Abstract
Improving the long‐term energy production performance of geothermal reservoirs can be accomplished by optimizing field development and management plans. Reliable prediction models, however, ...are needed to evaluate and optimize the performance of the underlying reservoirs under various operation and development strategies. In traditional frameworks, physics‐based simulation models are used to predict the energy production performance of geothermal reservoirs. However, detailed simulation models are not trivial to construct, require a reliable description of the reservoir conditions and properties, and entail high computational complexity. Data‐driven predictive models can offer an efficient alternative for use in optimization workflows. This paper presents an optimization framework for net power generation in geothermal reservoirs using a variant of the recurrent neural network (RNN) as a data‐driven predictive model. The RNN architecture is developed and trained to replace the simulation model for computationally efficient prediction of the objective function and its gradients with respect to the well control variables. The net power generation performance of the field is optimized by automatically adjusting the mass flow rate of production and injection wells over 12 years, using a gradient‐based local search algorithm. Two field‐scale examples are presented to investigate the performance of the developed data‐driven prediction and optimization framework. The prediction and optimization results from the RNN model are evaluated through comparison with the results obtained by using a numerical simulation model of a real geothermal reservoir.
Ground Source Heat Pumps, in the framework of Shallow Geothermal Energy Systems, outperform conventional Heating Ventilation and Air Conditioning systems, even the high efficiency Air Source Heat ...Pumps. At the same time, though, they require considerably higher installation costs. The utilization of dwellings' foundations as ground heat exchanger components has recently demonstrated the potential to generate significant cost reductions primarily attributed to the reduction in expenses associated with drilling and backfill material (grout). These elements are referred to in the literature as Thermo-Active Structures or Energy Geo-structures (EGs). The current study employs a ‘mixed studies’ review (i.e., literature review, critical review and state-of-the-art review) methodology to comprehensively examine and assess the compatibility and integration of different renewable energy sources and environmentally friendly technologies with foundation elements deployed as EGs. These mainly include heat pumps, district heating and cooling networks, solar-thermal systems, waste heat, biomass and other types such as urban structures. Emphasis has been given on the advancement on this area, with the current study identifying and addressing two primary categories. The first category involves the integration of EG elements with sources that are able to supply green electricity, referring to renewable energy electricity obtained from on-grid or off-grid integration. The second category, involves a direct or indirect integration with sources that provide heat, or vice versa. The technical and non-technical barriers of such integrations have been discussed in detail, with the technical challenges generally involving engineering design, and system optimization, whereas non-technical challenges encompassing the economic, social, and policy domains.
•Heat transfer experiments of an extra-long gravity heat pipe are conducted.•The heat pipe is long (40 m in length) and thin (7 mm in diameter).•Heat pipe performance is correlated with the four ...multiphase flow regimes inside.•Heat pipe working in the film boiling regime performs the best.•Using water as working fluid is better than ethanol and acetone at high heat load.
The exploitation of deep geothermal energy has created a great demand for super-long distance heat transportation technology. As one of the most highly-efficient heat transfer devices, the super-long gravity-assisted heat pipe is promising to achieve this heat transportation. The performance of the super-long heat pipe is related to the multiphase flow status inside, the details of which are yet unknown. In this paper, a systematic experimental study on the multiphase flow regimes and the performance of an extra-long heat pipe was conducted. The experimental heat pipe is 40 m in length, 7 mm in diameter, which mimics the major geometric characteristic of the super-long heat pipes that can be practically used for geothermal heat extraction. Thermal performance and surface temperature of the extra-long heat pipe using water, ethanol or acetone as working fluid were measured and analyzed. Particular focus was placed on correlating the heat transfer performance of the heat pipe with the multiphase flow regime inside it. It was found that the extra-long heat pipe works in the following four different flow regimes successively with the increase in inflow heat: (1) nucleating pool boiling regime; (2) geyser boiling regime; (3) evaporating film boiling regime; and (4) overheated boiling regime. The thermal performances of extra-long heat pipe are significantly affected by the flow regimes, while the transition between these flow regimes is influenced by the properties of working fluid, the fluid fill height, and the heat load. It is found that the heat pipe working in the evaporation film boiling regime shows the best thermal performance and the heat pipe using water as working fluid is more suitable for relatively high heat load use. The reachable maximum axial heat fluxes for the water, ethanol, and acetone heat pipes are found to be about 6.5 × 106, 2.21 × 106, 2.08 × 106 W·m−2, respectively. These characteristics of heat transfer and multiphase flow provide very useful hints for the design and development of super-long geothermal heat pipes.
