Transcritical Power Cycle Research Articles

A goal-oriented Design Method of CO2 Power Cycle (CPC) System

The CO2 power cycle (CPC) system is an efficient and environmentally friendly method for waste heat recovery (WHR). However, the traditional design and optimization process of a CPC system is very complex and time-consuming. This paper proposes a novel goal-oriented design method based on machine-learning methods for quickly designing an optimized CPC system with given performance indicators. And taking the design of the CO2 transcritical power cycle (CTPC) system for internal combustion engines (ICEs) as an example. Firstly, the net output power and the total cost of the system prediction models are trained by simulated data. Then the multi-objective optimization of the system is carried out by using the genetic algorithm coupled with the prediction models, and the optimization results are used to train a classification model. Finally, the given target indicators are input into the classification model for goal-oriented designing and getting the optimal configuration. The results of the goal-oriented design validation show that the goal-oriented design method can design the CTPC system well. And, once the classification model is trained, the CTPC system's future goal-oriented design process only needs to be calculated once, significantly reducing design time. In conclusion, the goal-oriented design method based on machine-learning proposed is a novel and promising method. This is a technology that combines computer science and energy science and can provide users with a quick and reliable CPC system design method.

Waste heat recovery of an UAV propulsion system based on PEM fuel cell by a novel transcritical CO2 - LNG hybrid cycle; thermodynamic and multiple linear regression analyses

ABSTRACT In this work, the performance of a proposed hybrid system consisting of a transcritical carbon dioxide-natural gas cycle for recovery of waste heat produced in a proton exchange membrane fuel cell has been evaluated. The effects of different parameters on proposed cycle performance have been investigated thermodynamically. This hybrid system can convert fuel cell’s released heat to electricity, augment production power, convert natural gas from the liquid phase to gas, and appropriate use of heat energy from consumed water. Results show that increasing the cell’s power by about 52% leads to a growth in overall efficiency of transcritical power cycle. Also, in a constant fuel cell power, the higher carbon dioxide mass flow rate tends to lower carbon dioxide turbine output power, and consequently, the efficiency of transcritical power cycle decreases. Changes in waste heat recovery efficiency among models with different values of CO2 mass flow rate increases very slightly as fuel cell power augments. For instance, at lowest examined fuel cell power (790 kW), growth in CO2 mass flow rate by about 26% causes a decline in cycle efficiency by about 6.35%. By increasing fuel cell thermal efficiency by 30%, improvement in overall cycle efficiency rises significantly by about 109.92%. On the other hand, augmentation in fuel cell thermal efficiency by about 30% leads to a very slight growth in improvement of the waste heat recovery efficiency by about 2.67%. Moreover, by increasing adiabatic efficiency of turbines by about 21.43%, improvement in waste heat recovery efficiency declines by about 10.75%. Increasing carbon dioxide turbine’s inlet temperature and reducing carbon dioxide mass flow rate have beneficial effects on efficiency of carbon dioxide transcritical power cycle. Eventually, two high-accuracy models have been presented for output power and efficiency of proposed hybrid cycle using multiple linear regression.

Experimental characterisation of CO2 + C6F6 mixture: Thermal stability and vapour liquid equilibrium test for its application in transcritical power cycle

• Analysis of CO 2 blend as working fluid in transcritical cycle for CSP application. • Experimental vapour liquid equilibrium measurements. • Equation of state calibration with VLE data. • Maximum operating temperature identified through thermal stability test. • Preliminary thermodynamic assessment of the power cycle. Nowadays supercritical CO 2 cycles are considered as a promising alternative to the traditional steam cycle for the power block in CSP plants with the aim of enhancing the system efficiency and reducing costs. This work deals with the experimental characterisation of a CO 2 blend as working fluid in transcritical cycle: the addition of C 6 F 6 as a dopant increases the fluid critical temperature allowing for a condensing cycle in hot environment with ambient temperature higher than 40 °C. The potential benefits on adopting this mixture passes through thermal stability test for identifying its maximum operating temperature and Vapour Liquid Equilibrium measurements for tuning the Equations of State, thus having a good prediction of the thermodynamic properties. The static method with thermal stress test at different operating temperatures shows that the mixture can withstand to about 600 °C in an Inconel 625 vessel. Furthermore, the standard Peng-Robinson with the optimised binary interaction parameter is selected for a preliminary thermodynamic assessment of the power cycle. An efficiency of 41.9% is found for an optimum mixture composition with a CO 2 molar content of 84% considering a turbine inlet pressure of 250 bar and a maximum and minimum cycle temperature of 550 °C and 51 °C respectively.

