Waste Heat Power Research Articles

100-kWe-class supercritical organic Rankine cycle turbine with magnetic bearing for waste heat power generation system

100-kWe-class supercritical organic Rankine cycle turbine with magnetic bearing for waste heat power generation system

Enhancing exergy and economical performance of a waste heat power generation system: Multi-objective optimization and comparative analysis

Enhancing exergy and economical performance of a waste heat power generation system: Multi-objective optimization and comparative analysis

Harnessing waste palm-based activated carbon/difluoromethane pair for sustainable low-emission cooling systems

An adsorption cooling system (ACS) offers distinct advantages over conventional systems, including improved energy efficiency, waste heat power, low-emission refrigerant employment, and simplified mechanical design. The performance of ACS is greatly affected by the selection of the adsorbent/refrigerant pair. In this study, we experimentally investigate the adsorption capacity of difluoromethane (CH2F2) onto several highly porous waste palm-based activated carbons (PACs). Elemental analysis, SEM, XRD, and FT-IR spectroscopy are performed on raw, carbonized, and activated samples to gain deeper insights into their surface morphology and functional groups. Difluoromethane adsorption isotherms of the PACs are obtained using a high-precision thermogravimetric analyzer at typical operating adsorption and desorption temperatures of ACS. One of the studied PAC/difluoromethane pairs achieves a benchmark uptake of 2.741 kg difluoromethane per kg adsorbent at 30°C and 1893 kPa equilibrium pressure. The experimental data are correlated with substantial accuracy using the Dubinin-Astakhov (D–A) and Tóth isotherm models to predict adsorption performance under experimentally unexamined operating conditions. Furthermore, for this PAC/difluoromethane pair, key performance indicators such as specific cooling effect (SCE), coefficient of performance (COP), Clapeyron cycle (P-T-W) diagram, and heat of adsorption (Qst) are evaluated. The results demonstrate that the PAC/difluoromethane pairs have excellent potential for the development of high-performance, low-emission ACS.

Bi2X (X = Ge, Sn) monolayers: Promising thermoelectric materials with ultra-low thermal conductivity

Thermoelectric materials can realize the direct conversion between heat and electricity, which provides a new strategy for waste heat treatment and power generation. The dimensionless value ZT determines the efficiency of the device. Here, we report a record ZT maximum of about 6.96 at 700 K by performing first-principles calculations on penta-Bi2X (X = Ge, Sn) monolayers. We verified the stability of all systems and calculated the thermoelectric transport properties. The multiband energy degeneracy leads to large Seebeck coefficients, while the small phonon group velocity and strong anharmonic phonon scattering result in ultra-low thermal conductivity. Thus, in both systems, the higher ZT values are found. The high performance of Bi2Ge and Bi2Sn monolayers provide a new guidance for finding layered thermoelectric materials.

Integrating thermoelectric devices in pyrolysis reactors for biochar and electricity co-production

This study proposed an innovative approach to integrating thermoelectric devices with small-scale pyrolysis reactors by using Mizunara (Japanese oak) as the feedstock for biochar production. The primary objective of the study was to enhance the energy efficiency and carbon sequestration potential of the biochar production process by converting waste heat into electricity through thermoelectric devices. Comprehensive steady-state thermal balance analysis revealed that although covering the entire reactor surface with thermoelectric devices can result in excessive heat loss and reduced biochar yield, strategically limiting the installation area allows efficient power generation without considerably compromising biochar production. This balance between electricity generation and biochar yield is critical for optimizing the system’s efficiency. Historically, small-scale waste-heat power generation has been underdeveloped, but our studies have demonstrated that incorporating naturally cooled thermoelectric devices allows the generation of kilowatt-hour (kWh)-scale electricity from waste heat, which would otherwise be discarded. Furthermore, the analysis revealed that with optimized conditions, the CO2 equivalent values of the sequestered carbon can be substantially increased, providing a viable solution for long-term carbon storage. The results highlight the potential of this integrated approach to improve the energy efficiency of biochar production and provide a solution for waste-heat management. Moreover, we assessed the implementation effects by assigning reasonable values for the thermoelectric device performance and provide a robust framework for biomass utilization, waste-heat recovery, and CO2 sequestration.

