Conventional Organic Rankine Cycle Research Articles

Thermo-Economic Comparison between Three Different Electrolysis Technologies Powered by a Conventional Organic Rankine Cycle for the Green Hydrogen Production Onboard Liquefied Natural Gas Carriers

The high demand for natural gas (NG) worldwide has led to an increase in the size of the LNG carrier fleet. However, the heat losses from this type of ship’s engines are not properly managed, nor is the excess boil-off gas (BOG) effectively utilised when generation exceeds the ship’s power demand, resulting in significant energy losses dissipated into the environment. This article suggests storing the lost energy into green H2 for subsequent use. This work compares three different electrolysis technologies: solid oxide (SOEC), proton exchange membrane (PEME), and alkaline (AE). The energy required by the electrolysis processes is supplied by both the LNG’s excess BOG and engine waste heat through an organic Rankine cycle (ORC). The results show that the SOEC consumes (743.53 kW) less energy while producing more gH2 (21.94 kg/h) compared to PEME (796.25 kW, 13.96 kg/h) and AE (797.69 kW, 10.74 kg/h). In addition, both the overall system and SOEC stack efficiencies are greater than those of PEME and AE, respectively. Although the investment cost required for AE (with and without H2 compression consideration) is cheaper than SOEC and PEME in both scenarios, the cost of the H2 produced by the SOEC is cheaper by more than 2 USD/kgH2 compared to both other technologies.

Experimental investigation of a zeotropic organic Rankine cycle system with liquid-separation condensation for composition adjustment

Organic Rankine cycle (ORC) systems often experience a decline in operating performance when subjected to off-design conditions. To address this issue, an emerging method for improving the ORC performance under variable operating conditions is the use of composition adjustment through liquid-separation condensation. In the present study, an experimental facility of a 1 kW zeotropic ORC system that allows for composition adjustment based on liquid-separation condensation is developed. A composition adjustment strategy based on the proposed composition adjustment system is developed, and the stability and effectiveness of the composition adjustment system are experimentally investigated. An experimental comparison is conducted to demonstrate the superiority of the composition-adjustable ORC over the conventional composition-fixed ORC under variable operating conditions. The results indicate that the proposed composition adjustment system can effectively separate mixtures at different compositions within a short period of time. Under variable operating conditions, the composition of R134a/R245fa in the ORC is effectively adjusted from 0.300/0.700 to 0.172/0.828 using the proposed composition adjustment system. As a result, the net power output of the composition-adjustable ORC is found to be 4.79–9.71% higher than that of the composition-fixed ORC.

Comparative analysis and optimization of waste-heat recovery systems with large-temperature-gradient heat transfer

Efficient utilization of waste heat is crucial for reducing waste heat emissions and minimizing environmental impact. Organic Rankine cycle (ORC) systems are commonly employed for waste heat recovery. However, conventional ORC systems have limitations in effectively harnessing waste heat resources because of differences in the pinch point temperature and the relatively small temperature difference between the heat source inlet and outlet. To address this issue, we designed two absorption organic Rankine cycle (AORC) systems in this study based on absorption heat exchangers. We analyzed the energy, exergy, and economy of three ORC system models with heat source temperatures within the range from 363.15 K to 413.15 K. The results indicated that the AORC system represented a optimal waste heat recovery system, capable of reducing the outlet temperature to 298.70 K and achieving a high temperature efficiency of 1.037. Thus, an AORC system can facilitate heat exchange with substantial temperature differences, enabling the efficient utilization of heat sources. The AORC system in this study exhibited a high net power of up to 151.8 kW, and an electrical exergy efficiency of 55.45%. Additionally, the AORC consistently outperformed other systems in terms of economy, as evidenced by its electricity production cost, which was the lowest among all three systems with heat source temperatures lower than 398.15 K.

Thermodynamic analysis of photothermal-assisted liquid compressed CO2 energy storage system hybrid with closed-cycle drying

Liquid compressed carbon dioxide (CO2) energy storage (LCES) is promising by mechanically storing the electricity into the high-pressure liquid CO2. However, the thermal efficiency of the expander, i.e., energy release process, is strictly limited by the outlet temperature of the compression heat storage. To this end, a photothermal-assisted LCES system is proposed to increase the inlet temperature of expander. A heat integration scheme of the new system is proposed by deploying the closed-cycle drying chamber for the waste heat recovery, whose performance is compared with the conventional organic Rankine cycle (ORC) method. By developing the thermodynamic models of the systems, numerical results indicate that the photothermal assistance significantly enhances the thermal performance of LCES system, with the exergy efficiency increased by 16.00 % to 62.23 % and the energy storage density increasing from 8.06 kWh/m3 to 18.59 kWh/m3, respectively. The comparative results of different waste heat recovery schemes show that the closed-cycle drying is of 2.77 times waste heat recovery benefit of the ORC method, with a dehumidification capacity being 63.45 kg/h. Moreover, the closed-cycle drying subsystem with a recuperator is designed to recover the sensible heat of the moist air at the outlet of the drying chamber, which further improves the dehumidification capacity by 52.04 % at a drying chamber outlet temperature of 319.15 K.

