Organic Rankine Cycle System Research Articles

Green and Efficient Recovery and Optimization of Waste Heat and LNG Cold Energy in LNG-Powered Ship Engines

This study focuses on the Wartsila 9L34DF engine and proposes an integrated system for low-temperature carbon capture using the coupling of cold and hot energy recovery with membrane separation in LNG-powered ships. By utilizing a series dual-pressure organic Rankine cycle (SDPORC) system to recover waste heat from the engine exhaust gases and generate electricity, the system provides power support for the low-temperature carbon capture compression process without consuming additional ship power. To validate the accuracy and reliability of the mathematical model, the simulation results are compared with the literature’s data. Once the model’s accuracy is ensured, the operational parameters of the integrated system are analyzed. Subsequently, working fluid optimization and genetic algorithm sensitive parameter optimization are conducted. Finally, under the optimal operating conditions, the thermodynamic performance and economic evaluation of the integrated system are assessed. The results demonstrate that the net power output of the integrated system is 100.95 kW, with an exergy efficiency of 45.19%. The unit carbon capture cost (UCC) is 14.24 $/ton, and for each unit of consumed LNG, 1.97 kg of liquid CO2 with a concentration of 99.5% can be captured. This integrated system significantly improves the energy utilization efficiency of ships and reduces CO2 emissions.

Operation characteristic research on organic Rankine cycle-free piston linear generator (ORC-FPLG) based on multi-module combination

Free piston linear generator (FPLG) presents great potential in organic Rankine cycle (ORC) system to replace traditional expanders because of low friction loss, simple structure and good sealing. Drawing on the concept of multi-cylinder engines, ORC-FPLG simulation model coupled with vehicle have been established based on multi-module combination with GT-suite/Simulink. Then, the operation characteristics in parallel mode, series mode and different intake distribution modes are analyzed. And the influence of engine parameters, and the energy-saving potential under road conditions are explored. The results show that: there exists an optimal module number in parallel mode to maximize net output power and thermal efficiency. When the number of modules is 4, the maximum net output power and thermal efficiency are 11.19 kW and 7.73%. The more parallel modules in series mode is, the higher net output power and thermal efficiency is, which is more conducive to improve output performance. Net power output and thermal efficiency gradually increase with engine speed and fuel injection. There exists an optimal injection timing and exhaust timing to maximize net power output and thermal efficiency. Compared to urban road conditions, ORC-FPLG system under suburban conditions achieves better energy recovery results with waste heat recovery efficiency of 2.22%.

Fast two-layer nonlinear economic predictive control using machine learning for ORC systems with non-Gaussian disturbances

This study proposes a machine learning-based generalized correntropy two-layer nonlinear economic model predictive control (ML-GC-TL-NEMPC) algorithm to improve the computational speed for Organic Rankine Cycle (ORC) systems with non-Gaussian disturbances. In the upper layer, the ratio of the net output power to the total heat transfer area is used as the economic performance index to optimize the optimal reference trajectory. In the lower layer, the generalized correntropy-based MPC (GC-MPC) is used to track the optimal trajectory. To quickly obtain an optimal solution, a Deep Neural Network (DNN) neural network controller is combined with kernel support vector machine (SVM). It learns the possible optimal solution via off-line training. Then it can be quickly implemented on on-line applications, so it can save the optimal calculation time. The proposed ML-GC-TL-NEMPC is applied to ORC. Its computation and performance are faster and better than the traditional two-layer EMPC and single-layer EMPC.