Multifaceted analysis of K2InAgX6 (X = F, Cl, Br, I) for photovoltaic and thermoelectric applications

Halide double perovskites represent a diverse class of materials, with wide range of properties and functionalities which opens up opportunities for innovation in various technological applications. In this study, we present a broad theoretical exploration of K2InAg(F/Cl/Br/I)6, halide double perovskites (HDPs) using Density Functional Theory focusing on its prospect for advanced solar cell applications and thermoelectric device design. We can tailor the material's band gap and thermoelectric efficiency by changing the halide atoms (F/Cl/Br/I) of the halide double perovskite. The HDPs K2InAg(Cl/Br/I)6 exhibits a bandgap of 2.69, 1.82 and 0.66 eV. The mechanical properties calculation shows that the studied compound is mechanically stable showing anisotropic behavior and ductile in nature. Moreover, our calculations reveal a promising thermoelectric efficiency of 1.29, 1.45 and 2.19 at room temperature for K2InAg(Cl/Br/I)6, suggesting its viability for waste heat recovery and power generation. Furthermore, our analysis using SCAPS-1D also indicates a noteworthy solar power conversion efficiency of 21.88 % for K2InAgBr6. This study provides a bird's-eye view of the theoretical analysis of these halide double perovskite compounds.

Performance prediction and regression analysis of scroll expander based on response surface methodology

The Organic Rankine Cycle (ORC) plays a pivotal role in the domain of renewable energy, adeptly harnessing thermal energy from sources such as solar and geothermal to generate electrical power. Central to this system is the scroll expander, whose operational efficacy directly influences the ORC's overall efficiency. This study initiates with a detailed numerical analysis of the impact of various operational parameters on both the steady and transient output performance of the scroll expander. Following this, a sophisticated performance prediction model is developed employing the response surface methodology. The model boasts high coefficients of determination, R2,values of 0.9967 and 0.9916, respectively, underscoring its superior predictive accuracy. Further, this model delves into the complex interactions among operational parameters and their consequent effects on the expander's performance. Validation of this predictive model is achieved through rigorous testing on an experimental platform designed for the ORC low-temperature waste heat power generation system. The discrepancies between predicted and actual performance measurements fall within a commendable margin of 15 %, affirming the model's robustness in forecasting scroll expander performance. The culmination of this research furnishes a novel and efficacious optimization strategy, establishing a robust theoretical foundation and offering fresh insights for the enhancement and prediction of scroll expander performance. This not only underscores the innovation of the approach but also its practical applicability in advancing the efficiency of renewable energy systems.

High wide-temperature-range thermoelectric performance in GeTe through hetero-nanostructuring

GeTe is emerging as promising medium-temperature thermoelectric material due to its highly competitive performance and good mechanical properties. Strong Rashba spin splitting was harnessed to markedly improve the Seebeck coefficient and power factor of Bi and Sn codoped GeTe at low-medium temperature. Moreover, it is found that Bi-Sn-Cu doping reduces the phase-transition temperature to extend better electrical transport behavior of cubic phase to low temperature. As a result, the electrical transport properties in low-medium temperature were overall enhanced. In the meanwhile, endotaxial hetero-nanostructures efficiently scatter phonons and play a dominant role on affecting phonon propagation. The lattice thermal conductivity was reduced to 0.2 W m−1K−1 at 673 K. Drive by strengthening Rashba effect and endotaxial hetero-nanostructures, a record-high average ZT (300–823 K) of 1.6 and a high ZT of 2.1 were obtained in lead-free GeTe-based compounds. The vast increase of ZT promotes GeTe as a promising candidate for a wide range of applications in waste heat recovery and power generation.

