Search Results (2)

The high initial cost of ground heat exchanger (GHE) systems, particularly in applications with significant annual building thermal load imbalances, remains a major barrier to their adoption. In traditional rectangular grid patterns of boreholes, thermal saturation in cooling-dominated buildings mainly affects the central zone, rendering central boreholes less effective. This study investigates an innovative approach to enhance the thermal performance of vertical GHEs by removing these central boreholes using the pygfunction Python package. The central borehole removal design (CBRD) was implemented across various building thermal loads and ground conditions, resulting in reduced borehole interaction and a substantial decrease in total GHE length. Specifically, the CBRD approach achieved up to 51% savings in total GHE length compared to traditional rectangular grid patterns, significantly lowering the initial cost without additional expenses. Although energy consumption savings over a 30-year period were modest (up to 2.2%), the initial cost savings were substantial. Further optimizations indicated that additional reductions in borehole length could be achieved by removing boreholes beyond the central ones, while still maintaining the maximum entering fluid temperature (EFT). Yet, additional optimizations are needed as achieving optimal configurations requires detailed information on factors such as available land area and drilling depth limits, which are site-specific. Full article

For decades, bad practices in municipal and industrial waste management have had negative environmental impacts, generating high health risks for people and the environment. The use of badly designed, not engineered, and not well-operated landfills has, around the world, produced a large number of potentially contaminated sites, for which there are urgent needs to assess the actual risk and to proceed, in case, with reclamation activities. One of these sites, an abandoned waste disposal site located near a Site of Community Importance on the central-eastern coast of Sardinia (Italy), is the subject of the case history described in this work. As a part of a multi-method geophysical characterisation, a frequency-domain electromagnetic (FDEM) mapping survey was carried out with the specific aim of detecting the presence of buried materials (waste) and of delineating the lateral extent of the landfill by identifying the electrical conductivity anomalies produced, for the most part, by the conductive waste fill. Using an EM31 device in the vertical-dipole configuration, at a height of 0.9 m above the ground, both quadrature and in-phase electromagnetic responses were collected over a 7-hectare area with elevation varying between 6 m and 2.8 m above sea level. After removing the measurements identified as data coming from any recognisable surface man-made features within the survey area or near its perimeter, the filtered quadrature response (expressed as apparent conductivity) ranged from 5.5 mS/m to about 188.6 mS/m. All values are beyond the low induction number (LIN) condition and valid for the classical EM31 mapping, thus requiring advanced data processing. To obtain undistorted, meaningful, and interpretable high-resolution maps, measured data have been processed to correct the bias, introduced by the nonlinearity of the device, as a function of height above ground and the topography. The comparative analysis of the apparent conductivity map, obtained by the properly processed EM31 data and some aerial photos that clearly documented the site history, has allowed unequivocal delineation of the landfill extent, in good agreement with the results obtained with other geophysical methods (not described in this paper) and with the ground truthing data provided by three boreholes, which were core-drilled at the end of the study at three locations selected on the basis of the apparent conductivity map. Full article