Thermodynamic efficiency of subcritical and transcritical power cycles utilizing selected ACZ working fluids

An improvement of the thermodynamic efficiency of machines and devices applied for energy conversion is nowadays one of the most important research topics. Increased thermodynamic efficiency brings elevated power production with relatively lower sources/consumption, positively affecting sustainability. This paper presents the research results aimed at comparing various subcritical and transcritical power cycles, and novel results related to their thermodynamic efficiencies. Simulations were proceeded using selected wet (or ACZ type) working fluids for given maximal and minimal cycle temperatures. Three novel markers, two of them are special points (ACZ-S and ACZ-T), and the third is an efficiency characteristics band on the inlet temperature-efficiency diagram, are introduced in this study. They can provide a novel perspective on the efficiency of subcritical and transcritical power cycles with predetermined temperature ranges. Engineers and scientists may obtain the greatest efficiency of the system based on a special configuration in the architecture or an enhancement in the present thermal power plant. In specific conditions (e.g., one can find certain combinations of vapour quality and operating cycle temperature ranges), the efficiency of superheated ORC (Sup-ORC) outperforms the maximal efficiency of ORC. The Sup-ORC may perform lower efficiency than subcritical ORC towards the critical point of working fluids.

Development and comparative selection of surrogate models using artificial neural network for an integrated regenerative transcritical cycle

Surrogate models are becoming increasingly important in replacing the computationally-expensive physics-based simulation models in many applications, such as system optimization, sensitivity analysis and design space exploration. As one of the fastest-growing field, machine learning, specifically artificial neural networks (ANN) have been adapted to model various energy systems. In the present study, five ANN-based surrogate models are developed in replacing the physics-based model of a novel regenerative transcritical power cycle using methanol as the working fluid that is integrated with a small modular reactor. The input layer of the surrogate models consists of the seven design parameters of the cycle, and the output layer returns the 1st-law efficiency, levelized cost of energy and penalty. The evaluation results show that all five candidate surrogate models have demonstrated high R2 score, low relative absolute errors (RAE) and low L1 losses, with the separate multi-layer feed-forward (MLF) neural network model outperforming the others. Once coupled with global optimization, the surrogate model is expected to find the optimal design parameters in order to minimize levelized cost of energy (LCOE) and penalty value in the system.

Reducing the operational fluctuation via splitting CO2 transcritical power cycle in engine waste heat recovery

CO2 power cycle has been considered a promising technology to recover the engine waste heat at a fixed condition. Nevertheless, the large variation of engine conditions may bring about the operational fluctuation, which is reflected on the system performance deterioration. In this study, a splitting CO2 power cycle layout is proposed and optimized from the point of both design and off-design phases to match the large-fluctuated engine conditions. The mass flow through different heat exchangers can be adjusted when the engine heat sources are altered, which means that a higher system degree of freedom can be achieved. Results showed that the system operational fluctuation could be reduced effectively when the operation parameters were deviated from the design phase. Specifically, the total mass flow rate decreased apparently when the engine speed and torque decreased, whereas a moderate decrease was found in the splitting layout thanks to the flexible mass flow through each splitting branch. In addition, the deviation fluctuation of pressure ratio was also reduced especially at higher engine conditions. Average improvements of 12.2%, 17.5% and 8.5% in net generated power, exhaust utilization and exergy efficiency could be achieved, respectively. And the minimum brake specific fuel consumption could be improved by 5.5%.

Theoretical Analysis of a self-condensing CO2 Transcritical Power Cycle with regeneration involving DPS in a Solar Thermal Power Plant

Abstract The choice of heat transfer fluids(HTF) significantly dictates the thermal efficiency of the solar power plant. Presently, molten salt is widely used choice owing to its phase, low cost and non-toxic nature. Along with other alternatives like liquid metals, multiphase fluids, these HTFs are limited to peak operating temperatures ranging from 300-550°C. With the introduction of Dense Particle Suspensions (DPS) as an HTF, the highest operating temperatures in a Solar thermal power plant can reach up to 700°C, offering considerable scope for improving thermal efficiency. Due to the higher average specific heat as compared to the alternatives, CO2 is a promising working fluid in the considered range of moderately high operating temperatures. The cost of the components and size of the power block makes the transcritical CO2 cycle an attractive alternative. The present work analyses the theoretical efficiency of the proposed cycle, with the peak operating temperature ranging from 550°C to 700°C. The effects of the variation in the lower operating pressure and the condensation temperature have also been analysed. It is observed that thermodynamic efficiencies as high as 40% can be reached at the maximum operating temperature. The optimum combination of the lower operating pressure and the condensation temperature is also noted.