A novel trading optimization strategy of source-load bilateral thermoelectric spot based on industrial parks interior

With the continuous reform of the electricity market in the whole world, internal trading models in parks are generally studied in terms of load peaking, load flexibility and energy management. In this paper, the regional differential trading method is adopted for industrial users with different energy needs, and the interests of all parties within the industrial park are considered. Spot transactions involving surplus energy on both the supply side and the demand side are considered, and the weight allocation of transactions in each park is coordinated. Firstly, the way of circulating waste heat and power within the industrial park is analyzed from the composition of the trading system of the industrial park. The demand side is transported heat and electricity while the energy storage device is considered. The contact line is modeled on the basis of the energy transmission line characteristics. Secondly, the industrial park is disaggregated regionally using cascade analysis within the target area to decide load regulation mode between systems and modules. Thirdly, regional differences in trading are adopted for industrial users with different energy needs while the interests of all parties within the park are considered. Both sides of the supply side and the demand side participate in spot trading of surplus energy. The allocation of weights is coordinated for trading in the various industrial parks. Finally, The DICOPT solver optimizes operating costs and takes into account energy abandonment penalties. In the waste heat power transaction in the industrial park, the remaining power can be saved by 9.78 %, and the waste heat can be saved by 4.35 %. Numerical results from instances indicate that this method surpasses traditional trading approaches, aligning with the rigorous standards of scientific research.

Design and behaviour estimate of a novel solar and fuel cell complementary driven supercritical-CO2 cycle thermal system

Solar-integrated fuel cell systems are widely regarded as an effective means of saving energy and reducing emissions, given their ability to decrease reliance on fossil fuels. However, solar thermal power systems are intermittent, whereas fuel cell waste heat power generation has continuous power output. The paper proposes a novel solar and molten carbonate fuel cell complementary driven supercritical-CO2 cycle system. The performance of multi-energy complementary driven supercritical-CO2 cycle and system operation mode conversion is being investigated. The complementary operation mode ensures the continuous output of the proposed system through the switching of the solar module and the fuel cell module. The result indicates that the fuel cell module operates for 23.5 % of the time in a year, resulting in a reduction of the storage tank volume by 14,723 m3 and a decrease of the fixed heliostat area by 108,237 m2. The efficiency of the supercritical-CO2 cycle individually is 43.1 %, and with the addition of the waste heat utilization subsystem, the cycle efficiency of the proposed system reaches 50.89 %. Furthermore, the levelized cost of electricity for the proposed system is 0.1861$/kWh, and the research results can serve as a reference for the design of complementary energy systems.

Flexible wood-based composite for solar water evaporation and waste heat power generation

Solar water evaporation shows great promise in the utilization of sunlight resources. However, currently available evaporators suffer from poor mechanical properties, easy leakage and failure of heat conversion materials, and single utilization pattern limit the equipment can not be widely used. In this study, a wood composite with good flexibility, efficient photothermal conversion was prepared using delignified wood (DW), polymerizable deep eutectic solvent (PDES) and Ti3C2Tx (MXene) nanosheets. DW was a hydrophilic substrate to provide water transport channels. The MXene nanosheets were uniformly dispersed in the DW matrix through hydrogen bonding for efficient light absorption and photothermal conversion, while PDES provided flexibility to the material, allowing it to be shaped as desired. Meanwhile, the addition of PDES not only effectively prevents the oxidation of MXene nanosheets, but also helps MXene to be encapsulated in the composite material and provides some flame retardant effect. In addition, through the combined use of semiconductor thermoelectric power modules (SP modules), waste heat can be directly used for power generation. Under 1 solar irradiation, the water evaporation rate could reach 1.59 Kg/m2/h, the power density of photothermal power generation was 0.71 W m−2, and the photothermal conversion efficiency is 95.24%. The device can operate for a long time in extreme environments, providing fresh water and electricity to resource-constrained areas.

