Local standard time and Apparent solar time

andfranz · Posts: 81

Hello.
I’m considering the data of Cordova, Alaska, USA.
The origin of the data is the database ASHRAE/TMY3
In the “Users Manual for TMY3 Data Sets” http://www.nrel.gov/docs/fy08osti/43156.pdf
I found that the Time of data record is the local standard time (according to the local law).
Cordova is in the time zone GMT -9:00 and its longitude is -145,5°
The central meridian of the time zone GMT -9:00 is -9*15° = -135°
Therefore there is a difference between the longitude of Cordova and the latitude of its central meridian of 10.5°. I would expect a difference of apparent solar time of 10,5/360*24h = 0.7h. I would expect that if the Local standard time is 12 (noon) then the azimuth is close to 180° at the central meridian and that it isn’t in Cordova. In Cordova the azimuth should be close to 180° more or less at 12.7, i.e. fast at 13 (1 p.m.). Instead, as you can see in the following picture, in Cordova the azimuth is practically 180° at 12. Did you correct the data considering the difference between Local standard time and Apparent solar time (the data of the database were measured according to the Local standard time, but the sun azimut in DesignBuilder seems to be according to Apparent solar time)?

With Regards

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