Organic Rankine Cycle Waste Heat Recovery Research Articles

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.

Data-driven identification and fast model predictive control of the ORC waste heat recovery system by using Koopman operator

Organic Rankine Cycle (ORC) has received its wide application in low-grade waste heat recovery (WHR) technology for its significant performance and easy access to its components. Given the highly fluctuating nature of the waste heat source, Model Predictive Control (MPC) is usually utilized to realize the reasonable adjustment of ORC based WHR systems and has performed satisfactorily. In order to apply MPC, a relatively precise model should be built up for the ORC system which ensures acceptable control performance. However, popular modeling methods based on the mechanism of the ORC establish the high-dimensional nonlinear model and suffer from computational costs when utilizing complicated nonlinear MPC. Even if linear MPC is employed for the purpose of reducing the calculation amount, the model obtained by linearization near the operating points usually makes it valid locally, thus bringing about suboptimal or unstable control performance. To address this problem, the Koopman operator is introduced for the data-driven identification and MPC of the ORC system. Koopman identification constructs a linear model in the lifted space in which the ORC system possesses nearly global linear evolution and enables the prediction of the nonlinear ORC dynamics from measurement data. In view of the possible online calculation burden increment caused by the rise of variable dimension through lifting action, the fast Koopman MPC (FKMPC) algorithm is thus proposed based on the invariance of the Hessian matrix of the optimization problem to shorten the computing time. Simulations on setpoint tracking and disturbance rejection are performed to verify the established model accuracy and the control effectiveness of the proposed strategy in comparison with other approaches.

Information theory-based dynamic feature capture and global multi-objective optimization approach for organic Rankine cycle (ORC) considering road environment

Efficient capture and global optimization of organic Rankine cycle (ORC) operating features in road environment is the key to obtain actual waste heat recovery potential. The complexity of time-varying characteristics intensifies the nonlinear coupling relationship between ORC performance and parameters. This paper first designs and builds an ORC experimental system for recovering waste heat from internal combustion engine (ICE). The experimental system includes ICE and its measurement subsystem, ORC subsystem, expander lubrication subsystem, cooling subsystem, and ORC measurement subsystem. R245fa is used as working fluid; The expander adopts a specially designed single screw expander. The performance of ORC waste heat recovery is tested by adjusting the operating conditions of the ICE, expander, pump, and valve opening. The temperature range of waste heat is 627–686 K. Subsequently, a dynamic feature capture and global multi-objective optimization approach for ORC is proposed. The results show that the precision of dynamic feature capture can be improved at least 41.78% with the introduction of information theory in complex environment. Frequent fluctuation of vehicle speed is not conducive to the improvement of evaporator inlet temperature at working fluid side. As the speed of the vehicle is greatly reduced, the evaporator inlet temperature drops sharply. The frequent fluctuation of speed will intensify the nonlinear correlation between operating parameters and system performance and make the system performance more dependent on the coupling correlation between operating parameters. The approach proposed in this paper can provide a new idea for efficient capture of dynamic characteristics and global multi-objective optimization of ORC in road environment.

Alleviating the thermal aging of three-way catalyst applied to natural gas engine based on organic Rankine cycle

Natural gas (NG) is a possible pathway for developing countries to reduce transportation carbon footprint. However, its high exhaust temperature decreases the thermal efficiency of NG engines and accelerates the thermal aging of three-way catalyst (TWC). This study proposes to place an organic Rankine cycle waste heat recovery (ORC-WHR) system between an NG engine and its TWC to recover exhaust energy and extend the useful life of TWC. The feasibility of this design concept is confirmed by the simulation results of an experimentally validated 1D NG engine model combined with an ORC-WHR model at three TWC working temperatures representing field-average, modern, and future TWC technologies. Results show that the decrease in the outlet temperature of the ORC-WHR system benefits the availability of exhaust energy, improving the overall efficiency of the engine plus ORC-WHR system and extending the useful life of the TWC. Hence, more advanced catalyst technologies, which can achieve high conversion efficiency at lower temperatures, are deemed more favorable for ORC-WHR coupling. The cost-effectiveness of such combinations is better due to more exhaust energy recovered and less noble metal catalyst needed to be added.