Bi2Te3-Based Thermoelectric Modules for Efficient and Reliable Low-Grade Heat Recovery.

Bismuth-telluride-based alloy has long been considered as the most promising candidate for low-grade waste heat power generation. However, optimizing the thermoelectric performance of n-type Bi2Te3 is more challenging than that of p-type counterparts due to its greater sensitivity to texture, and thus limits the advancement of thermoelectric modules. Herein, the thermoelectric performance of n-type Bi2Te3 is enhanced by incorporating a small amount of CuGaTe2, resulting in a peak ZT of 1.25 and a distinguished average ZT of 1.02 (300-500 K). The decomposed Cu+ strengthens interlayer interaction, while Ga+ optimizes carrier concentration within an appropriate range. Simultaneously, the emerged numerous defects, such as small-angle grain boundaries, twin boundaries, and dislocations, significantly suppresses the lattice thermal conductivity. Based on the size optimization by finite element modelling, the constructed thermoelectric module yields a high conversion efficiency of 6.9% and output power density of 0.31W cm-2 under a temperature gradient of 200 K. Even more crucially, the efficiency and output power little loss after subjecting the module to 40 thermal cycles lasting for 6 days. This study demonstrates the efficient and reliable Bi2Te3-based thermoelectric modules for broad applications in low-grade heat harvest.

A robust internal model control design for low-quality waste heat power generation systems

Recovering low-quality waste heat using industrial waste heat is challenging, and the reuse technology needs to erupt. Moreover, the gas source of low-quality waste heat is relatively volatile, which makes it challenging to keep the actual working condition of the plant stable. Therefore, it is inspiring to research the robustness of root-waste heat power generation processed measurement and control system to improve the stability of the plant operation. Hence, in this paper, we have applied uncertainty theory to analyze it and formulate the uncertainty model based on the Bode diagram. We also proposed a control method based on the uncertainty model, which combines robust control and internal model control to make the roots waste heat power generation system operate stably under the effect of external disturbances and changes of internal structure or parameters in actual operation. Experimental results show that the robust internal model control method has a speed deviation of no more than 7.9 r/min compared with the PID control method. The adjustment time to track the set value does not exceed 73.1 seconds within the allowed fluctuation range. The fluctuation variance is 30.95% of that of the PID controller. The dynamic performance is better, with strong anti-interference capability and significantly improved tracking performance. It ensures the stability of the roots-type waste heat utilization system, which is essential for future intelligent grid-connected power generation.

Structural design and performance optimization of Co/Bi0.5Sb1.5Te3 artificially tilted multilayer thermoelectric devices

Due to the complex principle of transverse thermoelectric conversion and the specific preparation technique, there are few studies on the three-dimensional structure of artificially tilted multilayer thermoelectric devices (ATMTDs), which also lags the development of ATMTDs for applications. It is necessary to optimize the three-dimensional structure of ATMTDs to satisfy the requirements of practical applications in thermal sensors, power generation, refrigeration, and so on. In this paper, Co/Bi0.5Sb1.5Te3 ATMTDs are selected as the research object. A COMSOL Multiphysics simulation analysis and experimental validation are used to establish the relationship between the structure and its thermal sensing, power generation, and cooling performance. Results indicate that increasing the length significantly improves the thermal response voltage. Increasing the length and width enhances output power while increasing the height of the ATMTD improves the thermoelectric conversion efficiency. The effective cooling temperature improves when the heat transfer area decreases or the height increases. Based on these findings, flexible thin-film thermal sensors, high-efficiency waste heat power generation tubular devices, and high-efficiency refrigeration pyramidal devices are designed. The results will lead to effective optimization and promote the multi-field application of ATMTDs.

Advances in Nanoparticle-Enhanced Thermoelectric Materials from Synthesis to Energy Harvesting: A Review.

