Relative Efficiency Improvement Research Articles

A multiscale stochastic particle method based on the Fokker-Planck model for nonequilibrium gas flows

The Fokker-Planck (FP) model characterizes the intermolecular collisions as continuous stochastic processes in velocity space. Compared to the Direct Simulation Monte Carlo (DSMC) method, which is grounded in the Boltzmann equation, the stochastic particle method based on the FP model, referred to as the SP-FP method, demonstrates a relative improvement in computational efficiency. However, the traditional SP-FP method, utilizing operator splitting scheme, encounters analogous limitations to DSMC, thereby limiting the application of large temporal-spatial discretization for simulating near-continuum and continuum flows. In this study, two critical advancements are introduced to improve the traditional SP-FP method. First, the exact integration scheme of the ellipsoidal-statistical FP (ESFP) model is derived, enabling the replication of the theoretical solutions for homogeneous relaxation with any time step. Furthermore, leveraging the integration scheme of the ESFP model, we propose a Multiscale Stochastic Particle (MSP) method. The MSP method quantifies the numerical errors stemming from the operator splitting scheme and corrects them in the relaxation step. This capability allows the MSP method to be employed with larger temporal-spatial discretization for inhomogeneous problems, achieving second-order accuracy while retaining implementation simplicity. Application of the MSP method to various benchmark problems, including Couette flow, Fourier flow, Poiseuille flow, Sod tube flow, Lid-driven cavity flow, and flow through a slit, demonstrates its promise for simulating multiscale nonequilibrium gas flows with high computational efficiency and accuracy.

Enhancing Small Millet Farming Resilience through Conservation Agriculture in Rainfed Regions

The Centre of Excellence in Millets, located in Athiyandal, Tamil Nadu, conducted an extensive study from kharif 2020 to 2022, focusing on the impact of conservation agriculture practices on small millet crops in rainfed areas. The experiment, designed in a split-plot layout, included three main plot treatments: No tillage, Minimal tillage, and Mulching, with six sub-plot treatments comprising various millet varieties. Results indicated that a single ploughing significantly reduced weed populations, while mulching played a crucial role in curbing weed growth and conserving water. This led to substantial increases in grain yield and straw yield, ranging from 24.3% to 36.1% over the control, alongside an improvement in relative water use efficiency (RWUE) from 5.16 to 7.03 kg/ha/mm. Among the various millets cultivated with the mulching treatment (S3) emerged as the most favorable option in terms of grain yield. Finger millet, Kodomillet, and Foxtail millet exhibited the highest yields under this treatment, with 3010 kg/ha, 2234 kg/ha, and 2003 kg/ha, respectively. Additionally, Little millet, Barnyard millet, and Proso millet also demonstrated improved yields under Mulching, recording 1015 kg/ha, 1004 kg/ha, and 910 kg/ha, respectively. These results conclude that small millet cultivation in rainfed areas with mulching practices effectively enhances grain production, reduces weed growth, and ensures optimal water conservation, thereby providing sustainable alternatives to herbicide usage.

MOCVD grown ultraviolet microlight-emitting diodes with an InGaN/GaN/AlGaN active region design

In this work, we present an InGaN/GaN/AlGaN active region design for high-efficiency UV LED grown by MOCVD. The use of the GaN layer allows the AlGaN layer to be grown in optimized conditions which will enhance the overall crystal quality and device performance. The InGaN/GaN/AlGaN structure showed an improvement in the internal quantum efficiency (IQE) simulation in comparison with the conventional InGaN/AlGaN structure, with 15% and 14% at operating current density of 20 and 30 A/cm2, respectively. The IQE advantage remains at more than 10% in the operating current density range from 0 to 100 A/cm2 due to an enhanced electron-hole wavefunction overlap. The InGaN/GaN/AlGaN quantum wells were utilized to grow UV-A structures and micro-LEDs with sizes ranging from 20 × 20 to 100 × 100 μm2 were fabricated. The fabricated micro-LEDs showed a reliable emission at around 372 nm with 9 nm FWHM. Micro-LED devices with smaller sizes showed an improvement in relative external quantum efficiency due to its advantage in current spreading. This manuscript presents the potential to achieve both improved crystal quality and high-efficiency device using InGaN/GaN/AlGaN active region design.

