraction and assume that the observer is at sea level.

# REFERENCES

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[Bla01] | M Blanco–Muriel, D.C. Alarcón–Padilla, T. López–Moratalla and M. Lara–Coira, "Computing the solar vector," *Solar Energy* **70** (5), pp. 431–441, 2001. |

[Mic88] | J.J. Michalsky, "The astronomical almanac's algorithm for approximate solar position (1950–2050)," *Solar Energy*, **40** (3), pp. 227–235, 1988. |

[Mic88b] | J.J. Michalsky, Errata, *Solar Energy* **41** (1), p. 113, 1988. |

[Wal78] | R. Walraven, "Calculating the position of the Sun," *Solar Energy* **20** (5), pp. 393–397, 1978. |

[Wal79] | R. Walraven, Erratum *Solar Energy* **22**, p. 195, 1979. |

# FEEDBACK

Please email corrections, comments or suggestions to support@pvlighthouse.com.au.

# DISCLAIMER

Neither PV Lighthouse nor any person related to the compilation of this calculator make any warranty, expressed or implied, or assume any legal liability or responsibility for the accuracy, completeness or usefulness of any information disclosed or rendered by this calculator.