3DHIP-Calculator A New Tool to Stochastically Assess Deep Geothermal Potential Using the Heat-In-Place Method from Voxel-Based 3D Geological Models

The assessment of the deep geothermal potential is an essential task during the early phases of any geothermal project. The well-known 'Heat-In-Place' volumetric method is the most widely used technique to estimate the available stored heat and the recoverable heat fraction of deep geothermal reservoirs at the regional scale. Different commercial and open-source software packages have been used to date to estimate these parameters. However, these tools are either not freely available, can only consider the entire reservoir volume or a specific part as a single-voxel model, or are restricted to certain geographical areas. The 3DHIP-Calculator tool presented in this contribution is an open-source software designed for the assessment of the deep geothermal potential at the regional scale using the volumetric method based on a stochastic approach. The tool estimates the Heat-In-Place and recoverable thermal energy using 3D geological and 3D thermal voxel models as input data. The 3DHIP-Calculator includes an easy-to-use graphical user interface (GUI) for visualizing and exporting the results to files for further postprocessing, including GIS-based map generation. The use and functionalities of the 3DHIP-Calculator are demonstrated through a case study of the Reus-Valls sedimentary basin (NE, Spain)

Geo-SIV: a new free tool MATLAB-based for the preliminary technical, economic and environmental evaluation of small to medium shallow geothermal energy projects in Catalonia based on GIS datasets

Peer ReviewedPostprint (published version

3DHIP-calculator-A new tool to stochastically assess deep geothermal potential using the heat-in-place method from voxel-based 3D geological models

The assessment of the deep geothermal potential is an essential task during the early phases of any geothermal project. The well-known "Heat-In-Place" volumetric method is the most widely used technique to estimate the available stored heat and the recoverable heat fraction of deep geothermal reservoirs at the regional scale. Different commercial and open-source software packages have been used to date to estimate these parameters. However, these tools are either not freely available, can only consider the entire reservoir volume or a specific part as a single-voxel model, or are restricted to certain geographical areas. The 3DHIP-Calculator tool presented in this contribution is an open-source software designed for the assessment of the deep geothermal potential at the regional scale using the volumetric method based on a stochastic approach. The tool estimates the Heat-In-Place and recoverable thermal energy using 3D geological and 3D thermal voxel models as input data. The 3DHIP-Calculator includes an easy-to-use graphical user interface (GUI) for visualizing and exporting the results to files for further postprocessing, including GIS-based map generation. The use and functionalities of the 3DHIP-Calculator are demonstrated through a case study of the Reus-Valls sedimentary basin (NE, Spain)

Contribution of isotopic research techniques to characterize highmountain-Mediterranean karst aquifers: The Port del Comte (Eastern Pyrenees) aquifer.

Water resources in high mountain karst aquifers are usually characterized by high rainfall, recharge and discharge that leads to the sustainability of the downstream ecosystems. Nevertheless, these hydrological systems are vulnerable to the global change impact. The mean transit time (MTT) is a key parameter to describe the behavior of these hydrologic systems and also to assess their vulnerability. This work is focused on estimating MTT by using water stable isotopes in the framework of high-mountain karst systems with a very thick unsaturated zone (USZ). To this end, it is adapted to alpine zones an existing methodology that combines in a row a semi-distributed rainfall-runoff model used to estimate recharge time series, and a lumped-parameter model to obtain through a convolution integral. The methodology has been applied to the Port del Comte Massif (PCM) hydrological system (Southeastern Pyrenees, NE Spain), a karst aquifer system with an overlying1000 m thick USZ. Six catchment areas corresponding to most important springs of the system are considered. The obtained results show that hydrologically the behavior of the system can be described by an exponential flow model (EM), with MTT ranging between 1.9 and 2.9 years. These values are shorter than those obtained by considering a constant recharge rate along time, which is the easiest and most applied aquifer recharge hypothesis when estimating through lumped-parameter models. This methodology can be useful to improve the characterization and understanding of other high mountain karst aquifers with an overlying thick USZ that are common in many alpine zones elsewhere the globe

Identification of Natural and Anthropogenic Geochemical Processes Determining the Groundwater Quality in Port del Comte High Mountain Karst Aquifer (SE, Pyrenees)