Assessment of ternary CO2 mixtures as working fluids in supercritical Brayton cycles with floating critical points

The performance of the supercritical CO2 (sCO2) Brayton cycle deteriorates due to the mismatch between critical temperature and cold source temperature. An innovative solution based on ternary CO2 mixtures with adjustable compositions is proposed to expand the variation range of the critical temperature. An in-house MATLAB code is developed to investigate the design-point performance of the proposed system. The results indicate that the effect of improving cycle efficiency by using the modified floating critical point method becomes increasingly significant as the target critical temperature deviates from that of CO2. The CO2–H2S–Kr is screened out as the best ternary mixture, with the cycle efficiency being increased by over 8 % compared to the sCO2 cycle at very high (45 °C) and low (−15 °C) temperatures. The long-term performance is also evaluated based on the hourly historical weather data of two typical climate regions. The annual performance depends on both the average value and the distribution characteristics of the local ambient temperature. A relative improvement in annual average efficiency of 7%–9.56 % can be obtained depending on the regions. The present work is helpful to make the supercritical Brayton cycle give full play to its efficiency advantage in a wide cold source temperature range.

Thermodynamic analysis of heat transfer reduction in spark ignition using thermal barrier coatings

This work uses a 0D thermodynamic engine model coupled to a 1D surface temperature solver to study the potential of low thermal inertia thermal barrier coatings (TBCs) on combustion chamber surfaces to increase the efficiency of spark ignition engines. Under ideal conditions, coating the piston crown, head, and valve faces with a TBC with a thermal inertia of 640 J/m2 K s1/2 resulted in less than a 1% relative improvement in efficiency. Despite using a low thermal inertia coating to avoid open cycle charge heating, the reduction in closed cycle heat transfer, which is the pathway to increasing efficiency, increased knock propensity. Therefore, any efficiency gain through closed cycle heat transfer reduction in spark ignition is offset by the need to retard spark timing to counter knock. An exergy analysis of completely blocking heat transfer for a 10 crank-angle degree window showed that on a low compression engine, like those used for stoichiometric gasoline spark ignition, the maximum efficiency gain achievable was limited compared to a higher compression ratio engine. Furthermore, the high gas temperatures of stoichiometric operation mean that even state-of-the-art TBCs cannot elevate surface temperatures enough purely through temperature swing to achieve a significant reduction in heat transfer near top dead center, where work availability is highest. Overall, these results indicate that low thermal inertia TBCs are ill-suited for achieving an efficiency benefit in spark ignition through a heat transfer reduction pathway. Instead spark ignition TBC research should explore ways to use low thermal inertia TBCs to achieve open cycle charge cooling to reduce knock propensity.

The Potential of a Hybrid Optical Photovoltaic Converter–Thermoelectric Receiver to Enhance Conversion Efficiency

This paper presents a 3D simulation model for an optical photovoltaic power converter hybridized with a thermoelectric generator and shows the potential of hybridization for applications at very low temperatures. To carry out the study, the methodology for designing the hybrid converter optimizes the thermoelectric couple height under different air temperature conditions. This design considers two thermoelectric device scenarios: a low ZT (~1) and a high ZT (~2.4). Additionally, a state-of-the-art power converter based on a multijunction vertical structure made up of GaAs is considered. The results of the simulation procedure show maximum relative efficiency improvement factors of 6.16% (temperature matched) and 48.71% (temperature mismatched) compared to a nonhybrid power converter at 200 K of air temperature and high ZT. These results open a promising path for the development of a new generation of highly efficient hybrid converters.

RAINBOW Organic Solar Cells: Implementing Spectral Splitting in Lateral Multi-Junction Architectures.

While multi-junction geometries have the potential to boost the efficiency of organic solar cells, the experimental gains yet obtained are still very modest. This work proposes an alternative spectral splitting device concept in which various individual semiconducting junctions with cascading bandgaps are laid side by side, thus the name RAINBOW. Each lateral sub-cell receives a fraction of the spectrum that closely matches the main absorption band of the given semiconductor. Here, simulations are used to identify the important material and device properties of each RAINBOW sub-cell. Using the resulting design rules, three systems are selected, with narrow, medium, and wide effective bandgaps, and their potential as sub-cells in this geometry is experimentally investigated. With the aid of a custom-built setup that generates spectrally spread sunlight on demand, the simulations are experimentally validated, showing that this geometry can lead to a reduction in thermalization losses and an improvement in light harvesting, which results in a relative improvement in efficiency of 46.6% with respect to the best sub-cell. Finally, a working proof-of-concept monolithic device consisting of two sub-cells deposited from solution on the same substrate is fabricated, thus demonstrating the feasibility and the potential of the RAINBOW solar cell concept.

