The application of energy balance at the bare soil surface to predict annual soil temperature distribution

• We model the annual soil temperature distribution.
• We develop the energy balance equation at the soil surface.
• We present the individual elements of the energy balance at the soil surface formula.
• We validate the model by comparing the simulated results with the measured values.
• We receive high correlation factor between the simulated and measured values, of around 0.9 at all analyzed depths.

A complex model for the prediction of annual soil temperature distribution is presented in the study. This model is based on a transient heat conduction differential equation with the energy balance at the soil surface as a boundary condition. The boundary condition involves both shortwave and longwave radiation energy, convection and latent evaporation energy, which makes the model dependent on meteorological data such as air temperature, air relative humidity, total solar radiation on a horizontal plane, wind velocity, cloud cover and snow cover. The computer program FlexPDE, based on the finite elements numerical solutions of energy flow equations, was used for simulating the soil temperature distribution inside the domain. Next, the model was validated on the basis of the measured soil temperature distribution at depths of 5 cm, 50 cm and 100 cm. The measured and simulated values are in high agreement, as the correlation factor reaches 0.99 [-].The model is useful for the prediction of thermal performance of the building’s partitions in direct contact with soil, like that of green roofs. The model has already been used in the hybrid model for energy demand analysis of earth-sheltered buildings and may be used for buildings with green roofs.