Investigation of the Rotokawa Geothermal System and Feasibility of Supercritical Fluid Production within the TVZ through Supercritical TOUGH2 Numerical Modeling.

Mapping Intimacies ◽

10.26686/wgtn.17148266.v1 ◽

2021 ◽

Author(s):

◽

Benjamin Carson

Keyword(s):

Supercritical Fluid ◽

Process Model ◽

Large Scale ◽

Numerical Models ◽

Natural State ◽

Geothermal System ◽

Convection Flow ◽

Fixed Temperature ◽

Single Fault ◽

Brittle Ductile Transition

A single fault process model was created to test the sensitivity of each TOUGH2 rock parameter on the convection flow rate and fluid enthalpy within a simulated fault. With a fixed temperature base the single fault process model found a negative correlation with the fault permeability and convection fluid enthalpy and a positive liner increases in mass flow with fault area. Next a large scale Supercritical TOUGH2 model was built to simulate the entire Rotokawa geothermal system incorporating findings of the fault process model. The single porosity model 20 x 10 x 6km with 20 layers and 57,600 grid blocks. Unlike previous models of the Rotokawa reservoir and larger scale TVZ numerical models a fixed temperature base with a no flow boundary was used to represent the brittle ductile transition. The model permeability below the currently explored reservoir was bounded by 3-D magnetologic data. Lower resistivity zones were given higher bulk permeability in the model. The model resulted in a comparable temperature and pressure match to the Rotokawa natural state conditions. Convection of supercritical fluid reached depths shallower than -4500mRL but only occurred in zones with a bulk vertical permeability less than 2 mD. Further modelling work with a supercritical wellbore coupled reservoir model will be need to evaluate the potential deliverability of a super critical well from the Rotokawa geothermal system.

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Investigation of the Rotokawa Geothermal System and Feasibility of Supercritical Fluid Production within the TVZ through Supercritical TOUGH2 Numerical Modeling.

10.26686/wgtn.17148266 ◽

2021 ◽

Author(s):

◽

Benjamin Carson

Keyword(s):

Supercritical Fluid ◽

Process Model ◽

Large Scale ◽

Numerical Models ◽

Natural State ◽

Geothermal System ◽

Convection Flow ◽

Fixed Temperature ◽

Single Fault ◽

Brittle Ductile Transition

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Vanadium Redox Flow Batteries: A Review Oriented to Fluid-Dynamic Optimization

Energies ◽

10.3390/en14010176 ◽

2020 ◽

Vol 14 (1) ◽

pp. 176

Author(s):

Iñigo Aramendia ◽

Unai Fernandez-Gamiz ◽

Adrian Martinez-San-Vicente ◽

Ekaitz Zulueta ◽

Jose Manuel Lopez-Guede

Keyword(s):

Large Scale ◽

Numerical Models ◽

Fluid Dynamic ◽

Renewable Energy Sources ◽

Vanadium Redox Flow Battery ◽

Redox Flow Batteries ◽

Design Flexibility ◽

Flow Batteries ◽

Exchange Membrane ◽

Vanadium Redox

Large-scale energy storage systems (ESS) are nowadays growing in popularity due to the increase in the energy production by renewable energy sources, which in general have a random intermittent nature. Currently, several redox flow batteries have been presented as an alternative of the classical ESS; the scalability, design flexibility and long life cycle of the vanadium redox flow battery (VRFB) have made it to stand out. In a VRFB cell, which consists of two electrodes and an ion exchange membrane, the electrolyte flows through the electrodes where the electrochemical reactions take place. Computational Fluid Dynamics (CFD) simulations are a very powerful tool to develop feasible numerical models to enhance the performance and lifetime of VRFBs. This review aims to present and discuss the numerical models developed in this field and, particularly, to analyze different types of flow fields and patterns that can be found in the literature. The numerical studies presented in this review are a helpful tool to evaluate several key parameters important to optimize the energy systems based on redox flow technologies.

