Jessica Maria Chicco

Geopolitical developments since February 2022 and the numerous debates on climate change such as the COP27 are pushing for a greater acceleration in decarbonising the energy sector. The use of geothermal energy for thermal energy production and storage in district heating and cooling (DHC) grids may also be a key element in overcoming short-term energy peaks. This work aimed at evaluating the efficiency and performance of one of the most promising underground thermal energy storage systems, which uses boreholes to store heat or cold (BTES). Numerical simulations allowed for understanding how these technologies can be used as backup systems, or when the energy demand overcomes that supplied by conventional heating systems. The knowledge on how to exploit this energy source shows that a continuous heat extraction from the storage volume can meet both the base and peak load requests for several users, with cumulative energy amounting to 476,000 kWh over the first month. This study proved how the integration of these technologies in DHC contexts can contribute to greater energy and economic savings, becoming an efficient and flexible solution to meet the energy demand from the grid, and also as a backup system.

A comparative study was carried out aiming at characterizing the thermal conductivity of rocks sampled in a borehole heat exchanger field. Twenty-three samples were analysed with four different methods based on both steady-state and transient approaches: transient divided bar (TDB), transient line source (TLS), optical scanning (OS), and guarded hot plate (GHP). Moreover, mineral composition (from XRD analyses), P-wave velocity, and density were investigated to assess the petrophysical heterogeneity and to investigate possible causes of divergence between the methods. The results of thermal conductivity showed that TLS systematically underestimates thermal conductivity on rock samples by 10-30% compared to the other devices. The differences between TDB and OS, and GHP and OS are smaller (about 6% and 10%, respectively). The average deviation between TDB and GHP, for which the specimen preparation and the measurement procedure were similar, is about 10%. In general, the differences are ascribable to sample preparation, heterogeneity and anisotropy of the rocks, and contact thermal resistance, rather than the intrinsic accuracy of the device. In case of good-quality and homogeneous samples, uncertainty can be as low as 5%, but, due to the above-mentioned factors, usually uncertainty is as large as 10%. Opposite relationships between thermal conductivity and P-wave velocity were observed when analysing parallel and perpendicular to the main rock foliation. Perpendicular conductivity values grow with increasing perpendicular sonic velocity, while parallel values exhibit an inverse trend. Thermal conductivity also appears to be inversely correlated to density. In quartz-rich samples, high thermal conductivity and low density were observed. In samples with calcite or other likely dense mineral phases, we noticed that lower thermal conductivity corresponds to higher density. The presence of micas is likely to mask major differences between silicate and carbonate samples.

Structural features such as faults and fractures play an important role in fluid circulation within the crust, and influence geothermal exchange potential. Based on this consideration, we examined the subsurface structural setting of the Marche Region (Central Italy) in terms of detailed data we obtained on the groundwater in wells; detailed analyses of its physical properties, particularly electrical conductivity, revealed some anomalies in several localities which appear to be related to the local tectonic structures. In addition, we interpreted data from seismic reflection profiles provided by ENI S.p.A, and kindly shared with us, for the SW-NE area crossing the Apennine chain and extending to the Adriatic Sea. Our interpretation indicates the presence of important subsurface and deep Plio-Quaternary structures linked to outcropping ones with possible hydrogeological implications. Our interpretation of these seismic profiles enabled us to identify some high angle structures affecting the whole sedimentary sequence and routed at depth (> 10 km), thus allowing us to gain an understanding of the recent structural evolution of the Apennine Marche sector. We interpreted these mainly NW-SE trending structures to be transpressive structures, related to lower depth SW and NE-dipping high-angle reverse faults (positive flower structures), probably involving the upper crust basement. We identified them along three main parallel alignments (transects) from SW to the coastline, crossing the Mio-Pliocene Apennine range and its external Plio-Quaternary sector. Our analyses of the groundwater in wells throughout the study area indicated possible relationship with deep geological structures. It seems that the high degree of fracturing that accompanies these complex and recent fault systems could facilitate the exchange between superficial and deeper fluids. This is supported by the observation that there is a direct relationship between the electrical conductivity of the water in wells located along the calcareous-marly Apennine Marche ridge, and the amount of rainfall.

A detailed investigation aimed to optimize the knowledge about the realization of low enthalpy geothermal plants, answering to the energy related challenges proposed by Horizon 2020 and trying to move toward a better integration between research and industry, is currently in progress in the Marche Region (Central Italy). The main goals of this project are: i) to improve the present-day knowledge about the heat transfer coming from two geothermal boreholes 100 m in depth and with a distance of 9 m from each other, in order to better understand the behaviour of a geothermal probes in a particular geological, hydrogeological and structural context; ii) to control the behaviour of two commercial grouts and to study the thermo-physical and mineralogical properties of new grouts performing laboratory tests and monitoring; iii) to test a new hybrid geothermal/micro-cogeneration system for the heating of the buildings. As part of the project, an experimental plant is in progress at the University of Camerino (Geology Division). An interdisciplinary research team as well as private companies and University spin off, are engaged for the project development.