Cogeneration system based on large temperature difference heat transfer with stepwise utilization

Organic Rankine cycle (ORC) plays a critical role in systems such as waste heat recovery, cogeneration, renewable energy generation and energy storage. No matter which field ORC is applied in, the evaporator side of ORC has an extremely poor utilization of the thermal energy from heat source, resulting in the outlet temperature of hot side fluid being much higher than the inlet temperature of cold side fluid. In order to fully capitalize on the thermal energy, this study introduces the two-stage absorption heat exchanger (AHE) and integrates it into ORC to obtain an original high-efficiency cogeneration system (AHEORC-CHP), which is parametrically analyzed by constructing and operating thermo-economic model in terms of the expansion pressure ratio and working fluid of ORC, the type and flow rate of heat source, and the inlet temperature of generator in AHE. Due to the existence of pinch point temperature difference, conventional ORC design can only reduce the outlet temperature of the heat source with an inlet temperature of 130 °C to about 70 °C under the condition of ideal heat transfer. The AHEORC-CHP configuration proposed in this work can achieve a significant reduction in the final outlet temperature of waste heat source (as low as 24.69 °C) and realize heat exchange with large temperature difference and efficient utilization of the heat source. Besides, the thermoelectric efficiency and temperature effectiveness can reach 90.9% and 1.2 respectively, while the profit ratio of investment rises to 8.46. Further improving the performance of AHEORC-CHP system requires optimizing the design of the pressure in absorption heat pump (AHP) cycle as well as the concentration and flow rate of LiBr-H2O solution. This study can provide a simulation pathway for the application of two-stage AHE in ORC, and likewise for future experimental investigations.

Experimental assessment of an Organic Rankine Cycle with a partially evaporated working fluid

The Organic Rankine Cycle (ORC) has the potential to play a vital role in the mitigation of climate change by enabling low-temperature heat sources for power generation. This paper describes an experimental investigation of a variant of the ORC, known as the partially evaporated ORC (PEORC), and compares its power generating performance for a variety of heat source conditions to that of a conventional ORC. In contrast to the latter, the working fluid is only partially evaporated in the PEORC, which allows better matching of the temperature profiles of the heat source and working fluid during heat transfer.In the power cycle, the low GWP refrigerant R1233zdE was employed as working fluid. The mass flow and temperature of the heat source were varied from 0.25 to 0.35 kg/s and 110 to 140 °C, respectively. For each combination of heat source mass flow and temperature, the optimum operating point was identified by experiment in terms of exergy efficiency. Therefore, the evaporation pressure was varied in case of the ORC. In case of the PEORC, evaporation pressure and vapor quality at the evaporator outlet were varied. The results show that the PEORC outperforms the ORC in terms of exergy efficiency by up to 80 % for all investigated heat source conditions due to the much higher heat source utilization of the PEORC. The net thermal efficiency however is higher with the ORC due to the higher exergy level of the working fluid at the evaporator outlet.

Thermoeconomic analysis of conventional and recuperative ORC for heat recovery of exothermic reactions

The possibility of using medium temperature (478–506 K) saturated steam from a reactor cooling system as heat source for generating electricity is evaluated in this work. Both usual Organic Rankine Cycle (ORC) and recuperative (RORC) configurations were modeled for 3 different boiler heat loads (Cases 1, 2 and 3) so that the electricity generation capacity effect on the economic performance could be evaluated. From the power cycle simulations, methanol and ethanol had shown the best performance in the ORC configuration with average First and Second Laws’ efficiencies of 16% and 44%, respectively. By adding a recuperator, most of the dry fluids have also shown similar performances. In the economic analysis, net power generation plays a major role. For Case 2 ( ≈ 250 kW net) and Case 3 ( ≈ 850 kW net), the power generation revenue was insufficient to cover the operational expenses, yielding unfeasible scenarios. However, for Case 1 ( ≈ 2.5 MW net), economic feasibility was achieved even for low operating pressures. The best power cycle thermoeconomic performance was found for methanol as working fluid. In the best scenario, an attractive internal rate of return of 14.5% was achieved for an specified electricity cost of US$ 0.0671 per kW h. • Heat from medium temperature latent heat source is recovered to power an ORC. • Optimal evaporation temperature for dry fluids in RORC configuration is defined. • Minimum temperature difference automatic adjustment during power cycle simulation. • Heat exchanger detailed design based on literature correlations. • Power cycle NPV and pay-back calculation.