Design of the Organic Rankine Cycle for High-Efficiency Diesel Engines in Marine Applications

Over the past few years, fuel prices have increased dramatically, and emissions regulations have become stricter in maritime applications. In order to take these factors into consideration, improvements in fuel consumption have become a mandatory factor and a main task of research and development departments in this area. Internal combustion engines (ICEs) can exploit only about 15–40% of chemical energy to produce work effectively, while most of the fuel energy is wasted through exhaust gases and coolant. Although there is a significant amount of wasted energy in thermal processes, the quality of that energy is low owing to its low temperature and provides limited potential for power generation consequently. Waste heat recovery (WHR) systems take advantage of the available waste heat for producing power by utilizing heat energy lost to the surroundings at no additional fuel costs. Among all available waste heat sources in the engine, exhaust gas is the most potent candidate for WHR due to its high level of exergy. Regarding WHR technologies, the well-known Rankine cycles are considered the most promising candidate for improving ICE thermal efficiency. This study is carried out for a six-cylinder marine diesel engine model operating with a WHR organic Rankine cycle (ORC) model that utilizes engine exhaust energy as input. Using expander inlet conditions in the ORC model, preliminary turbine design characteristics are calculated. For this mean-line model, a MATLAB code has been developed. In off-design expander analysis, performance maps are created for different speed and pressure ratios. Results are produced by integrating the polynomial correlations between all of these parameters into the ORC model. ORC efficiency varies in design and off-design conditions which are due to changes in expander input conditions and, consequently, net power output. In this study, ORC efficiency varies from a minimum of 6% to a maximum of 12.7%. ORC efficiency performance is also affected by certain variables such as the coolant flow rate, heat exchanger’s performance etc. It is calculated that with the increase of coolant flow rate, ORC efficiency increases due to the higher turbine work output that is made possible, and the condensing pressure decreases. It is calculated that ORC can improve engine Brake Specific Fuel Consumption (BSFC) from a minimum of 2.9% to a maximum of 5.1%, corresponding to different engine operating points. Thus, decreasing overall fuel consumption shows a positive effect on engine performance. It can also increase engine power output by up to 5.42% if so required for applications where this may be deemed necessary and where an appropriate mechanical connection is made between the engine shaft and the expander shaft. The ORC analysis uses a bespoke expander design methodology and couples it to an ORC design architecture method to provide an important methodology for high-efficiency marine diesel engine systems that can extend well beyond the marine sector and into the broader ORC WHR field and are applicable to many industries (as detailed in the Introduction section of this paper).

Design and Optimization of a Waste Heat Recovery Organic Rankine Cycle System with a Steam–Water Dual Heat Source

The organic Rankine cycle (ORC) system in plants, powered by dual steam–water heat sources, has significant power generation potential and practical research value. Herein, the conditions of 700 kPa saturated steam and 650 kPa, 90 °C water heat source are considered. Four configurations of steam–water dual heat source waste heat recovery ORC systems are proposed. The independent parameters affecting the net output power of the system are obtained by developing a mathematical model and optimizing it using the particle swarm optimization method. The results show that the location of the pinch‐point temperature difference in various ORC loops and the allowable working pressure of the heat exchanger are determinants of independent parameters. The net output powers of the conventional dual‐loop ORC (CD‐ORC), single‐loop ORC (S‐ORC), split‐flow dual‐loop ORC (SFD‐ORC), and split‐flow triple‐loop ORC SFT‐ORC systems under the optimal design parameters are 2415.73, 2168.6, 2599.62, and 2716.75 kW, respectively. In addition, S‐ORC has the highest exergy efficiency of 55.17%. SFD‐ORC and SFT‐ORC have ≈48% exergy efficiency, and CD‐ORC has the lowest exergy efficiency of 45.33%.

