Heat Engine Model Research Articles

A Thermodynamic Study on Information Power in Communication Systems.

Modern information theory pioneered by Shannon provides the mathematical foundation of information transmission and compression. However, the physical (and especially the energetic) nature of the information has been elusive. While the processing of information incurs inevitable energy dissipation, it is possible for communication systems to harness information to perform useful work. In this article, we prove that the thermodynamic cost (that is, the entropy production of the communication system) is at least equal to the information transmitted. Based on this result, a model of a communication heat engine is proposed, which can extract work from the heat bath by utilizing the transmission of information. The communication heat engine integrates the manipulation of both energy and information so that both information and power may be transmitted in parallel. The information transmission rate and the information power of the communication heat engine are derived from a pure thermodynamics argument. We find that the information power of the communication heat engine can be increased by increasing the number of communication channels, but the absolute energy efficiency of the heat engine first increases and then decreases after the number of channels of the system exceeds a threshold. The proposed model and definitions provide a new way to think of a classical communication system from a thermodynamic perspective.

Proposal for composite quantum electromagnetically induced transparency heat engine coupled by a nanomechanical mirror

Abstract This paper introduces a quantum heat engine model that utilizes an ultracold atomic gas coupled with a nanomechanical mirror. The mirror’s vibration induces an opto-mechanical sideband in the control field, affecting the behavior of the cold gas and subsequently influencing the output radiation of the engine. The model incorporates mirror vibration while omitting cavity confinement, establishing a bridge between a multi-level atom–laser interacting system that plays with coherences and the mechanical vibration of the nanomechanical mirror, which jointly function as heat engines. Three distinct heat engine configurations are proposed: the first involves a vibration-free three-level Λ-type system, the second introduces nanomechanical vibration to the three-level Λ-type system, and the third constitutes a composite engine that combines the previous setups along with nanomechanical vibration. The spectral brightness of a three-level heat engine is diminished with mirror vibration, whereas for a composite heat engine, there is a slight enhancement in the brightness peak. However, the maximum brightness is attained when there is no vibration. Comparisons between the proposed model and an ideal system are made regarding entropy balance, adhering to the constraints of the second law of thermodynamics. The model observed that when subjected to mirror vibration, the proposed heat engines diverged from the characteristics expected in an ideal heat engine.

Energetic optimization and local stability of heliothermal plant models under three thermo-economic performance regimes

Solar power plants have the advantage of not producing greenhouse gases into the atmosphere. In their operation, some design and construction parameters can be identified for improving their performance. In this work within the context of Finite-Time Thermodynamics (FTT), we analyze a Müser–Curzon–Ahlborn heat engine model by maximizing economic-objective functions which not only provide optimal operation modes, but also they can reduce the energy dissipated in the form of heat towards the atmosphere. In our thermo-economic study we take into account both investment as well as operation and maintenance (O&M) costs. From operation data of three commercial tower-power plants: Eurelios, Gemasolar and Ivanpah, we find optimal values of solar concentration (Ci) for each economic-operation regime, accounting for the effect of internal irreversibilities (through a lumped parameter R). The Ci-values that we found are in the range of current reported values for the three power plants aforementioned. Besides, we present a local stability analysis for the three aforementioned solar plants and we show that for large size plants, disturbed isothermal branches return faster to their respective steady states, in less dissipative regimes, (e.g. the ecological regime).

Inferring entropy production in anharmonic Brownian gyrators

A non-vanishing entropy production rate is one of the defining characteristics of any non-equilibrium system, and several techniques exist to determine this quantity directly from experimental data. The short-time inference scheme, derived from the thermodynamic uncertainty relation, is a recent addition to the list of these techniques. Here we apply this scheme to quantify the entropy production rate in a class of microscopic heat engine models called Brownian gyrators. In particular, we consider models with anharmonic confining potentials. In these cases, the dynamical equations are indelibly non-linear, and the exact dependences of the entropy production rate on the model parameters are unknown. Our results demonstrate that the short-time inference scheme can efficiently determine these dependencies from a moderate amount of trajectory data. Furthermore, the results show that the non-equilibrium properties of the gyrator model with anharmonic confining potentials are considerably different from its harmonic counterpart - especially in set-ups leading to a non-equilibrium dynamics and the resulting gyration patterns.

