Sustainability of an Open-Loop GWHP System in an Italian Alpine Valley

Abstract

Shallow geothermal systems (SGSs) for building climatization represent an advantageous alternative to traditional air-conditioning systems, resulting in economic and environmental benefits. Installation of these systems requires knowledge of site-specific geological and hydrogeological conditions, which in feasibility studies are often evaluated only at the single plant scale, lacking a comprehensive view and risking not to guarantee the system sustainability over time. In this paper a methodology for the sustainable design of SGSs is presented. The methodology is developed from an example on the aquifer scale in Longarone (Belluno, Italy), where three groundwater heat pumps (GWHPs) were installed in an industrial area located in a mountain basin hosting a coarse-grained phreatic aquifer, characterized by sediments with high hydraulic conductivity and proximal to a large river (Piave River). Open-loop systems were first analyzed through numerical modeling using FEFLOW software, identifying peculiar features of the aquifer, due to its interaction with surface waters, and suggesting the possibility of its greater geothermal exploitation. Subsequently, a relationship between flow rates and thermal plume extensions was obtained, which is useful to providing support in the evaluation of potential interference with neighboring systems. The study at the aquifer scale proved representative of the system, highlighting the criticalities of the area, such as trends of aquifer temperature alteration, interference between plants, and thermal feedback.

Potential of low-enthalpy geothermal energy to degrade organic contaminants of emerging concern in urban groundwater

“…One of these activities consist in the use of the subsurface for cooling and heating of buildings and other infrastructures by means of low-enthalpy geothermal energy (LEGE), which does not emit greenhouse gases and is a renewable energy with great potential to mitigate climate change. LEGE can be defined as the energy stored in the first 400-m depth from the ground 20 , 21 , where temperatures typically remain below 30 °C and, thus, it is also known as low-temperature geothermal energy or shallow-geothermal energy 22 . The use of LEGE in urban areas has significantly increased during the last decade 23 , and today, the market growth rate shows a steady trend of 9% 24 .…”

The Influence of Water Temperature on the Hydrogeochemical Composition of Groundwater during Water Extraction and Reinjection with Geothermal Heat

“…Therefore, the reinjection well should be placed in the gradient direction. This problem can be easily solved because the locations of both wells can be planned or predicted to avoid such problems, mostly through coupled hydrogeological and thermal modeling [25][26][27] and also by less known, but fully coupled thermo-hydraulic-mechanical modeling [28,29], which includes changes in the stress field. Instead of reinjection wells, other methods, such as artificial gabion draining, were also proposed to decrease thermal feedback risks [30].…”