Heat Bath Research Articles

Advances in enhanced geothermal systems: Integrating laboratory, numerical and field insights

An enhanced geothermal system is a designed and engineered thermal reservoir that has been deliberately stimulated to extract economically viable amounts of heat from geothermal resources having no natural permeability. Enhanced geothermal system projects are typically initiated to meet the industrial production standards, usually via techniques such as chemical stimulation, hydraulic fracturing, or thermal processes to enhance the permeability of the reservoir. The main aim of this study is to evaluate the current advancements in enhanced geothermal system through a comprehensive examination of laboratory experiments, numerical simulation, and fieldwork investigations from numerous studies that are insufficient captures and combined by current open literature. This study highlighted the critical importance of precisely developing fracture systems, whether natural or artificially induced, in ensuring the effectiveness of such projects. Notably, hydraulic fracturing techniques have been proven instrumental in enhancing the performance of enhanced geothermal systems. On the contrary, research conducted through numerical simulations has demonstrated consistent findings that it is beneficial to enhance the permeability of low-permeability rock for the efficient use of enhanced geothermal systems. Additionally, this study has highlighted the intricate and expensive nature of designing enhanced geothermal systems due to uncertainties in subsurface conditions especially from projects that are in initial stages of development. This study enables researchers and operators to improve the efficiency and safety of geothermal energy extraction, paving the way for more sustainable enhanced geothermal system projects in the future.

Optical Characteristics of Rectangular Cross-Section Torus Waveguide

The rectangular cross-section waveguide made of PMMA is designed to efficiently transfer solar radiation from the source to the receiver, whether it be a (solar cell or a thermal reservoir) by the total internal reflection of the radiation within the waveguide. The waveguide is designed with a torus, like the letters U and S, which provides greater flexibility to reach previously inaccessible areas with traditional waveguide shapes. To design the waveguide, the simulation program (ANSYS Zemax OpticStudio 2022) uses the analysis tool in the program (detector viewer). The optical efficiency of the system was calculated by varying a set of optical parameters, such as the radius of curvature of the waveguide, the width of the entrance aperture, and the angle of rotation. The results showed that the designed (U) model offers more design flexibility than the (S) model, enabling greater geometric freedom in solar system design and providing greater diversity in design based on its intended purpose without significantly affecting the efficiency of the system.

Assessment and Modeling of Geothermal Potential in Northeastern Morocco

The northeast of Morocco is known for many hot water aquifers that emerge at Liasic formations which are the source of the primary thermal springs. In this region of Morocco, the geothermal gradient and heat flow are in relationship with the upward water circulation from Neogene volcanism at depth to the surface of their path through the area's tectonic fractures. Studies on thermal characteristics have revealed promising potential. However, no study has been carried out to estimate the possible exploitation of geothermal energy at the origin of thermal manifestations on the surface. In this paper, we model the geothermal potential stored in thermal reservoirs, using the volumetric method to evaluate and model the power potential through frequency distribution results by Monte Carlo simulation with Python. The model reveals a promising result for the Beni Snassen-Triffa and Eastern Rif areas an advantage for power generation and they could initially support 36-47.4 MWe and 10.6-13.9 MWe power plant respectively for 25 years.

Noise-induced transport in the Aubry-André-Harper model

We study quantum transport in a quasiperiodic Aubry-André-Harper (AAH) model induced by the coupling of the system to a Markovian heat bath. We find that coupling the heat bath locally does not affect transport in the delocalized and critical phases, while it induces logarithmic transport in the localized phase. Increasing the number of coupled sites at the central region introduces a transient diffusive regime, which crosses over to logarithmic transport in the localized phase and in the delocalized regime to ballistic transport. On the other hand, when the heat bath is coupled to equally spaced sites of the system, we observe a crossover from ballistic and logarithmic transport to diffusion in the delocalized and localized regimes, respectively. We propose a classical master equation, which in the localized phase, captures our numerical observations for both coupling configurations on a qualitative level and for some parameters, even on a quantitative level. Using the classical picture, we show that the crossover to diffusion occurs at a time that increases exponentially with the spacing between the coupled sites, and the resulting diffusion constant decreases exponentially with the spacing.

