Efficient Waste Heat Recovery Research Articles

Optimizing waste heat recovery for hydrogen production: Modeling and simulation of ternary size metallic granule flow in a cooling cylinder

In order to recover the waste heat of high temperature metallic granules to produce steam for hydrogen production, a waste heat recovery cooling cylinder with cooling water channel is innovatively developed. The simulation is carried out based on DEM and soft sphere model to study the flow characteristics of ternary size metallic granules. The model of cooling cylinder is established and verified by comparing to the experiment data. The change rule of bed shape in the waste heat recovery cooling cylinder is examined, and the inclination angle, rotational speed and filling rate are assessed to find their influence on the flow characteristics of ternary size metallic granules. The results indicated that, with the increase of inclination angle, the axial velocity increases by 482.76%, which means the reduce of residence time of granules. With the increase of rotational speed, the axial velocity has an increase of 161.54%, the sum velocity increases by 158.49%, leading to a decrease of residence time. As the filling rate increases from 1.5% to 15.5%, the contact number has an increase of 91.53%, which lead to the increase of heat transfer area. The residence time and heat transfer area will directly affect the waste heat recovery efficiency, so a proper arrangement of granule flow is significant for enhancing the heat transfer efficiency.

Optimisation of Brayton cycle CO2-based binary mixtures: An application for waste heat recovery of marine low-speed diesel engines exhaust gas

The energy-saving capabilities and efficient operation of marine low-speed diesel engines (MLDE) is a key emphasis for the main power source for ocean transportation. The purpose of the supercritical carbon dioxide recompression Brayton cycle (SCRBC) is to capture and utilise waste heat emitted by the engine's exhaust gas. However, the SCRBC performance will be severely affected by the large temperature fluctuations of ocean-going vessels during operation and high ambient temperatures in the cabin. A SCRBC model was built using the exhaust gas test data as the boundary conditions and validated using the Sandia National Laboratory (SNL) test data. The physical characteristics of the working fluids were evaluated by adding other fluids to CO2 in specific proportions to modify the critical point and increase cycle efficiency. The results demonstrated that employing CO2-based binary working fluids with low alkane and hydrogen sulfide (H2S) enhanced the recovery power, with the most significant increase obtained by the addition of 16.48 % H2S, which increased the power by 9.72 kW and improved the Brayton cycle efficiency by 3.31 %. Compared to the MLDE at 100 % load, the total efficiency increased by 1.77 % and the BSFC decreased by 6.76 (g kW−1 h−1) using CO2-H2S as the working fluid. The analysis of the SCRBC system component exergy losses showed that the cooler had the highest exergy losses. Adding other fluids to CO2 reduced the exergy losses of each component with the SCRBC system exergy losses decreasing from 162.97 to 129.90 kW and the exergy loss efficiency decreasing from 24.24 % to 22.65 %. The use of CO2-based binary working fluids specifically designed for ambient temperature may be expanded to other engines to enhance the efficiency of waste heat recovery.

Explicitly defined empirical constant for phase-change simulation in a two-phase closed thermosyphon

Over several decades, the importance of energy recovery has grown because of the global shift from fossil fuels to renewable energy sources. Among various energy-recovery approaches, waste heat recovery has emerged as a prominent method owing to its ease of adoption in various fields such as power plants and commercial buildings and high amount of recovery by adopting in the heavy industry. A heat exchanger with a heat pipe offers superior waste heat recovery efficiency through its highly effective heat transfer in a two-phase closed thermosyphon (TPCT). Numerous investigations have explored the thermal hydraulic performance of TPCTs in various geometries and operation conditions, mostly relying on experimental methods owing to the challenges in accurately simulating phase change in TPCT systems. These challenges arise from using the mass-transfer intensity factor, r—an empirically selected constant in phase-change models—which lacks a robust basis in fundamental principles. This study introduces a novel approach to selecting the r value for simulating the phase-change process in TPCTs. By employing the volume-of-fluid model for multiphase interfaces along with the widely used Lee model for phase change, the proposed model establishes a correlation between evaporation and condensation mass fluxes to define the r value in condensation heat transfer within a TPCT. The utilisation of the proposed model in simulations yielded improved temperature predictions, deviating by 4–7 K from experimental results while offering a significant reduction in the number of r values to choose from, achieved by explicitly defining the r value for condensation heat transfer. The conventional approach was to set both empirical constants to re = rc = 0.1 s−1. However, this model, which provides a relationship between the two empirical constants based on mass balance, revealed that rc should be 9.8 s−1 rather than 0.1 s−1 corresponding to re = 0.1 s−1. Furthermore, the study examines the diverse thermal performance outcomes associated with varying r values for evaporation in a wide range of re (0.1–100 s−1). rc was in the range of 9.8–12.7 s−1, denoting an increase of only 30% as re increased 1000 times from 0.1 to 100 s−1. This research offers a comprehensive understanding of the computational modelling of TPCTs, providing valuable insights into their thermal characteristics based on the intricate phase-change phenomena occurring within them.

