Parametric optimisation of a combined supercritical CO2 (S-CO2) cycle and organic Rankine cycle (ORC) system for internal combustion engine (ICE) waste-heat recovery

Song, Jian; Li, Xiaoya; Wang, Kai; Markides, Christos N.

doi:10.1016/j.enconman.2020.112999

Cited by 115 publications

(23 citation statements)

References 48 publications

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“…The topping sCO 2 cycle is used to recover the waste heat of the exhaust gas, and the bottoming ORC is used to absorb the heat rejection of the sCO 2 cycle, waste heat of the engine coolant, and residual heat of the exhaust gas. The maximum net power output and minimum specific investment cost of the combined system were 58% and 4% higher than those of the single sCO 2 power cycle (Song et al, 2020). Combined systems have broad potential for engine waste heat recovery and other similar industrial applications.…”

Section: Combined Power Cyclementioning

confidence: 96%

System Design and Application of Supercritical and Transcritical CO2 Power Cycles: A Review

2021

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Improving energy efficiency and reducing carbon emissions are crucial for the technological advancement of power systems. Various carbon dioxide (CO2) power cycles have been proposed for various applications. For high-temperature heat sources, the CO2 power system is more efficient than the ultra-supercritical steam Rankine cycle. As a working fluid, CO2 exhibits environmentally friendly properties. CO2 can be used as an alternative to organic working fluids in small- and medium-sized power systems for low-grade heat sources. In this paper, the main configurations and performance characteristics of CO2 power systems are reviewed. Furthermore, recent system improvements of CO2 power cycles, including supercritical Brayton cycles and transcritical Rankine cycles, are presented. Applications of combined systems and their economic performance are discussed. Finally, the challenges and potential future developments of CO2 power cycles are discussed. CO2 power cycles have their advantages in various applications. As working fluids must exhibit environmentally-friendly properties, CO2 power cycles provide an alternative for power generation, especially for low-grade heat sources.

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Section: Combined Power Cyclementioning

confidence: 96%

System Design and Application of Supercritical and Transcritical CO2 Power Cycles: A Review

2021

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“…A gear pump driven by a variable speed electric In the current application, R236fa was selected as the working fluid, so that a direct comparison would be possible with the experimental results from previous studies by the authors [9,45]. Moreover, R236fa shows a lower cost and similar thermophysical properties to R245fa, which is one of the most suitable working fluids for waste heat recovery in internal combustion engines [46,47] despite other fluids such as ethanol and R236ea showing better thermodynamic performance [48], and it has been successfully employed in small-scale ORC systems [49].…”

Section: Experimental Layoutmentioning

confidence: 99%

Design and Operational Control Strategy for Optimum Off-Design Performance of an ORC Plant for Low-Grade Waste Heat Recovery

et al. 2020

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The applicability of organic Rankine cycle (ORC) technology to waste heat recovery (WHR) is currently experiencing growing interest and accelerated technological development. The utilization of low-to-medium grade thermal energy sources, especially in the presence of heat source intermittency in applications where the thermal source is characterized by highly variable thermodynamic conditions, requires a control strategy for off-design operation to achieve optimal ORC power-unit performance. This paper presents a validated comprehensive model for off-design analysis of an ORC power-unit, with R236fa as the working fluid, a gear pump, and a 1.5 kW sliding vane rotary expander (SVRE) for WHR from the exhaust gases of a light-duty internal combustion engine. Model validation is performed using data from an extensive experimental campaign on both the rotary equipment (pump, expander) and the remainder components of the plant, namely the heat recovery vapor generator (HRVH), condenser, reservoirs, and piping. Based on the validated computational platform, the benefits on the ORC plant net power output and efficiency of either a variable permeability expander or of sliding vane rotary pump optimization are assessed. The novelty introduced by this optimization strategy is that the evaluations are conducted by a numerical model, which reproduces the real features of the ORC plant. This approach ensures an analysis of the whole system both from a plant and cycle point of view, catching some real aspects that are otherwise undetectable. These optimization strategies are considered as a baseline ORC plant that suffers low expander efficiency (30%) and a large parasitic pumping power, with a backwork ratio (BWR) of up to 60%. It is found that the benefits on the expander power arising from a lower permeability combined with a lower energy demand by the pump (20% of BWR) for circulation of the working fluid allows a better recovery performance for the ORC plant with respect to the baseline case. Adopting the optimization strategies, the average efficiency and maximum generated power increase from 1.5% to 3.5% and from 400 to 1100 W, respectively. These performances are in accordance with the plant efficiencies found in the experimental works in the literature, which vary between 1.6% and 6.5% for similar applications. Nonetheless, there is still room for improvement regarding a proper design of rotary machines, which can be redesigned considering the indications resulting from the developed optimization analysis.