A readily synthesized ZnIn2S4/attapulgite as a high-performance photocatalyst for Cr(VI) reduction

Herein, a ZnIn2S4-decorated attapulgite photocatalyst (ZnIn2S4/ATP) was successfully synthesized by a facile oil bath heating method. It shows superior reduction efficiency for the removal of Cr(Ⅵ). The improved photocatalytic performance is primarily attributed to the intercalation effect of ZnIn2S4 and attapulgite (ATP), enhanced separation efficiency of photogenerated electron-hole pairs, and improved transport efficiency of photogenerated carriers. Moreover, insight into the photocatalytic mechanism demonstrates that •O2− and e− are the major active species in the photocatalytic reduction of Cr(VI) over ZnIn2S4/ATP. This work serves as a reference for integrating natural clay with semiconductors for photocatalytic wastewater treatment.

Computational Issues of Quantum Heat Engines with Non-Harmonic Working Medium

In this work, we lay the foundations for computing the behavior of a quantum heat engine whose working medium consists of an ensemble of non-harmonic quantum oscillators. In order to enable this analysis, we develop a method based on the Schrödinger picture. We investigate different possible choices on the basis of expanding the density operator, as it is crucial to select a basis that will expedite the numerical integration of the time-evolution equation without compromising the accuracy of the computed results. For this purpose, we developed an estimation technique that allows us to quantify the error that is unavoidably introduced when time-evolving the density matrix expansion over a finite-dimensional basis. Using this and other ways of evaluating a specific choice of basis, we arrive at the conclusion that the basis of eigenstates of a harmonic Hamiltonian leads to the best computational performance. Additionally, we present a method to quantify and reduce the error that is introduced when extracting relevant physical information about the ensemble of oscillators. The techniques presented here are specific to quantum heat cycles; the coexistence within a cycle of time-dependent Hamiltonian and coupling with a thermal reservoir are particularly complex to handle for the non-harmonic case. The present investigation is paving the way for numerical analysis of non-harmonic quantum heat machines.

Finite temperature dynamics in a polarized sub-Ohmic heat bath: A hierarchical equations of motion-tensor train study.

The dynamics of the sub-Ohmic spin-boson model under polarized initial conditions at finite temperatures is investigated by employing both analytical tools and the numerically accurate hierarchical equations of motion-tensor train method. By analyzing the features of nonequilibrium dynamics, we discovered a bifurcation phenomenon, which separates two regimes of the dynamics. It is found that before the bifurcation time, increasing temperature slows down the population dynamics, while the opposite effect occurs after the bifurcation time. The dynamics is highly sensitive to both initial preparation of the bath and thermal effects.

Autonomous quantum heat engine based on non-Markovian dynamics of an optomechanical Hamiltonian

We propose a recipe for demonstrating an autonomous quantum heat engine where the working fluid consists of a harmonic oscillator, the frequency of which is tuned by a driving mode. The working fluid is coupled two heat reservoirs each exhibiting a peaked power spectrum, a hot reservoir peaked at a higher frequency than the cold reservoir. Provided that the driving mode is initialized in a coherent state with a high enough amplitude and the parameters of the utilized optomechanical Hamiltonian and the reservoirs are appropriate, the driving mode induces an approximate Otto cycle for the working fluid and consequently its oscillation amplitude begins to increase in time. We build both an analytical and a non-Markovian quasiclassical model for this quantum heat engine and show that reasonably powerful coherent fields can be generated as the output of the quantum heat engine. This general theoretical proposal heralds the in-depth studies of quantum heat engines in the non-Markovian regime. Further, it paves the way for specific physical realizations, such as those in optomechanical systems, and for the subsequent experimental realization of an autonomous quantum heat engine.