Knowledge of the thermal behaviour around and throughout borehole heat exchangers (BHEs) is essential for designing a low enthalpy geothermal plant. In particular, the type of grout used in sealing the space between BHE walls and the pipes is fundamental for optimizing the heat transfer and minimizing the thermal resistance, thereby promoting the reduction of total drilling lengths and installation costs. A comparison between grouts with different thermal conductivities coupled with common hydrogeological contexts, was modelled for a typical oneyear heating for continental climates. These data have been used for a sensitivity analysis taking into account different flow rates through pipes. The results highlight that in groundwater transient conditions, porous lithologies allow for greater heat power extractions to be obtained with an increasing grout thermal conductivity than limestone or clayey silt deposits do. Moreover, increasing the inlet flow rates through the pipe greatly improves the final heat power extraction. As a result, when the underground allows for high extraction rates, the use of high performing grouts is warmly suggested ensuring greater productions.

In the warm summer of 2017, a landslide failed from the south-east side of the Col des
Clochettes on the top of the underlying Trajo Glacier. The study area is at an elevation of about 3500 m a.s.l. in the Gran Paradiso Massif and can be hardly reached by walking from Cogne (Aosta Valley, NW Italy). Studies conducted by field surveys, photogrammetry (structure from motion) and satellite images analysis, integrated with the evaluation of data from meteorological stations have been used to reconstruct the phenomenon and infer its causes. The site is very complex to be studied especially due to logistic problems, therefore, measurements and observations that are common practice in other landslides are very difficult to apply here. So, many of the results achieved are not adequately supported by field studies. Anyway, the following factors could have affected the stability on the slope: i) the tectonic structure of the area, which is reflected on the morphology and on the geomechanics.

Monitoring of hydrothermal fluid emissions can provide detailed information about convective upwelling of geothermal fluids and their geochemical characteristics, as a function of tectonic stress or deeper gas input. In particular, at the Salinelle of Mt. Etna Geosite (Paternò and Belpasso, Eastern Sicily) natural emissions mainly consist of a fluid phase made of salty water, mud, gas and liquid hydrocarbons from an admixture of magmatic and hydrothermal gases. In this framework, our study mainly focused on the thermal and geochemical monitoring of hydrothermal fluids of the most active site, Salinelle dei Cappuccini. N earby hydrothermal vents (Salinelle del Fiume; Salinelle di San Biagio), were also investigated. Analysis of the magnitude and frequency of seismic events all around Mt. Etna were conducted as well. Analysis of daily temperatures showed a constant trend: higher values (> 35° C) within the first monitoring period, followed by a strong decrease (down to 9° C), and a new gradual increase over the following months. This trend seems to be linked to magmatic processes occurring at depth below Mt. Etna, and could lead to a modification of the geochemical and thermal characteristics of the fluids issuing at the mud-pools and gas vents of Salinelle. The higher the frequency of seismic events corresponding to higher daily energy released, the higher fluid temperatures observed. Understanding how these fluids blend and what is their relationship with Mt. Etna volcanism can be of great importance in forecasting new eruptive cycles in the case they precede changes in volcanic activity.

Water in rock masses is a key factor in geo-mechanics, hydrogeology, mining, geo-thermics, and more. It is relevant in interpreting rock mass behavior (e.g., water-rock interaction or slope stability), as well as in defining heat transfer mechanisms. Pointing out the contribution of secondary porosity in increasing advective heat transfer instead of the conduction phenomenon, this study aims to highlight a different thermal response of sound rocks and faulted zones. Moreover, it provides some methodological suggestions to minimize environment disturbance in data collection and a robust interpretation of the results. An interesting outcrop was identified in a carbonate quarry near Valdieri (north-west Italian Alps): it was studied coupling a geo-mechanical and a thermo-physical approach. In particular, geo-mechanical and photogrammetric surveys, InfraRed Thermography (IRT), and Thermal Conductivity (TC) measurements were conducted. The rationale of the research is based on the fact t...

In the framework of heating and cooling of buildings, the underground can be used as thermal energy storage to smooth the difference between production and demand. The heat transfer performances vary significantly depending on the type of soil where the plant is set up, but also with the water content and the presenceof groundwater flow. A lab scale modelling aimed at the simulation of thermal energy storage behaviour in porous materials was begun by Giordano et al. (2013) in order to better design the field scale living lab set up in Torino (Giordano et al., 2016). In this work, an implementation of the laboratory device is proposed with a monitoring system made of a low-cost open-source electronic platform based on Arduino®. With respect to the previous version, the heat sources have been eplaced with small scale borehole heat exchangers fed by a heating bath circulator equipped with in/out temperature sensors and flow rate control. Temperature and moisture monitoring within the medium has been improved with new and more accurate sensors. In addition, load sensors have been set up below the box to monitor the moisture migration induced during the heat injection. All the sensorsare read by Arduino® boards and shields thanks to on purpose scripts and the data are monitored by a lab PC.

Results from laboratory analyses of thermophysical properties and mineralogical composition of rocks belonging to the main geological formations of the Umbria-Marche stratigraphic succession are presented. We carried out measurements of thermal conductivity, porosity, and density. The samples were mineralogically characterized by means of powder X-ray diffraction and by calcimetry. Scanning electron microscope analyses were conducted to ascertain the absence of mineralized veins, which could have biased the mineralogical composition. A mixing model was also applied to infer the thermal conductivity. The results can be useful to characterize the behavior of shallow geothermal systems in the study region.