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Process-Based Model Prediction of Coastal Dune Erosion through Parametric Calibration

Journal of Marine Science and Engineering ◽

10.3390/jmse9060635 ◽

2021 ◽

Vol 9 (6) ◽

pp. 635

Author(s):

Hyeok Jin ◽

Kideok Do ◽

Sungwon Shin ◽

Daniel Cox

Keyword(s):

Large Scale ◽

Numerical Models ◽

Model Performance ◽

Coastal Dunes ◽

Wave Transformation ◽

Storm Event ◽

Face Model ◽

Dune Erosion ◽

Simulation Performance ◽

Sand Bar

Coastal dunes are important morphological features for both ecosystems and coastal hazard mitigation. Because understanding and predicting dune erosion phenomena is very important, various numerical models have been developed to improve the accuracy. In the present study, a process-based model (XBeachX) was tested and calibrated to improve the accuracy of the simulation of dune erosion from a storm event by adjusting the coefficients in the model and comparing it with the large-scale experimental data. The breaker slope coefficient was calibrated to predict cross-shore wave transformation more accurately. To improve the prediction of the dune erosion profile, the coefficients related to skewness and asymmetry were adjusted. Moreover, the bermslope coefficient was calibrated to improve the simulation performance of the bermslope near the dune face. Model performance was assessed based on the model-data comparisons. The calibrated XBeachX successfully predicted wave transformation and dune erosion phenomena. In addition, the results obtained from other two similar experiments on dune erosion with the same calibrated set matched well with the observed wave and profile data. However, the prediction of underwater sand bar evolution remains a challenge.

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Vascular cambium necrosis in forest fires: using hyperbolic temperature regimes to estimate parameters of a tissue-response model

Australian Journal of Botany ◽

10.1071/bt03111 ◽

2004 ◽

Vol 52 (6) ◽

pp. 757 ◽

Cited By ~ 18

Author(s):

M. B. Dickinson ◽

J. Jolliff ◽

A. S. Bova

Keyword(s):

Pinus Ponderosa ◽

Forest Fires ◽

Ponderosa Pine ◽

Process Model ◽

Acer Rubrum ◽

Tissue Response ◽

Vascular Cambium ◽

Red Maple ◽

Fixed Temperature ◽

Temperature Regimes

Hyperbolic temperature exposures (in which the rate of temperature rise increases with time) and an analytical solution to a rate-process model were used to characterise the impairment of respiration in samples containing both phloem (live bark) and vascular-cambium tissue during exposures to temperatures such as those experienced by the vascular cambium in tree stems heated by forest fires. Tissue impairment was characterised for red maple (Acer rubrum), chestnut oak (Quercus prinus), Douglas fir (Pseudotsuga menziesii), and ponderosa pine (Pinus ponderosa) samples. The estimated temperature dependence of the model’s rate parameter (described by the Arrhenius equation) was a function of the temperature regime to which tissues were exposed. Temperatures rising hyperbolically from near ambient (30°C) to 65°C produced rate parameters for the deciduous species that were similar at 60°C to those from the literature, estimated by using fixed temperature exposures. In contrast, samples from all species showed low rates of impairment, conifer samples more so than deciduous, after exposure to regimes in which temperatures rose hyperbolically between 50 and 60°C. A hypersensitive response could explain an early lag in tissue-impairment rates that apparently caused the differences among heating regimes. A simulation based on stem vascular-cambium temperature regimes measured during fires shows how temperature-dependent impairment rates can be used to predict tissue necrosis in fires. To our knowledge, hyperbolic temperature exposures have not been used to characterise plant tissue thermal tolerance and, given certain caveats, could provide more realistic data more efficiently than fixed-temperature exposures.

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Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

MRS Proceedings ◽

10.1557/proc-663-561 ◽

2000 ◽

Vol 663 ◽

Cited By ~ 2

Author(s):

J. Samper ◽

R. Juncosa ◽

V. Navarro ◽

J. Delgado ◽

L. Montenegro ◽

...

Keyword(s):

Large Scale ◽

Reference Model ◽

Numerical Models ◽

Full Scale ◽

Small Scale ◽

Model Parameters ◽

In Situ Test ◽

Wide Range ◽

Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

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Bayesian active learning of interatomic force field for molecular dynamics simulation of Pt/Ag(111)

10.26434/chemrxiv-2021-sk6lf-v2 ◽

2021 ◽

Author(s):

Kai Xu ◽

Lei Yan ◽

Bingran You

Keyword(s):

Molecular Dynamics ◽

Active Learning ◽

Force Field ◽

Density Functional ◽

Process Model ◽

Large Scale ◽

Computational Cost ◽

Dynamics Simulation ◽

Potential Energy Landscape ◽

Three Body

Force field is a central requirement in molecular dynamics (MD) simulation for accurate description of the potential energy landscape and the time evolution of individual atomic motions. Most energy models are limited by a fundamental tradeoff between accuracy and speed. Although ab initio MD based on density functional theory (DFT) has high accuracy, its high computational cost prevents its use for large-scale and long-timescale simulations. Here, we use Bayesian active learning to construct a Gaussian process model of interatomic forces to describe Pt deposited on Ag(111). An accurate model is obtained within one day of wall time after selecting only 126 atomic environments based on two- and three-body interactions, providing mean absolute errors of 52 and 142 meV/Å for Ag and Pt, respectively. Our work highlights automated and minimalistic training of machine-learning force fields with high fidelity to DFT, which would enable large-scale and long-timescale simulations of alloy surfaces at first-principles accuracy.