A Proposed Method and Case Study of Waste Heat Recovery in an Industrial Application

Abstract Waste heat recovered from a refrigeration machine is associated with the double benefit of generating cold and heat with just one unit. Additional energy is required in most cases to achieve these benefits. To evaluate the efficiency of waste heat recovery, two novel efficiency indicators are described. The overhead coefficient of performance (OCOP) describes additional electrical power required to raise the temperature to make waste heat usable. The coefficient of savings describes power reduction when condenser heat is fed into a cold district heating network instead of exhausting it to high-temperature outside air. Results are reported from a case study in a food logistic center with high cooling demand in Isny, Germany. Waste heat at this facility was previously released unused to outside air. We describe how this waste heat can be used to supply sustainable heat supply to a new residential area. During the design phase, it is difficult to choose the best operating temperature for district heating networks (DHNs). The novel indicators are used to value the effort to make waste heat usable. Whereas a supply temperature of 20 °C has no disadvantages for the operator, a supply temperature of 40 °C is associated with an increase in electricity consumption. The resulting OCOPs are above 5.0 even under unfavorable conditions and exceed the theoretically calculated (Holm and Pehnt, 2023, Wärmeschutz und Wärmepumpe-Warum Beides Zusammengehört, Forschungsinstitut für Wärmeschutz e.V., Institut für Energie und Umweltforschung, München/Berlin/Heidelberg, p, 13, 14; Agora Energiewende, Fraunhofer IEG, 2023, Roll-out von Großwärmepumpen in Deutschland, Strategien für den Markthochlauf in Wärmenetzen und Industrie, Berlin) and measured (Fraunhofer Institut für Solare Energiesysteme, 2020, “Wärmepumpen in Bestandsgebäuden, Ergebnisse aus dem Forschungsprojekt, WP-Smart im Bestand.”) coefficients of performance (COPs) for air-sourced heat pumps. Although using waste heat is not free, it is beneficial when overall efficiency is considered.

Comprehensive study and design optimization of a hybrid solar-biomass system for enhanced hydrogen production and carbon dioxide reduction

This study introduces an innovative multi-generation system powered by biomass, which aims to tackle the urgent problem of climate change by reducing CO2 emissions and increasing sustainability. The main problem being tackled is the ineffectiveness and environmental consequences of conventional biomass systems, which do not have methods for generating and injecting hydrogen. The proposed method combines solar panels with proton exchange membrane electrolyzers to generate green hydrogen, hence improving the quality of combustion byproducts. The methods utilized consist of integrating a supercritical carbon dioxide cycle with a thermoelectric generator to enhance the efficiency and cost-effectiveness of power generation. Additionally, flue gas condensation, a multi-effect desalination unit, and efficient waste heat recovery are employed to maximize the utilization of passive energy. The study concludes that under the optimal design, the proposed system outperforms the standard model that exclusively depends on biomass. The key results demonstrates that these characteristics are clearly demonstrated by its superior net power productivity of 3927 kW, exergy efficiency of 32.9 %, and drinkable water production rate of 9.4 kg/s. In addition, the suggested system has a lower levelized energy cost of 17.6 dollars per megawatt-hour and an emission index of 75.5 kg per MWh. However, upon comparing the rates at which exergy is being destroyed, it becomes evident that the majority of the components in the proposed model, such as photovoltaic panels and the electrolyzer unit, have a higher rate of exergy destruction. Ultimately, it can be noted that the fluctuations in combustion and turbine inlet temperature are crucial design parameters that substantially influence the power cycle and the system’s overall performance.