Numerical simulation and low speed experiment of a low partially admitted rate axial turbine for small scale organic Rankine cycle

High rotating speed is a prominent feature of turbine used for small-scale organic Rankine cycle (ORC) system, which can bring the problems of safety, reliability, sealing, vibration, economics, etc. Partial admission method has potential to reduce the rotating speed of small turbine. In this study, an axial turbine with low partially admitted rate of 0.033 was tested in ORC loop using R1233zde as working fluid, and numerically researched using Ansys CFX software with k-omega turbulence model. Results showed that the specific powers of turbine resulting from CFD should be corrected with losses to match well with the experimental results. Losses could reduce the optimal rotating speed of turbine. The optimal rotating speed, mass flow rate, power and efficiency of turbine under rated condition were 8000 RPM, 115.8 g/s, 611.8 W and 35.8 %, respectively. The corresponding power and thermal efficiency of ORC were 551.0 W and 2.15 %. The influences of inlet and back pressures on the performance of turbine were different. With constant inlet pressure and temperature, the mass flow rate kept almost unchanged after chocking, but the power continued to increase. Under allowable conditions, reducing back pressure of turbine played an important role in improving turbine performance.

Thermo-economic optimization of an ORC system for a dual-fuel marine engine

The Organic Rankine Cycle (ORC) is one of the most promising systems to recover the waste heat sourced from internal combustion engines. In this study, thermodynamic, economic and environmental analyses of the scavenge air cooling water-driven Waste Heat Recovery System (WHRS) based on the organic Rankine cycle are conducted for a dual-fuel marine engine integrated with exhaust gas recirculation (EGR) system. Zero ozone-depleting and low global warming potential working fluids; R245fa, R236ea from hydrofluorocarbons, R600a, R601a from hydrocarbons, R1234ze and R1234yf from hydrofluoroolefins are selected for the low-grade WHRS. In addition to the thermal analyses, the mass and volume of the system along with the safety factors of the working fluids are evaluated to judge the physical applicability of the system for ships. Thermo-economic performances of the fluids are analyzed, optimized and compared under various engine loads, Tier II and Tier III modes to reveal the effects of different engine operating conditions on the parameters. According to the results, scavenge air has a significant amount of waste heat at medium and heavy loads and switching the engine mode remarkably affects the performance of the WHRS. R601a shows the best thermo-economic performance, however, considering the applicability of the system R236ea is the most suitable working fluid for the ORC WHRS. The overall thermal efficiency of the power generation system can be increased by about 2.8%.

Potential of Variable Geometry Radial Inflow Turbines as Expansion Machines in Organic Rankine Cycles Integrated with Heavy-Duty Diesel Engines

This work evaluates the feasibility of utilizing an organic Rankine cycle (ORC) for waste heat recovery in internal combustion engines to meet the stringent regulations for reducing emissions resulting from the combustion of fossil fuels. The turbine is the most crucial component of the ORC cycle since it is responsible for power production. In this study, a variable geometry radial inflow turbine is designed to cope with variable exhaust conditions. A variable geometry turbine is simply a radial turbine with different throat openings: 30, 60, and 100%. The exhaust gases of a heavy-duty diesel engine are utilized as a heat source for the ORC system. Different engine operating points are explored, in which each point has a different exhaust temperature and mass flow rate. The results showed that the maximum improvements in engine power and brake specific fuel consumption (BSFC) were 5.5% and 5.3% when coupled to the ORC system with a variable geometry turbine. Moreover, the variable geometry turbine increased the thermal efficiency of the cycle by at least 20% compared to the system with a fixed geometry turbine. Therefore, variable geometry turbines are considered a promising technology in the field and should be further investigated by scholars.

Analysis of the use of waste heat from a glass melting furnace for electricity production in the organic Rankine cycle system

Analysis of the use of waste heat from a glass melting furnace for electricity production in the organic Rankine cycle system

Proposal a new hybrid system comprising of LNG regasification and geothermal sources: Exergy, exergo-economic, and optimization