Theoretical Study of a Novel Power Cycle for Enhanced Geothermal Systems

As obtained geofluids from enhanced geothermal systems usually have lower temperatures and contain chemicals and impurities, a novel power cycle (NPC) with a unit capacity of several hundred kilowatts has been configured and developed in this study, with particular reference to the geofluid temperature (heat source) ranging from 110 °C to 170 °C. Using a suitable CO2-based mixture working fluid, a transcritical power cycle was developed. The novelty of the developed power cycle lies in the fact that an increasing-pressure endothermic process was realized in a few-hundred-meters-long downhole heat exchanger (DHE) by making use of gravitational potential energy, which increases the working fluid’s pressure and temperature at the turbine inlet and, hence, increases the cycle’s power output. The increasing-pressure endothermic process in the DHE has a better match with the temperature change of the heat source (geofluid), as does the exothermic process in the condenser with the temperature change of the sink (cooling water), which reduces the heat transfer irreversibility and improves the cycle efficiency. Power cycle performance has been analyzed in terms of the effects of mass fraction of the mixture working fluids, the working fluid’s flowrate and its DHE inlet pressure, geofluid flowrate, and the length of the DHE. Results show that, for a given geofluid’s temperature and mass flowrate, the cycle’s net power output is a strong function of the working-fluid’s flowrate, as well as of its DHE inlet pressure. Too high or too low of a DHE inlet pressure results in a lower power output. When geofluid temperature is 130 °C, the optimum DHE inlet pressure is found to be 11 MPa, corresponding to an optimum working-fluid flowrate of 6.5 kg/s. The longer the DHE, the greater the corresponding working-fluid flowrate and the higher the net power output. For geofluid temperature ranging from 110 °C to 170 °C, the developed NPC has a better thermodynamic performance than the conventional ORC. The advantage of using the developed NPC becomes obvious when geofluid temperature is low. The maximum net power output difference between the NPC and the ORC happens when the geofluid temperature is 130 °C and NPC’s working fluid mass fraction (R32/CO2) is 0.5/0.5.

Analysis of printed circuit heat exchanger (PCHE) potential in exhaust waste heat recovery

Exhaust waste heat recovery technology based on power cycles requires high efficiency, low flow resistance, and a compact structure for exhaust gas heat exchangers. It is a huge challenge for traditional heat exchangers, such as double tube or shell and tube heat exchangers. A printed circuit heat exchanger (PCHE), which is a compact heat exchanger, has not been used in the heat exchange process between the exhaust gas and supercritical CO2. Focusing on this application, a novel design concept of PCHE based on a comprehensive performance index is proposed, which fully considers the differences in physical properties and working conditions between the exhaust gas side and the CO2 side. A series of experiments were carried out in a CO2-based transcritical power cycle system. The experimental test results show that the PCHE with a novel structure is stable and feasible. To further optimise the PCHE, a numerical analysis of different structures was conducted. The calculation results show that the comprehensive performance of the PCHE with an optimised structure was improved by 11.92%. This research shows that PCHE has great potential for achieving a compact design with excellent performance, especially for use in engine waste heat recovery.

Adoption of the CO2 + SO2 mixture as working fluid for transcritical cycles: A thermodynamic assessment with optimized equation of state

