Ground Domain - Ground Undisturbed Temperatures

Ground Undisturbed Temperature tab on Ground Domain Dialog.

 

During the simulation EnergyPlus needs to have access to the distribution of temperatures in the "undisturbed" ground at the site. This means the temperature that would exist in the ground over the year if the building(s) were not present. EnergyPlus provides three ways to calculate these undisturbed ground temperatures:

 

 

More information on these options is provided below. Note that all of the calculation methods also require the ground thermal properties as defined by the soil material on the Soil tab.

Finite Difference

The Finite Difference method uses a 1-D finite difference heat transfer model which uses the weather file to obtain surface boundary conditions. An annual simulation is run on the ground model during it’s initialization until the annual ground temperature profile has reached steady periodic behaviour. Once steady periodic behaviour is reached, the ground temperatures are cached for retrieval during the rest of the simulation.

 

No additional data needs to be entered for this option.

 

Kusuda-Achebach

The Kusuda-Achebach method provides an undisturbed ground temperature based on the correlation developed by Kusuda T. and P. Achenbach. 1965. The correlation uses three parameters for ground temperature at the surface to define a correlation for undisturbed ground temperatures as a function of depth and time. If one thinks of the ground temperature for a given depth as a sinusoid, the average ground temperature, amplitude (average difference between maximum ground temperature and minimum ground temperature), and the phase shift (day of minimum surface temperature) are all required to define the correlation.

 

Kusuda-Achebach annual average ground surface temperature

The average ground surface temperature throughout the entire year (in °C or °F)

Kusuda-Achebach average amplitude of annual ground surface temperature

The average amplitude of the ground surface temperature (in °DeltaC or °DeltaF)

Kusuda-Achenbach phase shift of minimum surface temperature

The day of the year which has the lowest ground surface temperature (in days).

Xing

This model uses the correlation developed by Xing, 2014 to predict undisturbed ground temperature. The correlation is a 5 parameter, 2 harmonic model based on the work of Lord Kelvin (Thomson, 1862). The average soil surface temperature and two sets of surface temperature amplitude and phase shift must be provided.

 

Average soil surface temperature

The average annual surface temperature of the soil (in °C or °F).

Soil surface temperature amplitude 1

First soil surface temperature amplitude parameter (in °C or °F).

Soil surface temperature amplitude 2

Second soil surface temperature amplitude parameter (in °C or °F).

Phase shift of surface temperature amplitude 1

Phase shift of surface temperature amplitude 1, in days.

Phase shift of surface temperature amplitude 2

Phase shift of surface temperature amplitude 2, in days.