In the current research, a novel hybrid cascade power generation system including an organic Rankine cycle (ORC), Kalina cycle (KC), and LNG regasification system assisted by geothermal energy is proposed and investigated. Geothermal fluid energy is used to drive the ORC and KC; at the same time, the waste heat of ORC and KC is utilized to power the LNG cycle. The main new aspect of the current work is the integration of cold energy of re-gasification with low-temperature geothermal source combined with a thermoelectric generator. The introduced system is investigated from the thermodynamic and exergo-economic points of view by considering net power generation, energy efficiency, exergy efficiency, and sustainability index as performance indicators. The study results show that energy and exergy efficiencies of the suggested system are approximately 24.33% and 51.6%, respectively, while sustainability index and total cost rate are 2.066, and 12.68 $/h, accordingly. In addition, different operating parameters (valve 2 outlet pressure, valve 2 inlet temperature and turbines inlet and outlet pressures) are varied to assess the system’s performance comprehensively. The results of multi-criteria optimization for the suggested system represent that the output power can reach 32183.44 kW and SI = 2.062 with the total cost rate of 12.69 $/h.

Thermodynamic and environmental analysis of an auto-thermal supercritical water gasification system for ammonia and power production from chicken manure

Supercritical water gasification (SCWG) technology, a clean and efficient method for organic waste treatment, has considerable application prospects in the background of carbon emission reduction. In this study, an auto-thermal SCWG system of chicken manure for NH3 and power production was proposed for recycling waste resources. Thermodynamic analysis and environmental impact assessment were conducted under different operational conditions. The system exhibited optimal energy, exergy, and cold gas efficiencies of 62.34 %, 53.75 %, and 57.75 %, while simultaneously generating 3372.11 kg/h of NH3 and 1677.1 kW of net power, all within processing 10 t/h of dry chicken manure. The global warming potential of this system was only 3.31 kg CO2-eq/kg NH3 with carbon capture and storage. The sensitivity analysis indicated that the moderate increase in gasification temperature, higher feedstock concentration, appropriate preheated water flow, and suitable feedstock distribution ratio collectively enhanced system performance by mitigating exergy destruction in the partial oxidation and heat exchange process. By converting waste heat into electrical energy rather than industrial steam, the Organic Rankine Cycle system enhances the practical viability of waste heat recovery. This work expects to provide essential theoretical guidance for the scale-up and design of the biomass waste SCWG system.

A novel optimization method for transcritical-subcritical parallel organic Rankine cycle under variable engine loads and cooling water temperature

Organic Rankine cycle (ORC) is an effective technology for engine waste heat recovery. However, when engine loads and cooling water temperature are variable, the optimization of ORC system will be difficult and time-consuming, especially for complex system like transcritical two-stage ORC. In this study, a novel optimization method is proposed for optimizing the transcritical-subcritical parallel ORC (TSPORC) system, and the system operates under variable engine loads and cooling water temperature. The key idea of the optimization method is a combination of artificial neural network (ANN) and non-dominated sorting genetic algorithm (NSGA-II), the ANN is used to establish a fast and accurate prediction model of the system performance to reduce computing time significantly, and the NSGA-II is furtherly used to optimize system performance fast and accurately based on the ANN prediction model. To improve the accuracy of ANN model, three different artificial neural network models are optimized and compared. To satisfy different objective optimization for application, both single-objective and multi-objective optimization are conducted. The results demonstrate that the optimization method can achieve real time optimization for TSPORC system operating under variable engine loads and cooling water temperature fast and accurately.

Energy, Exergy and Environmental Analysis of ORC Waste Heat Recovery from Container Ship Exhaust Gases Based on Voyage Cycle

Recovering the waste heat of a marine main engine (M/E) to generate electricity was an environmental way to minimize the carbon dioxide emissions for ships, especially with organic Rankine cycle (ORC) technology. The M/E had variable loads and operating times during voyage cycle, which directly affected the ORC thermodynamic potential. In this paper, a voyage cycle-based waste heat utilization from the M/E was introduced to provide reliable evaluation for proposing and designing ORC. The effect of various M/E loads and operating times on ORC performance among three dry-type substances was analyzed. The environmental impact was presented based on the data from one voyage cycle navigation of objective container ship. The results showed that Cyclohexane was capable of net power while Benzene was more suitable for thermal efficiency. The evaporator and condenser were the main irreversible components of the ORC system and required further optimization. Taking the operational profile into consideration, the evaporation pressures were 922–1248 kPa (Cyclohexane), 932–1235 kPa (Benzene) and 592–769 kPa (Toluene), respectively. During the voyage cycle, the carbon dioxide emissions were 99.68 tons (Cyclohexane), 96.32 tons (Benzene) and 60.99 tons (Toluene), respectively. This study provided certain reference for the design and investigation of ORC application to further improve the energy efficiency for container ship.

