Grasshopper

algorithmic modeling for Rhino

I would like to conduct a radiation analysis using LadyBug. To do that I must input a sky matrix. To generate a sky matrix I need an .Epw weather file. I do not have a .epw file for my location but I do have the longitude/latitude location and I also have an hour by hour direct solar radiation values given in W/m^2. So I can generate a solar path and I know the direct radiation. I feel like this should be enough data to carry out a radiation analysis but I can't figure out how to do this be I am unsure how to generate a sky matrix from his data. I was thinking maybe I can create my own custom sky matrix? Or generate an .epw file (Although I have no clue on how to do either of these)?

Given the data that I have (direct solar radiation and location) how can I use the radiation analysis tool ?

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I have  created an issue for this on github: https://github.com/mostaphaRoudsari/ladybug/issues/370

Hi Mike,

That error has nothing to do with the EPW file and everything to do with how you updated the components.  If you updateAllUserObjs, you will see that the new sunpath component has an input called solarOrStandardTime_.  When you use the updateThisFile option, it only replaces code inside the sunpath component and not the inputs or outputs in the Grasshopper UI.  Hence the error.  Drag/drop a new sunpath component onto the canvas and all will work.

-Chris

Also, Mike, it looks like half of the day is missing from your sky dome component as only half the sky is showing values.  I would venture a guess that this has to do with the weather data replacement rather than a bug with geCumulativeSky.

-Chris

Chris, you are absolutely right. Dragging a new component on the canvas solved the problem.

You are also right about the data not being read in properly.

This is an image produced by the original EPW file:

The sky looks like it is being constructed properly using the original epw file.

With the "new" EPW file after data replacement, the genCumulativeSkyMtx component outputs some failures:

This list goes on all the way from January - December, so something is definitely wrong with the data replacement.

Sarith, Is there a nice way to view an .epw file? I tried opening one in excel and notepad but it looks pretty unorganized.

Thank you both for the continued help on this.

Hi Mike,

Based on the error message in your screenshot, it appears that the Ladybug is using cached values to generate the sky matrices. For the same date and times that you chose, everything seems to be working fine on my system.

Mike, You need to set useOldRes input to False so Ladybug regenerates the sky definition every time that you run the script.

Ok, thank you Mostapha.

I see. Hm. I guess I am confused because I expected the sky to look a bit more symmetric. For example..

Here is the sky produced by my original .epw file:

Looks nice!

But after changing the direct radiation values I get this for the same 24 hour analysis period:

As Chris pointed out, it seems to be missing half of the day. I double checked the direct radiation output numbers and your component is doing what it is supposed to from what I see.

Here is another view of the sky from the edited epw file:

Again, I expected a sky that more resembled the one produced by the original .epw file - just different values.

Maybe the raw data I supplied is not correctly formated - or the time step is off. The direct radiation replacement data was given by hour starting from the hour after midnight.

Any idea, Sarith?

Your radiation-data appears symmetrical with median around noon. I would suggest getting data from a proper source.

I suggest using the LB_3DChart to get a whole year picture, hour by hour, of your data. You'll see there where "weird" things are happening.

-A.

Here is the 3d Chart. The data is all correct from Jan-Dec. Does not explain the lack of symmetry of the sky that was generated. 

Is there any other data besides location, direct normal radiation and diffuse horizontal radiation that is taken into account to produce the sky? My only explanation for this asymmetry is that some other data is being calculated or considered from other data sets that exist in the original epw file.

Something looks weird to me, though your image shows only 3 months. The red color is the maximal value in the scale. Weird for me that you get the maximal values in winter months (assuming your site is in the north hemisphere).

Another weird thing is that there is no change at all on those 3 months.

-A.

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