Parallel Session B-4: Energy and energy product storage - Chair: Martin Bloemendal

The sustainability and long term safety of energy geostructures can be assessed only if a thorough understanding of the coupled thermo hydromechanical phenomena occurring in the soil is reached. Several laboratory testing methods are available to determine unsaturated hydraulic properties. In this study, Wind's method was used and compared to a faster alternate method using nuclear magnetic resonance imaging (MRI). These experimental developments allow the non intrusive and continuous quantification of water movement in unsaturated soils during the application of coupled thermo hydraulic solicitations. The understanding of these fundamental parameters is a step for studying thermo hydromechanical behavior of compacted.

The extended abstract discusses the potential of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) systems in storing thermal energy and bridging the supply-demand gap for renewable heat sources. A case study of an Expanded Diameter Gravel Well (EDGW) being used to reduce costs and increase capacity is presented. However, a knowledge gap exists on the stability of enlarged diameter boreholes in unconsolidated formations, and the study aims to investigate this through analytical and numerical simulations. The results will be critical for designing the EDGW field test for the HT-ATES system in Delft.

This work presents extended numerical simulations using an advanced constitutive model for the long-term stability of a deep gravity energy storage system (GES). Cumulative effects in sand due to a lifetime of about 100 years can be simulated using the HCA model. Throughout this period, changes in soil properties occur in both dry and saturated soil. However, there are no stability problems. Both the energy storage capacity and the energy efficiency are promising, suggesting that the presented gravity energy storage system has the potential to contribute to the energy transition.

Geothermal energy piles (GEPs) are foundation elements that allow heat rejection or extraction via fluid circulation through the loops. In winter, low-grade heat is extracted from the ground (source) and transferred to the building (sink) to achieve space heating. Conversely, heat is removed from the building in summer and rejected into the ground to achieve space cooling. It was found that the addition of phase change materials significantly improves the performance of GEPs, resulting in lower temperature developed in the surrounding soil and pile.

* the possibility of heat storage in backfill structures was investigated from a geotechnical point of view; * The thermo-hydro-mechanical properties of the compacted soil, typically used for building embankments, were investigated through laboratory testing. * coupled short and long term TH behaviours of a storage embankment were modelled with the finite element Code_Bright.