A hybrid approach for energy‐efficient routing in IoT using duty cycling and improved ant colony

AbstractThe promising technology of IoT in the fourth industrial revolution connects everything to the Internet in the digital world of the current era. Though the gigantic connectivity among things through the blend of multifarious technologies offers potential opportunities, it also increases the overhead to optimise the energy consumption in IoT networks. Energy optimisation has become the major concern in the IoT realm because of the continuous sensing of the constrained sensor nodes and data transmission to longer distances. The state‐of‐the‐art studies do not take into account the management of duty‐cycling and the process of efficient route discovery hand in hand. Also, the prevalent studies focus on the management of the sensor node's duty cycling (DC) solely instead of adaptive DC scheduling of the communication unit of the sensor node that consumes more energy during transmission. Therefore, keeping in view the existing tribulations regarding energy consumption, the authors attempt to devise an energy‐efficient routing approach using On‐Demand Duty Cycling and Ant‐Colony optimisation (DC‐ACO) for IoT. The ACO‐based routing approach is applicable in IoT networks because the ants’ environment is conceptualised as a distributed set of interconnected graph nodes. The proposed approach poses the empirical notion to manage the energy consumption of the IoT network by considering the key performance indicators (KPI) like energy consumption, packet delivery rate, average residual energy, mobility factor, distance, throughput, and network lifespan to accomplish the tangible outputs. The proposed approach is modelled using Data flow Diagrams (DFDs) and algorithms supported by results. Experimental results show significant improvement in relative throughput, network lifetime, and energy efficiency by 45%, 78%, and 68%, respectively, after simulating for successive iterations.

Multiple injection strategies with high water port injection rates for enhancing performance and emissions in a boosted SI engine

• Multiple injection strategies are applied to enable high water injection rates up to 1.0 by mass. • Detailed thermodynamic state analyses were conducted with high water injection rates. • The relative thermal efficiency improvement was 3.90% with 1.0 water to fuel mass injection ratio and triple injections. • Nitrogen oxides emissions were reduced up to 52.7% with combined multiple and water injections. • The major drawbacks of high-water injection rates (particulate matter and unburned hydrocarbon emissions) were significantly improved with multiple fuel injections. Water injection has been proven both to reduce emissions of nitrogen oxides and to improve fuel conversion efficiency via knock limit extension in turbocharged spark ignition (SI) engines. However, water injection still has several obstacles to maximize the benefits, such as an increase of particulate matter and unburned hydrocarbon emissions. In order to ameliorate the problems with a sufficient amount of water injection (water to fuel mass ratio > 0.5), this study adopted multiple fuel injection strategies, which inject fuel multiple times in a cycle. A boosted single-cylinder research engine equipped with a water port injector and a piezoelectric gasoline direct injector was utilized for this study over a range of water to fuel mass ratio (up to 1.0) and multiple fuel injection (single vs. triple) conditions. The results show that the drawbacks of water injection including combustion instability, unburned hydrocarbon, and particulate emissions were significantly improved with multiple fuel injections, and the relative thermal efficiency improvement and nitrogen oxide emission reduction were maximized up to 3.9% and 52.7%, respectively, with the combined injection strategy. In addition, the increased carbon monoxide emissions typical with multiple fuel injections were largely mitigated by the water injection strategy.

Impact of Saccharomyces Cerevisiae Boulardii Supplementation As Probiotic On Productive Performance And Economic Efficiency Of Growing Rabbits