Optimizations of multilevel quantum engine with N noninteracting fermions based on Lenoir cycle

We consider optimizations of Lenoir heat engine within a quantum dynamical field consisting of $N$ noninteracting fermions trapped in multilevel infinite potential square-well. Fermions play role as working substance of the engine with each particle nested at different level of energy. We optimized this quantum heat engine model by analysing the physical parameter and deriving the optimum properties of the engine model. The model we investigated consists of one high-energy heat bath and one low-energy sink bath. Heat leakage occurs between these two bathes as expected will degenerate the efficiency of quantum heat engine model. The degeneration increased as we raised the constant parameter of heat leakage. We also obtained loop curves in dimensionless power vs. efficiency of the engine, which efficiency is explicitly affected by heat leakage, but in contrast for the power output. From the curves, we assured that the efficiency of the engine would go back to zero as we raised compression ratio of engine with leakage. Lastly, we checked Clausius relations for each model with various levels of heat leakage. We found that models with leakage have a reversible process on specific compression ratios for each variation of heat leakage. Nevertheless, the compression ratio has limitations because of the $\oint dQ/E>0$ after the reversible point, i.e. violates the Clausius relation.

Математичне моделювання процесів в дизель-газотурбінних енергетичних комплексах з термохімічною обробкою палива

This paper discussed the methodological aspects of the study using methods of mathematical modeling of processes in ship power plants with thermochemical fuel treatment. The results of the study of physical and chemical processes in structural and functional blocks, simulating individual links of the thermodynamic cycle, are considered. The combination of blocks with links in the form of material and energy flows makes it possible to model the complete scheme of the mathematical model of the power module. Due to the diversity and complexity of the processes in the combined diesel-gas turbine power complex with a thermochemical fuel treatment system, when modeling, the characteristics of the power equipment were determined separately, followed by merging the results obtained and combining the models with links in the form of material and energy flows. Mathematical models of a gas turbine engine, a recycling circuit, a thermochemical fuel treatment unit were created using the Aspen Plus physical and chemical processes modeling system. Working processes in the internal combustion engine were modeled using the CHEMKIN software package. It has been proven that the universal mathematical models of heat engines, which are part of the power module with thermochemical fuel treatment, require adjustment of the selected basic characteristics. Therefore, mathematical models of structural-functional blocks and groups of blocks contain algorithms for setting up models when they are verified by objective functions. The proposed algorithms provide verification of the developed mathematical models in terms of existing or prospective gas turbine engines and internal combustion engines. These algorithms provide the possibility of correct adjustment of the equipment parameters of diesel-gas turbine power complexes with thermochemical fuel treatment. The mathematical model of the internal combustion engine operating cycle based on the CHEMKIN software package provides an opportunity to conduct a primary assessment of the efficiency of energy conversion in the working cylinder. The results of evaluating the adequacy of the mathematical model of the ICE operating cycle based on the CHEMKIN software package showed a satisfactory agreement between the obtained results and experimental data. The maximum root-mean-square error of the calculated data obtained on the basis of the model is within 8.5%.

Multi-Objective Optimization of an Irreversible Single Resonance Energy-Selective Electron Heat Engine

Based on the model of irreversible single resonance energy-selective electron heat engine established in the previous literature, this paper applies finite-time thermodynamic theory and NSGA-II algorithm to perform multi-objective optimization. Single-, bi-, tri- and quadru-objective optimizations are performed when the energy boundary and the resonance width are taken as the optimization variables, and the power output, thermal efficiency, efficient power and ecological function are taken as the optimization objectives. The deviation indexes of different optimization objective combinations are obtained by using LINMAP, TOPSIS and Shannon entropy approaches. The results show that the values of energy boundary and resonance width can be reasonably selected according to the design requirements of the system. When power output and efficiency are optimized, the minimal deviation index is obtained by TOPSIS approach and the value is 0.0748, which is the most ideal design scheme.

Collective effects on the performance and stability of quantum heat engines.

