Cella Dome vs Sky Dome vs Radiation Rose

Hello all,

Using the ladybug components and the saw epw file, why do I get very different kWh/m2 results.

The Cella Dome gives me radiation values that are similar to when I run radiation analysis on my geometry. The skydome show skypatch raditions only up to 26 kWh/m2.

The radiation rose also shows very different values.

Any insight would be helpful! Thanks.

Hi @aorukaya, They are not the same and so they should show different values.

  1. Sky dome shows the amount for each sky patch. This is the source for the radiation not the radiation on your model.
  2. Radiation rose shows the amount of the radiation on a surface (by default vertical) from different orientations.
  3. Calla dome shows the incoming radiation from different orientations and for surfaces with different angles all together in a single graph. It’s like a 3d-representation of radiation rose.

Hi @mostapha, thanks for the clarification.

The radiation rose takes into account of the context geometry but the cella dome doesn’t? And when you say “surfaces from different angles” this is the surface on the dome (similar to sky patch?) or the surface on the tested geometry?

@mostapha wrote “surfaces WITH different angles” and not “surfaces FROM different angles”. Little difference but meaningful.
So, it is the radiation that falls on “all” surfaces orientations. Check the Calla map in 3d and i’m sure you’ll understand the meaning.

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What @AbrahamYezioro said. Maybe it will be helpful to review what question each diagram is trying to answer.

Radiation rose is useful when you want to know how much radiation you get on a surface with a fixed tilt from different orientations. For instance before you start the design you want to know what is the difference if a wall is facing east vs south. Then you can use the radiation rose to get a sense. It’s similar to what wind-rose is for wind direction and intensity.

Radiation calla dome, on the other hand, is designed to be used when you want to know how much radiation you get on surface with different tilts and from different orientations. It’s useful when you want to figure out what is the best tilt and orientation for PV panels in a location.

We can implement the context input to Radiation calla dome as well. It has just never came up otherwise there is no technical limitations to add a similar input to call dome.


@mostapha If the Sky dome shows the amount of radiation for each sky patch, and the radiation rose it the amount falling on a surface, is there a correlation between the two?

  • If there is a correlation, what is it?
  • If there isn’t a correlation, why not?
  • Does the radiation rose take into account cloud cover?