This paper focuses on the use of the CO2 + SO2 binary mixture as innovative working fluid for closed transcritical power cycles with a minimum temperature above 50 °C. Starting from a literature review of the available experimental data on the mixture, the PC-SAFT EoS is identified as a suitable model to characterize the mixture behavior. Once the proper thermodynamic model is selected for this mixture, a comparison between the innovative transcritical cycle and the sCO2 cycle is proposed for various plant layouts in order to find out the advantages of the innovative mixture. The analysis is presented fixing the cycle maximum temperature at 700 °C and the maximum pressure at 250 bar: the results depict an increment in cycle electric efficiency and cycle specific work, along with a lower temperature of heat introduction in the cycle for any considered configuration of transcritical CO2 + SO2 cycle, when compared to pure sCO2.An economic analysis of the power block is then performed to support the selection of the innovative working fluid. Two of the most promising plant layouts are evidenced: the recompression layout is selected for highly efficient power blocks, while the dual recuperated layout works effectively in applications characterized by higher hot source exploitation. The recompression layout adopting the CO2 + SO2 mixture presents a power block electric efficiency of 48.67% (2.33% higher than the respective sCO2 cycle) and a reduction of the power block CAPEX from 1160 $/kWel to 1000 $/kWel when compared to the sCO2 configuration for a 100MWel size, while the dual recuperated layout exploiting the CO2 + SO2 mixture shows a power block electric efficiency of 39.58% (0.69% above the same sCO2 cycle), a decrease of power block CAPEX from 795 $/kWel to 718 $/kWel and 70 °C of additional heat recovery from the hot source with respect to the analogous sCO2 cycle.

Experimental investigation of a splitting CO2 transcritical power cycle in engine waste heat recovery

Since the great potential to improve engine efficiency was found in engine waste heat recovery, the recuperative CO2 transcritical power cycle (CTPC) was supposed to be a promising technological path, whereas high irreversibility in recuperator and low engine exhaust utilization were also found. Hence, a novel splitting design as well as the experimental system was constructed to improve the irreversibility and exhaust utilization.The main purpose of this study is to explore the splitting effect on system performances, to reveal the optimal splitting parameters and to verify the feasibility of the developed turbo-generator (TG) and print circuit heat exchangers (PCHE). Four cases were compared under various splitting ratios, and initial test results were given to reveal the performances of the developed TG and PCHE.In conclusion, the splitting design has been proved an effective way to improve the recuperative CTPC. Meanwhile, there exist different optimized splitting ratios under various operating conditions, which provides the instruction on application. The generating capacity of the TG reaches 7.57 kW, at the rotational speed of 23,875 RPM. The developed PCHE for exhaust-sCO2 (supercritical CO2) heat exchanger has also been verified a feasible exchanger with an acceptable exhaust pressure drop of 1.32 kPa in average.

A critical review on waste heat recovery utilization with special focus on Organic Rankine Cycle applications

In the recent era of development, energy consumption increased many folds. While tapping this energy from various resources, almost half of this energy is dumped back into the environment causing adverse environmental imbalance. This can be mitigated by the recovery and utilization of waste heat which will also lead to the conservation of fossil fuel. In the present study, various waste heat recovery (WHR) technologies are explored and a state-of-the-art review is conducted with a particular focus on Organic Rankine Cycle (ORC). It is concluded that ORC technology is a reliable and promising solution. In the present study research challenges associated with the selection of ORC working fluid are evaluated and described. It is found that zeotropic mixtures could be good alternatives because of their temperature glide reducing the irreversibility of the system. The research is conducted on different configurations of ORC such as Regenerative cycle, CO 2 transcritical power cycle (CTPC), and cascade ORC system. It is explored from the literature that the high thermal decomposition temperature of carbon dioxide reduces the irreversibility in CTPC systems. Multi-grade waste heat is efficiently recovered by the Cascade-Organic Rankine Cycle (C-ORC). Technical challenges in the application of Phase Change Material (PCM) into WHR and utilization of WHR in adsorption cooling and Hybrid vehicle is critically reviewed to identify the potential knowledge gap between the present status and futuristic research. The study also discussed the present Indian scenario of WHR utilization for ORC applications. • Different architectures of ORC based on WHR are investigated. • Selection of working fluid, system optimization in the purview of ORC are discussed. • Technical challenges associated with the application of PCM in WHR are identified. • Utilization of WHR in adsorption cooling and hybrid vehicles are studied.

Performances of Transcritical Power Cycles with CO2-Based Mixtures for the Waste Heat Recovery of ICE.

