I just noticed that you said you've used the Slab program, but the results weren't believable. Slab is a simple 2-D conduction program. You should check your inputs again, it sounds like you're not inputting the right deep ground temperature or building indoor air temperature. I can't see how one can get a ground temperature of 17 C if all
the driving temperatures are way above that.
Joe Huang White Box Technologies, Inc. 346 Rheem Blvd., Suite 108D Moraga CA 94556 yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx www.whiteboxtechnologies.com (o) (925)388-0265 (c) (510)928-2683 "building energy simulations at your fingertips"
On 1/18/2013 6:59 PM, Joe Huang wrote:
I hope you've also noticed that there's a time lag of about 90 days, i.e., minimum soil temperature occurs about 3 months after minimum air temperature.
The appropriate depth depends on what type of foundation the building has. Most large commercial buildings all have an underground space or basement, for which you should use the soil temperature at 2 m. Another problem is that buildings have a big effect on the soil temperature, heating it in the winter and cooling it during the summer. There's a
Slab program that allows you to calculate better soil temperatures accounting for the effects of the building itself.
Joe
Joe Huang White Box Technologies, Inc. 346 Rheem Blvd., Suite 108D Moraga CA 94556 yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx www.whiteboxtechnologies.com (o) (925)388-0265 (c) (510)928-2683 "building energy simulations at your fingertips"
On 1/18/2013 5:49 PM, academicryan wrote:Update: *EnergyPlus developer please respond*
OK I now know how to calculate soil temperature as a function of depth from Hillel, 1982.
Essentially his equation says that at 0 m depth, monthly average soil temperature is the monthly average air temperature plus 1°C. This is basically a sine wave. With increasing depth, the soil temperature gets closer to the annual mean air temperature plus 1°C.
NEW QUESTION: Is this what 'Site:GroundTemperature:BuildingSurface' wants? i.e. 0 m depth soil temperature. Or some other depth? Or some other 'ground temperature' altogether?
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "academicryan" wrote:
>
> Can somebody please help me do a very simple task.
>
> Calculate/find the monthly ground temperature for Singapore. To clarify, this is the input for the 'Site:GroundTemperature:BuildingSurface'.
>
> ------
>
> Extra info - I've already tried the Slab utility, it comes up with very unbelievable results. Calculating some months below 17°C when Singapore air temperatures never drops below 21°C.
>
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