Effect of tooth head modification on the performance of a scroll expander for ORC waste heat recovery system

In order to cope with the energy crisis and improve energy efficiency, the use of organic Rankine cycle (ORC) to convert low-quality heat energy into electricity and use it is an effective method. Based on the ORC waste heat recovery system of vehicle engine, this paper explores the flow heat transfer and deformation law of the core component scroll expander under different tooth head corrections. Deformation has a significant impact on the performance of the expander. In this study, several flow-thermal-solid coupling models based on double circular arc correction and double circular arc plus straight-line correction are established. The effects of tooth head correction on the strength and stiffness of tooth head, flow field distribution of suction chamber and deformation characteristics of tooth head are studied. Finally, the deformation law of scroll tooth head with different correction angles was discussed. The results show that the EA-SAL correction makes the wall curvature of the tooth head change greatly, and the flow field in the center of the tooth head becomes more uneven and complicated. The tooth head area under EA-SAL modification is larger, and the tooth head strength and stiffness are improved by about 6%. Within a certain angle range, the tooth head deformation after EA-SAL correction is slightly larger than that after PMP correction, but the difference between them decreases and even reverses with the increase of angle. The maximum deformation of the EA-SAL modified tooth head under internal pressure is about 20% smaller than that of PMP. With a given initial correction angle ∅, the deformation of the corrected tooth head caused by a pressure or temperature load reduces when the correction angle γ is reduced, Therefore, reducing the correction angle properly is helpful to reduce the deformation of the tooth head.

Waste heat recovery and reuse for ship hydraulic oil temperature control system

In order to solve the problems of high energy consumption and serious waste of heat energy in the traditional oil cooler of Marine hydraulic system, the waste heat recovery and reuse of Marine hydraulic oil temperature control system is proposed. The hydraulic system waste heat recovery test platform has been established, the influence of electrical load, oil flow rate and working medium flow rate on system operation and energy characteristics is studied. The experimental results show that under the same working condition, compared with the oil cooler of the same specification, the maximum thermal efficiency of the proposed organic Rankine cycle waste heat recovery system is increased to 2.56%. The expander pressure ratio and system thermal efficiency increase with the increase of electric load and oil flow. The experimental results analyzed the energy saving effect of waste heat recovery system on hydraulic system, and obtained the rule of system operation efficiency.

Low-Carbon Economic Dispatching of Multi-Energy Virtual Power Plant with Carbon Capture Unit Considering Uncertainty and Carbon Market

Multi-energy virtual power plants (MEVPPs) effectively realize multi-energy coupling. Low-carbon transformation of coal-fired units at the source side and consideration of demand response resources at the load side are important ways to achieve carbon peak and carbon neutralization. Based on this, this paper proposes a low-carbon economic dispatch model for the MEVPP system considering source-load coordination with comprehensive demand response. Combined with the characteristics of organic Rankine cycle (ORC) waste heat power generation and comprehensive demand response energy to increase the flexibility on both sides of the source and load, the problem of insufficient carbon capture during the peak load period in the process of low-carbon transformation of thermal power units has been improved. First, the ORC waste heat recovery device is introduced into the MEVPP system to decouple the cogeneration unit’s “heat-based electricity” constraint, which improves the flexibility of the unit’s power output. Secondly, we consider the synergistic effect of the comprehensive demand response and ORC waste heat recovery device and analyze the source-load coordination low-carbon dispatch mechanism. Finally, an example simulation is carried out in a typical system. The simulation example shows that this method effectively improves the carbon capture level of carbon capture power plants, takes into account the economy and low carbon of the system, and can provide a reference for the low-carbon economic dispatch of the MEVPP system.