•A novel methodology for evaluating EGS project performance with overall influencing factors.•The influencing factors encompass geological, technological, economic, and environmental parameters.•The ...proposed weighting system emphasizes the importance of chosen criteria in the decision-making process.•The approach is applicable for assessment and comparison of different end-usage options and projects.
When considering geothermal project development, the complex assignment of aggregating and quantifying the influencing factors and their interactions is an inevitable task that enables comprehensive assessment of the geothermal energy utilization from many different aspects. The main purpose of the scientific work is a revised set of criteria for comprehensive evaluation of geothermal project focusing on Enhanced Geothermal Systems (EGS) and considering the geological settings, technology, economic and financial aspects of project development, and societal and environmental parameters. The newly presented work is conceived as an addition to the previous work, defining and thoroughly describing twenty-eight influencing factors for evaluation of deep geothermal energy. The mentioned factors consist of 18 newly introduced criteria, 6 replaced criteria, and 4 modified criteria which are based on the extensive literature review and expertise integrating all aspects of EGS project development. One of the key findings of the presented methodology is that it provides broad assessment of an EGS project, applicable to different end-uses including only electricity generation, only heat production and combined heat and power production. The proposed methodology could serve as a preparatory guideline for more detailed analysis and calculations for a future project development, either greenfield or brownfield, encompassing technological, geological, economic, and environmental aspects. The methodology was tested in case study where two different geothermal sites were assessed for heat production and electricity production scenarios. Both sites, with their main geological parameters, resulted in production of electricity, from 263.51 GWh up to 927.69 GWh, and heat production from 334.25 GWh up to 5,207.68 GWh. Such increase of renewable energy production from geothermal source derived the avoidance of CO2 emissions ranging from 79,686 tonnes of CO2-eq up to 1,241,542 tonnes of CO2-eq. The final grades of each criterion for the heat and electricity production scenarios resulted in favor of Site 2, where better reservoir and economic performance values derived the higher final grade of site’s overall performance. The summarized results lead to a conclusion that the proposed methodology is applicable for assessment of different end-usage options for one geothermal site and for comparison of projects at different geothermal sites.
Abstract
Gudui geothermal field in Shannan, Tibet has great potential for geothermal energy development. The main purpose of our geophysical investigation is to study the geothermal structure in this ...region. Therefore, 363 stations were deployed around the intersection region of numerous faults to measure AMT observe data. The 2D and 3D inversion were carried out by optimal inversion method. The result shows that the geothermal reservoir under the three springs areas combine together and the source of this reservoir comes from a deeper geothermal reservoir.
Since energy sources are limited, any activity aimed at recycling energy waste or facilitating energy conversion systems is invaluable. Against this background, most scientists focus on the ...integration of energy systems and the coupling of different technologies. In this study, a variety of power systems are investigated for optimal power conversion configurations of geothermal sources. Three configurations, Organic Rankine Cycle Geothermal Cooling (GPR/ORC), Kalina Cycle Geothermal Cooling (GPR/Kalina), and Rankine Cycle and Feed water Heater (GPR/FWH) Geothermal Cooling, are classified according to exergy and Study energy economic analysis. Calculations show that the GPR/FWH system has the highest net output power of 2963 kW. In addition, the GPR/Kalina system has the lowest output power and lowest energy efficiency among the systems launched. Across the three proposed systems, the fuel cell generates 1254 kW of electricity, while the Kalina cycle in the GPR/Kalina system generates 487 kW. Exergy studies show that the GPR/Kalina and GPR/FWH systems have the lowest and highest irreversibility (3795.4 kW and 4365.56 kW, respectively). Furthermore, the fuel cell was found to have the greatest exergy destruction rate among the three configurations. The results of the economic analysis show that the fuel cell has the highest cost ratio among all designs. In addition, the values of the dissipation factor show that the absorption chiller has the highest dissipation factor value among the three configurations. Furthermore, the comparative parametric analysis provides new aspects to introduce into the system.
