On the heat storage in Solar Updraft Tower collectors – Influence of soil thermal properties

• I model mathematically a solar chimney ground thermal storage system.
• I simulate a ground thermal storage system under constant boundary conditions.
• I simulate the thermal behaviour of different soil materials in ground.
• I found out that common thermal properties returned no conclusive assertion about ground thermal behaviour.
• Water bags keep the soil warm and gypsum helps to break heat peaks.

This study goes along the previous study of Bernardes and Zhou (2013), namely “On the heat storage in Solar Updraft Tower collectors – Water Bags” analysing especially the sensible heat storage physical process in a Solar Updraft Tower collector taking into account the transient heat transfer in some typical soils through conduction, convection and solar radiation. For that, the mathematical model implemented in the earlier work was adapted to investigate the influence of thermal diffusivity and effusivity for some ground thermal properties. These simulations disclosed a complex ground thermal behaviour for different soil materials revealing that materials with lower thermal effusivity and diffusivity can decrease substantially output peaks for periods with greater heat gains.