Investigation of an organic Rankine cycle (ORC) incorporating a heat recovery water-loop: Water consumption assessment

This paper presents a thermodynamic analysis of an organic Rankine cycle with a water-loop (ORC-WL) as an efficient means of heat regeneration and saving Water Consumption (WC). The ORC-WL was simulated with wet, dry and isentropic refrigerants such as R717, R600a and R1234yf, respectively, in order to compare its technical performance to the conventional ORC (C-ORC) and ORC with internal heat exchanger (ORC-IHE). The thermodynamic analysis developed in the EES software was used to carry out the Energy Efficiency (EnE), Exergy Efficiency (ExE), Net Power Output (NPO), and WC as comparison performance parameters. A specific study has shown that the ORC-IHE, due to its remarkable contribution to the degradation of available energy and with a high WC compared to that of C-ORC, can be disqualified in favour of the ORC-WL which considerably improves these parameters thanks to the water-loop. For the same operating conditions and with reference to R600a, When C-ORC exhibited an EnE of 8.70 %, an ExE of 67.01 %, NPO of 8.57 kW and WC of 0.71 kg.s−1, those of ORC-IHE were 10.08 %; ExE of 64.87 %; NPO of 9.11 kW and WC of 5.30 kg.s.-1, respectively, whereas those of ORC-WL were 9.95 %, 84.85 %, 9.95 kW and 0.82 kg.s−1, respectively. The study on monitoring of evaporating temperature, superheating, and pinch showed that the ORC-WL can operate with evaporating temperature and superheating above 90 °C and 15 °C, respectively. A pinch of no more than 3 °C, on the other hand, is ideal. Finally, wet refrigerants are not suitable for ORC-WL, and dry refrigerants offer better performance than isentropic refrigerants,

Investigation on a novel pumpless module driven by thermal energy and gravity and its application in an ORC system

The “virtual” pump without power supply is a potential replacement for the electrically-driven pump in the conventional Organic Rankine Cycle (ORC) system. In this paper, a pumpless module and a 10 kW ORC system are designed and constructed, and the optimization for the system control method is studied with the performance evaluation of the pumpless module. The experimental results show that the generated power fluctuates periodically with applying the pumpless module. There exists an optimal liquid level range of (280–340) mm in a pumping cycle to stabilize the output power near the peak. By optimizing the input vapor flowrate, pressure balance time, and upper and lower limits of the liquid level of the pumpless module, the liquid flowrate and the average power generation can reach 1.25 kg/s and 11.76 kW respectively. In addition, the heat consumption and the equivalent power consumption of the pumpless module are analyzed. The heat consumption as a percentage of the total input heat increases from 4.2% to 14.7% as the heat source temperature increases from 90 °C to 130 °C, and its equivalent power consumption can save 36.1% at 90 °C compared to the electrically-driven pump while consumed 7.8% more than the electrically-driven pump at 130 °C.

Non-steady thermodynamic characteristics of a pilot-scale organic Rankine cycle system with a thermally-driven pump

A pilot-scale organic Rankine cycle (ORC) power generation system with a thermally-driven pump is constructed, and the working fluid of R245fa and a screw expander are adopted. Different heat source temperatures in the range of 90.00 °C–130.00 °C and the ambient temperature around 22 °C are employed to investigate the performance of the ORC system in the thermally-driven mode. The experimental results show that the generated electrical power indicates a stable fluctuation with the maximum time-averaged power of 11.61 kW at the heat source temperature of 130.00 °C, and the peak and valley values of 13.9 kW and 7.2 kW, respectively. The maximum thermal efficiency of 4.3% and the exergetic efficiency of 20.9% are obtained at the heat source temperature of 130.00 °C and 100.00 °C, respectively. Meanwhile, the proportion of full width at half maxima (PFWHM) is defined to illustrate the fluctuation characteristics of the output power, and the value is always between 0.70 and 0.72 at different heat source temperatures. Finally, the performance of the thermally-driven ORC system is compared with that of the conventional ORC system, and the results show that the ORC system in the thermally-driven mode adapts better to the heat source temperature below 110.00 °C.