Experimental investigation of combustion engine with novel jacket and flue gas heat recovery

Internal combustion engines (ICE) are utilized in a number of energy and transportation systems and with the prospect of synthetic green fuels have also secured a place in the future low emission systems. Still, aiming at the effective utilization of the fuel suggests an addition of waste heat recovery systems such as organic Rankine cycle (ORC) to boost electric efficiency. Greater widespread of the ORC integration into the ICE systems is however limited from multiple aspects. Furthermore, when these systems are employed, they are typically applied only for flue gas waste heat utilization, while the large amounts of lower temperature jacket cooling heat remain unutilized, or at the cost of high system complexity. Direct cooling of the ICE jacket by the ORC working fluid has been previously theoretically proposed to tackle some of them. Complexity of the system can be reduced while more waste heat can be effectively transferred from the ICE jacket cooling to the ORC. Here we propose further configuration of ICE waste heat sources integration into a biomass fired ORC unit, creating a multi-fuel system. Such system offers the possibility to increase the electricity demand while reducing biomass consumption. This system has been experimentally explored on a case of a 3 kWe/50 kWth micro-cogeneration ORC and an 8 kWeICE. The experimental data are evaluated in comparison to the theoretically predicted operation. A specific control system has been developed for this system to be easily operated. The results, experience and operation verification from the ICE jacket cooling with the ORC fluid can be also utilized in the construction for waste heat recovery ORC integrated to ICE for higher electrical efficiency. Integration of combined direct jacket and flue gas heat recovery increased the overall electrical efficiency of the system from about 5% for operation of standalone ORC to over 20% for full ICE power.

Direct integration of an organic Rankine cycle into an internal combustion engine cooling system for comprehensive and simplified waste heat recovery

Cogeneration systems based on internal combustion engines (ICE) provide decent efficiency and flexibility. In order to further improve the efficiency, organic Rankine cycle (ORC) can be used to convert high temperature (waste) heat from flue gas to electricity. There is a large amount of heat in jacket cooling at lower temperatures for which there is often no demand so it has to be rejected into the ambient. Previous systems trying to utilise this heat in the ORC cycle end up as too complex and expensive. This study introduces an innovative jacket cooling method. In the cooling system of an ICE, instead of typical water or oil-based heat transfer fluids, the working fluid of an ORC is used as the engine coolant, recovering the low-potential heat. Preheated organic fluid is then directly used in the bottoming ORC with further heat input from the flue gas. This concept allows utilising both low and high potential heat from the cooling of the ICE and from the flue gas recovery, while omitting the intermediate heat-transfer circuits commonly found in ORC waste heat recovery applications. Presented thermodynamic analysis shows a strong dependency of the ORC utilisation efficiency on cooling fluid allowed pressure in the ICE jacket and on the heat flow ratio between the coolant and the flue gas of the ICE. A baseline study with a specific 83 kWe ICE with the novel configuration provides an improvement of nearly 10 kW in comparison with 7 kW of an ORC utilising only flue gas. More general parametric analysis has shown the potential of the ORC power output improvement by more than 60% for specific ICE types and higher pressures and temperatures in the engine cooling circuit. In a cogeneration regime, these benefits in electrical power output come at the cost of a very slight decrease in overall efficiency.

Organic Rankine Cycle (ORC) as waste heat recovery system for micro-cogeneration: A preliminary study

Although the energy consumption pattern has been optimized, the main problem facing by energy revolution is the low conversion efficiency of renewable energy and waste heat. Among the utilization technologies of these waste heat, organic Rankine cycle (ORC), which has characteristics of simple structure and high efficiency is chosen as the potential candidate to overcome this situation. However, ORC is facing several limitations including having low turbine performance leading to low power production. Additionally, the design of ORC and the heat recovery system should be improved to reduce the investment cost. One of the ways to increase the performance of this ORC is to design ORC waste heat recovery system for cogeneration. Thus, this study will be focused on to identify the effect of different heat exchanger positions to the ORC thermal performance and to investigate the effect of integrating ORC for cogeneration. In order to achieve this, identification of the suitable heat exchanger for ORC will be performed by modelling and simulation to predict the effect of the new design to the ORC thermal performance. Then, the improved novel ORC design will be integrated to a cogeneration system to simulate the power produced by the combined system.

