Window Shade Benefit crashes (Solution exception:Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index)

grasshopper honeybee-legacy
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This is a continuation of this topic.

I am trying to use the Window Shade Generator component in order to create test shade areas for shade benefit evaluation after an energy simulation. However the component does not keep the data tree paths of heating, cooling, but it does for window beam energy.

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What can be the issue? Or this component works only with Ideal Loads?

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Okay yes I tested with simplier geometry than my project. It does not work with HVAC #11

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But it does work with Ideal Loads.
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However, even after running Ideal Loads, it does keeps data trees, but the next component “EnergyShadeBenefit” is crashing even before running it…

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  1. Solution exception:Index was out of range. Must be non-negative and less than the size of the collection.
    Parameter name: index

I am stack at this point and dont know how to fix that.
Does anyone knows why am I having this issue?

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OKAY,
the problem occurs if there are unconditioned zones in the OS simulation!!!

So I believe it is impossible to use this component to see shading benefit from an existing OS simulation. Thereby I had to make a “theoretical” model of my building, where all the spaces are conditioned.

The accuracy of this analysis is a little bit vaguely for me…

I understand that this component is just for visualization and shpe-finding of adequate overhangs (and it is extremely cool!), but calculating energy saving out of those shaders is very questionable on a real project.
I believe it is only useful on early stage design. (If not, how can I subtract saved LOAD from POWER energy?)
So in order to calculate the real savings, I still need to run OS simulation with full exterior/interior reflections?

Eh, life is never easy :C

P.S. I think it is useful to mention under the hydrashare file that this research works only with Ideal Loads and conditioned spaces, so people don’t spend 2 day figuring it out like me :smiley:

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@mrbro ,
Sorry for the late response here but it seems that you were mostly able to figure it out through trial and error.

To comment briefly on why the workflow does not work for systems with full HVAC systems, when you model a full HVAC, you really only have heating/cooling data for the HVAC components and not necessarily on a zone-by-zone basis as you do with ideal air loads. You need zone-level results for this analysis because the component is looking at the solar energy contributed by each window to each zone to determine the value of shade. So, with a fully-detailed HVAC system, you can’t easily account for the fact that one zone might need heating and not desire shade while another simultaneously is in cooling mode and therefore desires shade.

Hopefully this also clarifies the reason why the unconditioned zones break the workflow since these zones do not have heating or cooling to help them evaluate the shade. Instead of creating a “theoretical” model, though, I’d recommend only connecting up zones that are conditioned to the Shade generator component and I believe this will give you a workflow that runs. You can use the “Separate Conditioned Unconditioned” component to help you with this.

And, lastly, you are right that all analyses like this rely on abstractions that result in limitations. If you are curios about the specific method that this component uses and it’s limitations, the method is basically the same that is described in this paper by Sarget et al:
http://www.ibpsa.org/proceedings/BS2011/P_1209.pdf

To briefly list the limitations right now, I’ll say first that the estimated load savings are actually just approximations of the load that will actually be saved because:

  1. The analysis is only looking at solar radiation contributed by direct beam and not diffuse sky contribution.
  2. The instantaneous solar load at each hour is being compared to the instantaneous heating/cooling load and real thermal simulations have thermal lag that depends on the mass of the space.

Also, you point out that the load savings can’t be directly compared to the electricity and fuel used by the HVAC. While you can try to come up with rough approximations around this by multiplying the loads by the COP or boiler efficiency, the truth is that the tool really isn’t built to give exact predictions of saved energy. Rather, it’s meant to simply help you discern which shade geometry is better than another. To find out the actual energy savings, you are best off turning your shade into a HBContext surface and re-running it through the energy simulation.

And, good point about the hydra example description. I just add a note about the restrictions on systems and unconditioned ones shortly.

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I added the guidance into the example file description:

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Thank you Chris for such an elaborated respond!
After a while of working with this component, and “color HB zones” I realized that what you just described.
But it is still a great tool for an early-design stage, I bet!