Automobile exhaust flexible thermoelectric harvester enabled by liquid metal-based heatsink

The softening thermoelectric generator based on a deformable heatsink is expected to facilitate achieving remarkable temperature differences and thermal harvesting capabilities while alleviating exhaust back pressure and engine operating perturbations. However, the available soft polymer materials with poor thermal characteristics face challenges in realizing efficient heat transfer. Herein, we reported a highly integrated automobile exhaust flexible thermoelectric generator (IAE-FTEG) enabled by a liquid metal (LM)-based stretchable heatsink for cylindrical thermal sources to achieve efficiently harnessing waste heat energy and continuously powering multiple vehicle-mounted sensors. IAE-FTEG exhibits excellent flexibility (the bending radius at the apex of 0.57 cm) and outstanding heat transfer capability by introducing the porous sandwich-based soft electrode films and LM-based thermal interface material, achieving an output power enhancement of 25.7 %. The flexible heatsink is prepared by embedding LM droplets and copper particles into the elastic matrix forming solid–liquid multiphase composites, which obtain considerable thermal conductivity (2.40 W/mK@200 % stretching deformation) and excellent geometric conformity. We built the bench and the real vehicle test platform of the IAE-FTEG waste heat recovery system. The simulation test results demonstrate that the maximum power density achieved by the IAE-FTEG waste heat recovery system is 244 kW/m3. The real vehicle tests show that the IAE-FTEG waste heat recovery system has a relatively stable output performance with an average power density of 117 kW/m3 under urban conditions and can realize a stable power supply for back-end loads. Our IAE-FTEG can offer new opportunities in enabling efficient curved-surface waste heat recovery, flexible wearable electronics, and personalized thermal management.

Optimization analysis for thermoelectric performance improvement of biconical segmented annular thermoelectric generator

Thermoelectric generators have struggled with low efficiency, limiting their widespread use. To further improve the performance of the thermoelectric generator, this paper introduces the biconical pin structure into the segmented annular thermoelectric generator, and simultaneously incorporates exergy efficiency and economic cost to evaluate its performance. Experiments are first used to verify the accuracy of the simulation model, and then the effects of the cone angle θ, leg height H, leg length ratio δ and resistance ratio ε are discussed. Finally, correlation analysis is used to obtain the weight of the impact of research parameters on thermoelectric performance, and the optimized results are obtained. The results demonstrate that the output power of the biconical segmented annular thermoelectric generator is 20.23 % higher, the exergy efficiency is 8.55 % higher, and the economic cost is reduced by 21.36 % compared to the traditional segmented annular thermoelectric generator. As the θ and H increase, the thermoelectric performance enhances. The influence of δ on thermoelectric performance is more complicated. When ε is 1.5, the thermoelectric generator has optimal thermoelectric performance. This paper provides a reference for optimizing the segmented annular thermoelectric generator structure and is of paramount importance for enhancing the efficiency of waste heat recovery.

Thermodynamic performance evaluation and optimization of a hybrid system integrating vacuum graphene-anode thermionic converters with direct carbon fuel cells

An efficient hybrid system integrating a direct carbon fuel cell (DCFC) with a vacuum graphene-anode thermionic converter (VGTC) is proposed for cogeneration. The VGTC efficiently recycles waste heat released from the DCFC and generate additional electricity, significantly improving energy utilization efficiency and economic performance. A comprehensive mathematical model is developed to quantitatively assess the thermodynamic performance of the hybrid system, taking into account the overpotential losses of the DCFC and the irreversible energy losses occurring within the system. The results show that at an operating temperature of 923 K, the hybrid system can achieve a maximum power density of 466 W/m2, which is approximately 1.34 times that of a single DCFC, indicating a significant improvement in output performance. Besides, the optimal operating region and parameter selection criteria for the hybrid system are determined using finite-time thermodynamic optimization theory. Furthermore, the effects of essential parameters on the output performance of the hybrid system, such as the operating temperature of the DCFC, the heat transfer coefficient, the Fermi level of graphene, the work function of the cathode, the thermal emissivity, and the reflectivity of the back mirror, are investigated. Finally, the comparative study shows that the proposed hybrid system outperforms other previously reported hybrid systems regarding output electric power and conversion efficiency due to the efficient high-grade waste heat recovery and energy conversion by the VGTC.