Cycle and turbine optimisation for an ORC operating with two-phase expansion

• Novel ORC system operating with two-phase expansion and radial-inflow turbine. • Single- and multi-objective cycle optimisation for 150, 200 and 250 °C heat sources. • MM and MDM are optimal fluids producing up to 28% more power than single-phase ORC. • Mean-line turbine optimisation completed for two-phase radial-inflow turbine. • Feasible subsonic rotor geometries obtained, and candidate turbines designs proposed. Previous investigations suggest the power output from waste-heat recovery organic Rankine cycle (ORC) systems could be enhanced by up to 30% by operating with two-phase expansion, which could reduce cost and aid in the more widespread deployment of ORC technology. However, there are limited expander technologies suitable for such operation. The aim of this research is to investigate a novel ORC system that operates with wet-to-dry expansion permitting the use of a radial-inflow turbine. Specifically, through the exploitation of molecularly complex fluids the wet-to-dry expansion could be achieved across a single turbine stage, whilst the two-phase region is confined to the stator vane. Thermodynamic system optimisation is completed for potential fluids in which the degree of reaction is used to differentiate between the stator and rotor expansion processes. The results reveal that siloxanes are optimal fluids, and that for heat-source temperatures of 150, 200 and 250 ° C the two-phase systems could generate up to 28%, 14% and 3% more power than single-phase systems, respectively. Following this, existing mean-line turbine methods are extended to two-phase turbines under the assumption of a two-phase homogeneous fluid under thermal equilibrium, which is supported with numerical simulations of a two-phase stator vane. The mean-line turbine optimisation for the 200 ° C heat source is then conducted, with the optimal system corresponding to a turbine inlet vapour quality of 0.1 and degree of reaction of 0.4, with lower reaction leading to lower turbine efficiencies. More generally, feasible rotor geometries can be obtained, and conditions with the rotor are expected to remain subsonic. Whilst stator outlet Mach numbers range between 1.5 and 2.1, and stator throat widths below 1 mm are required, the CFD simulations indicate that wet-to-dry expansion can be successfully realised within the stator. In summary, these results provide the first positive demonstration that a 30% improvement in power output could be achieved with a two-phase ORC system operating with molecularly complex working fluids and a radial-inflow turbine.

A Q-learning based transient power optimization method for organic Rankine cycle waste heat recovery system in heavy duty diesel engine applications

In recent years, the organic Rankine cycle waste heat recovery (ORC-WHR) technology gains popularity in heavy-duty diesel engine applications. Drastic fluctuations of the waste heat caused by variable daily operation of mobile heavy-duty trucks bring an extreme transient power optimization challenge to ORC-WHR systems. Existing power optimization methods either neglect transient behavior of the Rankine cycle system or compromise model accuracy for computation efficiency. Different from literature, this study first time proposes a model-free reinforcement learning method to achieve online transient power optimization for the ORC-WHR system and explains the benefits of learning method in this application. A tabular Q-learning is formulated to optimize the net power on an experimentally validated ORC-WHR system. Q-learning is explained in detail using states, action, and policy information. To quantify the power optimization of the proposed method, Proper-Integral-Derivative method, state-of-art offline and online Dynamic Programming methods are implemented. The results showed that Q-learning generated 22% more cumulative energy than the energy Proper-Integral-Derivative method generated. Furthermore, Q-learning produces 96.6% of cumulative energy that the offline Dynamic Programming generates over a transient engine condition, while it requires less computation cost and is executed online. Additionally, the Q-learning produces 0.5% more cumulative energy than the machine learning-based online Dynamic Programming results and exhibits better vapor temperature robustness than the online Dynamic Programming method (4 °C-28 °C superheat by Q-learning vs. 5 °C-94 °C superheat by online Dynamic Programming). Given the excellent power production performance, low computation cost requirement and high robustness, the proposed Q-learning method has the potential to improve the power production of the ORC-WHR system with different configurations.