Effect of microwave and conduction heating on the adsorption ability of myofibrillar protein to pyrazine flavor compounds

In order to clarify the modulation of microwave and conduction heating on the aroma release and adsorption of meat, the effect of different myofibrillar proteins (MP) on the release ability of pyrazines (2-methylpyrazine, 2,5-dimethylpyrazine, and 2,3,5-trimethylpyrazine) was investigated. The adsorption ability, hydrophobicity of MP, and thermodynamic parameters were analyzed. Conduction heating by water bath exhibited stronger adsorption ability of MP for 2-methylpyrazine (17.17 ± 2.27%) than that of microwave, followed by 2,3,5-trimethylpyrazine (11.50 ± 0.91%) and 2,5-dimethylpyrazine (8.63 ± 5.24%), which accounted for the structures of pyrazines. Water bath heating promoted protein unfolding leading to increased exposure of hydrophobic regions thereby enhancing binding affinity with pyrazine flavor compounds. Furthermore, fluorescence quenching ability was enhanced with increasing substituents on pyrazine flavor compounds. The hydrophobic interaction between 2,5-dimethylpyrazine and MP was dominant in both heat treatments. The interactions of conduction-heated MP with 2-methylpyrazine and 2,3,5-trimethylpyrazine predominantly involved hydrophobic forces, whereas interactions with microwave-heated proteins were primarily driven by van der Waals forces and hydrogen bonding effects. The results obtained from this study provide valuable theoretical insights into understanding the differences in the flavor release of meat product resulting from microwave versus water bath heating.

Two-dimensional open quantum system in dissipative bosonic heat bath, external magnetic field, and two time-dependent electric fields

Two-dimensional open quantum system in dissipative bosonic heat bath, external magnetic field, and two time-dependent electric fields

Thermoacoustic Fano-based bistable energy converters: A new concept of thermoacoustic engine

In this work, we propose a highly efficient thermoacoustic energy converter based on the concept of Fano-based bistable systems. The proposed device, in its simplest version consists of a bilayer polymeric cylinder with harder core and softer and thinner shell. The heat source enforced at the core-shell interface induces thermo-mechanical stress fields. The stress field causes the occurrence of wrinkling patterns in the shell and the release of acoustic energy by a snap-through-buckling mechanism. We show that, when the shell is acoustically resonant at a specific frequency, the synergetic interplay of snap-through and Fano-resonances is capable of producing high amplitude and long-lasting pressure oscillations. In other words, under specifics conditions, the synergetic interaction between wrinkling instabilities and Fano resonance is able to extract mechanical energy from the heat source. The efficiency of the system in converting heat-into-work under resonant conditions is at least 6 times higher than that out of resonance. Notably, for a temperature difference of 1 K between the heat source (the hot thermal reservoir beneath the resonant shell) and the surrounding water (the cold thermal reservoir above the resonant shell), the system may reach a conversion efficiency above 70% of the theoretical Carnot efficiency. The so-generated mechanical oscillations can be converted in electrical energy for instance by using sound-to-energy converting systems such as conventional loudspeakers. The characteristics of the heat source have been selected to be representative of low-grade thermal sources (e.g. waste-heat, in particular intermittent sources) abundantly available in natural, and industrial contexts. Importantly, the systems may be adapted to many different geometries spanning from the proposed core-shell cylinders in which the heat source can be either inside the tube (for instance an exhaust gas/liquid outlet) or outside the tube, to plates (like a solar panel system).

Differences and Causal Mechanisms in the Lithospheric Thermal Structures in the Cratons in East China: Implications for Their Geothermal Resource Potential

The thermal structure of the lithosphere is key to understanding its thickness, properties, evolution, and geothermal resources. Cratons are known for their low heat flow and deep lithospheric roots. However, present-day cratons in East China have geothermal characteristics that are highly complex, with variable heat flow values, diverging from the typical thermal state of cratons. In this study, we conducted a detailed analysis of the geothermal geological background of the cratons in East China, summarizing the thermal state and tectono-thermal processes of different tectonic units, calculating the temperature at various depths, and discussing differences in temperature and thermal reservoirs at different depths. The observed lithospheric thermal thickness within the North Jiangsu Basin and the Bohai Bay Basin is notably reduced in comparison to that of the Jianghan Basin and the Southern North China Basin. The phenomenon of craton destruction during the Late Mesozoic emerges as a pivotal determinant, enhancing the geothermal resource prospects of both the Bohai Bay Basin and the North Jiangsu Basin. Our findings contribute significantly to the augmentation of theoretical frameworks concerning the origins of heat sources in global cratons. Furthermore, they offer invaluable insights for the methodical exploration, evaluation, advancement, and exploitation of geothermal resources.