The Port del Comte Massif (SE, Pyrenees) contains one of the most important vulnerable and strategic karst aquifers for supplying freshwater to the city of Barcelona (Spain). It is a fragile system, whose possible environmental impact is highly conditioned by land use. To improve the hydrogeological knowledge of the system, between September 2013 and October 2015, a detailed fieldwork was carried out for the revision of the geological model, the inventory of water points, and the in situ physico-chemical characterization on major elements and isotopes of up to a total of 43 springs, as well as precipitation water. This paper focuses on the characterization of the geochemical processes that allow explanation of the observed chemical variability of groundwater drained by the pristine aquifer system to determine the origin of salinity. The results show that the main process is the dissolution of calcite and dolomite, followed by gypsum and halite, and a minor cation exchange-like process. Sulfur and oxygen isotopes from dissolved sulfate in the studied springs point out a geogenic origin related to the dissolution of gypsum from Triassic and Tertiary materials, and that the contribution from anthropogenic sources, like fertilizers, is lower. Nitrate in groundwater is not an important issue, with a few localized cases related with agricultural activities. The multidisciplinary approach has allowed the development of a consistent hydrogeological conceptual model of the functioning of the aquifer system, which can be replicated in other places to understand the geogenic character of the hydrogeochemistry

Analysis of the geological control on the spatial distribution of potentially toxic concentrations of As and F- in groundwater on a Pan-European scale

The distribution of the high concentrations of arsenic (As) and fluoride (F-) in groundwater on a Pan-European scale could be explained by the geological European context (lithology and structural faults). To test this hypothesis, seventeen countries and eighteen geological survey organizations (GSOs) have participated in the dataset. The methodology has used the HydroGeoToxicity (HGT) and the Baseline Concentration (BLC) index. The results prove that most of the waters considered in this study are in good conditions for drinking water consumption, in terms of As and/or F- content. A low proportion of the analysed samples present HGT≥ 1 levels (4% and 7% for As and F-, respectively). The spatial distribution of the highest As and/or F- concentrations (via BLC values) has been analysed using GIS tools. The highest values are identified associated with fissured hard rock outcrops (crystalline rocks) or Cenozoic sedimentary zones, where basement fractures seems to have an obvious control on the distribution of maximum concentrations of these elements in groundwaters.This research was co-funded by the European Union’s Horizon 2020 research and innovation program (GeoERA HOVER project) under grant agreement number 731166. D. Voutchkova, B. Hansen, and J. Schullehner were also supported by Innovation Fund Denmark (funding agreement number 8055- 00073B). N. Rman participation was supported by the Slovenian Research Agency, research program P1-0020 Groundwaters and Geochemistry. A. Felter, J. Cabalska and A. Mikołajczyk participation was supported by the Polish Ministry of Education and Science. E. Giménez-Forcada is grateful for the support received from the CIPROM/2021/032 Project. Valencian Government. University of Valencia (Spain)

Fifth-Generation District Heating and Cooling Networks Based on Shallow Geothermal Energy: A review and Possible Solutions for Mediterranean Europe

This document presents a comprehensive review of research works, regulatory frameworks, technical solutions, and commercial trends related to the integration of shallow geothermal energy (SGE) technologies in modern 5th-generation district heating and cooling (5GDHC) networks. This literature and market analysis is contextualized by the present geopolitical, environmental, and societal scenario in Europe. In this sense, decarbonization of the heating and cooling sector is a crucial piece in the energy transition puzzle to keep global warming below the critical threshold of 1.5 °C by the next century. Moreover, Ukraine war has added urgency to end up with fossil fuel dependency. The most relevant outcome of this literature review is the synergistic relationship between SGE, 5GDHC networks, and urban environments. SGE is most efficiently deployed in urban environments when it is part of a district heating and cooling network, and the modern concept of 5GDHC is the most suitable scenario for it. Since the potential contribution of SGE to the decarbonization of the heating and cooling supply is mostly untapped across Europe, this synergistic effect represents a possible boost. Hybridization with solar photovoltaics and/or storage makes it even more attractive. Outstanding cases are reviewed, challenges for the future are presented, and tools to overcome social reluctance and/or lack of awareness are described, along with a discussion of the stimuli for the deployment of SGE and 5GDHC networks. A particular focus on Mediterranean countries is presented, where SGE systems and DHC networks of any kind show a particularly low deployment compared to the rest of Europe. To this end, the second part of this work evaluates, justifies, and analyzes the possibilities and potentialities of their application in this zone