Investigation of a Solar-Driven Organic Rankine Cycle with Reheating

The purpose of this simulation study is the examination of a solar-driven power cycle that is driven by collectors with evacuated tubes. The power cycle is an organic Rankine cycle (ORC) that works with cyclopentane. The novelty of the cycle is the use of reheating in order to enhance its thermodynamic efficiency, while the cycle also has a recuperator. Moreover, the cycle is compared with the conventional ORC in order to determine the performance enhancement with the examined idea. The analysis is done with a developed program in Engineering Equation Solver and both in steady-state and transient conditions for a typical year. The analysis was conducted in terms of energy and economic performance. According to an optimization procedure for maximizing the net present values of the investment, it is found that the novel design leads to a net present value of 68 k€, a simple payback of 10 years, and a yearly energy efficiency of 7.0%, while the respective values for the conventional ORC are 44 k€, 10.8 years, and 5.1% for its optimal design according to the net present values maximization. Thus, it is obvious that the suggested design increases both energy and financial performance, compared to the usual design.

Energy and exergy analysis of a hot dry rock geothermal resource power generation system based on organic Rankine cycle

Abstract Hot dry rock is an abundant, stable and low-carbon geothermal resource, which has a promising prospect for power generation in China. In this paper, a hot dry rock power generation system model based on conventional organic Rankine cycle was established. The performance of the system was evaluated by thermodynamic analysis, as well as energy and exergy analyses. Four types of organic working fluids were selected to investigate their effects on system energy efficiency. R114 had much higher energy efficiency (17.50%~ 19.00%) than other three organic working fluids (R245fa, R245ca and R601) when water flow rate ranged from 80 t/h to 260 t/h. When R245fa was used as working fluid and power output was set at 4 MW, energy and exergy efficiency of the system were 15.27% and 50.42%, respectively. According to the energy flow analysis, the major energy losses (15.67 MW) in the system were attributed to the discharge temperature of turbine exhaust. However, exergy flow analysis indicated that the energy loss from turbine exhausts was not as serious as expected, since the work potential of that energy was limited. The exergy destruction of each component in the system was calculated, and the results showed that heat exchanger and the vapor separator were the weakness components in the system, and they respectively contributed to 44.8% and 29.8% of the total exergy destruction. The results obtained in this study provide possible strategies to improve the overall performance of the hot dry rock power generation system based on conventional organic Rankine cycle.

Hydrate-based gas separation for working fluid mixtures: Application to composition-adjustable organic Rankine cycle

Composition-adjustable organic Rankine cycle (ORC) is deemed to improve the overall energy efficiency compared to the conventional ORC, bringing more energy saving and emission reduction. Inspired by hydrate-based gas separation, the hydrate-based composition regulation of working fluid was proposed and investigated experimentally using R22/R125 mixtures as feed gas. To improve the hydrate formation kinetics, stirring was employed and boosted the initial hydrate formation rate by about 200% compared with the unstirred cases. Cases with more R22 fraction in the feed gas showed faster initial hydrate formation rate. Partition of components between gas and hydrate phases was observed in a kinetic separation manner, i.e., R22 led the hydrate formation at the early stage while R125 was enclathrated more at the later stage. With proper formation time (45 – 135 min), the R125 fraction in the gas phase could increase by 9.5 – 18.7 mol% from various feed gas compositions (30 – 70 mol%). In the hydrate phase R22 was typically enriched with the best separation factor varied between 2.71 and 10.27. Compared to hydrate formation at a constant temperature (275.5 K), the temperature ramping down mode (from 278.5 K to 275.5 K) slowed down the hydrate formation kinetics but amplified the separation performance, with the best R22 separation factor 2.84 times higher than that of the constant-temperature case achieved at the same time. Visual images revealed a “wall-climbing” hydrate growth pattern for R125/R22 mixed hydrate formation particularly in unstirred conditions. These results support the proposal of a hydrate-based composition-adjustable ORC and could lead to further development of this technology with practical insights.