Our study was carried out at the farm of Faculty of Agriculture, Ain Shams University, Egypt. The average temperatures were 18.4°C and 23.9 °C from December 2017 - February 2018 to study the effects of Saccharomycescerevisiaeboulardii supplementation (as feed additives) on productive performance of growing rabbits. Sixty growing rabbits of the NZW (New Zealand White Rabbits), (4 weeks old) and weighted (603.62 gm mean body weight) were randomly distributed into 4 treated groups, n=15 rabbits per each group. Rabbits of supplemented groups were given 100 (R1), 200 (R2) and 400 (R3) gm/ton feed of Saccharomyces cerevisiaeboulardii mixed in the diet for 6 successive weeks. Individual live body weight was noted weekly from start till the end of the experiment. At the end of the experimental period, 10 rabbits (from each group) were fasting for 12 hrs, then slaughtered for carcass traits measure. Experimental lighting system was 16-hours photoperiod /day (16L: 8D) through both daily natural and the artificial fluorescent lighting. A pelleted ration of 17.3% crude protein, 13.37% crude fiber and 2510 kcal of digestible energy per kg feed was offered ad libitum all the time. Results revealed significant (P≤0.05) increases in the final body weight and daily weight gain with saccharomyces cerevisiae supplementation when compared with control group. Though, significantly (P≤0.05) improved feed conversion ratio in all treated groups compared with control one were noticed. Feed intake was the lower in treated groups than control group. There were significant (P≤0.05) increasing in hot carcass weight and carcass percentage with respect to the control group. Supplemented Saccharomycescerevisiae reduced (P≤0.05) the liver, heart, lungs and kidneys percentages compared the control group. Supplemented rabbit feeds with saccharomycescerevisiaeboulardii in their diets had highly increasing in relative economic efficiency and clear improvement of net revenue than control group.

Inclusion of 2D Transition Metal Dichalcogenides in Perovskite Inks and Their Influence on Solar Cell Performance.

Organic–inorganic hybrid perovskite materials have raised great interest in recent years due to their excellent optoelectronic properties, which promise stunning improvements in photovoltaic technologies. Moreover, two-dimensional layered materials such as graphene, its derivatives, and transition metal dichalcogenides have been extensively investigated for a wide range of electronic and optoelectronic applications and have recently shown a synergistic effect in combination with hybrid perovskite materials. Here, we report on the inclusion of liquid-phase exfoliated molybdenum disulfide nanosheets into different perovskite precursor solutions, exploring their influence on final device performance. We compared the effect of such additives upon the growth of diverse perovskites, namely CH3NH3PbI3 (MAPbI3) and triple-cation with mixed halides Csx (MA0.17FA0.83)(1−x)Pb (I0.83Br0.17)3 perovskite. We show how for the referential MAPbI3 materials the addition of the MoS2 additive leads to the formation of larger, highly crystalline grains, which result in a remarkable 15% relative improvement in power conversion efficiency. On the other hand, for the mixed cation–halide perovskite no improvements were observed, confirming that the nucleation process for the two materials is differently influenced by the presence of MoS2.

Multi-objective search group algorithm for thermo-economic optimization of flat-plate solar collector

This study aims to develop a multi-objective version of the search group algorithm (SGA) called the multi-objective search group algorithm (MOSGA) to help determine thermo-economic optimization of flat-plate solar collector (FPSC) systems. Search mechanisms of the SGA were modified to determine non-dominated solutions through mutation, generation, and selection stages. Authors also mined the Pareto archive with a selection mechanism to maintain and intensify convergence and distribution of solutions. The study tested the proposed MOSGA with well-known multi-objective benchmark problems. Results were compared with outcomes from conventional algorithms using the same performance metrics to validate the capability and performance of the MOSGA. Afterward, MOSGA was applied to find the best design parameters to simultaneously optimize thermal efficiency and the total annual cost of FPSC systems. Four case studies were conducted with four different working fluids (pure water, SiO2, Al2O3, and CuO nanofluids). Optimization results obtained by the MOSGA were analyzed and compared with solutions provided by other algorithms. The findings revealed relative improvement in thermal efficiency and reduced annual cost for all nanofluids compared to pure water. Thermal efficiency was improved by 2.2748%, 2.4298%, and 2.7948% for SiO2, Al2O3, and CuO case studies, respectively, compared to pure water. Meanwhile, TAC rates were increased by 2.4111%, 2.3403%, and 2.9133% for these case studies, respectively. Comparative results also demonstrated that MOGSA was robustly effective and superior in the selection of appropriate design parameters of FPSC systems.

