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•Starting from the energy grade, 12 typical industries are divided into three categories.•Evaluate the application potential of waste heat recovery technology in industry.•Compare the ...difference between advanced and traditional technology, highlight its contribution.•The future research directions with great potential are put forward.
Serious energy crises and ecological pollution have had negative impacts on all countries worldwide. These challenges are largely attributed to the production and operation of industries. Nevertheless, the advent of advanced waste heat recovery approaches has given rise to unprecedented opportunities and challenges in the current grave energy and environmental situation. The recovery and utilisation of waste-heat in various industries is an effective approach to improving economic benefits, conserving energy, and reducing emissions. In this review, 12 typical industries are preliminarily classified into three categories, according to the waste-energy grade. From the perspective of typical waste-heat sources, the waste heat recovery potentials of various technologies are analysed and discussed in terms of thermal performance, economic benefits, and environmental benefits. Subsequently, the development of a waste heat recovery approach is comprehensively reviewed, and the performance and structural configuration are summarised and scientifically compared. A detailed technical report is presented on the effective responses to pollutant emissions in various industries. Finally, the limitations in the current research and potential future directions are discussed. Through a comprehensive review of the recovery and utilisation of waste-heat in complex or large industries, this study provides constructive guidelines for researchers and enterprises engaged in related fields. Concurrently, its fills knowledge gaps by providing comprehensive information and the latest research results on the recovery and utilisation of waste-heat in various industries.
•A combined-cycle S-CO2/ORC system is presented for ICE waste-heat recovery.•Comparisons are shown with a standalone S-CO2 cycle system for a 1170 kW ICE.•The combined-cycle system has a 58% higher ...maximum net power output.•The combined-cycle system has a 4% higher minimum specific investment cost (4670 $/kW)•Significant performance improvements can be achieved for a range of ICEs of different sizes.
Supercritical CO2 (S-CO2) power-cycle systems are a promising technology for waste-heat recovery from internal combustion engines (ICEs). However, the effective utilisation of the heat from both the exhaust gases and cooling circuit by a standalone S-CO2 cycle system remains a challenge due to the unmatched thermal load of these heat sources, while a large amount of unexploited heat is directly rejected in the system’s pre-cooler. In this paper, a combined-cycle system for ICE waste-heat recovery is presented that couples an S-CO2 cycle to a bottoming organic Rankine cycle (ORC), which recovers heat rejected from the S-CO2 cycle system, as well as thermal energy available from the jacket-water and exhaust-gas streams that have not been utilised by the S-CO2 cycle system. Parametric optimisation is implemented to determine operating conditions for both cycles from thermodynamic and economic perspectives. With a baseline case using a standalone S-CO2 cycle system for an ICE with a rated power output of 1170 kW, our investigation reveals that the combined-cycle system can deliver a maximum net power output of 215 kW at a minimum specific investment cost (SIC) of 4670 $/kW, which are 58% and 4% higher than those of the standalone S-CO2 cycle system, respectively. A range of ICEs of different sizes are also considered, with significant performance improvements indicating a promising potential of exploiting such combined-cycle systems. This work motivates the pursuit of further performance improvements to waste-heat recovery systems from ICEs and other similar applications.
•A state of the art of marine Diesel engine emission technologies is proposed.•The synergy between between emission technologies and heat recovery is presented.•Organic Rankine Cycles are among the ...most studied systems to recover engines’ heat.
Reducing emissions from internal combustion engines is becoming one of the most important tasks for engine manufactures and transport regulatory organizations. In particular, the marine transportation sector is one of the most polluting, due to the intense maritime activity and the use of low-quality fuels, burned in Heavy Duty Diesel Engines, for ship propulsion and auxiliary power generation. In order to reduce the global shipping environmental impact, the IMO (International Maritime Organization) is restricting NOx and SOx ships’ emissions through the introduction of the IMO Tier III legislation, which requires to consider a wide spectrum of emissions reduction technologies and strategies, which are going to have an impact on the engine performance and fuel consumption.
In this work, the main solutions being currently developed or adopted for low and medium speed Diesel engines have been reviewed from a qualitative, and sometimes quantitative, point of view, but, in comparison to previous literature, focusing more on their potential with respect to possible waste heat recovery systems utilization, such as, in particular, steam Rankine cycles and Organic Rankine Cycles (ORC). Indeed, even though many of the considered emissions mitigation technologies lead to a certain amount of penalty in fuel economy, the use of waste heat recovery systems to recover wasted engines energy could become interesting in order to develop more efficient but, at the same time, cleaner engines.