In the waste heat recovery of the internal combustion engine (ICE), the transcritical CO2 power cycle still faces the high operation pressure and difficulty in condensation. To overcome these challenges, CO2 is mixed with organic fluids to form zeotropic mixtures. Thus, in this work, five organic fluids, namely R290, R600a, R600, R601a, and R601, are mixed with CO2. Mixture performance in the waste heat recovery of ICE is evaluated, based on two transcritical power cycles, namely the recuperative cycle and split cycle. The results show that the split cycle always has better performance than the recuperative cycle. Under design conditions, CO2/R290(0.3/0.7) has the best performance in the split cycle. The corresponding net work and cycle efficiency are respectively 21.05 kW and 20.44%. Furthermore, effects of key parameters such as turbine inlet temperature, turbine inlet pressure, and split ratio on the cycle performance are studied. With the increase of turbine inlet temperature, the net works of the recuperative cycle and split cycle firstly increase and then decrease. There exist peak values of net work in both cycles. Meanwhile, the net work of the split cycle firstly increases and then decreases with the increase of the split ratio. Thereafter, with the target of maximizing net work, these key parameters are optimized at different mass fractions of CO2. The optimization results show that CO2/R600 obtains the highest net work of 27.43 kW at the CO2 mass fraction 0.9 in the split cycle.

Performance Comparison of Advanced Transcritical Power Cycles with High-Temperature Working Fluids for the Engine Waste Heat Recovery

To efficiently recover the waste heat of mobile engine, two advanced transcritical power cycles, namely split cycle and dual pressure cycle, are employed, based on the recuperative cycle. Performances of the two cycles are analyzed and compared through the development of thermodynamic models. Under given gas conditions, seven high-temperature working fluids, namely propane, butane, isobutane, pentane, isopentane, neopentane, and cyclopentane, are selected for the two cycles. At the design system parameters, the highest work 48.71 kW, is obtained by the split cycle with butane. For most of fluids, the split cycle has a higher work than the dual pressure cycle. Furthermore, with the increase of turbine inlet pressure, net work of the split cycle goes up firstly and then decreases, while the work of dual pressure cycle increases slowly. For the split cycle, there exists a split ratio to get the maximum network. However, for the dual pressure cycle, the larger the evaporation temperature, the higher the net work. On this basis, system parameters are optimized by genetic algorithm to maximize net work. The results indicate that the highest work 49.96 kW of split cycle is obtained by pentane. For the considered fluids, except cyclopentane, split cycle always has a higher work than dual pressure cycle. Due to the higher net work and fewer system components, split cycle is recommended for the engine waste heat recovery.

Combustion Characteristic and Mechanism of a Mixture Working Fluid C3H8/CO2

In the CO2 transcritical power cycle, conventional cooling water can hardly condense subcritical CO2 because its critical temperature is as low as 30.98°C. In order to avoid this condensing problem, CO2-based mixtures have been proposed as working fluids for transcritical power cycle. They can raise the critical temperature by mixing a little C3H8 as the secondary component to CO2. However, the flammability of the mixture may limit its application. This article investigated laminar flame speed of C3H8/CO2 which represents the mixture’s combustion characteristic by a so-called heat flux method and studied the inhibition mechanism of CO2 on the combustion based on the Premixed Laminar Flame-Speed Calculation reactor of Chemkin-Pro. The experimental results showed that the laminar flame speed shows a peak value with changing the equivalence ratio and accelerates with raising the mole fraction of the organic gas. Additionally, a slight upwards trend was observed for the corresponding equivalence ratio of the peaks. The flammable range for the equivalence ratio extended with the mole fraction of C3H8 increasing. With the mole fraction of C3H8 of 0.15, the maximum laminar flame speed was 12.8 cm/s, 31.7% of that of the pure C3H8. The flammable range was from 0.41 to 1.33, decreasing by 23.3% compared with that of C3H8. A flammable critical mixing ratio was also found as 0.08/0.92 for C3H8/CO2 at the normal condition. By simulating, it was found that the most key free radical and elementary reaction which determine the inhibition of CO2 on the combustion are OH and H+O2=O+OH, respectively.

