Geothermal Water System Research Articles

Feasibility Investigation of Geothermal Energy Heating System in Mining Area: Application of Mine Cooling and Aquifer Thermal Energy Exploitation Technique

Mine heat hazards have resulted in large amounts of high-quality coal resources in deep that cannot be mined. The mining industry is paying more and more attention to the extraction and utilization of geothermal energy in mines, while at the same time reducing the underground temperature to realize co-extraction of coal and heat. In addition, coal mines tend to burn large amounts of coal to heat mine buildings and provide hot water for workers’ daily baths, creating operating costs and increasing greenhouse gas emissions. Therefore, it is of great significance to investigate the feasibility of extracting geothermal energy to provide the daily heat load for mines. Currently, there is little research on the feasibility of geothermal energy extraction and utilization in productive mines instead of abandoned mines. In this study, according to the actual situation of Xinhu mine in eastern China, a combined geothermal water system and heat-pump heating system is proposed, aiming to effectively realize mine cooling and geothermal exploitation and utilization. The geothermal storage capacity in the area is analyzed, and an economic analysis is developed. The economic analysis indicates that the main factors affecting the feasibility of the system are the number of mine users, the distance from the geothermal production well to the mine buildings, and the coal price. The research shows that the economic efficiency of the system is better when the heating scale is larger and the distance is smaller. As coal prices rise, the combined geothermal water and heat-pump heating system will be more economical than traditional coal heating. If a mine has 2000 workers, the application of this system can prevent 334.584 t of CO2 emissions per year.

Modelling of selected hydrodynamic and hydrochemical parameters of a geothermal water system: an example of Cieplice therapeutic waters

Article presents results of long-period observations made in the most interesting and perspective geothermal area of Poland. Moreover, Cieplice is one of the oldest spa resort in Poland where thermal waters are used for treating purposes for centuries. That is the only one region in Poland with geothermal waters in granitic rocks and this can be interesting for international readers. The region of Jelenia Góra-Cieplice has been considered a prospective area of geothermal water occurrence for many years. The earliest evidence of balneological use of these waters dates from the thirteenth century. Currently, they are being used for therapeutic purposes, and since 2014 also for recreation. The character of changes in intake discharge, water temperature and wellhead pressure observed in 1956–2019, as well as calculations of specific values (the mean, the minimum, the maximum and the standard deviation) have demonstrated considerable diversity and significant variation in these operating parameters. The main cause of changes in these parameters is changing intake operation conditions. Currently, thermal waters are being extracted chiefly from the deepened borehole C-1. Increased extraction from this intake has resulted in decreases in the temperature of thermal water from springs and borehole C-2 and a decline in their discharge or even the disappearance of their outflow. The exploitation of borehole C-1 in such conditions has also caused a drop in water pressure at its head (from 0.49 to 0.34 MPa) accompanied by an increase in water temperature (from 58 to 82 °C). The increase in water temperature is indicative of the presence of deep circulation waters in this intake. Based on the results of long-term (1963–2018) physico-chemical analyses of waters from particular intakes and deep boreholes, dominant chemical types have been distinguished: Na-HCO3–SO4 and Na–SO4–HCO3, containing fluorides and silica. By using chemical geothermometers, deposit temperatures of Cieplice thermal waters have been estimated (111–138 °C). The obtained results were verified by analysing the degree of saturation of these waters with selected rock-forming minerals by means of GeoT application. The deposit temperature estimated by modelling is c. 123 °C.

Anticorrosion and Scale Behaviors of Nanostructured ZrO2–TiO2Coatings in Simulated Geothermal Water

Corrosion and scaling phenomena often appear simultaneously and act synergistically in geothermal water system. We prepared the nano-ZrO2–TiO2 composite coatings on the AISI type 304 stainless steel with the chemical liquid phase deposition method. Surface morphology, crystal form, and chemical elements of the coatings were investigated with field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy analyzer, X-ray diffraction, and thermal gravimetric/differential thermal analyses instruments, respectively. Corrosion behaviors and scale properties were tested by potentiodynamic polarization and electrochemical impedance spectroscopy measurements in the simulated geothermal water at 50 °C. The results reveal that the anticorrosion performance of the ZrO2–TiO2 composite coating is markedly improved compared to the austenitic stainless steels. A pitting corrosion and scale deposition mechanism was proposed for the ZrO2–TiO2 composite coating in the simulated geothermal water. These fin...

Optimization of HAVC System with the Utilization of Geothermal Water System by Using High-Temperature Heat Pump and Fan-Coil

In view of the HVAC and fan-coil system utilizing geothermal water whose temperature range is from 60°C to 85°C,the objective function of system has been established. The temperature parameters of all levels and the optimum recharge temperature of geothermal water are obtained by using MATLAB software. At the end of the paper, supply-water temperature of load side influencing on the price and coefficient of performance of high temperature heat pump have been analyzed in theory.

Biogeochemistry of subsurface geothermal water system in the Hishikari gold mine

Biogeochemistry of subsurface geothermal water system in the Hishikari gold mine

Oxygen and hydrogen isotope exchange of geopressured thermal water in the central Guanzhong basin

Geothermal water of Xi'an and Xianyang in the central Guanzhong basin is typically geopressured thermal water in China. δ 18O and δD data of geopressured thermal water in Xi'an and Xianyang, combined with data from the perimeter of the basin, are analyzed to study features of hydrogen and oxygen shifts. The results show that 18O exchange of geothermal water at the perimeter of the basin and in the non-geopressured thermal water in the center of the basin is not evident, while in most of the geopressured thermal water in the central basin, in cities such as Xi'an and Xianyang, significant oxygen exchange had taken place as well as hydrogen exchange, suggesting that isotope exchanges would slowly move the geothermal water system towards equilibrium. Thermal water reservoirs in the central basin have passed through significant water-rock reactions. Moreover, the geothermal reservoir of Xianyang city is relatively much more enclosed than that of Xi'an city. It has been observed that the more enclosed the geological environment of geothermal water is, the more obvious the oxygen shifts are. With the increasing of the depth, residence time, total amounts of dissolute solids and temperatures of geothermal waters, the oxygen exchange accelerates.

Oxygen isotopic behavior of precipitating silica from geothermal water.

Oxygen isotopic ratios were measured for the silica which was precipitated from the solution in process of evaporative concentration of Otake geothermal water at 76 and 88°C. The oxygen isotopic ratios of the silica precipitates were extremely out of isotopic equilibrium with the solution in which the colloidal silica was observable. The fractionation factors for the “silica-solution in evaporative concentration system” were compared with those obtained for “the silica-flowing geothermal water system” where the silica is in oxygen isotopic equilibrium with the water. The difference is explained by isotopic zoning of the growing amorphous silica particles. The rearrangement and interlinkage of adsorbed silica on the surface of the amorphous silica contributes to attaining oxygen isotopic equilibrium between the silica precipitate and water. Amorphous silica phase once formed does not re-equilibrate with the solution at later stages. Hence the apparent oxygen isotopic fractionation between the bulk silica precipitate and the solution at the final stage seems to be out of equilibrium.