InAs nanostructures for solar cell: Improved efficiency by submonolayer quantum dot

The effect of different quantum structures in the intrinsic region of a pin junction solar cell (SC) on the optical and electrical properties have been investigated. SCs with different quantum structures, such as, Stranski-Krastanov (SK) quantum dots (QDs), quantum well (QW), submonolayer (SML) QDs (0.25 ML, 0.5 ML and 0.75 ML) and a quasi-monolayer (1 ML) InAs stack, were fabricated while keeping the total InAs content the same in all SCs. In a comparison of performance, the SML-QD sample delivered superior performance (Almost 23% relative efficiency improvement compared to reference SC) compared to the other devices. Moreover, different coverages of SML InAs have been tested for optimum performance improvement of solar cell and near 0.25 ML InAs deposition was found best for solar cell application. These findings present a promising alternative to SK-QDs as intermediate band in photovoltaic applications.

Performances of vertical-axis hydrokinetic turbines with chordwise-flexible blades

This paper presents a parametric study of Vertical-Axis Turbines (VAT) equipped with chordwise-flexible blades. The objective of this study is to assess the possibility of increasing the efficiency of VATs by allowing passive foil deformations that take advantage of the periodically changing hydrodynamic conditions inherent to VATs. The study is carried out with numerical simulations based on a partitioned Fluid–Structure Interaction (FSI) code implemented within OpenFOAM. Two-dimensional URANS numerical simulations are carried out at a Reynolds number of 107 based on the turbine diameter, which is representative of hydrokinetic applications. A single-blade rotor equipped with a chordwise-flexible NACA 0015 profile is considered. The flexibility is located in the rear part of the foil, between the attach point and the trailing edge. The tip-speed ratio range extends from 2 to 8 and the solidity is set to 0.286. The characteristics of the blade are specified with a dimensionless flexibility parameter and a so-called pressure-to-inertia ratio. The pressure-to-inertia values investigated are larger than one and are representative of hydrokinetic applications in water. The flexibility is varied from zero (rigid blade) to large values involving large deformations. The FSI effects related to these two parameters are investigated and the mechanisms that allow efficiency improvements are presented. It is shown that flexibility introduces a stall mitigation mechanism that helps in improving the efficiency of low tip-speed ratio configurations. Flexibility also reduces blades’ drag in the downstream portion of the cycle when the turbine operates at high tip-speed ratios. More specifically, relative efficiency improvement of about 12% to 15% are observed with moderate flexibilities at tip-speed ratios of 2 (lower than optimal) and 6 (higher than optimal). However, at the optimal tip-speed ratio, flexibility strictly reduces the efficiency, although this reduction remains small for moderate flexibilities. Overall, results also show that blade flexibility tends to extend the tip-speed ratio range of high-efficiency configurations, which may provide interesting advantages when the turbine operates in changing flow conditions.

Exergetic efficiency potential of double-stage ORCs with zeotropic mixtures of natural hydrocarbons and CO2

The present study investigates the exergetic efficiency potential of zeotropic mixtures of five natural hydrocarbons and CO2 as working fluids in double-stage Organic Rankine Cycles (DS-ZORCs) driven by waste heat at temperatures from 100 °C to 160 °C. The DS-ZORCs are optimized and their performance is compared to standard (SORCs), single-stage zeotropic (ZORCs) and double-stage pure fluid cycles (DSORCs). From a thermodynamic perspective, DS-ZORCs reach the highest exergetic efficiencies, especially at heat source temperatures of 100 °C (31.7%), 120 °C (35.5%) and 140 °C (38%). At 160 °C, the highest exergetic efficiency (42.4%) is achieved by a ZORC, followed by a DS-ZORC (39.8%). The maximum relative efficiency improvement of DS-ZORCs, ZORCs and DSORCs compared to SORCs at temperatures of 100 °C and 160 °C ranges from 50.5% to 22.5%, 44.5%–37.0% and 21.2%–6.7%, respectively. Because of their increased capital costs, DS-ZORCs are more appealing at heat source temperatures of 120 °C and 140 °C, at which their thermodynamic superiority over ZORCs is more significant. Due to their complexity, DS-ZORCs are subject to multiple thermodynamic constraints, which make them feasible under a limited set of boundary conditions. Furthermore, the selection of optimal mixture compositions and evaporator pressures greatly influences their feasibility and performance.

How Oxygen Exposure Improves the Back Contact and Performance of Antimony Selenide Solar Cells.

