Geothermics最新文献

The interest in the utilization of geothermal energy has increased exponentially in the past few decades, and researchers internationally are currently focusing on improving harvesting methods and promoting it due to its numerous benefits compared to traditional energy sources. Corrosion and scaling are two of the significant problems in modern geothermal industry that occur during the harvesting of geothermal energy. Scaling occurs due to the variety of anions and cations that the majority of geothermal reservoir waters contain. High levels of dissolved Fe³⁺ and silicate ions cause the formation of the elusive “iron silicate”, the latter term usually referring to ferric silicate. Its identity, as it is formed in geothermal waters, differs from its geological counterparts. Usually, deposits that contain Fe and Si are referred to as “iron silicate”, revealing very little about its true identity. This research is focused on revealing the true nature of the so-called “ferric silicate”, performing a series of synthesis experiments under various conditions that take into account iron and silicate concentrations (at the supersaturation regime), solution pH, temperature and different sources of iron. Although solutions containing 150 ppm silicate (no ferric) are stable and do not undergo any polycondensation at pH = 7.0, the presence of ferric induces variable silicate loss from solution. Its severity is enhanced as the ferric concentration increases. Ferric loss from solution in the presence of silicate ions is also severe, regardless of the silicate concentration. Both silicate and ferric loss from solution are pH-dependent processes, with a maximum observed around pH = 7.0. This loss is accompanied by precipitate formation, which is corroborated by turbidity measurements. The solubility of ferric silicate (under the conditions studied) increases with temperature. There is a roughly 4-fold solubility increase when the temperature is increased from 25 °C up to 220 °C. However, enhanced ferric incorporation into the final precipitate was observed at higher temperatures. The ferric silicate precipitates were characterized by several techniques, such as powder XRD, ATR-IR, SEM, and EDS, and showed that ferric silicate is an amorphous precipitate with variable Fe:Si atom ratios and a random Fe distribution throughout the solid. These results can serve as a roadmap for ferric silicate precipitation, taking into account the water chemistry of a specific scale-forming brine.

With the advancement of Hot Dry Rock (HDR) geothermal resources exploration in deep buried geological formations, the high radiogenic characteristics have garnered increasing attention and are considered to be the primary heat source for HDR development. The deep wells in the northeastern Gonghe basin geothermal area revealed a geothermal gradient of up to 45.2 ℃/km within the basal granitic basement, indicating its suitability for the exploration and development of HDR geothermal resources. Nonetheless, the research on HDR formation mechanisms is still under debate so far. Understanding the distribution of radiogenic heat production (RHP) with depth is crucial for comprehending the origin of the heat source mechanisms. Previous RHP calculations were mainly focused on samples extracted from outcroppings. Due to the limited available RHP datasets from deep wells, the variations of RHP with depth remain unclear.

In the present research, 134 new samples were continuously extracted from a 4 km-deep geothermal well to decipher the in-situ RHP characteristics with depth within the Gonghe basin. These samples contain, on average, 2.40 % potassium, 12.93 ppm thorium and 2.87 ppm uranium for sedimentary cover, and on average 3.61 % potassium, 24.11 ppm thorium and 14.01 ppm uranium for granitic basement. On average, the radioactive isotopes in sediments and granitoids generate 1.65 ± 0.81 and 5.54 ± 0.61 µW/m³ of heat, respectively. Additionally, a 1D thermal simulation model was established to assess the impact of RHP on the formation of HDR. Modeling results indicate that RHP has a significant impact on the origin of the geothermal anomaly. For the proposed geothermal models, the presence of RHP within granitoids contributed 39–70 °C to the formation of HDR at the depth of 4 km. While RHP may not be the sole origin of the geothermal anomaly in the Gonghe basin, it does have a substantial impact on the thermal structure. Our findings in this study enhance the understanding of the heat source of the HDR resource within the Gonghe basin.

Geothermal resources contribute to transitioning from fossil fuels but can also be vital for local energy production and furthering social development. In this paper, a fundamental methodology for economic evaluation of high temperature geothermal resources, consisting of a constrained net present value maximization model where geothermal system dynamics are represented by a three-parameter stock model, is streamlined and solidified. Definitions of sustainable production from geothermal resources are also reviewed. They tend to be vague and unhelpful for organizing energy production. The goal should be to utilize the resource responsibly by maximizing overall net benefits in a holistic evaluation process where all relevant factors are considered.

Two case studies based on full-physics model production simulations for Bjarnarflag geothermal area in Iceland reveal that appropriate production data for stock model calibration are vital to obtain realistic parameters which properly describe the geothermal reservoir and are useable within the framework. In general, the stock model fits better long-term production simulations from full-physics reservoir models which exhibit a production decline phase after a make-up well drilling phase compared to shorter more erratic series which are more likely to yield unrealistic parameter values, especially in terms of excessive recharge. Reservoir heat stock and electricity price are the most important determinants of optimal capacity and production path. Greater stock and higher prices lead to larger plant sizes.

Rigorous inclusion of real-life resource uncertainty is needed for more accurate evaluation and practical application of the framework. A future article is in development addressing this need where the model is transformed to a stochastic optimization model, thereby expanding the framework towards a more holistic evaluation methodology.

