NREL's Solar Position Algorithm (SPA) calculates the solar zenith and azimuth angles in the period from the year -2000 to 6000, with uncertainties of +/- 0.0003 degrees based on the date, time, and location on Earth.
(Reference: Reda, I.; Andreas, A., Solar Position Algorithm for Solar Radiation Applications, Solar Energy. Vol. 76(5), 2004; pp. 577-589).
This packages requires Go 1.13. If you installed it and set up your GOPATH, just run:
go get -u github.com/maltegrosse/go-spa
You can find some examples in the examples directory.
Please visit https://midcdmz.nrel.gov/spa/ for additional information.
Some additional helper functions have been added to the original application logic.
| NREL spa_tester.c | SPA GO | |
|---|---|---|
| Julian Day | 2452930.312847 | 2452930.312847 |
| L | 24.01826 | 24.018262 |
| B | -0.0001011219 | -0.000101121925 |
| R | 0.996542 | 0.996542 |
| H | 11.105902 | 11.105902 |
| Delta Psi | -0.003998404 | -0.003998404303 |
| Delta Epsilon | 0.001666568 | 0.001666568177 |
| Epsilon | 23.440465 | 23.440465 |
| Zenith | 50.111622 | 50.111622 |
| Azimuth | 194.340241 | 194.340241 |
| Incidence | 25.187000 | 25.187000 |
| Sunrise | 2003-10-17 06:12:43 | 2003-10-17 06:12:43 |
| Sunset | 2003-10-17 17:20:19 | 2003-10-17 17:20:19 |
Adoption in Golang under MIT license 2020 © Malte Grosse.