Bi2Te3‐based devices have long dominated the commercial market for thermoelectric cooling applications, but their narrow operating temperature range and high cost have limited their possible ...applications for conversion of low‐grade heat into electric power. The recently developed n‐type Mg3Sb2‐based compounds exhibit excellent transport properties across a wide temperature range, have low material costs, and are nontoxic, so it would be possible to substitute the conventional Bi2Te3 module with a reliable and low‐cost all‐Mg3Sb2‐based thermoelectric device if a good p‐type Mg3Sb2 material can be obtained to match its n‐type counterpart. In this study, by comprehensively regulating the carrier concentration, carrier mobility, and lattice thermal conductivity, the thermoelectric performance of p‐type Mg3Sb2 is significantly improved through Na and Yb doping in Mg1.8Zn1.2Sb2. Moreover, p‐ and n‐type Mg3Sb2 are similar in terms of their coefficients of thermal expansion and their good performance stability, thus allowing the construction of a reliable all‐Mg3Sb2‐based unicouple. The decent conversion efficiency (≈5.5% at the hot‐side temperature of 573 K), good performance stability, and low cost of this unicouple effectively promote the practical application of Mg3Sb2‐based thermoelectric generators for low‐grade heat recovery.
The thermoelectric performance of the p‐type Mg3Sb2‐based compound is improved by fully optimizing its carrier concentration, mobility, and lattice thermal conductivity. As a result, a unicouple comprised of p‐type Mg1.594Yb0.2Na0.006Zn1.2Sb2 and n‐type Mg3.2SbBi0.99Te0.01 is successfully constructed, and exhibits high conversion efficiency, good stability, and low cost, showing its great potential for low‐grade heat recovery.
•Proposing an efficient and green compressed air energy storage system.•Analyzing and comparing various waste heat recovery cycles combined with compressed air energy storage.•Using working fluids ...with near zero environmental effects.•Drawing detail temperature-entropy diagrams for all of the proposed systems.•Improving the energy and exergy round trip efficiencies by 2.67 and 2.69% by applying the ORC-R290 cycle.
Intermittent nature of the generated power from renewable energy resources and a higher demand for electricity during peak demand periods have intensified the need for grid-scale energy storage systems. Compressed air energy storage system, owing to significant merits such as minimum geographical and environmental limits and high reliability, has attracted attention in recent years. To improve efficiency, its hybridization with various waste heat recovery cycles has been taken into the account. To provide the grid with further power during peak demand periods, organic Rankine and Kalina cycles are the most practical alternatives. Hence, the combination of a green compressed air energy storage with various low- and medium-temperature waste heat recovery cycles is analyzed in the present article to address the most feasible choice in diverse working conditions. The subcritical and supercritical organic Rankine cycles with different working fluids (R717, R1270, R290, and R1234yf), as well as two Kalina cycles (KCS11 and KCS34) are analyzed from the perspective of the first and second laws of thermodynamics and compared with each other. The results indicate that the energy and exergy round trip efficiencies can be improved by 1.69–2.67% and 1.70–2.69%, compared to the stand-alone compressed air energy storage. The supercritical organic Rankine cycle with R290 as the working fluid is the best alternative, which recovers the highest amount of wasted heat and improves the production capacity by 2.47%.
•Improvement by cascade cycles for energy harvesting of solid oxide fuel cell.•New cascade system based on supercritical carbon dioxide cycle.•Analyses in terms of energy, exergy and economic ...performance.•Investigate three key parameters’ impacts on systemic performance.
Solid oxide fuel cell has become one of the most promising power generation methods today due to its diverse fuel sources, high efficiency, easy maintenance, and environmental friendliness. However, the exhaust gas temperature of the solid oxide fuel cell is still too high, and its direct emissions will cause a large amount of energy loss. To further improve the efficiency of the SOFC/GT system, a novel cascade waste heat recovery system is designed where the top cycle is the Brayton supercritical carbon dioxide cycle and the bottom cycle is the organic Rankine cycle. In order to better evaluate the performance of the system, this paper first carried out thermodynamic analysis of the subsystem respectively, and obtained the exergy flow process of the system. Then, an economic model is established for the entire system and calculated the annual total cost rate. The results are: the system efficiency can reach 73.97%, and the corresponding total cost rate of system operation is 36.25 $/MWh, reflecting excellent performance.
