Asal Bidarmaghz

Carrier fluid temperature data in vertical ground heat exchangers with a varying pipe separation

The dataset in this article is related to shallow geothermal energy systems, which efficiently provide renewable heating and cooling to buildings, and specifically to the performance of the vertical ground heat exchangers (GHE) embedded in the ground. GHEs incorporate pipes with a circulating (carrier) fluid, exchanging heat between the ground and the building. The data show the average and inlet temperatures of the carrier fluid circulating in the pipes embedded in the GHEs (which directly relate to the performance of these systems). These temperatures were generated using detailed finite element modelling and comprise part of the daily output of various one-year simulations, accounting for numerous design parameters (including different pipe geometries) and ground conditions. An expanded explanation of the data as well as comprehensive analyses on how they were used can be found in the article titled “Ground-source heat pump systems: the effect of variable pipe separation in ground heat exchangers” (Makasis N, Narsilio GA, Bidarmaghz A, Johnston IW, 2018) [1].

The Application of Retaining Walls and Slabs as Energy Structures in Underground Train Stations

Shallow geothermal technologies have proven to efficiently provide renewable energy for heating and cooling. Recently much attention has been given to utilising sub-surface structures, primarily designed for stability, to also transfer heat to and from the ground, converting them into energy geo-structures. This work investigates the potential of applying this technology to the geo-structures of underground train stations in the city of Melbourne (Australia) to fulfil some of their heating and cooling demands. The diaphragm retaining walls and slabs that form part of a case study station are designed to also incorporate geothermal pipe loops. A finite element numerical model comprising the station walls and slabs is presented and used to investigate the thermal performance of these systems, for the temperate climate and geological conditions of Melbourne, adopting an expected lifespan of at least 25 years. The technical applicability of this technology is discussed for different thermal load scenarios, showing the importance of thermal storage and the balanced distribution of the thermal load.

Impact of the Seasonal Variations in Ground Temperature on Thermal Response Test Results

© ASCE. Due to the prevalent use of the thermal response test (TRT) for estimating the key design parameters of ground source heat pump systems, it is important to understand how external factors may impact on their accuracy. The infinite line source model (ILSM) is typically used to interpret TRT data, relying on many simplifying assumptions, which when violated may lead to errors in the results. Seasonal variation causes the ground temperature profile to vary significantly at the surface, with decreasing effect at increasing depth, while the ILSM assumes this profile is constant. A numerical study of ILSM performance under different seasonal conditions using a state-of-the-art FE model is presented. The study aims to determine if TRT interpretation may become misleading when tests are conducted at different times of the year. Results suggest there is little variability in effective thermal conductivity, but up to ~50% in GHE thermal resistance, and as much as ~9°C in mean fluid temperature.