This comprehensive review analysis examines the domain of composite thermoelectric materials that integrate nanoparticles, providing a critical assessment of their methods for improving thermoelectric properties and the procedures used for their fabrication. This study examines several approaches to enhance power factor and lattice thermal conductivity, emphasizing the influence of secondary phases and structural alterations. This study investigates the impact of synthesis methods on the electrical characteristics of materials, with a particular focus on novel techniques such as electrodeposition onto carbon nanotubes. The acquired insights provide useful guidance for the creation of new thermoelectric materials. The review also compares and contrasts organic and inorganic thermoelectric materials, with a particular focus on the potential of inorganic materials in the context of waste heat recovery and power production within industries. This analysis highlights the role of inorganic materials in improving energy efficiency and promoting environmental sustainability.

Techno-economic-environmental analysis and fluid selection of transcritical organic Rankine cycle with zeotropic mixtures

Waste heat recovery is regarded as highly efficacious in ameliorating energy and environmental problems brought on by rapid economic and societal growth. The organic Rankine cycle (ORC), specifically transcritical ORC (tORC) garners significant attention for its potential in waste heat power generation. Researchers still seek to further improve performance for tORC, such as using zeotropic mixtures. Aimed at selecting the working fluid pairs that can bring better performance for tORC, this study provides a more comprehensive performance evaluation of tORC systems by developing a novel multi-attribute integrated assessment model that encompasses techno-economic-environmental aspects. To establish this model, the detailed mathematical models of the tORC are established first and used to obtain system performance indicators. Then, a refined analytic hierarchy process to assign weights to various performance indicators to complete the multi-attribute integrated assessment model. With the utilization of the proposed model, a thorough comparative analysis of the tORC system with ten groups of zeotropic mixtures is performed. Thus, the results of the working fluid selection can be obtained. Results show that R245fa/R600 and R600/R600a are more recommended than other working fluid pairs, with R600/R600a being the preferable choice when prioritizing environmental impact. While R245fa/R1234yf has the worst thermodynamic and environmental performance and R245fa/R227ea owns the worst economic performance. In conclusion, the findings show that employing a zeotropic mixture combines the benefits of the pure working fluids that comprise it. Compared to previous studies, this study provides a more comprehensive look at the selection of working fluids for tORC systems. It can offer valuable insights for selecting the appropriate working fluid more effectively for future applications.

Optimization waste heat recovery and power generation for industrial sustainability: A comparative study of supercritical CO2 Brayton, organic Rankine, and inverted Brayton cycles with synthesis natural gas as heat source

Generated waste heat in industrial processes, which is not applied in any functional work, is discharged into the environment by conduction, convection, and radiation from industrial products, processes, and equipment. Harnessing the waste heat carries significant attention because of its potential to decrease fossil fuel consumption and deterring of atmospheric pollutants. This study aims to provide an alternative for natural gas and reduce air pollution, serving the waste heat from the synthesis natural gas (SNG) production as the heat source for the cycles namely CO2 Brayton cycle, organic Rankine cycle, and Inverted Brayton cycles-organic Rankine cycle to the calculation of generated power, efficiencies, and total product unit cost of distinct layouts. By doing so, a comparison of the cost of synthetic natural gas between the two states can be made. Power output is analyzed concerning temperature and pressure, while exergy destruction calculations highlight the synthesis natural gas production process as the major contributor. Cost balance equations are applied to compute the cost of synthesized natural gas and total product unit cost. Objective functions encompass net power output, first law efficiency, and total product unit cost. Optimization employs the genetic algorithm method in MATLAB software. Results reveal that supercritical CO2 Brayton cycle achieves 17,100 kW power output, 0.8894 first law efficiency, and 26.32 $GJ total product unit cost. Conversely, with the inverted Brayton cycle-organic Rankine cycle, the outcomes are slightly lower, yielding 15,430 kW power output, 0.879 first law efficiency, and 25.41 $GJ total product unit cost.