Advanced Exergy-Based Analysis of an Organic Rankine Cycle (ORC) for Waste Heat Recovery.

In this study, advanced exergy and exergoeconomic analysis are applied to an Organic Rankine Cycle (ORC) for waste heat recovery to identify the potential for thermodynamic and economic improvement of the system (splitting the decision variables into avoidable/unavoidable parts) and the interdependencies between the components (endogenous and exogenous parts). For the first time, the advanced analysis has been applied under different conditions: constant heat rate supplied to the ORC or constant power generated by the ORC. The system simulation was performed in Matlab. The results show that the interactions among components of the ORC system are not strong; therefore, the approach of component-by-component optimization can be applied. The evaporator and condenser are important components to be improved from both thermodynamic and cost perspectives. The advanced exergoeconomic (graphical) optimization of these components indicates that the minimum temperature difference in the evaporator should be increased while the minimum temperature difference in the condenser should be decreased. The optimization results show that the exergetic efficiency of the ORC system can be improved from 27.1% to 27.7%, while the cost of generated electricity decreased from 18.14 USD/GJ to 18.09 USD/GJ.

Experimental validation of a 0.3 kW ORC for the future purposes in the study of low-grade thermal to power conversion

Organic Rankine cycle (ORC) is a promising development direction for energy conservation and environmental protection, as it can effectively convert low-temperature waste heat into mechanical work. This article focuses on the experimental performance study of what is likely the world's smallest scroll expander used in a 0.3 kW micro-ORC system. The system uses R1233zd-E as the working fluid, and the expander is repurposed from a scroll compressor of an air conditioner, with a displacement of 11.1 mL/rev. In the first part of the experiments, the influence of the system pressure difference and the expander rotational speed on the system performance is investigated while keeping the expander inlet superheating fixed. The maximum system efficiency, expander efficiency, and power output were 5.46 %, 72.4 %, and 0.266 kW, respectively. In the second part of experiments, the effect of changing the heating source temperature on the system is explored while keeping the expander rotational speed and inlet pressure fixed. As the superheat increased, both the expander and cycle efficiency increased. In addition, this study combines the experimental results with previous data on small-scale ORC systems and discusses the similar trends, indirectly demonstrating that the 0.3 kW micro-ORC can achieve similar behavior as predicted in a large-scale ORC.

Research on the characteristics of the exhaust energy splitting method for the two-stroke low speed marine diesel engine

Efficient waste heat recovery (WHR) is the key to improve the thermal efficiency of the marine diesel engine and reduce the cost. According to the characteristics of long stroke of low-speed marine diesel engine, the exhaust energy splitting (EES) method based on exhaust energy distribution is proposed in this paper. EES is a new method of improving waste heat grade by separating high temperature exhaust gas and low temperature scavenging air. Compared with other studies on increasing exhaust temperature, EES significantly increases exhaust temperature and improves waste heat recovery efficiency without negatively affecting engine performance. Moreover, due to the adjustable EES valve, the optimal performance of engine and WHR system can be achieved under various operating conditions by adjusting the exhaust splitting phase (ESP). The One-Dimension and Three-Dimension simulation models for a two-stroke low speed marine diesel engine with waste heat recovery system are established. The exhaust energy distribution and the splitting phase to be optimized are also explored synchronously. The results show that by using the exhaust energy splitting method, temperature after turbine can be increased by more than 100 K compared with the baseline of the original engine system. Using Organic Rankine cycle (ORC) as WHR system, the waste heat recovery efficiency can reach over 17 %. Compared with the original engine, the total output power of the optimized EES low-speed engine and ORC system Increase by 100.90 kW under 75 % load and 154.72 kW under 100 % load, and the NOx emissions can be reduced by 5 %.