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•Improve the performance of an available CCHP plant by propose three arrangements.•Themo-economic comparison of three introduced systems.•Determine the effects of adding fuel cell to the available CCHP system.•Comparative parametric analysis of three suggested plants.
•Thermal performance investigation of thermosyphons at shallow geothermal temperature.•Development and validation of CFD modelling for ammonia thermosyphons.•Two-phase flow filed distribution in ...ammonia thermosyphons.•Relevance of inner phase-change heat transfer behaviors to thermal performance.
The steady thermal performance of ammonia thermosyphons at shallow geothermal temperature, with the feature of low heat flux, are experimentally investigated in this work. In addition, a CFD (Computational Fluid Dynamic) modelling considering the phase-change heat transfer in the thermosyphon is established to reproduce the inside heat transfer behaviors and explore the corresponding relevance to thermal performance of these thermosyphons. The experimental results show that the influence of flow rate of cooling water qcooling on the total thermal resistance is significant, but the heat transfer power Qpractical is mainly dependent on the temperature of cooling water Tcooling. The maximum Qpractical for the thermosyphon of 30% filling ratio under testing conditions is about 38 W, which is obtained with the heating length at 0.6 m. Both the increase and decrease of le can reduce Qpractical and raise Rtotal. For filling ratio at 20%, the heat transfer power almost halves comparing to 30% filling ratio. The simulation results reveal that dropwise condensation is the main heat transfer mechanism at the condenser of these thermosyphons, and a better thermal performance is expected when the steady boiling liquid pool is nearly identical to the evaporator length for these thermosyphons operating at shallow geothermal temperature. This work provides a deep insight into the inner heat transfer behaviors of ammonia thermosyphons at low heat flux and can be used to facilitate the performance optimization of thermosyphons in shallow geothermal energy utilization.
The geothermal potential of cities Bayer, Peter; Attard, Guillaume; Blum, Philipp ...
Renewable & sustainable energy reviews,
05/2019, Letnik:
106
Journal Article
Recenzirano
What is the heat beneath our feet? There is a growing interest in the geothermal resources available at shallow depth beneath cities. However, there exists no general procedure for quantifying the ...low-temperature geothermal potential in urban ground and groundwater. This review categorizes previous work based on different definitions of the geothermal potential and compares the different assessment methods used. It is demonstrated that the theoretical potential of the available heat at a shallow depth is enormous, especially when not only the heat in place, but also compensating heat fluxes are considered. The technical potential describes the extractable heat by a specific technology. The methods to evaluate the extractable heat are manifold, including the use of technical performance standards, analytical and numerical simulation tools and mathematical regression procedures. These are different for groundwater well based open-loop systems and heat-exchanger-based closed loop systems, and the results depend on variable local factors, the density of systems applied and whether heat and/or cold is utilized. We contrast the published findings based on the power density and the relative contribution to the demand of a city. The broad span of the results highlights the need for a more consistent framework that distinguishes between the conceptual assumptions for calculating the technical geothermal potential and the local city-specific factors. This will be the basis for a reliable analysis of the economic geothermal potential of low-temperature geothermal applications on a local, district or city scale. This will also enhance the reliability and the trust in these technologies, and thus the public acceptance reflected in the acceptable geothermal potential.
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•Exploration of the manifold computational concepts behind geothermal potential.•Development of a common novel framework with differently defined potential classes.•Assessment of available approaches for quantification of different potential types.•Contrasting of previous findings for the geothermal potential to the energy demand.
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