Design and optimization of hydrogen production by solid oxide electrolyzer with marine engine waste heat recovery and ORC cycle

Hydrogen is considered as a promising alternative to future energy systems. Water or steam electrolysis at elevated temperature consumes less electricity due to the highly efficient utilization of thermal energy. In this paper, a solid oxide electrolyzer cell (SOEC) is integrated with a marine diesel engine to use both electricity and waste heat for hydrogen production. An Organic Rankine Cycle (ORC) is applied to produce electricity from SOEC production streams. A comprehensive thermodynamic analysis model of SOEC, ORC and marine diesel engine waste heat recovery is conducted. The results indicated that the system could produce hydrogen at a rate of 0.431 kg/s and power output of 32386.45 kW with a power reduction of 60%. An efficiency of 104.41%, 12.12% and 53.56% could be achieved for the electrolyzer cell, ORC and integration system, respectively. The waste heat available efficiency could reach only 44.13% under the design conditions. To study the impact of some key parameters on the system performance, sensitivity analysis of current density, H2O inlet flow rate and total SOEC area were performed. It was found that an optimal current density and H2O flow rate can be obtained. Moreover, higher total cell area benefits the integration system thermodynamically.

Bioethanol produced from regenerative wooden resource to operate an organic Rankine cycle-waste heat recovery system in case of a tractor propulsion Diesel engine: preliminary simulation results

Bioethanol has become by nowadays a common-used organic agent by thermal installations in direct modes, like dual or single alternative fuel for classic engines, or in indirect modes, as primary source in fuel cells, or operating thermal energy recovery systems, which is the subject of the present work. Among all the other well-known industrial obtaining methods, avoiding higher costs and improving process efficiency, the enzymatic fermentation of the saccharide components coming from wooden biomass ensures a more profitable way to produce bioethanol, with the requested properties in order to operate as a thermal agent in an Organic Rankine Cycle (ORC) installation. The aim of using this system is to increase the efficiency of a tractor-turbocharged Diesel engine by its waste heat recovery (WHR).

Thermodynamic and techno-economic assessment of pure and zeotropic fluid ORCs for waste heat recovery in a biomass IGCC plant

The present study includes a thermodynamic and techno-economic assessment of Organic Rankine Cycle (ORC) for waste heat recovery (WHR) from three types of waste heat sources in biomass-fuelled integrated gasification combined cycle (BIGCC) plants equipped with carbon capture and storage (CCS). These include (1) the air separation unit (ASU) air compression intercoolers, (2) the CCS CO2 compression intercoolers and (3) syngas cooler at the water gas shift reactor outlet. The use of ORCs operating with pure working fluids and zeotropic mixtures is investigated. In each scenario, the optimal cycles that maximize plant efficiency improvement are determined and are subsequently economically evaluated. Among the three, the syngas cooling integration scenario leads to the highest plant efficiency improvement (2.81%) and best economic performance, showing a levelized cost of electricity (LCOE) and discounted payback period (DPP) of 35.42–35.67 €/MWhe and 5.7–5.8 years. Meanwhile, if all three heat sources are utilized, an efficiency improvement of 4.61% is achieved, while the corresponding LCOE and DPP are about 49.76–51.08 €/MWhe and 9.3–9.7 years. In all scenarios, the best thermodynamic and economic results are obtained by ORCs operating with mixtures. Despite their thermodynamic superiority, however, zeotropic ORCs have a relatively small economic advantage over pure fluid cycles.