Design and Thermo-Economic Analysis of an Integrated Solar Field Micro Gas Turbine Biomass Gasifier and Organic Rankine Cycle System

A micro gas turbine (MGT) is an advanced technology with a simple structure and fast load response. It represents a good choice for the next generation of distributed power systems, where fossil fuels are going to be largely replaced by biofuels and renewable sources. In this context, this work aims to investigate and compare the performance of gradually more complex energy systems integrating a micro gas turbine plant: simple cogenerating asset, integrating a solar field, presence of a gasifier, and the addition of a bottoming ORC. In all cases, a thermo-economic analysis has been carried out for an application in the agricultural sector. Agricultural waste can be used to create a syngas as fuel for MGT through a gasifier, promoting the utilization of carbon-neutral alternative fuels to reduce harmful emissions. The authors considered the electrical and thermal needs of a hypothetical agri-food company to build the electrical and thermal load curves. The new and more complex cogeneration plant, designed by using the Thermoflex 30 software, leads to an increase in electrical power, recovered thermal power, overall electrical efficiency, carbon neutrality, and cogeneration indexes. In particular, the presence of the solar field promotes a reduction in fuel consumption as well as greater heat input to the thermal unit. The addition of a bottoming ORC system increases the electrical power by 36.4%, without significantly penalizing the thermal unit. Moreover, thanks to the gasifier that offsets the fuel reduction costs, through an economic analysis of the entire plant, a payback time of the investment of less than 4 years is obtained.

Optimization and exergy analysis of a cascade organic Rankine cycle integrated with liquefied natural gas regasification process

One of the most efficient methods of exergy recovery during the regasification process is integrating the LNG stream with an Organic Rankine Cycle (ORC) to generate electricity. This study employs a cascade structure of ORC consisting of two double-stage condensations operating at 6 bar regasification pressure. To obtain an optimal ORC system integrated with an LNG, three optimization levels for a specific heat source are addressed, including process variables, working fluids, and structure. Ten process variables and two working fluid variables for the top and bottom cycle among 13 candidates of refrigerants were optimized to provide the maximum power output. The results determined that refrigerants of R41 and R1150 have the best performance in the optimized process conditions for the top and bottom cycles, respectively. For the regasification of 36 tonnes per hour of an LNG stream, the produced net power and the exergy efficiency are achieved by 2116.76 kW and 0.29, respectively. The exergy analysis revealed that employing the double-stage condenser ORC is not a good choice. Accordingly, a cascade-parallel structure is proposed for further studies.

The theoretical approach of the solar organic Rankine cycle integrated with phase change material for the Hungarian region

AbstractHungary is not only dependent on imports of natural gas and fossil fuels, but Hungary is also the lowest in renewable energy utilization; otherwise, only 11.3% compared to other Central European countries in renewable energy utilization, above 13%. The percentage of renewables in power generation quadrupled from 8% to 16% between 2010 and 2020, with most of the gains coming from the rapid expansion of solar energy, particularly after 2016. Regarding solar energy resource potential, Hungary has a daily total of around 3.2–3.6 kWh/m2 and a yearly total of about 1168–1314 kW.h/m2. This makes it a suitable location for putting solar thermal collectors in conjunction with an organic Rankine cycle (ORC) system. In this study, the authors analyzed solar thermal as a heat source to generate electricity with ORC using two types of working fluids (R245fa and R123). Hungary's weather data for a whole year is used as primary data to look for solar radiation characteristics and ambient temperature. Based on the general solar collector equation, the parabolic tube collector was selected as the best solar collector to utilize solar radiation by producing a maximum heat of around 654.68 kW. Therefore, the evacuated flat plate collector was selected as the solar collector that can produce the maximum outlet temperature of around 372.15 K with a similar size aperture area. Producing a temperature output from the solar collector for heat transfer in the ORC system and from the performance showed that R245fa resulted in better Wnet performance compared with R123 with values of 45.82 and 28.17 kW, respectively, under the same solar collector. Meanwhile, the material suitable for the thermal energy storage‐evaporator combination is organic phase change material using N‐Octacosane, which in the same temperature range (350–375 K) has the smallest ζ(T) value (1.08–1.103), so the mass required for the system is very efficient.