The improvement of antimony selenide solar cells by short-term air exposure is explained using complementary cell and material studies. We demonstrate that exposure to air yields a relative efficiency improvement of n-type Sb2Se3 solar cells of ca. 10% by oxidation of the back surface and a reduction in the back contact barrier height (measured by J-V-T) from 320 to 280 meV. X-ray photoelectron spectroscopy (XPS) measurements of the back surface reveal that during 5 days in air, Sb2O3 content at the sample surface increased by 27%, leaving a more Se-rich Sb2Se3 film along with a 4% increase in elemental Se. Conversely, exposure to 5 days of vacuum resulted in a loss of Se from the Sb2Se3 film, which increased the back contact barrier height to 370 meV. Inclusion of a thermally evaporated thin film of Sb2O3 and Se at the back of the Sb2Se3 absorber achieved a peak solar cell efficiency of 5.87%. These results demonstrate the importance of a Se-rich back surface for high-efficiency devices and the positive effects of an ultrathin antimony oxide layer. This study reveals a possible role of back contact etching in exposing a beneficial back surface and provides a route to increasing device efficiency.

X-Band High-Efficiency High-Power GaN Power Amplifier Based on Edge-Triggered Gate Modulation

A novel method called the edge-triggered gate modulation method is proposed in this letter to decrease the voltage overshoot while maintaining high efficiency for high-power amplifiers (HPAs). In this method, the HPA is biased in high-efficiency mode, i.e., Class B/C, during the pulse-on period and switched to Class A on the rising/falling edge of the pulse. For verification, a pulsed HPA prototype operating in the X-band with an output power of ~ 1 kW is fabricated. Based on the proposed method, a relative efficiency improvement of more than 23.2% compared with conventional Class A has been achieved with the voltage overshoot thoroughly suppressed under a 1 0 / 00 duty cycle.

A 28.7V Modular Supply Multiplying Pulser With 75.4% Power Reduction Relative to CV2 f

This brief presents a high voltage modular supply multiplying pulser in a 0.18-$\mu m$ BCD CMOS process. Two prototypes of the pulser were implemented for target loads of 55pF and 1nF, and generated up to 1MHz and 28.7V pulse from 1.2 and 5V supplies. Proposed modular based stepwise pulse generation achieved a peak power reduction of 75.4% relative to CV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> f and a peak power efficiency of 82.3%. The proposed pulser was used for driving piezoelectric micromachined ultrasound transducer (pMUT) and achieved a relative efficiency improvement of 113.7% against conventional two-level square wave pulsing.

Separating Hydrocarbon Mixtures by Driving the Components in Opposite Directions: High Degree of Separation Factor and Energy Efficiency.

A radically different approach for separation of molecular mixtures is proposed. A judicious combination of levitation effect observed in zeolites with a counter intuitive Landauer blow torch effect provides driving forces for the two components of the mixture to move in opposite directions. Using nonequilibrium MonteCarlo simulations, we illustrate the efficacy of the method for separating real mixtures of both linear n-pentane and its branched isomer, neopentane, and linear n-hexane and its branched isomer, 2,2-dimethylbutane. The method yields several orders of magnitude improvement in separation factor and relative energy efficiency by using submicron zeolite column. The extremely high purity of the resulting single components makes the method best suited for green chemistry.

Exergetic performance of CO2 and ultra-low GWP refrigerant mixtures as working fluids in ORC for waste heat recovery

Environmental regulations target refrigerants with global warming potential (GWP) above 150. Meanwhile, zeotropic mixtures are proven to increase the exergetic efficiency of Organic Rankine Cycles (ORCs). The present study investigates the exergetic performance of binary mixtures of R32 and 8 ultra-low GWP fluids (n-pentane, NOVEC649, R1233zd, isobutane, R1234ze, R1234yf, propylene, and CO2) in standard and recuperative ORCs. The ORCs are optimized with respect to the molar concentrations of their components and evaporation pressure. The relative exergetic efficiency improvement of zeotropic (ZORCs) compared to pure fluid ORCs (PORCs) is negatively correlated with the heat source temperature and ranges from a maximum of 36.39% (at 100 °C) to less than 5% at temperatures above 200 °C. For each mixture, ZORCs are favorable over PORCs of their components for heat source temperatures primarily below and secondarily between the critical temperatures of their components, while the average relative performance improvement is about 30–50%. At increasing heat source temperatures, ZORCs operating with isobutane, NOVEC649, R1233zd and n-pentane are successively optimal. Although recuperative ZORCs are superior to standard ZORCs for dry mixtures of components with a large critical temperature difference at higher temperatures, standard cycles are ultimately superior considering the global optimization results.