This study investigates the integration of an innovative combined power and cooling (CPC) system into the existing infrastructure of the DORA 1 geothermal power plant in Aydın, Turkey. Using real operational data, this research models the integration of an ejector refrigeration cycle to enhance both power generation and cooling capabilities. The proposed system utilizes waste heat from the geothermal power plant's re-injection wells, which operate at temperatures of 81.7 °C and 69.1 °C. Four environmentally friendly refrigerants (R290, R717, R600 and R1234ze) were evaluated for their performance in the refrigeration cycle. Of these, R717 and R1234ze showed superior performance, achieving the highest coefficients of performance (COPs) and exergy efficiencies. The integration of the ejector refrigeration cycle resulted in a 12 % improvement in overall energy efficiency compared to traditional power-only systems, with a maximum COP of 0.72 under optimal conditions. This study fills a significant research gap by providing a practical application of combined geothermal power and refrigeration, and provides valuable insights into the feasibility, efficiency and sustainability of such systems. The results suggest that the proposed system not only improves energy utilization, but also contributes to environmental sustainability by reducing reliance on conventional cooling methods. This research has the potential to guide future developments in the field of geothermal energy and refrigeration, promoting the adoption of integrated energy systems for improved efficiency and reduced environmental impact.

Enhanced geothermal systems (EGSs), particularly hydraulic stimulation techniques, show promise in extracting high-enthalpy geothermal energy from hot dry rocks. However, creating an efficient volumetric fracture network in hot dry rocks remains challenging due to issues such as inadequate connectivity, significant water injection loss, and early thermal breakthrough. In this study, a damage variable is introduced into the improved thermal-hydro-mechanical coupled model to describe fracture propagation using damage evolution. Numerical simulations consider the effects offracture aperture, injection temperature, stress state, well position, etc. The results indicate that the damage zone tends to propagate parallel to the maximum primary stress in hot dry rocks. Additionally, the extent of rock damage due to thermal stress is directly proportional to the temperature difference between the fluid and the rock. The placement of double wells and the orientation of the maximum principal stress greatly affects the spatial distribution of the damaged zone under specific natural fracture network conditions.

In recent years, yearly climatic changes, continuous temperature increases, and the impact of global environmental change have seriously affected agricultural production. The solar greenhouse (SG) system is designed to maintain suitable temperatures and humidity levels for cultivating plants. For this purpose, an earth-to-air heat exchanger (EAHE) can be coupled with the SG to provide the necessary heating and cooling required to maintain suitable conditions for vegetation. This review presents a comprehensive literature survey on SG-EAHE systems. The thermal characteristics of heating and cooling modes are presented for SG-EAHE systems. Reports indicate that integrating EAHE with the SG can meet the heating and cooling needs of the SG while significantly reducing water consumption. The design parameters of EAHE, such as configuration, pipe diameter, pipe length, and buried depth, can affect the performance of SG-EAHE systems. Additionally, integrating photovoltaic (PV) and photovoltaic/thermal (PVT) systems with SG-EAHE systems was discussed. Moreover, the challenges and prospective aspects of SG-EAHE systems were identified.

The urgent need to address climate change necessitates a reduction in carbon emissions, particularly within the building sector. To achieve carbon neutrality, innovative technologies such as carbon capture, renewable energy systems, and carbon-neutral materials have been developed. However, there remains a dearth of research quantitatively analyzing carbon emissions through a life cycle assessment while implementing these technologies in real-world building scenarios. Additionally, Ground-source Heat Pumps (GSHPs) demonstrate superior efficiency compared to Air-source Heat Pumps (ASHPs) by leveraging stable ground temperatures, yet their widespread adoption is hindered by high initial investment costs. This study compares and analyzes the carbon emissions of GSHPs with Modular Ground Heat Exchangers (MGHXs), designed to mitigate initial investment barriers, alongside Vertical Ground Heat Exchangers (VGHXs) and ASHPs. The primary objective is to evaluate technology adoption feasibility from a carbon equivalent perspective, focusing on energy demand through building energy simulation. Results indicate that MGHXs exhibit a 6.7 % reduction in carbon emissions compared to VGHXs during production and construction (stage A). However, MGHXs generate 0.57 CO2-eq more per square meter per year during building operation (stage C). The implementation of geothermal energy systems in new buildings across South Korea could potentially achieve a maximum reduction effect of 11.6 % concerning the country's NDC (Nationally Determined Contributions) 2030 carbon reduction target.

Retrieving land surface temperature originating from subsurface thermal data using satellite images has some challenges, especially in tropical areas. The vegetation, cloud cover, and thick soil layers affect the detected ground temperatures. The low-to-medium spatial resolution of thermal infrared images leads to low accuracy compared with ground measurements. Therefore, proper image correction, calibration, and spatial resolution are required for comparison with kinetic temperature measured from the ground. The objective of this study is to detect thermal and vegetation anomalies related to steam spots in subsurface geothermal systems using multivariable thermal infrared corrections and the red band angle of a high spatial resolution optical image, respectively. In this study, the Kamojang–Guntur Volcanic Complex, West Java, Indonesia was selected as the study area. The exploitation and exploration of steam fields were used to assess the accuracy of the proposed method. Thermal infrared images were obtained using an advanced spaceborne thermal emission and reflection radiometer (ASTER). Principal and multivariable corrections were applied to obtain the surface temperature related to steam spots using ground thermal measurements and land cover classification to recognize surface emissivity originating from vegetation, urban areas, bare land, and water bodies. To improve multivariable analyses and interpretations, we used the high spatial resolution image of PlanetScope to obtain vegetation indices from steam spots. The gradient redness index was calculated from the atmospherically corrected PlanetScope image and used as an indicator of ground steam spot signatures. A field measurement campaign was performed to verify and analyze the thermal and vegetation indices at the ground level. Accordingly, we found that the high anomalies of the corrected surface temperature and physiological leaves were concordant with the opened and closed steam spots in the Kamojang–Guntur Volcanic Complex. Thermal and vegetation indices have the potential to estimate hidden geothermal systems and can be used in other similar areas.