Implement a method to specify monthly ground temperature schedule

[manuvarkey]

Enhancement Request

Implement a method to specify monthly ground temperature schedule.

Detailed Description

Currently there seems to be no way in the GUI to specify a ground temperature schedule. As per information available online, this requires the use of a measure. Since in warm climates the default 18 degC ground temperature value (is it the case ?) is causing considerable errors in zone heat load, a feature to specify this (at least a constant value through out the year) is essential.

Possible Implementation

1. Somewhere under Thermal Zones

[macumber]

I would add this on the Site tab rather than Thermal Zones.

Which ground temperature objects are you thinking about exposing?

The SiteGroundTemperatureShallow and SiteGroundTemperatureDeep objects say:

       \memo These temperatures are specifically for the Surface Ground Heat Exchanger and
       \memo should probably be close to the average outdoor air temperature for the location.
       \memo They are not used in other models.

These seem more generally useful:

• SiteGroundTemperatureFCfactorMethod
• SiteGroundTemperatureBuildingSurface
• SiteGroundTemperatureUndisturbedXing
• SiteGroundTemperatureUndisturbedKusudaAchenbach

If we wanted to wrap them all it would probably be best on a new Ground sub tab of the Site tab. That could also include:

• SiteGroundReflectance
• SiteWaterMainsTemperature

[manuvarkey]

Ground sub tab under Site tab seems to be a good place to keep these.

Which object should be set as default ? For estimating building losses SiteGroundTemperatureBuildingSurface seems to be the one suitable as the default option (?). The EnergyPlus documentation recommends against using undisturbed ground temperatures from weatherfile for calculating building losses, but recommends instead to run Slab/ Basement programs for calculating monthly average ground temperatures. I am not sure how this can be achieved. At least exposing the option to set monthly ground temperatures and setting a sane default for this would be a good starting point.

Also an option to define a SurfaceProperty:OtherSideCoefficients against a surface for setting a custom temperature schedule or other coefficients would be a nice to have. Currently there is an option in dropdown against a surface to select this. But nothing seems to happen on selection.

[jmarrec]

I realized it'd be nice if OS SDK could help you fill that out from the EpwFile object, so I filed https://github.com/NREL/OpenStudio/issues/5272

[iansabourin-somers]

Hello @manuvarkey & @macumber,

I hope you won't mind me pitching in ! I agree that this would be very useful indeed to have a more forward use in the GUI.

EnergyPlus has integrated Kiva which is used to calculate heat loss through the building foundations.

At the moment, when using OpenStudio, our team overcomes this issue (constant ground temperature, way too high for Nordic countries) with BLC's Whole Building Measure named "Set Ground temperature monthly" (I haven't tested it yet in the newest 1.8 version though).

We are using Kiva to approximate the ground temperature which is then entered in the model through the measure. The measure modifies Site:GroundTemperature:BuildingSurface, which is called when the "Ground" outdoor boundary condition is used. It's not perfect, but it's definitely better than leaving this constant 18°C temperature [Site:GroundTemperature:BuildingSurface default values] ! We did many simulations using this Kiva approach and the measure always leads to good (maybe I should say 'better') approximations.

We have yet to try out the other methods you mentionned @macumber, but the "Shallow" and "Deep" are only useful for heat exchangers (geothermal energy, etc.) as I understood it.

It also seems that you can use the SketchUp Ruby Command to write a script : https://unmethours.com/question/40542/setting-ground-temperature-in-os/

Here is the most important documentation :

Kiva

• https://kiva.readthedocs.io/en/stable/
• https://bigladdersoftware.com/epx/docs/8-7/engineering-reference/ground-heat-transfer-calculations-using-kiva.html
• https://bigladdersoftware.com/epx/docs/8-8/input-output-reference/group-advanced-surface-concepts.html#foundationkiva

Default temperature Energyplus

• https://energyplus.readthedocs.io/en/latest/schema.html#site-groundtemperature-buildingsurface

Varia

• https://bigladdersoftware.com/epx/docs/8-2/auxiliary-programs/ground-heat-transfer-in-energyplus.html
• https://bigladdersoftware.com/epx/docs/9-3/auxiliary-programs/use-of-the-ground-temperatures-with-slabs.html

Tell me if I can help !

Cheers,

Ian