Direct Sun only calculation

Hi @Bing ,

It’s a little more complicated than what you describe. The direct sun doesn’t really come “free” with annual daylight since it can greatly increase the simulation time when running thousands of sensors. I don’t want to get into all of the details of exactly why this is the case but it’s related to us being unable to use binary formats for the illuminance matrices when the direct illuminance is output.

Also, we really don’t want people using this type of direct illuminance out of annual-daylight for computing ASE since it’s not coordinated with the LM standard used by LEED. We will be adding a dedicated recipe for ASE soon that will be capable of outputting blind/shade control schedules that can be applied to the Annual Daylight results to get LM-compliant sDA and ASE. So, if what you actually need is ASE, then using this dedicated ASE recipe is going to be my ultimate recommendation for your case. Using Annual Irradiance with visible_ right now is just to give you a temporary workaround.

Also, please don’t use -ab 0 for annual-daylight right now as it can result in negative illuminance values (given how the illuminance matrices have to be added/subtracted from one another). I still have yet to add a check that prevents the use of -ab 0 for annual-daylight.

Totally understand your concern on ASE. Saw discussion on other posts. No this is all good to me.

And thanks for the tips of ab0 calc. I recall I saw it before now as you mentioned it.

Looking forward to the LM-compliant sDA and ASE. We are doing manual post-processing for now and happy to have a tool for that of course.

Thanks Chris.

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hi @chris , i am using the HB Direct Sun Hours for investigating the only direct beams. as you can see i set a panel (for checking) with one testpoint towards under the panel. i am wondering why the result is 14 (hours); should not it be zero? i am sure the sun can not meet under the panel.

is there anyone knows this problem?

Hi @Aliarch,

Can you upload an example that produces this result and let me know which EPW you are using?

thanks @mikkel (46.6 KB)

@mikkel Hi
i have uploaded the file and could you check it please?


looking at it quickly it seems that
Direct Sun Hours does not use ray tracing from radiance so it only calculates the hours with direct sun.
The direction of your surface only serves to point where to offset the test points.
if you offset 30 cm below your panel, it makes sense that sun reaches there.

according the description of component " HB Direct Sun Hours

Calculate the number of hours of direct sun received by grids of sensors in a Honeybee model. _ The fundamental calculation of this recipe is the same as that of the “LB Direct Sun Hours” component except that this recipe uses Radiance, which allows the simulation to scale better for large numbers of sensors. -"
i think it must analysis only direct rays and also i try with 5 cm distance under a big panel but 11 hours was appeared and i think it does no longer make sense. maybe it calculates some reflections or there is a bug

(by LB Direct Sun Hours shows zero hour)

Checked your file and i believe it makes sense you get what you get.
You are analyzing a whole year. I think those lower sun hours (late afternoon) are hitting the point.
I suggest checking the LB_ViewFromSun component to better understand when it is happenning.