A Comprehensive Review of Thermal Management in Solid Oxide Fuel Cells: Focus on Burners, Heat Exchangers, and Strategies

Solid Oxide Fuel Cells (SOFCs) are emerging as a leading solution in sustainable power generation, boasting high power-to-energy density and minimal emissions. With efficiencies potentially exceeding 60% for electricity generation alone and up to 85% when in cogeneration applications, SOFCs significantly outperform traditional combustion-based technologies, which typically achieve efficiencies of around 35–40%. Operating effectively at elevated temperatures (600 °C to 1000 °C), SOFCs not only offer superior efficiency but also generate high-grade waste heat, making them ideal for cogeneration applications. However, these high operational temperatures pose significant thermal management challenges, necessitating innovative solutions to maintain system stability and longevity. This review aims to address these challenges by offering an exhaustive analysis of the latest advancements in SOFC thermal management. We begin by contextualizing the significance of thermal management in SOFC performance, focusing on its role in enhancing operational stability and minimizing thermal stresses. The core of this review delves into various thermal management subsystems such as afterburners, heat exchangers, and advanced thermal regulation strategies. A comprehensive examination of the recent literature is presented, highlighting innovations in subsystem design, fuel management, flow channel configuration, heat pipe integration, and efficient waste heat recovery techniques. In conclusion, we provide a forward-looking perspective on the state of research in SOFC thermal management, identifying potential avenues for future advancements and their implications for the broader field of sustainable energy technologies.

Study on the thermal performance of the cross-flow plate heat exchangers

The exhaust gas emitted by a stenter machine will lead to energy waste and environmental heat pollution. Therefore, designing an efficient waste heat recovery apparatus for exhaust gas not only protects the environment but also saves production costs. In the article, the heat transfer performance and pressure drop of three types of heat exchangers: flat-plate heat exchanger (PHE), wavy-PHE, and zigzag-PHE were numerically studied in the context of waste heat recovery from the exhaust gas of stenter machines. The heat transfer rate (Q), Nusselt number (Nu), Colburn factor (j), pressure drop, Fanning friction factor (f), and comprehensive performance factor (JF) were investigated while Reynolds numbers ranged from 1000 to 9000. An experimental measurement was devised to validate the accuracy of the numerical simulation. The results of the research indicate that the wavy-PHE exhibits improved heat transfer efficiency and reduced pressure drop, primarily attributed to the substantial generation of secondary flow. Three new correlations for Nusselt number in different PHEs were developed based on commonly existing empirical formulas. The prediction accuracy for the Nusselt number based on the new correlations has been significantly improved in the present study.

Assessing Efficient Waste Heat Recovery System for Marine Engine – A Thermodynamic Comparison of Organic Rankine Cycle and Kalina Cycle

Assessing Efficient Waste Heat Recovery System for Marine Engine – A Thermodynamic Comparison of Organic Rankine Cycle and Kalina Cycle

Experimental Research on Effects of Combustion Air Humidification on Energy and Environment Performance of a Gas Boiler

Abstract To increase the waste heat recovery (WHR) efficiency of gas boiler and decrease NOx emissions, a flue gas total heat recovery (FGTHR) system integrating direct contact heat exchanger (DCHE) and combustion air humidification (CAH) is put forward. The experimental bench and technical and economic analysis models are set up to simulate and evaluate the WHR performance and NOx emissions in various operation situations. The results show that when the air humidity ratio elevates from 3 g/kgdry air to 60 g/kgdry air, the dew point temperature increases by 7.9 °C. When the flue gas temperature approaches the dew point temperature, the rate of improvement of the FGTHR system's total heat efficiency notably rises. With spray water (SW) flowrate and temperature of 0.075 kg/s and 45 °C, the WHR efficiency relatively increases by up to 8.4%. The maximum sensible and latent heat can be recovered by 4468 w and 3774 w, respectively. The flue gas temperature can be reduced to 46.55 °C, and the average NOx concentration is 39.6 mg/m3. Compared with the non-humidified condition, the NOx and CO2 emissions relative reduction of the FGTHR system are 61.2% and 8.7%. The payback period of FGTHR system is 2 years. Through simulation, it can be concluded that the decrease in exhaust flue gas temperature and velocity, as well as the increase in exhaust flue gas humidity, has a negative impact on the diffusion of NOx in the atmosphere.