Recent predictions for quantum-mechanical enhancements in the operation of small heat engines have raised renewed interest in their study both from a fundamental perspective and in view of applications. One essential question is whether collective effects may help to carry enhancements over larger scales, when increasing the number of systems composing the working substance of the engine. Such enhancements may consider not only power and efficiency, that is, its performance, but, additionally, its constancy, that is, the stability of the engine with respect to unavoidable environmental fluctuations. We explore this issue by introducing a many-body quantum heat engine model composed by spin pairs working in continuous operation. We study how power, efficiency, and constancy scale with the number of spins composing the engine and introduce a well-defined macroscopic limit where analytical expressions are obtained. Our results predict power enhancements, in both finite-size and macroscopic cases, for a broad range of system parameters and temperatures, without compromising the engine efficiency, accompanied by coherence-enhanced constancy for finite sizes. We discuss these quantities in connection to thermodynamic uncertainty relations.

Exactly solvable model of a passive Brownian heat engine and its comparison with active engines

We perform an extensive analysis of passive as well as active micro-heat engines with different single-particle stochastic models. Using stochastic thermodynamics we calculate the thermodynamic work, heat, entropy production and efficiency of passive and active Brownian heat engines analytically, as well as numerically, and compare them. We run the heat engines with a protocol for which the average thermodynamic quantities are calculated exactly for an arbitrary cycle time. We also discuss the group of protocols for which exact non-quasistatic calculations can be done, completely in the passive engine case and partially in the active engines. We obtain detailed thermodynamics of non-quasistatic (i.e. powerful) single-particle micro heat engines. The quasistatic (i.e. zero power) limit of the results is obtained by taking a long (infinite) cycle time. We also study the distributions of position of the confined particle in both passive and active engines. We compare their characteristics in terms of the parameter that measures the competition between the active persistence in the particle position (due to active noises) and the harmonic confinement. We also calculate excess kurtosis that measures the non-Gaussianity of these distributions. Our analysis shows that the efficiency of such thermal machines can be enhanced or reduced depending on the activity present in the model.

Differentiation of correlated fluctuations in site energy on excitation energy transfer in photosynthetic light-harvesting complexes

One of the promising approaches to revealing the photosynthetic efficiency of close to one unit is to investigate the quantum regime of excitation energy transfer (EET). The majority of studies, however, have concluded that different pigment molecules contribute equally to EET, rather than differently. We investigate the roles of different site-energies in EET by evaluating the correlated fluctuations of site-energies in two adjacent pigment molecules (namely Site 1 and Site 2), and we attempt to demonstrate different site roles in EET with the j–V characteristics and power via a photosynthetic quantum heat engine (QHE) model rather than an actual photosynthetic protein. The results show that fluctuations at Site 1 (the pigment molecule absorbing solar photons) provide ascending and then descending EET. At Site 2, the EET is reduced through the use of correlated fluctuation increments (the pigment molecule acting as the charge-transfer excited state). Furthermore, when investigating the correlated fluctuations at Site 2, the different gap differences of the output terminal play a positive role in EET, but a sharply decreasing EET process is also achieved with less correlated fluctuations at Site 2 compared to those at Site 1. The findings show that different pigment molecules contribute differently to EET. The significance of this work is that it not only clarifies the roles of different pigment molecules in EET, but it also deepens our understanding of the fundamental physics of EET as it transports through the molecular chain in photosynthetic light-harvesting complexes. Furthermore, the results are appropriate to the EET in organic semiconductors, photovoltaic devices, and quantum networks, when these systems couple to the environment of photons via the vibrational motion of sites in the molecular chain.

Second moments of work and heat for a single-particle stochastic heat engine in a breathing harmonic potential

Abstract We consider a simple model of a stochastic heat engine, which consists of a single Brownian particle moving in a one-dimensional periodically breathing harmonic potential. The overdamped limit is assumed. Expressions for the second moments (variances and covariances) of heat and work are obtained in the form of integrals, whose integrands contain functions satisfying certain differential equations. The results in the quasi-static limit are simple functions of the temperatures of hot and cold thermal baths. The coefficient of variation of the work is suggested to give an approximate probability for the work to exceed a given threshold. During the derivation, we get the expression of the cumulant-generating function.

Extracting work from random collisions: A model of a quantum heat engine.