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Revised hydrogeological model of the hydrothermal system Waiwera (New Zealand)

10.5194/egusphere-egu21-12196 ◽

2021 ◽

Author(s):

Andreas Grafe ◽

Thomas Kempka ◽

Michael Schneider ◽

Michael Kühn

Keyword(s):

Water Management ◽

New Zealand ◽

Water Level ◽

Hot Water ◽

Hydrogeology Journal ◽

Natural State ◽

Geothermal System ◽

Geological Model ◽

Species Transport ◽

Study Region

The geothermal hot water reservoir underlying the coastal township of Waiwera, northern Auckland Region, New Zealand, has been commercially utilized since 1863. The reservoir is complex in nature, as it is controlled by several coupled processes, namely flow, heat transfer and species transport. At the base of the aquifer, geothermal water of around 50&#176;C enters. Meanwhile, freshwater percolates from the west and saltwater penetrates from the sea in the east. Understanding of the system&#8217;s dynamics is vital, as decades of unregulated, excessive abstraction resulted in the loss of previously artesian conditions. To protect the reservoir and secure the livelihoods of businesses, a Water Management Plan by The Auckland Regional Council was declared in the 1980s [1]. In attempts to describe the complex dynamics of the reservoir system with the goal of supplementing sustainable decision-making, studies in the past decades have brought forth several predictive models [2]. These models ranged from being purely data driven statistical [3] to fully coupled process simulations [1]. Our objective was to improve upon previous numerical models by introducing an updated geological model, in which the findings of a recently undertaken field campaign were integrated [4]. A static 2D Model was firstly reconstructed and verified to earlier multivariate regression model results. Furthermore, the model was expanded spatially into the third dimension. In difference to previous models, the influence of basic geologic structures and the sea water level onto the geothermal system are accounted for. Notably, the orientation of dipped horizontal layers as well as major regional faults are implemented from updated field data [4]. Additionally, the model now includes the regional topography extracted from a digital elevation model and further combined with the coastal bathymetry. Parameters relating to the hydrogeological properties of the strata along with the thermophysical properties of water with respect to depth were applied. Lastly, the catchment area and water balance of the study region are considered. The simulation results provide new insights on the geothermal reservoir&#8217;s natural state. Numerical simulations considering coupled fluid flow as well as heat and species transport have been carried out using the in-house TRANSport Simulation Environment [5], which has been previously verified against different density-driven flow benchmarks [1]. The revised geological model improves the agreement between observations and simulations in view of the timely and spatial development of water level, temperature and species concentrations, and thus enables more reliable predictions required for water management planning. [1] K&#252;hn M., St&#246;fen H. (2005): &#160; &#160; &#160; Hydrogeology Journal, 13, 606&#8211;626, &#160; &#160; &#160; https://doi.org/10.1007/s10040-004-0377-6 [2] K&#252;hn M., Altmannsberger C. (2016): &#160; &#160; &#160; Energy Procedia, 97, 403-410, &#160; &#160; &#160; https://doi.org/10.1016/j.egypro.2016.10.034 [3] K&#252;hn M., Sch&#246;ne T. (2017): &#160; &#160; &#160; Energy Procedia, 125, 571-579, &#160; &#160; &#160; https://doi.org/10.1016/j.egypro.2017.08.196 [4] Pr&#228;g M., Becker I., Hilgers C., Walter T.R., K&#252;hn M. (2020): &#160; &#160; &#160; Advances in Geosciences, 54, 165-171, &#160; &#160; &#160; https://doi.org/10.5194/adgeo-54-165-2020 [5] Kempka T. (2020): &#160; &#160; &#160; Adv. Geosci., 54, 67&#8211;77, &#160; &#160; &#160; https://doi.org/10.5194/adgeo-54-67-2020

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Innovative Volumetric Solar Receiver Micro-Design Based on Numerical Predictions

Volume 8B: Heat Transfer and Thermal Engineering ◽

10.1115/imece2015-50597 ◽

2015 ◽

Cited By ~ 3

Author(s):

Raffaele Capuano ◽

Thomas Fend ◽

Bernhard Hoffschmidt ◽

Robert Pitz-Paal

Keyword(s):

