Ground temperature is constant

[kamilakrych]

Currently, the building archetypes don't include an object specifying ground temperatures. As a result, a default value of 18 degrees is used by EnergyPlus throughout the year. This should be fixed at some point because it can influence energy demand of the buildings (to what extent?). If I have enough time during my summer internship, I can try to fix it, but at this point other issues have more priority I think.

[kamilakrych]

I've had a look at this issue (finally!). The error we get looks like this:

** Warning ** GetHTSurfaceData: Surfaces with interface to Ground found but no "Ground Temperatures" were input.
   **   ~~~   ** Found first in surface=EXTFLOOR_UNIT1
   **   ~~~   ** Defaults, constant throughout the year of (18.0) will be used.

I've managed to solve this issue. It was caused by the fact that GroundHeatTransfer objects were not really actively used because GroundHeatTransfer:Control fields were telling EP not to run preprocessing simulations of ground heat transfer. This preprocessing is required, so we need to set this field to 'Yes'.

Additionally, I needed to do a few more things:

1. The idf file had both GroundHeatTransfer:Slab and GroundHeatTransfer:Basement objects. It doesn't make sense to keep both of them, as only one type of building-ground interface can be used at a time. I kept the "slab" objects, deleted the others. "Slab" solution is simpler, takes less time to simulate - an idf file that normally takes 75 seconds to simulate, takes 86 s with slab, and as much as 515 s with basement.
2. BuildME code did not include the possibility of "Slab" preprocessing, only "Basement" preprocessing. I needed to edit the code a bit, particularly files 'settings.py' and 'energy.py'.
3. BuildingSurface:Detailed also needs to be updated. Outside boundary conditions of the external floor need to be changed from 'Ground' to 'GroundSlabPreprocessorAverage'.

The influence of these changes on energy need of the buildings can be seen below, on the example of a single family house, with window opening routine implemented using Fanger thermal comfort model. BEFORE: fixed ground temperature (default of 18 degC) AFTER: preprocessing simulation enables to use real ground temperature values

As can be seen, the differences were not so big, with at most 5 kWh/m2/year of change.

[nheeren]

This is fixed, right?

[kamilakrych]

Yes, it is!

[nheeren]

Thanks!