We study the statistical distribution of the ergotropy and of the efficiency of a single-qubit battery ad of a single-qubit Otto engine, respectively fueled by random collisions. The single qubit, our working fluid, is assumed to exchange energy with two reservoirs: a nonequilibrium "hot" reservoir and a zero-temperature cold reservoir. The interactions between the qubit and the reservoirs are described in terms of a collision model of open system dynamics. The qubit interacts with the nonequilibrium reservoir (a large ensemble of qudits all prepared in the same pure state) via random unitary collisions and with the cold reservoir (a large ensemble of qubits in their ground state) via a partial swap. Due to the random nature of the interaction with the hot reservoir, fluctuations in ergotropy, heat, and work are present, shrinking with the size of the qudits in the hot reservoir. While the mean, "macroscopic" efficiency of the Otto engine is the same as in the case in which the hot reservoir is a thermal one, the distribution of efficiencies does not support finite moments, so that the mean of efficiencies does not coincide with the macroscopic efficiency.

Heat transfer effect on the performance of thermal Brownian heat engine

A new finite time thermodynamic model of thermal Brownian heat engine is established. The heat transfer between heat reservoir and viscous medium is considered and is assumed to be obeyed Newton’s heat transfer law. The effects of heat transfer process on system performance are studied in detail. The key performance parameters of system are derived. For the fixed temperature of reservoirs, the temperatures of viscous medium are optimized for maximizing the power. For a fixed total heat exchanger inventory, the distribution of heat exchanger inventory is also optimized for maximizing the power. The effects of key parameters on the performance of the system are investigated, and the optimal operating region is given. The results show that the thermodynamic performance of system can be improved by enhancing the heat transfer between reservoir and heat engine. There exist optimal distribution of heat exchanger inventory and optimal temperatures of viscous medium corresponding to the maximum power, respectively. There also exists a pair of barrier height and external load corresponding to double maximum power. The efficiency decreases versus barrier height and increases versus external load. The asymmetry potential is relevant to the heat flow caused by overcoming external load of particles. The efficiency is irrelevant to the working temperature, and it only depends on the internal parameters of heat engine.

Maximum-power heat engines and refrigerators in the fast-driving regime

We study the optimization of the performance of arbitrary periodically driven thermal machines. Within the assumption of fast modulation of the driving parameters, we derive the optimal cycle that universally maximizes the extracted power of heat engines, the cooling power of refrigerators, and in general any linear combination of the heat currents. We denote this optimal solution as ``generalized Otto cycle'' since it shares the basic structure with the standard Otto cycle, but it is characterized by a greater number of fast strokes. We bound this number in terms of the dimension of the Hilbert space of the system used as working fluid. The generality of these results allows for a widespread range of applications, such as reducing the computational complexity for numerical approaches, or obtaining the explicit form of the optimal protocols when the system-baths interactions are characterized by a single thermalization scale. In this case, we compare the thermodynamic performance of a collection of optimally driven noninteracting and interacting qubits. Remarkably, for refrigerators the noninteracting qubits perform almost as well as the interacting ones, while in the heat engine case there is a many-body advantage both in the maximum power, and in the efficiency at maximum power. Additionally, we illustrate our general results studying the paradigmatic model of a qutrit-based heat engine. Our results strictly hold in the semiclassical case in which no coherence is generated by the driving, and finally we discuss the noncommuting case.

Optimization of a Thermomagnetic Heat Engine for Harvesting Low Grade Thermal Energy

Thermomagnetic energy harvesters are one form of technology that can be effectively used to extract energy from low grade heat sources, without causing damage to the environment. In this study, we investigated the output performance of our previously designed thermomagnetic heat engine, which was developed to extract thermal energy by exploiting the magnetocaloric effect of gadolinium. The proposed heat engine uses water as the heat transfer fluid, with heat sources at a temperature in the range 20–65 °C. Although this method turned out to be a promising solution to extract thermal energy, the amount of energy extracted through this geometry of thermomagnetic engine was limited and depends on the interaction between magnetic flux and magnetocaloric material. Therefore, in this paper we carry out an in-depth analysis of the designed thermomagnetic heat engine with an integrated approach of numerical simulation and experimental validation. The computational model improved recognition of the critical component to developing an optimized model of the thermomagnetic heat engine. Based on the simulation result, a new working model was developed that showed a significant improvement in the rpm and axial torque generation. The results indicate that the peak RPM and torque of the engine are improved by 34.3% and 32.2%, respectively.

