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EnergyPlus KIVA error

asked 2021-06-24 06:59:40 -0500

Tim gravatar image

updated 2021-07-01 12:15:32 -0500

Hi - following the walkout basement example for KIVA provided with EnergyPlus I am getting the following error when I remove vertical and horizontal insulation from the Foundation:Kiva object.

 Program Version,EnergyPlus, Version 9.4.0-998c4b761e, YMD=2021.06.23 22:13,
   ** Severe  ** Kiva: A cell has been assigned to multiple surfaces.
   **  Fatal  ** Kiva: Errors discovered, program terminates.

I can circumvent the issue by using 1mm of insulation as shown below. But what if I don’t want to model insulation? When I remove the ground coupled basement walls and just set their boundary condition to “ground” the error goes away but I suppose Kiva will work with incorrect section profiles as it does not know about the walls anymore.

Foundation:Kiva,
    KIVA_Zone_0,             !- Name
    ,                        !- Initial Indoor Air Temperature {C}
    Basement Insulation,     !- Interior Horizontal Insulation Material Name
    ,                        !- Interior Horizontal Insulation Depth {m}
    0.001,                   !- Interior Horizontal Insulation Width {m}
    ,                        !- Interior Vertical Insulation Material Name
    ,                        !- Interior Vertical Insulation Depth {m}
    ,                        !- Exterior Horizontal Insulation Material Name
    ,                        !- Exterior Horizontal Insulation Depth {m}
    ,                        !- Exterior Horizontal Insulation Width {m}
    Basement Insulation,     !- Exterior Vertical Insulation Material Name
    0.001,                     !- Exterior Vertical Insulation Depth {m}
    0.001,                     !- Wall Height Above Grade {m}
    0.001;                     !- Wall Depth Below Slab {m}

And what is the best way to troubleshoot the above error. Is there a way to export the FE slices/profiles and take a look at them?

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@Tim this is a very rare error that could indicate a defect in the source code. I will try to reproduce the error and see if I can't figure out what's going on. By the way, if you remove the walls and set their boundary condition to "Ground" you are basically just modeling a slab foundation (and no longer a basement) in Kiva.

Neal Kruis gravatar image Neal Kruis  ( 2021-06-24 09:28:00 -0500 )edit

@Tim did you make any change to the default settings in the Foundation:Kiva:Settings object?

shorowit gravatar image shorowit  ( 2021-06-24 10:41:53 -0500 )edit

I tried without (then KIVA should use defaults) and I tried with the provided settings from the example.

Tim gravatar image Tim  ( 2021-06-24 10:47:40 -0500 )edit

1 Answer

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answered 2021-06-24 10:29:17 -0500

updated 2021-06-30 10:27:33 -0500

Update 2

There is a bug where the automatic deep ground depth for shallow water tables isn't getting set to 1m below the bottom of the foundation like it should. You can get around this in your file by explicitly defining the deep ground depth in Foundation:Kiva:Settings:

Foundation:Kiva:Settings,
  ,                        !- Soil Conductivity {W/m-K}
  ,                        !- Soil Density {kg/m3}
  ,                        !- Soil Specific Heat {J/kg-K}
  ,                        !- Ground Solar Absorptivity {dimensionless}
  ,                        !- Ground Thermal Absorptivity {dimensionless}
  ,                        !- Ground Surface Roughness {m}
  ,                        !- Far-Field Width {m}
  GroundWater,             !- Deep-Ground Boundary Condition
  14;                      !- Deep-Ground Depth {m}

We will work on a fix for this in the next release of EnergyPlus.

Note: The water table depth can have a large impact on foundation heat transfer. Boston's airport is all of 20 feet above sea level, but your actual building's location may be further from the water table. You may want to adjust your assumptions accordingly.

Update (unrelated bug)

When I run your file through the debugger I get a memory access error related to the daylighting controls. This error won't appear in the release version of EnergyPlus. If I remove your daylight control object everything runs through fine (daylighting controls don't do much without windows in your model anyway 😉).

My best guess is that the memory that is actually being accessed (and written to) is overriding a value used in the Kiva setup and preventing it from generating surface assignments properly. Crazy, right!? (Turns out this isn't the case.) We will work on a fix for this in the next release.

By the way, I'm curious why you are splitting the floor into two surfaces? The way you have it set up, you should modify the SurfaceProperty:ExposedFoundationPerimeter objects to exclude the perimeter of each floor surface where they meet, otherwise the simulation will treat each surface as though the ground on the other side is the exterior grade (and overestimate the heat losses through the ground). You can also resolve this by defining a single floor surface with an exposed perimeter fraction of 1.0.

Previous answer:

I am unable to reproduce the problem you are describing in the walkout basement example. How are you removing the insulation from the Foundation:Kiva object?

This is what I used (notice the prior field values that are commented out):

Foundation:Kiva,
  Basement Foundation,     !- Name
  ,                        !- Initial Indoor Air Temperature {C}
  , !Basement Insulation,  !- Interior Horizontal Insulation Material Name
  ,                        !- Interior Horizontal Insulation Depth {m}
  , !1,                    !- Interior Horizontal Insulation Width {m}
  ,                        !- Interior Vertical Insulation Material Name
  ,                        !- Interior Vertical Insulation Depth {m}
  ,                        !- Exterior Horizontal Insulation Material Name
  ,                        !- Exterior Horizontal Insulation Depth {m}
  ,                        !- Exterior Horizontal Insulation Width {m}
  , !Basement Insulation,  !- Exterior Vertical Insulation Material Name
  , !2.9,                  !- Exterior Vertical Insulation Depth {m}
  0.2,                     !- Wall Height Above Grade {m}
  0.3,                     !- Wall Depth Below Slab {m}
  ;                        !- Footing Wall Construction Name

Even if this works for you, can you send the file that you used to produce the original error? That error really should never appear for a user, and ... (more)

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Comments

Thanks for your reply, Neal. Maybe I am missing something in my setup. I am attaching my IDF file here: https://www.dropbox.com/s/kals8xwrnmu...

Tim gravatar image Tim  ( 2021-06-24 10:46:15 -0500 )edit

just leaving the Wall Height Above Grade and Wall Depth Below Slab in the Foundation:KIVA object does not work for me. Gives me the same error.

Tim gravatar image Tim  ( 2021-06-24 10:56:32 -0500 )edit

@Tim I updated my answer after looking into your file. Turns out it isn't a problem with your Kiva set up at all...

Neal Kruis gravatar image Neal Kruis  ( 2021-06-24 11:47:59 -0500 )edit

@neal-kruis thanks that's an interesting find. The model I sent was just a stripped-down example. Does this memory leak still happen when there are DL controls with windows?

The split slab was just added for testing. No particular reason.

Tim gravatar image Tim  ( 2021-06-24 12:13:46 -0500 )edit

I believe you could also resolve the issue by adding a window to the zone (but I haven't tested this). The actual problem is that many of the daylighting arrays are not allocated unless there is a window in the zone.

Neal Kruis gravatar image Neal Kruis  ( 2021-06-24 12:18:32 -0500 )edit

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Asked: 2021-06-24 06:59:40 -0500

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Last updated: Jun 30