Earwig Releases Provide Accumulative Biological Control of the Woolly Apple Aphid over the Years

Nature-based solutions, such as biological control, can strongly contribute to reducing the use of plant protection products. In our study, we assessed the effect of augmentative releases of the European earwig (Forficula auricularia) to control the woolly apple aphid (Eriosoma lanigerum), a worldwide pest that causes serious damage to apple trees. The trials were carried out in two organic apple orchards located in Catalonia (NE Spain) from 2017 to 2020. Two treatments were compared: with vs. without earwig release. For the treatment, 30 earwigs per tree were released by means of a corrugated cardboard shelter. These releases were performed once per season and were repeated every year. We periodically assessed the length of the woolly apple aphid colonies, the number of colonies per tree, the percentage of aphids parasitized by Aphelinus mali, and the number of earwigs per shelter. Our results showed that earwig releases reduced the length of the colonies, but this effect was noticeable only for the second year onwards. Moreover, we found that those releases were compatible with A. mali. Overall, we demonstrated the positive impact of earwig releases on the woolly apple aphid control and the importance of considering time on augmentative biological control strategies

Characterization of shallow geothermal energy instalations through remote minute-resolved monitoring. A case study

This work enlightens how remote monitoring of a shallow geothermal energy (SGE) system with minuteresolved data collection can contribute to the identification and quantification of efficiency-related problems. A specific SGE installation located in Tremp (Lleida, Spain), equipped with a vertical borehole heat exchanger (BHE) and a ground source heat pump (GSHP) was analyzed for this purpose. It was found a current average heating/cooling capacity over 10% under declared values of the GSHP equipment. In addition, the influence of part-load operation in seasonal performance was identified. The results were obtained from more than one complete year of data collection. The quality of the information obtained through data analysis was assessed in terms of the datacollection frequency. Weekly averaged data (available for more than 3 years) revealed that the capacity reduction is taking place progressively. Moreover, the seasonal coefficient of performance and seasonal energy efficiency ratio measured at the SGE installation under study were compared with those simulated by the software ground loop design (GLD, v2016). This supported the observations pointing to a progressive decay in performance.Peer Reviewe

3D modeling to evaluate the thermal interferences between borehole heat exchangers in a Mediterranean area

Thermal interference between Borehole Heat Exchangers (BHEs) results in a loss of performance of a geothermal installation. An analysis of this phenomenon can provide key information for enhance and optimize the design of a closed-loop geothermal system. To study this thermal effect in the subsoil, a simulation tool is needed to solve numerically the equations of flow and heat transport in a porous medium. The main objective of this research is to analyze and compare the influence of the distance between different BHE in three types of geometrical arrays using a 3D finite element modelling software. By fixing the heating and cooling demand of a group of single-family houses, different numbers of vertical BHEs in a closedloop system with simple parallel U-tubes were simulated. The 3D finite elements model was performed including the geological and hydrogeological settings of the northern part of Valencia city (SE, Spain) situated in the Mediterranean area. The applied geological, hydrogeological and thermal conceptual model is based on previously available information. The thermal model was calibrated in transient state with two different datasets: a set of operating data of a monitored shallow geothermal installation located in the ETSII-UPV (Escuela Técnica Superior de Ingenieros Industriales - Universidad Politécnica de Valencia - UPV), and data of a Thermal Response Test (TRT) did at the same area. The resulting model set the initial conditions to model the thermal interference between the different BHEs arrays. The studied configurations were matrices of 2, 4 and 9 BHEs, with variable distances between 3 and 20 m. The radius of thermal perturbation on the subsoil for each array of BHEs simulated was determined and the variation of the performance was characterized. The simulation results showed that there was a slight increase in temperature in the subsoil between the BHEs and its surroundings. Thermal interference was usually not visible in the first year, but in a long-term analysis, for a certain range of distances between BHEs, it was observed that a hot area appeared. The temperature increase calculated in one layer at an average depth was reproduced for different types of arrays. Even though the experimental data and the simulated scenarios corresponds to a specific place in Valencia City, the methodology scheme applied could be used in other cases, helping to understand the subsoil and BHEs behavior from a long-term point of view.Peer Reviewe