Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
To give credit where credit is due, the simple algorithm used in the EnergyPlus WeatherConverter program was lifted by yours truly from a 12-line GTEMP routine in DOE-2 and provided to the EnergyPlus Development Team, back in 2001 when I was still part of the Team. The GTEMP routine was coded up in the early 1980's utilizing the equation in the Kusuda report that gives the ground temperature as a simple sine curve with a lag and amplitude depending on the depth below ground and the soil diffusivity. Both of these parameters - 5 ft, 1.0 diffusivity for moist soil (IP units) - were held fixed in the DOE-2 as well as EnergyPlus implementations. At the time I supplied this algorithm to the EnergyPlus Team, I had suggested that they just use the equation rather than the calculated monthly values, because I didn't like the staircase appearance of the monthly values. I'm not sure if that's also true for EnergyPlus, or whether somebody added an interpolation to the routine at some point. It's always been known that these ground temperatures are very approximate. If there's a high water table or a geothermal hot spot , the temperatures could be off a lot. Also, these temperatures are meant for undisturbed soil away from any building. In truth, any construction above grade will change the ground tempreature below.
| | 2 | No.2 Revision |
To give credit where credit is due, the simple algorithm used in the EnergyPlus WeatherConverter program was lifted by yours truly from a 12-line GTEMP routine in DOE-2 and provided to the EnergyPlus Development Team, back in 2001 when I was still part of the Team. The GTEMP routine was coded up in the early 1980's utilizing the equation in the Kusuda report that gives the ground temperature as a simple sine curve with a lag and amplitude depending on the depth below ground and the soil diffusivity. Both of these parameters - 5 ft, ft down, 1.0 diffusivity for moist soil (IP units) - were held fixed in the DOE-2 as well as EnergyPlus implementations.
At the time I supplied this algorithm to the EnergyPlus Team, I had suggested that they just use the equation rather than the calculated monthly values, because I didn't like the staircase appearance of the monthly values. temperature and thus heat flows through the foundation in DOE-2. I'm not sure if that's also true for EnergyPlus, or whether somebody added an interpolation to the routine at some point.
point.
It's always been known that these ground temperatures are very approximate. If there's a high water table or a geothermal hot spot , spot, the temperatures could be off a lot. Also, these temperatures are meant for undisturbed soil away from any building. In truth, any construction above grade will change the ground tempreature temperature below.
| | 3 | No.3 Revision |
To give credit where credit is due, the simple algorithm used in the EnergyPlus WeatherConverter program was lifted by yours truly from a 12-line GTEMP routine in DOE-2 and provided to the EnergyPlus Development Team, back in 2001 when I was still part of the Team. The GTEMP routine was coded up in the early 1980's utilizing the equation in the Kusuda report that gives the ground temperature as a simple sine curve with a lag and amplitude depending on the depth below ground and the soil diffusivity. Both of these parameters - 5 ft down, 1.0 diffusivity for moist soil (IP units) - were held fixed in the DOE-2 as well as EnergyPlus implementations. implementation, but in the EnergyPlus implementation ground temperatures are given at three different depths.
At the time I supplied this algorithm to the EnergyPlus Team, I had suggested that they just use the equation rather than the calculated monthly values, because I didn't like the staircase appearance of the monthly temperature and thus heat flows through the foundation in DOE-2. I'm not sure if that's also true for EnergyPlus, or whether somebody added an interpolation to the routine at some point.
It's always been known that these ground temperatures are very approximate. If there's a high water table or a geothermal hot spot, the temperatures could be off a lot. Also, these temperatures are meant for undisturbed soil away from any building. In truth, any construction above grade will change the ground temperature below.