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“…To sum up, analyzing and evaluating the dynamic response characteristics of the DORC system under full operating conditions of the CNG engine will help to obtain comprehensive waste heat recovery performance [16]. Table 1 briefly lists the selection of operating conditions when recovering waste heat from IC engine in recent years [17][18][19][20][21][22][23][24][25][26][27][28][29]. It can be seen from the table that researchers have carried out a lot of research on ORC systems from different perspectives, but most of them use constant heat source (usually the rated condition of engine) as the high-temperature heat source for the ORC system.…”

Section: Introductionmentioning

confidence: 99%

“…Engine power output: 996 kW; engine speed: 1500 r/min; engine torque: 6340 N•m; exhaust temperature: 573.15 K; exhaust mass flow rate: 1.91 kg/s Song et al [21] 2020…”

Section: Introductionmentioning

confidence: 99%

Dynamic Response Characteristics Analysis and Energy, Exergy, and Economic (3E) Evaluation of Dual Loop Organic Rankine Cycle (DORC) for CNG Engine Waste Heat Recovery

Yao

Zhang

2021

Energies

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Frequent fluctuations of CNG engine operating conditions make the waste heat source have uncertain, nonlinear, and strong coupling characteristics. These characteristics are not conducive to the efficient recovery of the DORC system. The systematic evaluation of the CNG engine waste heat source and the comprehensive performance of the DORC system is conducive to the efficient use of waste heat. Based on the theory of internal combustion (IC) engine thermal balance, this paper analyzes the dynamic characteristics of compressed natural gas (CNG) engine waste heat energy under full operating conditions. Then, based on the operating characteristics of the dual loop organic Rankine cycle (DORC) system, thermodynamic models, heat transfer models, and economic models are constructed. The dynamic response characteristics analysis and energy, exergy, and economic (3E) evaluation of the DORC system under full operating conditions are carried out. The results show that the maximum values of net power output, heat exchange area, and the minimum values of EPC (electricity production cost) and PBT (payback time) are all obtained under rated condition, which are 174.03 kW, 25.86 kW, 37.54 kW, 24.76 m2, 0.15 $/kW·h and 3.46 years. Therefore, the rated condition is a relatively ideal design operating point for the DORC system. The research in this paper not only provides a reliable reference for the comprehensive analysis and evaluation of the performance of the DORC system, but also provides useful guidance for the selection of appropriate DORC system design operating points.

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Parametric optimisation of a combined supercritical CO2 (S-CO2) cycle and organic Rankine cycle (ORC) system for internal combustion engine (ICE) waste-heat recovery

Cited by 115 publications

References 48 publications

System Design and Application of Supercritical and Transcritical CO2 Power Cycles: A Review

System Design and Application of Supercritical and Transcritical CO2 Power Cycles: A Review

Design and Operational Control Strategy for Optimum Off-Design Performance of an ORC Plant for Low-Grade Waste Heat Recovery

Dynamic Response Characteristics Analysis and Energy, Exergy, and Economic (3E) Evaluation of Dual Loop Organic Rankine Cycle (DORC) for CNG Engine Waste Heat Recovery

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