Solar Radiation ◽

Energy Demand ◽

Large Scale ◽

Solar Power ◽

Numerical Models ◽

Numerical Predictions ◽

Proper Design ◽

Global Increase ◽

Solar Power Tower ◽

Solar Receiver

Due to the continuous global increase in energy demand, Concentrated Solar Power (CSP) represents an excellent alternative, or add-on to existing systems for the production of energy on a large scale. In some of these systems, the Solar Power Tower plants (SPT), the conversion of solar radiation into heat occurs in certain components defined as solar receivers, placed in correspondence of the focus of the reflected sunlight. In a particular type of solar receivers, defined as volumetric, the use of porous materials is foreseen. These receivers are characterized by a porous structure called absorber. The latter, hit by the reflected solar radiation, transfers the heat to the evolving fluid, generally air subject to natural convection. The proper design of these elements is essential in order to achieve high efficiencies, making such structures extremely beneficial for the overall performances of the energy production process. In the following study, a parametric analysis and an optimized characterization of the structure have been performed with the use of self-developed numerical models. The knowledge and results gained through this study have been used to define an optimization path in order to improve the absorber microstructure, starting from the current in-house state-of-the-art technology until obtaining a new advanced geometry.

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A general Cluster data and global MHD simulation comparison

Annales Geophysicae ◽

10.5194/angeo-26-3411-2008 ◽

2008 ◽

Vol 26 (11) ◽

pp. 3411-3428 ◽

Cited By ~ 3

Author(s):

P. Daum ◽

M. H. Denton ◽

J. A. Wild ◽

M. G. G. T. Taylor ◽

J. Šafránková ◽

...

Keyword(s):

Large Scale ◽

Numerical Models ◽

Mhd Simulation ◽

Global Context ◽

Cluster Data ◽

Verification Methods ◽

Modelling Studies ◽

Global Mhd Simulation ◽

The Many

Abstract. Among the many challenges facing the space weather modelling community today, is the need for validation and verification methods of the numerical models available describing the complex nonlinear Sun-Earth system. Magnetohydrodynamic (MHD) models represent the latest numerical models of this environment and have the unique ability to span the enormous distances present in the magnetosphere, from several hundred kilometres to several thousand kilometres above the Earth's surface. This makes it especially difficult to develop verification and validation methods which posses the same range spans as the models. In this paper we present a first general large-scale comparison between four years (2001–2004) worth of in situ Cluster plasma observations and the corresponding simulated predictions from the coupled Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) MHD code. The comparison between the in situ measurements and the model predictions reveals that by systematically constraining the MHD model inflow boundary conditions a good correlation between the in situ observations and the modeled data can be found. These results have an implication for modelling studies addressing also smaller scale features of the magnetosphere. The global MHD simulation can therefore be used to place localised satellite and/or ground-based observations into a global context and fill the gaps left by measurements.

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Large-scale features of Pliocene climate: results from the Pliocene Model Intercomparison Project

Climate of the Past Discussions ◽

10.5194/cpd-8-2969-2012 ◽

2012 ◽

Vol 8 (4) ◽

pp. 2969-3013 ◽

Cited By ~ 6

Author(s):

A. M. Haywood ◽

D. J. Hill ◽

A. M. Dolan ◽

B. Otto-Bliesner ◽

F. Bragg ◽

...

Keyword(s):

Data Model ◽

Large Scale ◽

Model Comparison ◽

Numerical Models ◽

Model Intercomparison ◽

System Sensitivity ◽

Sensitivity Tests ◽

Intercomparison Project ◽

Known Unknowns ◽

Shed Light

Abstract. Climate and environments of the mid-Pliocene Warm Period (3.264 to 3.025 Ma) have been extensively studied. Whilst numerical models have shed light on the nature of climate at the time, uncertainties in their predictions have not been systematically examined. The Pliocene Model Intercomparison Project quantifies uncertainties in model outputs through a co-ordinated multi-model and multi-model/data intercomparison. Whilst commonalities in model outputs for the Pliocene are evident, we show substantial variation in the sensitivity of models to the implementation of Pliocene boundary conditions. Models appear able to reproduce many regional changes in temperature reconstructed from geological proxies. However, data/model comparison highlights the potential for models to underestimate polar amplification. To assert this conclusion with greater confidence, limitations in the time-averaged proxy data currently available must be addressed. Sensitivity tests exploring the "known unknowns" in modelling Pliocene climate specifically relevant to the high-latitudes are also essential (e.g. palaeogeography, gateways, orbital forcing and trace gasses). Estimates of longer-term sensitivity to CO2 (also known as Earth System Sensitivity; ESS), suggest that ESS is greater than Climate Sensitivity (CS), and that the ratio of ESS to CS is between 1 and 2, with a best estimate of 1.5.

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