Manufacture of potassium chloride from cement kiln bypass dust: An industrial implementation case for transforming waste into valuable resources

The recirculation of chlorine within the kiln presents a major hurdle in co-processing domestic waste in cement kilns. This chlorine enrichment not only adversely affects the quality of cement, but also pose a serious challenge to the subsequent eco-friendly disposal of kiln dust. To solve this problem, a proper bypass system has been implemented in this study on a 4000 t/d new dry process cement rotary kiln, and the collection of chlorine-rich bypass dust outside the kiln (30 t/d) has been achieved. In addition, a comprehensive and innovative system has been developed, including water washing and subsequent triple-effect salt extraction, to achieve leaching of K+ and Cl from the bypass dust in the water rinsing liquid, while effectively removing harmful metal ions such as Pb2+. Finally, the extraction of high-purity KCl salt (6 tons/day, purity of 90 %) has been successfully achieved. It is worth noting that high-temperature flue gas rich in CO2 has been used to precipitate certain heavy metal ions, while steam from the waste-heat power generation system has been employed as a heat source for the potassium salt evaporation process. More importantly, all the materials, except for the KCl salt product, are returned to the cement kiln system without causing any secondary pollution. This study not only effectively addresses the negative impacts of chlorine element circulation within cement kilns during domestic waste co-processing, but also achieves a highly innovative engineering practice of transforming waste into valuable resources from kiln dust to high-purity KCl products. In brief, this work provides a reference example for future approaches to clean production, carbon reduction and resource utilization in the cement industry.

Design and Characterization of Flue Gas Waste Heat Power Generation Plant

This paper proposes a waste heat recovery system based on temperature difference power generation, which aims to utilize the residual heat in the exhaust flue of chimneys or kilns. The system consists of three parts such as heat collection module, semiconductor power generator, and heat dissipation module, and the residual heat is directly converted into electrical energy and output by temperature difference power generation. The voltage and resistance are measured and analyzed on this basis. This design realizes the waste heat recovery of boiler flue gas, prevents a large amount of waste heat from being discharged into the environment, reduces the greenhouse effect and makes secondary use of the waste heat.

Exploring energetic, exergetic, economic and environmental (4E) performance of waste heat power generation in nuclear power plant systems: A perspective of pattern recognition

Combined cogeneration systems are employed to recover waste heat from the sCO2 cycle in nuclear power generation systems. However, dealing with their multidimensional and nonlinear design and optimization spaces is a complex challenge for designers. In this study, the combined cogeneration system is parameterized and modeled: 4E models including energetic, exergetic, economic and environmental are established for sCO2 combined Organic Rankine Cycle (sCO2/ORC) and trans-critical CO2 Cycle (sCO2/tCO2) respectively. Several decision variables and five performance indicators are selected. To gain a deeper understanding of the mechanisms and optimize the combined cogeneration system, pattern recognition methods including the Self-Organizing Map (SOM), an unsupervised competitive learning approach, and Statistical Sobol Global Sensitivity Analysis methods are proposed. These techniques help identify key parameters and system patterns within the design space. Then, the Non-Dominated Sorting Whale Optimization Algorithm (NSWOA) is adopted to build a Pareto-optimal decision space, and the SOM and PCPs are proposed to visualize and mining based on pattern recognition and graph visualization interaction. The design parameters of the top cycle, P2, PRc, and x, have been confirmed as having a substantial impact on the system's performance. The multiple attributes, criterions and objectives problems in the combined cogeneration system are ultimately simplified to “Economy-Environment”, double objectives problem, and three trade-offs’ solutions are discussed: prioritizing economics, prioritizing the environment, and finding a balanced economic-environmental compromise. Pattern recognition method provides decision-makers with a fresh perspective for gaining a deeper understanding of the multi-criteria objectives space and potential trade-offs. The integration of pattern recognition into the thermodynamic, economic, and environmental models outlined in this paper represents a substantial and valuable advancement in the analysis and optimization of combined cogeneration cycles.