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%.

Experimental examination of the effect of thermal barrier coating in a 2-stroke gasoline engine on recovery performance in exhaust waste heat recovery system with thermoelectric generator and engine performance

In internal combustion engines, while the decrease in in-cylinder wall temperature increases the amount of energy passing towards the cooling system, it decreases temperature and pressure at the end of compression and accordingly reduces thermal efficiency of the engine. Moreover; combustion chamber elements are exposed to chemical corrosion and deformation as a result of uncompleted combustion in the cylinder. With thermal barrier coating application, the energy lost in cooling system will decrease and exhaust temperatures will increase in 2-stroke engines. Placement of a waste heat recover system with thermoelectric generator into the exhaust system can provide exhaust waste heat recovery and increase thermal efficiency of the engine. There is no study in the literature, which examines waste heavy recovery systems with thermal barrier and thermoelectric generator altogether. In this article, yttria stabilized zirconia coating has been applied by means of plasma spraying method in the combustion chamber of a 2-stroke gasoline engine, and effect of thermal barrier coating application on engine performance and exhaust waste heat recovery system has been examined experimentally. According the results of the experiment, maximum engine power has increased by 6.23%, maximum engine torque has increased by 6.02%, and specific fuel consumption decreased by 5.56%. While the exhaust temperatures have increased by 78.5 °C at maximum by means of thermal barrier coating application; by means of thermal barrier coating application with waste heat recovery system with thermoelectric generator, a higher waste heat recovery has been obtained by 64.8%.

Energy management and performance analysis of an off-grid integrated hydrogen energy utilization system

In integrated hydrogen energy utilization systems, due to the low efficiency of hydrogen/electricity conversion, coordination of energy management and efficient waste heat recovery is required to optimize performance. To address this challenge, this paper presents a comprehensive and sophisticated modeling and energy management strategy to enhance the off-grid energy utilization rate while prolonging the main components’ lifetime. The developed model incorporates multiphase flow and heat transport balance for electricity and heat production, enabling a highly accurate representation of real-world behaviors of the system. The proposed off-grid operation strategy is complemented by a designed heat recovery scheme, ensuring the use of energy resources and waste heat. In addition, the proposed energy management strategy monitors the real-time status of each subsystem, actively reducing the number of harmful start-stop cycles of the hydrogen production system, thereby mitigating short-term power impacts and delaying its aging. Specifically, the voltage degradation of the reduction cell is reduced from 4.67 mV to 4.48 mV, the energy utilization rate is increased from 47.6 % to 53.9 %, and the energy efficiency of fuel cells significantly increases from 53.6 % to 78.1 %.

Efficient waste heat recovery from molten carbonate fuel cells through graphene-collector thermionic generators

The waste heat released by molten carbonate fuel cells (MCFCs) contains considerable energy that can be captured for electric power generation. Nonetheless, the current high-grade heat harvesting devices for the MCFC cogeneration of electrical power are still constrained by low power output or energy conversion. To address this challenge, we present a novel hybrid system that combines an MCFC and a graphene-collector thermionic generator (GCTG), in which the GCTG can efficiently harness the exhaust heat released from the MCFC and generate additional electricity. The results show that the hybrid system’s maximum power density reaches 0.298 W/cm2, which is 1.6 times that of the sole MCFC at 923 K, demonstrating that the hybrid system delivers a significant boost in output performance. Furthermore, finite-time thermodynamics estimates the hybrid system’s optimal operating regions and key parameter designs. The optimal performance of the hybrid system can be further improved by selecting the optimal area ratio, raising the MCFC operating temperature, strengthening the heat transfer coefficient, lowering the thermal emissivity of the thermionic emitter, and manufacturing the perfect optical reflector. The MCFC-GCTG outperforms other MCFC-based hybrid systems regarding output performance, demonstrating that GCTG can more effectively exploit the waste heat released from MCFCs than other heat recovery devices. This study offers valuable theoretical guidance for the strategic optimization of the MCFC-GCTG hybrid system, thereby paving a constructive strategy towards realizing advanced, high-performance MCFC cogeneration systems.