Organic Rankine Cycle Waste Heat Recovery for Passenger Hybrid Electric Vehicles

Electrification of road transport is a major step to solve the air quality problem and general environmental impact caused by the still widespread use of fossil fuels. At the same time, energy efficiency in the transport sector must be improved as a steppingstone towards a more sustainable future. Multiple waste heat recovery technologies are being investigated for low-temperature waste heat recovery. One of the technologies that is being considered for vehicle application is the Organic Rankine Cycle (ORC). In this paper, the potential of ORC is discussed in detail for hybrid vehicle application. The modelling and testing of multiple systems such as the hybrid vehicle, engine, and ORC waste heat recovery are performed using the computational approach in GT-SUITE software environment correlated against available engine data. It was found that the maximum cycle efficiency achieved from the ORC system was 5.4% with 2.02 kW of delivered power recovered from the waste heat available. This led to 1.0% and 1.2% of fuel economy improvement in the New European Driving Cycle (NEDC) and Worldwide Harmonised Light Vehicle Test Procedure (WLTP) driving cycle test, respectively. From the driving cycle analysis, Hybrid Electric Vehicles (HEV) and ORC are operative in a different part of the driving cycle. This is because the entire propulsion power is provided by the HEV system, resulting in less engine operation in some part of the cycle for the ORC system to function. Apart from that, a brief economic analysis of ORC Waste Heat Recovery (WHR) is also performed in this paper and a comparative analysis is carried out for different waste heat recovery technologies for hybrid vehicle application.

Energy recovery efficiency analysis of organic Rankine cycle system in vehicle engine under different road conditions

The organic Rankine cycle (ORC) system can effectively recover the waste heat energy of the engine, but its performance is substantially affected by the operating conditions of the engine. The road conditions control the operating conditions of the engine, which determine the amount of waste heat energy of the engine and the performance of the ORC system. Therefore, the energy recovery efficiency of the ORC system in a vehicle engine under different road conditions must be studied. This study establishes a vehicle model including engine, ORC system, power transmission system, and control system, and verifies the accuracy of the engine and ORC system. The vehicle model is used to simulate and analyze the operating characteristics and energy recovery efficiency of the engine and ORC system under New York City Cycle (NYCC) and motorway of Common Artemis Driving Cycles (CADC) road conditions. Results show that the exhaust energy is low and fluctuates frequently under NYCC road condition, ranging from 5.45 kW to 24.28 kW, with an average exhaust energy of 10.4 kW and an average energy recovery efficiency of 1.43%. The exhaust energy is high and fluctuates slightly under motorway of CADC road condition, ranging from 5 kW to 44.5 kW, with an average exhaust energy of 26.9 kW and an average energy recovery efficiency of 5.50%. Therefore, the ORC waste heat recovery system is more suitable for motorway road conditions with high, stable vehicle velocity, while the urban road conditions with low or fluctuant vehicle velocity must be avoided as much as possible.

Assessing fuel consumption reduction in Revercycle, a reversible mobile air conditioning/ Organic Rankine Cycle system

Organic Rankine Cycle (ORC) is a promising solution to improve vehicle efficiency, but its commercial success is hindered by the compactness and cost requirements of the automotive sector. In an attempt to overcome these limitations, a reversible mobile air conditioning (MAC)/ORC, hereafter called ReverCycle, is proposed in this work. ReverCycle is a compact system that operates in two different modes: a standard MAC system when cabin cooling is required or an ORC recovering mechanical energy from the waste heat of an engine’s cooling system.This study presents a simulation methodology to assess the ReverCycle fuel consumption gain. A global light duty vehicle model allows the estimation of the yearly working hours for each ReverCycle operating mode and quantifies the recovered mechanical energy in ORC mode. The ORC module is validated with experimental results. Validation has shown a normalized root-mean-square deviation between 5% and 11% for the main ORC variables (pressures, temperatures and electric powers).The average fuel consumption reduction in ReverCycle was 1.3 and 2% with cold start and hot start conditions, respectively. The reversible system lost 25% of the ORC waste heat recovery potential owing to MAC activation time; however, the significant reductions in cost and compactness were advantageous.