Correlation functions for open strings and chaos

We study the holographic interpretation of the bulk instability, i.e. the bulk Lyapunov exponent in the motion of open classical bosonic strings in AdS black hole/brane/string backgrounds. In the vicinity of homogeneous and isotropic horizons the bulk Lyapunov exponent saturates the MSS chaos bound but in fact has nothing to do with chaos as our string configurations live in an integrable sector. In the D1-D5-p black string background, the bulk Lyapunov exponent is deformed away from the MSS value both by the rotation (the infrared deformation) and the existence of an asymptotically flat region (the ultraviolet deformation). The dynamics is still integrable and has nothing to do with chaos (either in gravity or in field theory). Instead, the bulk Lyapunov scale captures the imaginary part of quasinormal mode frequencies. Therefore, the meaning of the bulk chaos is that it determines the thermal decay rate due to the coupling to the heat bath, i.e. the horizon.

Entropy and the Stirling engine

The thermodynamic approach developed in the Romanelli (2017 Am. J. Phys. 85 926–31). achieves, among other things, an adequate description of the experimental pressure-volumes diagrams of Stirling engines. However, an unusual and relevant result of such an approach is that, during part of its cycle, the working gas reaches temperatures above and below the temperatures of the two thermal reservoirs that keep the engine running. Within this framework, the present paper essentially shows that the predictions of the above model are not in conflict with the second law of thermodynamics. Analytical expressions for the entropies of the working gas and the environment are developed, and the definition of efficiency is discussed. The theoretical results are applied numerically to a specific Stirling engine.

Influences and implications of water-rock interaction on physical properties of geothermal reservoirs along the Red River Fault

Geothermal resources are composed of rock and water, in which water-rock interaction (WRI) has a great influence on the physical properties of thermal reservoirs. The Red River Fault is abundant in different kinds of geothermal resources and the main thermal reservoirs are sandstones and limestones. The study has used the water chemistry, X-ray diffraction (XRD), N2 adsorption, mercury injection, scanning electron microscopy (SEM), physical parameters, and WRI simulation experiments to study the physical properties changes in thermal reservoirs. The pores of thermal reservoirs are mainly intragranular and intergranular pores, in which sandstones are dominated by micropores and mesopores while limestones are dominated by macropores. Through the WRI simulation experiment, the reservoirs have generated many dissolution pores and microfractures, of which the pore-throat connectivity has deteriorated. The changes of physical parameters can be divided into two stages with opposite trends, in which the first stage is controlled by temperature and pressure while the second stage is influenced by dissolution and precipitation. The study has suggested that the change stage of physical properties should be clarified to update the resource quantity dynamically in the development process and the components of fracturing fluids should be studied to achieve the optimal improvement of physical properties and reduce the adverse impact on pore-throat connectivity before the development engineering.

Gain-assisted quantum heat engine based on electromagnetically induced transparency

We propose a scheme to realize a gain-assisted quantum heat engine (QHE) based on electromagnetically induced transparency (EIT), which consists of a three-level Λ-type atomic system interacting with two thermal reservoirs and a coupling field. The gain without inversion is induced to the system via spontaneously generated coherence (SGC) between two lower levels. The SGC has significantly affect on the system’s dynamics, resulting in an enhancement of the emission cross-section and spectral brightness of the QHE.