Optimizing heat transfer characteristics in dry centrifugal Granulation: Impact of particle population trajectory and cooling strategies

Efficient recovery of heat and utilize blast furnace slag resources are crucial for achieving energy savings and reducing consumption in the steel industry. This study focuses on applying dry centrifugal pelletizing technology for recovering waste heat from slag. A comprehensive two-dimensional model was developed to investigate heat transfer dynamics within particle clusters, considering the variable physical parameters of the slag, latent heat of the phase change, and slag particle characteristics. Through an extensive analysis of the heat exchange within the granulation bin, we examined the temperature variations of slag particles and the distribution of absorbed heat by the water-cooled and air. Findings underscore the significant influence of flight trajectory, residence time, air-inlet flow rate, and temperature on heat exchange efficiency. Additionally, we explored the impact of auxiliary cooling measures and investigated how slag particle characteristics affect the bin wall, highlighting their importance for safe operations. Our results provide valuable insights for enhancing waste heat recovery efficiency from blast furnace slag and optimizing the implementation of dry centrifugal granulation technology. It serves as a vital reference for promoting energy-saving initiatives and reducing consumption in the steel industry.

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 %.

A technically feasible strategy using liquid-state thermocells to efficiently recover the waste heat released from proton exchange membrane fuel cells

Proton exchange membrane fuel cells (PEMFCs) generate a large amount of exhaust heat during operation, leading to environmental pollution and the greenhouse effect. To recover the low-grade exhaust heat produced by PEMFCs, a technically feasible approach is proposed by integrating liquid-state thermocells (LTCs) with PEMFCs for the cogeneration of electric power and efficient waste heat recovery. Considering the three overpotential losses in the PEMFC and the irreversible heat losses in the LTC, a comprehensive mathematical model of a PEMFC-LTC hybrid system is developed to explore the energetic performance characteristics and optimal device design. The results show that the hybrid system’s maximum power density and corresponding conversion efficiency are 0.3007 W cm−2 and 24.59%, which is increased by 6.22% and 19.41% compared to a single PEMFC, respectively. Furthermore, raising the PEMFC temperature, optimizing the length of the individual LTC cell, reducing the heat sink temperature, and lowering the thermal convection coefficient can significantly improve the optimal output performance of the hybrid system. Finally, the optimal performance comparisons between the PEMFC-based cogeneration systems reveal that LTCs can more efficiently recycle the waste heat released from the PEMFC than other previously reported devices. This work offers crucial theoretical guidance for the optimal design and parametric analysis of PEMFC-LTC hybrid systems, thus paving the way for developing high-performance energy cascade utilization systems based on PEMFCs.

Energy Efficiency and Environmental Benefits of Waste Heat Recovery Technologies in Fishmeal Production Plants: A Case Study in Vietnam

The fishmeal production industry is essential for providing protein for animal feed in the aquaculture sector. However, the industry faces challenges related to energy consumption and environmental sustainability. This study evaluates the energy efficiency and environmental benefits of waste heat recovery (WHR) technologies in a fishmeal production plant in Vietnam. Data were collected from the plant between 2016 and 2022, and a specific energy consumption (SEC) indicator and a comprehensive methodology were utilized. Implementing an economizer as a WHR technology resulted in a 55.5% decrease in SEC compared to the state before installation. The enhanced energy efficiency also translated to reduced energy consumption per output unit. Moreover, the economizer contributed to annual energy savings of 4537.57 GJ/year and cost savings of USD 26,474.49. Additionally, carbon dioxide (CO2) emissions associated with producing one ton of fishmeal decreased by 58.37%. These findings highlight the potential for WHR technologies to improve energy efficiency and reduce the environmental footprint of fishmeal production. The study’s results provide valuable insights for practitioners and policymakers in promoting energy efficiency practices and reducing environmental impact in this and similar industries.