Optimization of CO2 Transcritical Power Cycle (CTPC) for engine waste heat recovery based on split concept

CO2 Transcritical Power Cycle with a preheater and regenerator has emerged as a promising technology to recover engine waste heat. Jacket water, engine exhaust gas and CO2 exhaust after expansion have been considered the main recovery sources in terms of external and internal utilization objectives. During the three consecutive heating processes, however, the issue of temperature interference may reduce the exhaust gas utilization and thermal efficiency. Therefore, this research proposes a split concept for the objective of investigating temperature interference. Three corresponding split systems are studied. This article develops comprehensive mathematical models to compare the performances and a detailed analysis of each advantage is carried out. The results showed that temperature interference could be solved to achieve maximum utilization of the exhaust gas and increase the thermal efficiency. In addition, the net power could be improved from 14.7 kW to 19.0 kW after optimization. Among the studied systems, the low-temperature split system showed an increment of 90.0% in cycle efficiency, and the medium-temperature split system was found 4.9% improvement in heat recovery efficiency. The high-temperature split system displayed superior characteristics to the others in both the cycle and heat recovery efficiency, which were improved by 18.3% and 10.4%.

Adaptive flow assignment for CO2 transcritical power cycle (CTPC): An engine operational profile-based off-design study

CO2 transcritical power cycle (CTPC) is regarded as a promising energy conservation means in engine waste heat recovery. One of the most significant characteristics that should be noted is the considerable variation of waste heat caused by the variable engine operating conditions. Hence, the ability to follow the heat-sources variation should be enhanced to maximize its energy-saving potential. In this paper, an effective and efficient approach is proposed to deal with the different degree of variability of heat sources through a novel CTPC system configuration controlling the internal mass flow rate of the working fluid actively. An adaptive flow assignment strategy is also developed to enhance the ability to follow the heat-sources variation. A comprehensive input-optimization-output framework is constructed consisting of performances analysis under both design and off-design procedures. Results show that the CTPC adaptation to the heat-sources variation can be effectively improved with the proposed system and operational strategy. Promising energy-saving potential is found when the proposed system and strategy with adaptive flow assignment are implemented. The effective operating conditions are expanded from 8 to 22 points based on the engine operational profile, and the net generated power is increased by 47.5% considering the European stationary cycle (ESC) 13-mode.

Experimental Characterisation of Co2 + C6f6 Mixture: Thermal Stability and Vapour Liquid Equilibrium Test for its Application in Transcritical Power Cycle

Experimental Characterisation of Co2 + C6f6 Mixture: Thermal Stability and Vapour Liquid Equilibrium Test for its Application in Transcritical Power Cycle

Modeling and simulation of an integrated regenerative transcritical cycle with a small modular reactor

In recent years, small modular reactors (SMR) have gained substantial development advancement and world-wide acceptance. While various advanced power cycles (e.g. supercritical CO2 Brayton cycle) have been proposed for Gen IV reactors, the steam cycle remains the only cycle for light water reactors. In this work, a unique regenerative transcritical power cycle using small molecule organic fluids (methanol and ethanol) was modeled with the reactor coolant loop of a small modular light-water reactor. In addition to modeling the thermodynamic cycle and associated transport processes for prominent components, the solution algorithms of the combined cycle model using MATLAB/REFPROP are illustrated in this article. The simulation results show that, by leveraging the superior thermophysical properties around the critical points of the working fluids, the transcritical methanol/ethanol cycles have shown similar performance as the steam cycle in terms of thermal efficiency and power output. With further system optimization, the regenerative transcritical cycle is expected to offer increased power output from the small modular light-water reactor as an alternative energy conversion system.

Carbon Dioxide Mixtures as Working Fluid for High-Temperature Heat Recovery: A Thermodynamic Comparison with Transcritical Organic Rankine Cycles

This study aims to provide a thermodynamic comparison between supercritical CO2 cycles and ORC cycles utilizing flue gases as waste heat source. Moreover, the possibility of using CO2 mixtures as working fluids in transcritical cycles to enhance the performance of the thermodynamic cycle is explored. ORCs operating with pure working fluids show higher cyclic thermal and total efficiencies compared to supercritical CO2 cycles; thus, they represent a better option for high-temperature waste heat recovery provided that the thermal stability at a higher temperature has been assessed. Based on the improved global thermodynamic performance and good thermal stability of R134a, CO2-R134a is investigated as an illustrative, promising working fluid mixture for transcritical power cycles. The results show that a total efficiency of 0.1476 is obtained for the CO2-R134a mixture (0.3 mole fraction of R134a) at a maximum cycle pressure of 200 bars, which is 15.86% higher than the supercritical carbon dioxide cycle efficiency of 0.1274, obtained at the comparatively high maximum pressure of 300 bars. Steam cycles, owing to their larger number of required turbine stages and lower power output, did not prove to be a suitable option in this application.