Energetics of the dissipative quantum oscillator

In this paper, we discuss some aspects of the energetics of a quantum Brownian particle placed in a harmonic trap, also known as the dissipative quantum oscillator. Based on the fluctuation–dissipation theorem, we analyze two distinct notions of thermally-averaged energy that can be ascribed to the oscillator. These energy functions, respectively dubbed hereafter as the mean energy and the internal energy, are found to be inequivalent for arbitrary system–bath coupling strength when the dissipation kernel has a non-zero memory timescale, as in the case of a Drude bath. Remarkably, both the energy functions satisfy the quantum counterpart of the energy equipartition theorem, but with different probability distributions on the frequency domain of the heat bath. Moreover, the Gibbs approach to thermodynamics provides us with yet another thermally-averaged energy function. In the weak-coupling limit, all the above-mentioned energy expressions reduce to ϵ=ħω02coth(ħω02kBT), which is the familiar result. We generalize our analysis to the case of the three-dimensional dissipative charged oscillator placed in a spatially-uniform magnetic field.

Integration of geoelectrical, hydrochemical and geothermal data to identify the origin of thermal water in the foothills of the Tlemcen mountains, Northwestern Algeria

In previous studies, the mean geothermal gradient of the Tlemcen region has been estimated as low (3.7°C/100m). The existing boreholes in the Remchi plain (North of the Tlemcen Mountains) reveal thermal waters (26-48°C) and a remarkable artesianism. To understand the hydrodynamics and origin of thermalism of this groundwater, we merged geophysical and physical-chemical data. Geophysical data allowed us to improve the resolution of the fault network, to estimate the thickness of various sandstone beds connected with the thermal reservoir and to delimit the productive aquifer. Chemical characteristics of waters have been used for a statistical analysis, which displayed two independent water clusters resulting from two hydrodynamic patterns throughout the aquifer. The hydrothermal analysis identifies the depth reached by water and the relationship between water circulation and the fault network. Comparison with previous studies allowed us to build a schematic geological model, which explains hydrodynamics, origin and role of this structure in the groundwater flow.

Thermal rectification in novel two-dimensional hybrid graphene/BCN sheets: A molecular dynamics simulation

The graphene-like monolayer of carbon, boron and nitrogen that maintains the native hexagonal atomic lattice (BCN), is a novel semiconductor with special thermal properties. Herein, with the aid of a non-equilibrium molecular dynamics approach (NEMD), we study phonon thermal rectification in a hybrid system of pure graphene and BCN (G-BCN) in various configurations under a series of positive and negative temperature gradients. We begin by investigating the relation of thermal rectification to sample’s mean temperature, T, and the imposed temperature difference, ΔT, between the two heat baths at its ends. We then move to explore the effect of varying strain levels of our sample on thermal rectification, followed by Kapitza resistance calculations at the G-BCN interface, which shed light on the interface effects on thermal rectification. Our simulation results reveal a BCN-configuration-dependent behavior of thermal rectification. Finally, the underlying mechanism leading to a preferred direction for phonons is studied using phonon density of states (DOS) on both sides of the G-BCN interface.

Numerical investigation of electricity generation potential by water circulating through three horizontal wells at Fengshun geothermal field in China

Fengshun geothermal field is the first medium and low temperature geothermal area in China, which is used for electricity generation. At present only vertical wells are employed to extract heat energy. After about 40 years of exploitation, the production temperature and rate are all declined. In this work, based on the hydrogeological data of the study area, the deep reservoir temperature and corresponding circulation depth of underground hot water are predicted with a silica thermometer. To fully develop the deep heat reservoir, we proposed a new heat exploitation scheme through three horizontal wells, computed the electricity generation potential and efficiency, and analyzed the main factors affecting heat production. The results indicate that under the reference conditions, the three horizontal well system attaches an electric power of 2.70–1.5 MW, a reservoir impedance of 0.13–0.27 MPa/(kg/s), a pump power of 0.29–1.16 MW, and energy efficiency of 7.34–1.30 during the reservoir lifetime of 43.6 years. Thus, this three-horizontal-well system has significant development potential in Fengshun deep geothermal reservoir. Sensitivity analysis indicates that water production rate, injection temperature and initial reservoir temperature have a significant impact on heat production performance. Reducing the water production rate and injection temperature within a certain range can improve energy efficiency. For the precise design of power generation systems and the accurate evaluation of production performance, field logging data is necessary.