Superstructure-based mixed-integer nonlinear programming framework for hybrid heat sources driven organic Rankine cycle optimization

Organic Rankine cycle (ORC) is a promising technology capable of harnessing low-grade energy, e.g. renewable energy and waste heat, and converting it into electricity. Conventional ORC often operates with single heat source, which can be unfavorable to its efficiency due to the poor matching between its working fluid and heat source. Implementing hybrid heat sources is generally more energy-efficient as multiple heat sources can effectively match with the working fluid, however, the design can be a challenging task. This study proposes a superstructure-based method for the ORC design that simultaneously synthesizes heat exchanger network for hybrid heat sources and working fluid, and optimizes the ORC and heat sources' parameters. A mixed-integer nonlinear programming model is formulated to achieve the simultaneous optimization. We also develop a tailored multi-step initialization algorithm to facilitate the optimization. The model is applied to the design and analysis of ORCs driven by solar energy and waste heat with four different working fluids. Results demonstrate that the hybrid heat source-driven ORC improves the system performance. Cyclohexane is found to be the optimal working fluid for the proposed ORC system with a 48.19% increase in net power output compared with the single heat source-driven ORCs running separately.

Simulation and experiment investigation of a heating and power double function system with multi-objective optimization

As conventional organic Rankine cycle (ORC) power generation and reverse Carnot cycle (RCC) heat pump systems have some limitations for a fixed heat source. This study proposed a novel RCC and ORC double function system which can work in the ORC power generation mode and RCC heat pump mode for district heating and power output, respectively. The energy model is firstly established to analyze the system thermal performance and then a test rig is built to verify the performance of the system and validate the mathematical model. The economic and environmental analysis are conducted and the multi-objective optimization (MOP) method has been conducted to solve the conflicting problem between the capital cost and payback period under the different operating conditions. Results indicate that the system has good feasibility and stability which can provide 5.96 kW power output with the thermal efficiency of 5.23 % and 60.02 kW heating capacity with the COP of 2.85. The errors of the experiment to simulation COP and the error of experiment to simulation thermal efficiency value are all less than 10%. The optimization consequences based on the TOPSIS decision-making and NSGA-II technology indicate that the MOP solution has a better performance compared with the single-objective optimization.

Performance evaluation of ORC system using evacuated flat plate Photovoltaic-Thermal collector as an evaporator

Low temperature saturated solar organic Rankine cycle (ORC) utilizing evacuated flat plate photovoltaic-thermal (EFPV-T) collector as an evaporator is investigated. A detailed mathematical model for the novel solar thermal collector and ORC has been worked out for the performance analysis of the proposed system. The system is comprised of, stationary solar thermal collector working as an evaporator and other conventional ORC components. A subcritical cycle is considered, and saturated vapor obtained at the solar collector outlet expands in the expander producing useful shaft power. Solar collector’s collection efficiency, PV conversion efficiency, Rankine cycle efficiency, system’s thermal efficiency, and net power output for 5 working fluids have been comparatively investigated at five different pressure ratios (PR) and in three different collector’s configurations including Evacuated Flat Plate Photovoltaic-Thermal Collector (EFPV-T)). Simulation outcomes revealed that solar collector’s performance dropped in FPV-T collector’s configuration while it significantly improved in the case of EFPV-T configuration consequently enhancing the ORC system’s thermal efficiency. The results also revealed that at the same pressure ratio, the fluid with low evaporation temperature will result in better PV performance because the corresponding collector’s absorber plate temperature will be lower. Based on the system’s overall performance, fluid R245fa appears to be a suitable candidate and exhibited system’s overall electrical output of 76.81 W/m2 and overall electrical efficiency of 8.24%, followed by R601 with a system overall power output of 75.97 W/m2 and overall electrical efficiency of 8.13%, at 3.5 pressure ratio in EFPV-T collector’s configuration.

Thermo-economic design, optimization, and evaluation of a novel zeotropic ORC with mixture composition adjustment during operation

Organic Rankine cycle (ORC) is a proposing technology that converting low temperature (usually lower than 200 °C) thermal energy into power. Mostly, the ORC is operated under off-design conditions and the operation performance is deteriorated remarkably from that achieved under rated condition. In the present study, a novel composition-adjustable zeotropic ORC is proposed. A liquid separation condenser-based unit, coupling the heat transfer intensification and mixture composition tuning, is conceptually designed, and integrated into the zeotropic ORC. A regulation strategy for working fluid composition is developed. A thermo-economic evaluation and optimization model and a mixture composition adjustment model are formulated to investigate the superiority of the proposed ORC. A sequential method and genetic algorithm (GA) are applied to conduct the thermodynamic optimization, component design, and thermo-economic optimization of the proposed ORC. A case study is conducted to validate the thermo-economic superiority of the proposed composition adjustable ORC driven by geothermal energy. Results show that the proposed ORC features 0.52% higher annual average net power output, 2.20% higher annual average thermal efficiency, and 21.43% lower average electricity production cost than conventional ORC. The fluid composition-regulating system can achieve the target composition within acceptable time.

