Prediction of undisturbed ground temperature using analytical and numerical modeling. Part II: Methodology for developing a world-wide dataset

Abstract

Analyses of building heating and cooling load calculations and design of ground heat exchangers often require the undisturbed ground temperatures as inputs. In a companion article (Xing and Spitler 2017), a two-harmonic analytical model which is used for the estimations of undisturbed ground temperatures for engineering applications has been developed. This model relies on a second-order harmonic relationship and five weather-related constants—annual average ground temperature, two temperature amplitudes, and two phase lags to predict the ground temperatures. These parameters are estimated using temperature results calculated from the numerical method developed by Xing and Spitler (2017). The two-harmonic model is validated using measured ground temperature data at 19 sites in the United States; these sites are located in three different climates—arid climates, warm climates, and snow climates. The model is convenient and provides with good accuracy. It relies on inputs such as soil diffusivity, vegetation density, and snow depth to estimate the ground temperatures; these inputs vary from site to site or vary with time. In order to generate typical year ground temperatures for thousands of sites over a worldwide range, the method described in Xing and Spitler (2017) needs some automated procedures to estimate these inputs for each site. These procedures are developed and described in this article. The two-harmonic model estimated typical year ground temperatures was compared to the experimental results at the 19 sites in the United States to validate the automated procedures. The validated procedures and model are applied for estimating typical year ground temperatures over a worldwide range for engineering application (Xing et al. 2017).

Notes

1 SCAN provides a significant amount of data (191 at six standard depths: 5, 10, 20, 50, 100, and 200 cm for, roughly, the last 15 years). The SCAN data provides detailed information on soil properties, weather conditions and undisturbed ground temperatures inside the United States.