Exergoeconomic analysis of an integrated electric power generation system based on biomass energy and Organic Rankine cycle

ABSTRACT The present study investigates the thermodynamics analysis of a trigeneration system using a gasifier system. An Organic Rankine Cycle (ORC) system is used to heat recovery and consequently, supplying the cooling demand. The first and second laws of thermodynamics are used to energy and exergy analysis of the system. Some thermodynamic parameters which affect the system performance including combustion temperature, gasifier temperature, compressor isentropic efficiency, gas turbine isentropic efficiency, compressor pressure ratio, and ORC pressure are parametrically analysed and their contribution in improving the efficiency and economy of the system is investigated. To the sustainable performance of the combined system, we need an evolutionary algorithm to identify the optimum values of thermodynamic parameters that have an impact on system performance. Hence, the Multi-Objective Particle Swarm Optimization (MOPSO) algorithm is used to find the best values of decision variables. The most striking result to emerge from the optimisation.optimisation is that implementing the MOPSO algorithm improves the exergy efficiency by 5.17% and reduces the total cost of the system by 1.9%.

Exergy and energy analysis of Organic Rankine Cycle integration in the carbon black industry using pinch technology

Industrial Carbon black production is a petrochemical process that has high level of waste heat and emissions. Main points of CB process include furnace and stack lines. Also, the use of different feedstocks can be effective in level of waste heat and amount of emission pollutants. So the main objective of this research use from the pinch technology in CB process in order to minimize the level of waste heat by utilization of waste heat recovery (WHR) applications for power generation. By numerical investigation and modelling of WHR in furnace and stack points, can be defined best location for power generation in CB process. Moreover, through the analysis of Organic Rankine Cycle (ORC) systems integrated with WHR from both energy and exergy perspectives, second target to enhance their thermal efficiency. The results indicate that the presence of blowers on stacks leads to an increase in RoHR and RoHC. In order to determine the optimal location for power generation cycle installation, an ORC energy and exergy analysis was conducted. The results showed that the energy and exergy values at the SLC stack were higher than those at the HLC point. Also, numerical results showed the points that have suitable thermal efficiency and rate of exergy of WHR where have higher temperature gradient than other points. So SLC (ĖxWHR=166.7kW) and HLC (ĖxWHR=136.1kW) stacks integrated with blower are the optimal location for WHR utilization in the CB production process.

Design and analysis of an axial turbine for high-temperature organic Rankine cycle

The organic Rankine cycle (ORC) system is of great importance to achieving the effective exploitation of waste energy. As the essential component of the ORC system, the expander is directly related to the performance and structure size of the ORC system, which deserves to be studied in detail. A single-stage axial turbine with a U-shaped volute is presented for the high-temperature ORC system in this paper. Based on preliminary design and modeling, the turbine aerodynamic performance under design and off-design conditions is investigated in numerical simulation. Results show that the turbine efficiency is 77% with a pressure ratio of 4.78 at the design point and the turbine efficiency can still be maintained above 70% as the pressure ratio reaches 6. It can be concluded that low Reynolds number flow and negative incidence angle are the main reasons for low turbine efficiency under the low pressure ratio, while the shock wave becomes the key factor influencing turbine efficiency under the high pressure ratio. In addition, blade profile optimization and shock wave management is the primary way to maintain high turbine efficiency under a high pressure ratio. Results indicate that the turbine proposed in this paper is proven suitable for high-temperature ORC systems and the relevant research has a certain guiding value for the efficient and compact single-stage axial turbine design.