Carnot cycle in practice: compensating inefficiencies of ORC expanders through thermal regeneration

The Organic Rankine Cycle (ORC) is a thermodynamic cycle that can operate with a hot source over a wide range of temperatures, especially with low-grade heat (below 200°C). One of the main limitations for the success of small-scale ORC cycles (few to 100 kWe) is the relatively low isentropic efficiency of the typically used turbomachinery. Low turbine efficiency leads to low ORC cycle performance. To increase the performance of the cycle, the turbine efficiency must be increase, however, this significantly increases the cost of the machinery, making the cycle less profitable. In this work, the performance evaluation of low-temperature ORC cycles (100-150°C) with heat extraction along the expansion process is investigated, in an attempt to overcome this limitation. The studied cycle works in the same way as a conventional ORC, except that during the expansion process, heat is extracted. This heat is re-used later in the cycle, just before the hot source, allowing to reduce its load. The different cycles presented in this paper, using pentane as working fluid, are compared based on their exergetic and energetic efficiencies. The influence of three parameters on the cycle performance is studied: the regeneration ratio, the maximum temperature of the cycle and the turbine isentropic efficiency. In the case of a cycle using pentane with a maximum temperature of 150 °C and an turbine isentropic efficiency of 65%, the energy efficiency increases from 6.2% to 16.3% when going from no regeneration to full regeneration, and the exergy efficiency increases from 21.1 to 45.8%.. Secondly, the influence of the maximum temperature of the cycle is studied. Using pentane as the working fluid, the higher the maximum temperature is, the larger the benefits of heat extraction. However, this temperature cannot exceed the critical temperature of the organic fluid to stay in the case of a subcritical cycle. Finally, considering the turbine isentropic efficiency, it is possible to demonstrate that using a less efficient turbine, for example in small ORC systems, the performance of a cycle with an ideal turbine isentropic efficiency (100%) can be achieved compensating at cycle level the turbine losses with the heat extraction along the expansion process.

Thermodynamic analysis of a Carbon Carrier Cycle (CCC) for low temperature heat recovery

The aim of the paper is to study the thermodynamic behavior of a non-conventional power cycle, named Carbon Carrier Cycle (CCC), which is expected to obtain interesting performance with low temperature heat source. The CCC may be regarded as derived from an absorption machine, where an expander replaces the condenser, the throttling valve and the evaporator. The working fluid is a mixture of CO2 and a proper absorber. In the paper, the thermodynamic model of this kind of cycles is described, and the results obtained considering Acetone as the absorber are discussed. A first performance comparison is then conducted with a more conventional Organic Rankine Cycle (ORC).

Understanding the 3D construction method of thermodynamic cycle: Insights from limiting performance of pure working fluid

The 2D temperature-entropy diagram, which is commonly applied to construct and analyze conventional thermodynamic cycles, cannot clearly express novel thermodynamic cycles with multi-working fluids. The 3D construction method provides a methodological guidance to the construction and analysis of novel thermodynamic cycles. In order to understand the mechanism of the 3D construction method, in this study, the limiting performance of 3D thermodynamic cycle with pure working fluid is analyzed and compared with the limiting performance of organic Rankine cycle. Based on the diagram of the 3D coordinates in terms of temperature, entropy, and mass flow rate, the 3D limiting thermodynamic cycle is defined and decoupled into two limiting organic Rankine cycle first. Then, equations of limiting thermal efficiency and thermodynamic perfection are derived based on pure working fluid. Three parameters affecting limiting performance are revealed, namely the latent heat, the slope of the saturated liquid line in the temperature-entropy diagram, and the separation quality. Lastly, effects of key operating parameters on the limiting efficiency of the 3D cycle are analyzed. With the increase of high temperature or middle temperature, the limiting thermal efficiency increases, and thermodynamic perfection increases first and then declines. With the increase of separation quality, the limiting thermal efficiency shows a downward trend. However, the trend of thermodynamic perfection with separation quality depends on values of high temperature and middle temperature. Besides, the limiting performance between the 3D cycle and conventional organic Rankine cycle is compared. The limiting thermodynamic perfection of 3D cycle using R245fa is 7.3%-16.42% higher than that of conventional organic Rankine cycle.