Space-fractional quantum heat engine based on level degeneracy

In order to examine the work and efficiency of the space-fractional quantum heat engine, we consider a model of the space-fractional quantum heat engine which has a Stirling-like cycle with a single particle under infinite potential well as an example. We numerically compute the work and efficiency for various fractional exponents. We show the work and the efficiency of the engine depending on the length of the potential well and fractional exponent of the engine. Furthermore, we show that fractional exponent plays a substantial role in the operating range of the quantum heat engine. Thus, we conclude that the fractional parameter can be used as a tuning parameter to obtain positive work and efficiency for the large size of the quantum heat engine. Additionally, the numerical results and model imply that the size of the engine can be enlarged in the nano-scale by using fractional deformations. As a result, in this study, we have not only shown that fractional deformations in space play an important role on the work and efficiency of the quantum heat engines but also introduced the concept of fractional quantum heat engines to the literature.

Hybrid Electric Vehicles: A Review of Existing Configurations and Thermodynamic Cycles

The mobility industry has experienced a fast evolution towards electric-based transport in recent years. Recently, hybrid electric vehicles, which combine electric and conventional combustion systems, have become the most popular alternative by far. This is due to longer autonomy and more extended refueling networks in comparison with the recharging points system, which is still quite limited in some countries. This paper aims to conduct a literature review on thermodynamic models of heat engines used in hybrid electric vehicles and their respective configurations for series, parallel and mixed powertrain. It will discuss the most important models of thermal energy in combustion engines such as the Otto, Atkinson and Miller cycles which are widely used in commercial hybrid electric vehicle models. In short, this work aims at serving as an illustrative but descriptive document, which may be valuable for multiple research and academic purposes.

The Role of Internal Irreversibilities in the Performance and Stability of Power Plant Models Working at Maximum ϵ-Ecological Function

Abstract The proposal of models that account for the irreversibilities within the core engine has been the topic of interest to quantify the useful energy available during its conversion. In this work, we analyze the energetic optimization and stability (local and global) of three power plants, nuclear, combined-cycle, and simple-cycle ones, by means of the Curzon–Ahlborn heat engine model which considers a linear heat transfer law. The internal irreversibilities of the working fluid measured through the r-parameter are associated with the so-called “uncompensated Clausius heat.” In addition, the generalization of the ecological function is used to find operating conditions in three different zones, which allows to carry out a numerical analysis focused on the stability of power plants in each operation zone. We noted that not all power plants reveal stability in all the operation zones when irreversibilities are considered through the r-parameter on real-world power plants. However, an improved stability is shown in the zone limited by the maximum power output and maximum efficiency regimes.

Work Generation from Thermal Noise by Quantum Phase-Sensitive Observation.

We put forward the concept of work extraction from thermal noise by phase-sensitive (homodyne) measurements of the noisy input followed by (outcome-dependent) unitary manipulations of the postmeasured state. For optimized measurements, noise input with more than one quantum on average is shown to yield heat-to-work conversion with efficiency and power that grow with the mean number of input quanta, the efficiency and the inverse temperature of the detector. This protocol is shown to be advantageous compared to common models of information and heat engines.

Thermodynamic Uncertainty Relation in Slowly Driven Quantum Heat Engines.

Thermodynamic uncertainty relations express a trade-off between precision, defined as the noise-to-signal ratio of a generic current, and the amount of associated entropy production. These results have deep consequences for autonomous heat engines operating at steady state, imposing an upper bound for their efficiency in terms of the power yield and its fluctuations. In the present Letter we analyze a different class of heat engines, namely, those which are operating in the periodic slow-driving regime. We show that an alternative TUR is satisfied, which is less restrictive than that of steady-state engines: it allows for engines that produce finite power, with small power fluctuations, to operate close to reversibility. The bound further incorporates the effect of quantum fluctuations, which reduces engine efficiency relative to the average power and reliability. We finally illustrate our findings in the experimentally relevant model of a single-ion heat engine.