The aim of this study is to investigate the thermo-economic performance of the transcritical organic Rankine cycle (TORC) system using R1234yf/R32 mixtures as the working fluids for the lower-grade ...waste heat recovery (WHR). The components of R32 and R1234yf are selected due to their zero ozone depletion potential, lower global warming potential and complementary thermodynamic properties. The influences of the mass fractions of R1234yf/R32 mixtures, isentropic efficiencies of the expander, condensation temperature, turbine inlet pressure and temperature on performances have been investigated. The results show that R1234yf/R32 at optimal mass fraction is superior to pure R1234yf and pure R32 by 1.46% and 4.88% in thermo-economic performance, respectively. The optimal compositions of mixtures and the optimal temperature entropy diagrams are obtained to fit the various isentropic efficiencies possessed by the different types of expanders. In thermo-economic evaluation, the lower the condensation temperature is, the larger the optimal mass fraction of R32 in the mixtures will be. The increase of optimal expander inlet pressure and temperature are proportional to that of mass fraction of R32 in mixtures. The relationships among mass fraction, optimal expander inlet pressure and temperature and performance are expressed as the correlations for convenient design in lower-grade WHR.
•The optimal mass fraction and the thermo-economic performance of R1234yf/R32 in TORC are obtained.•The optimal T-s diagrams are obtained to fit various isentropic efficiencies of the expanders in TORC.•The lower the condensation temperature is, the larger the optimal mass fraction of R32 will be.•The correlations of the optimal mass fraction, pressure, temperature and performance are reported.
•Test bench of combined diesel engine and ORC waste heat recovery system is developed.•An ANN based prediction model of the ORC system is established.•Effects of operating parameters on power output ...of the ORC system are investigated.•Prediction accuracy comparison between thermodynamic and ANN models are presented.•Performance prediction and parametric optimization are conducted based on ANN model.
This paper presents performance prediction and optimization of an organic Rankine cycle (ORC) for diesel engine waste heat recovery based on artificial neural network (ANN). An ANN based prediction model of the ORC system is established with consideration of mean squared error and correlation coefficient. A test bench of combined diesel engine and ORC waste heat recovery system is developed, and the experimental data used to train and test the proposed ANN model are collected. A genetic algorithm (GA) is also considered in this study to increase prediction accuracy, and the ANN model is evaluated with different learning rates, train functions and parameter settings. A prediction accuracy comparison of the ANN model with and without using GA is presented. The effects of seven key operating parameters on the power output of the ORC system are investigated. Finally, a performance prediction and parametric optimization for the ORC system are conducted based on the proposed ANN model. The results show that prediction error of the ANN model with using the GA is lower than that without using GA. Therefore, it is recommended to optimize the weights of the ANN model with GA for a high prediction accuracy. The proposed ANN model shows a strong learning ability and good generalization performance. Compared to the experimental data, the maximum relative error is less than 5%. The experimental results after optimizing the operating parameters are very close to ANN’s predictions, indicating one or more operating parameters can be adjusted to obtain a higher power output during the experiment process.
•A thermoelectric generator was manufactured for hybrid electric vehicle application.•System dimensions and pressure drop characteristics were used as design criteria.•A hybrid electric vehicle ...engine was used as a heat source for experiments.•The performance of the generator was tested under real operating conditions.•A maximum power of 118 W and an energy conversion efficiency of 2.1% were obtained.
A compact thermoelectric generator is developed for waste-heat recovery in a sedan-type hybrid electric vehicle. The shape and dimensions of the thermoelectric generator are precisely determined by performing a series of theoretical analyses to meet spatial and maximum allowable pressure drop restrictions. The waste-heat recovery performance of the thermoelectric generator is experimentally evaluated using a hybrid electric vehicle engine under the nine most commonly experienced driving conditions. One surface of the thermoelectric modules is heated by the exhaust gas flow, whereas the other surface is cooled by the engine coolant flowing at 10 L/min and 353 K. A maximum power output of ~118 W and an energy conversion efficiency of ~2.1% are obtained using 12 thermoelectric modules under the engine operating conditions that led to the highest exhaust gas flow rate and temperature. The waste-heat recovery characteristics of the present thermoelectric generator are systematically analyzed, and the results corresponding to thermal energy flow and heat recovery efficiency, as well as the voltage output–current output and power output–load resistance curves, are presented.
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