SunPath and sunlight hours - true equinox


#1

Hello,

I use mentioned two components a lot. For legislative reasons in my country, sunlight hours is extremely important for buildings - it is measured in equinox (march and september).

For caluculating sunVectors (needed for sunlight hours analysis) component takes location into account (and - I am not sure about that - a fact that earth is in fact elyptical in section). I guess that due to that sun center point on 7 o’clock and 17 o’clock is not on the same height and 12 o’clock is not exactly in the middle of sun path (as it would happen in “true equinox” - 6 and 18 are on the ground level and are endpoints of an arc).

I know that “true equinox” may never happen in given location and that it is only theoretical, but it is needed for calculations and documentation in my country.

I know that i can generate Vectors for true equinox on my own and use it for SunlightHours but I was wondering if this could be done somehow with existant component of LB (to have all the other outputs like sun altitudes and azimuths) - as I am not familiar with coding I’d appreciate your help on that matter.

Thanks for your time and help


#2

I should say that I’m not sure if I fully understand the question but in case it helps you don’t have to use Ladybug’s sun-path for calculating the sun vectors. If you already have a list of sun vectors based on code then just type them in and use them for the study.

Also you can use construct location :constructlocation: component to create the exact location if the location from epw file doesn’t match what you need.


#3

@Wujo ,

It sounds like you have confused the notion of equinox, which has to do with the position of Earth within it’s orbit around the sun, with solar time, which has to do with the position of the sun in the sky over the course of the day (aka. the Earth’s rotation). To phrase it another way, it seems like you just want the sunpath to reflect solar sunrise and solar sunset, which occur at 6AM and 6PM solar time respectively on the equinox (and this happens everywhere on Earth except perhaps right at the poles). To get the sunpath to work this way, just set solarOrStandardTime_ to True on the component.

And, just for clarification, the fact that noon on the sun path does not usually align with the highest sun altitude of the day is because we have time zones. So, by saying that a large swath of land is all going to have the same “standard” time, we create a situation where each city along that swath of land will experience the highest sun altitude at a different time (depending how far east or west the city is within the time zone).


#4

@mostapha @chris thank you for your responses. Especially to latter, your post clarified a lot for me. Also the boolean on solarOrStandardTime does exactly what i needed :slight_smile: