Thermal Management Subsystem Research Articles

Innovative Design of Solid-State Hydrogen Storage and Proton Exchange Membrane Fuel Cell Coupling System with Enhanced Cold Start Control Strategy

This paper presents an innovative thermally coupled system architecture with a parallel coolant-heated metal hydride tank (MHT) designed to satisfy the hydrogen supply requirements of proton exchange membrane fuel cell s(PEMFCs). This design solves a problem by revolutionising the cold start capability of PEMFCs at low temperatures. During the design process, LaNi5 was selected as the hydrogen storage material, with thermodynamic and kinetic properties matching the PEMFC operating conditions. Afterwards, the MHT and thermal management subsystem were customised to integrate with the 70 kW PEMFC system to ensure optimal performance. Given the limitations of conventional high-pressure gaseous hydrogen storage for cold starting, this paper provides insights into the challenges faced by the PEMFC-MH system and proposes an innovative cold start methodology that combines internal self-heating and externally assisted preheating techniques, aiming to optimise cold start time, energy consumption, and hydrogen utilisation. The results show that the PEMFC-MH system utilises the heat generated during hydrogen absorption by the MHT to preheat the PEMFC stack, and the cold start time is only 101 s, which is 59.3% shorter compared to that of the conventional method. Meanwhile, the cold start energy consumption is reduced by 62.4%, achieving a significant improvement in energy efficiency. In conclusion, this paper presents a PEMFC-MH system design that achieves significant progress in terms of time saving, energy consumption, and hydrogen utilisation.

Thermal dynamic analysis and multi-objective optimization of a 10 kW dual preheating solid oxide fuel cell system

The increasingly serious environmental problems caused by the excessive development of fossil fuels necessitate the promoting of novel and effective energy technologies. As an environmentally friendly and effective promising solution in terms of its low emission, and fuel adaptability, the solid oxide fuel cell (SOFC) system has attracted widespread attention. To better promote the progress of SOFC, the SOFC testing system (SOFC TS) is very important. In this paper, we have established a dual preheating SOFC TS configuration where the fuel is first preheated by exhaust gas, and then preheated by the electric heater to the setting temperature. A comprehensive thermodynamic analysis is conducted to investigate the characteristic of this SOFC TS. Building upon this designed testing system, a multi-objective optimization approach is adopted to enhance the performance of the thermal management subsystem. The results showed that the SOFC stack is the main exergy component in the SOFC TS, the selected point of multi-objective optimization can reduce the thermal management costs by 60$ and improve system efficiency by 4.5%.

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.

Comprehensive performance assessment and multi-objective optimization of high-power proton exchange membrane fuel cell system under variable load

Due to the advantages of zero emission, high efficiency and low noise, Proton Exchange Membrane Fuel Cell (PEMFC) has grown to be the spotlight in the field of new energy in recent years. In this work, a high-power PEMFC system model is designed, which consists of the fuel feed Subsystem, the air feed subsystem, the thermal management subsystem and the stack. Among them, the material diffusion in the catalyst layer of the stack is intensively studied and derived. For the comprehensive system performance assessment, the thermodynamic, economic and environmental evaluation models have been developed. The mapping relationships between the operating parameters, the structural parameters and the system comprehensive performance under variable load conditions are obtained. The results of the study prove that increasing the operating temperature and decreasing the membrane thickness under high load current conditions are conducive to increase the system net power output, but at the same time increase the levelized cost of energy and the carbon mass specific emission. In addition, a multi-objective optimization strategy based on the NSGA-Ⅱ is designed to obtain the optimal performance of the system under different operating conditions. The optimized net power, the levelized cost of energy and the carbon mass ratio emission of the system for the final optimal operating point are increased by 40.5 %, 10.3 % and 33.3 % respectively. The aforementioned evidence substantiates the effectiveness of the proposed multi-objective optimization strategy in enhancing the overall performance of the PEMFC system.

Fault Diagnosis of Sensors for Multi-stack Fuel Cell Thermal Management Subsystem Based on UKF

Fault Diagnosis of Sensors for Multi-stack Fuel Cell Thermal Management Subsystem Based on UKF

System modeling and temperature control for a fuel cell system based on local model networks

ABSTRACT Fuel cells have been studied for use in stationary power generation and vehicle propulsion systems. The fuel cell thermal management subsystem is coupled and nonlinear, posing challenges for modeling and temperature control. This paper aims to integrate the physical models of the fuel cell stack, pump, thermostat, and other components combined with intelligent algorithms into an efficient system-level thermal management model framework and develop a model predictive controller to solve the temperature control problem. First, a physics-based nonlinear model of the fuel cell system is developed and used as a basis to identify the linearized model for different operating points. Then, the global model is obtained by fusing the local models with Gaussian validity functions using the local linear model tree method. Third, a multi-step prediction model is derived based on the local model networks, and a parameterized linear state space form is obtained and used for controller design. Furthermore, an online correction method is developed to reduce the model discrepancy. Finally, the accuracy of the system model and the performance of the proposed controller are verified by open-loop experimental data and a series of closed-loop simulation cases.

Fault Diagnosis and Fault‐Tolerant Control Method for a Multistack Fuel Cell Thermal Management Subsystem

Multistack fuel cell systems (MFCS) are promising developments of fuel cell technology. For MFCS, faults affect durability and stability, and appropriate fault diagnosis methods and control strategies need to be proposed for different multistack structures. Herein, the integrated MFCS thermal management subsystem (TMS), which is based on the optimized split‐stack approach, is first studied, and its possible sensor and actuator faults are analyzed. The sensor fault signal is corrected based on the unscented Kalman filter (UKF), the controller design under the hardware in the loop platform is carried out, and an active fault‐tolerant control (FTC) strategy based on sliding mode control is deployed for the TMS to enable it to recover its performance quickly and effectively in case of faults. The results show that the estimated values are closer to the true values after using the UKF on the sensor signals, avoiding the impact of sensor faults on the system performance. Under New European Driving Cycle dynamic conditions, the FTC controller also exhibits better control compared to the conventional proportional–integral controller, with smaller maximum overshoot and shorter system recovery and stabilization time in the event of a TMS fault, mitigating the impact of system fault on performance.

A novel heat pipe bipolar plate for proton exchange membrane fuel cells

The proton exchange membrane fuel cell (PEMFC) system is appealing for electric vertical takeoff and landing vehicles, but its power density needs to be improved for practical applications. Ultra-thin flat heat pipes (UTFHP) have potential to improve the power density of PEMFC system by reducing the complexity of thermal management subsystem, but the large stack volume have hindered their wider adoption. This paper proposes a novel design of heat pipe bipolar plates (HPBP) to reduce the volume of heat pipe cooled stack. A three-dimensional numerical model has been developed for analyzing and comparing the performance of the PEMFCs with HPBP and UTFHP. Compared to the UTFHP, the HPBP could significantly reduce the stack volume while maintaining comparable maximum heat load. It can also significantly reduce the maximum temperature and improve the temperature uniformity over the cathode catalyst layer middle plane. The operating range and the peak power density of the PEMFC cooled by HPBP are larger than that cooled by UTFHP. We also performed system-level evaluations and found that the PEMFC system with HPBP cooling exhibits 22% and 36% higher gravimetric and volumetric power densities than that with conventional liquid cooling, respectively.

Comparison of Different Topologies of Thermal Management Subsystems in Multi-Stack Fuel Cell Systems

The performance of a fuel cell stack is affected by the operating temperature of the stack. The thermal management subsystem of a multi-stack fuel cell system (MFCS) is particularly significant for the operating temperature control of each stack in the MFCS. To study the influence of different topologies of a MFCS thermal management subsystem, this paper proposes and establishes two different topologies. Firstly, the integrated topology is proposed. Secondly, seven component models, namely the mixer, thermostat, radiator, tank, pump, bypass value, and proton exchange membrane fuel cell stack temperature models, are described in detail. Finally, the performance of the two topologies of the MFCS thermal management subsystem under two working conditions, steady (200 A) and variable (China heavy-duty commercial test cycle, C-WTVC), is compared. Furthermore, there are two evaluating indicators, including the stability duration and deviation of the operating temperatures of the single stack in the MFCS. Results show that when the MFCS operates under steady working conditions, the integrated topology is superior in operating temperature control accuracy (ΔT<0.5 K), while the distributed topology is superior in the adjustment process (t ≤ 100 s). Moreover, when the MFCS operates under variable working conditions, the distributed topology is superior in operating temperature control accuracy.

Decentralized event-triggered adaptive control for interconnected nonlinear dynamics of constrained air supply and thermal management systems of PEMFCs

This paper investigates a decentralized event-triggered adaptive control problem for uncertain interconnected air supply and thermal management nonlinear dynamics of proton exchange membrane fuel cells (PEMFCs). In addition, the constraint problems of the oxygen excess ratio (OER) and stack temperature (ST) are addressed for preventing oxygen starvation, parasitic loss, membrane dehydration, and electrode flooding of PEMFCs. First, the practical nonlinear interaction problem between the air pressure of the air supply subsystem and the ST of the thermal management subsystem is formulated. Then, a decentralized adaptive control design strategy is established to guarantee the constraint satisfaction of each subsystem and the asynchronously event-triggered regulation of the OER and ST. In contrast to the previous studies on the control of PEMFCs, this study first addresses the nonlinear interaction problem of the air supply and thermal management systems and their decentralized control design in the control field of PEMFCs. Based on the Lyapunov stability theorem, the stability of the resulting overall control scheme is analyzed.

Optimization and Database Management in Smart Modeling of Aviation Heat Exchangers

Analytical tools for modern aviation heat exchangers (HEXs), such as those that are additively manufactured, have to be advanced and smart. To develop such tools, procedures are presented in this paper that obviate the need for the standard -number-of-transfer-units method of analysis, enable multiple-rating capabilities, and support the generation and exporting of lookup tables that could be readily inserted into a system-level multidisciplinary design optimization platform. Three practical optimization procedures are evaluated and compared for their ability to efficiently handle the design variables and the performance rating, constraints, and objective functions in the optimization of aviation thermal management components and subsystems. Modern database management techniques are also implemented to enable the generation of the training data that are required for building intelligence into the developed HEX software. The mathematical and qualitative details of the heat transfer aspects of a few of these capabilities are presented in this paper, as are two case studies pertaining to optimization where we compare two of the developed approaches. To the knowledge of the authors, no previous studies have addressed the issues resolved in this paper.

Thermal design, analysis and comparison on three concepts of space solar power satellite

Space solar power satellites (SSPS) have been widely studied as systems for collecting solar energy in space and transmitting it wirelessly to earth. A previously designed planar SSPS concept collects solar power in two huge arrays and then transmits it through one side of the power-conduction joint to the antenna. However, the system's one group of power-conduction joints may induce a single point of failure. As an SSPS concept, the module symmetrical concentrator (MSC) architecture has many advantages. This architecture can help avoid the need for a large, potentially failure-prone conductive rotating joint and limit wiring mass. However, the thermal control system has severely restricted the rapid development of MSC, especially in the sandwich module. Because of the synchronous existence of five suns concentration and solar external heat flux, the sandwich module will have a very high temperature, which will surpass the permissible temperature of the solar cells. Recently, an alternate multi-rotary joints (MR) SSPS concept was designed by the China Academy of Space Technology (CAST). This system has multiple joints to avoid the problem of a single point of failure. Meanwhile, this concept has another advantage for reducing the high power and heat removal in joints. It is well known to us that, because of the huge external flux in SSPS, the thermal management sub-system is an important component that cannot be neglected. Based on the three SSPS concepts, this study investigated the thermal design and analysis of a 1-km, gigawatt-level transmitting antenna in SSPS. This study compares the thermal management sub-systems of power-conduction joints in planar and MR SSPS. Moreover, the study considers three classic thermal control architectures of the MSC's sandwich module: tile, step, and separation. The study also presents an elaborate parameter design, analysis and discussion of step architecture. Finally, the results show the thermal characteristics of each SSPS concept, and the three concepts are compared. The design layouts, analysis results and parameter discussions of the thermal management sub-system proposed in this study can help inform future SSPS thermal designs.

Performance characteristics of a supplementary stack-cooling system for fuel-cell vehicles using a carbon dioxide air-conditioning unit

In fuel-cell-powered vehicles, the fuel-cell system requires a thermal-management subsystem to dissipate heat released during the reaction of hydrogen with oxygen. When the stack generates power at a high rate, a large amount of heat is also generated. If cooling by the radiator is insufficient, a supplementary stack-cooling system is needed to maintain a safe operating temperature. In this study, the performance of a CO2 air-conditioning unit for stack cooling was investigated under various conditions, and the relationship between cabin cooling and stack cooling was also studied. The coefficient of performance (COP) increased from 1.9 to 2.4, with an increase in cabin-air inlet flow rate from 0 to 8 m3/min. When the air-conditioning unit was turned off, the cooling capacity of the stack cooler was increased; correspondingly, as the cabin-cooling capacity was increased, that of the stack cooler decreased. With an increase in ambient-air inlet temperature from 38°C to 45°C, the COP decreased by 24%. Additionally, both the stack-cooling capacity and cabin-cooling capacity were decreased by about 12% and 16%, respectively, due to reduced heat transfer in the gas cooler as the ambient air inlet temperature was increased. It is expected that the experimental results can serve as a resource in designing a stack-cooling system using a CO2 air-conditioning unit to enhance stack power generation and efficiency.

Design of thermal management subsystem for a 5 kW polymer electrolyte membrane fuel cell system

High-efficiency thermal management subsystem has a key role on the PEM fuel cell performance and durability. In this study, design of thermal management subsystem for a 5kW PEM fuel cell system is investigated. A numerical model is presented to study the cooling flow field performance. The number of parallel channels in parallel serpentine flow field is selected as the design parameter of the flow field and its optimum value is obtained by compromising between the minimum pressure drop of coolant across the flow field and maximum temperature uniformity within the bipolar plate criteria. The optimum coolant flow rate is also determined by compromising between different criteria. Test results of a 5-cells short stack are presented to verify the numerical simulation results.

Development of kW Class SOFC Systems for Combined Heat and Power Units at KEPRI

The Korea Electric Power Research Institute (KEPRI) has been developing planar solid oxide fuel cells (SOFCs) and power systems for combined heat and power (CHP) units. The R&D work includes solid oxide fuel cell (SOFC) materials investigation, design and fabrication of single cells and stacks, and kW class SOFC CHP system development. Anode supported cells composed of Ni-YSZ/FL/YSZ/LSCF were enlarged up to 15×15 ㎠ and stacks were manufactured using 10×10㎠ cells and metallic interconnects such as ferritic stainless steel. The first-generation system had a 37-cell stack and an autothermal reformer for use with city gas. The system showed maximum stack power of about 1.3 ㎾ e,DC and was able to recover heat of 0.57~1.2 ㎾ th depending on loaded current by making hot water. The second-generation system was composed of an improved 48-cell stack and a prereformer (or steam reformer). The thermal management subsystem design including heat exchangers and insulators was also improved. The second-generation system was successfully operated without any external heat source. Under self-sustainable operation conditions, the stack power was about 1.3㎾ e,DC with hydrogen and 1.2 ㎾ e,DC with city. The system also recuperated heat of about 1.1 ㎾ th by making hot water. Recently KEPRI manufactured a 2 kW class SOFC stack and a system by scaling up the second-generation 1 ㎾ system and will develop a 5 ㎾ class CHP system by 2010.

Modelling results for the thermal management sub-system of a combined heat and power (CHP) fuel cell system (FCS)

Although the fuel cells research and development community has traditionally focused the majority of its efforts on improving the fuel cell stack’s voltage (electrical efficiency), combined heat and power (CHP) fuel cell system (FCSs) may achieve a competitive advantage over conventional generators only if the research and development community refocuses its efforts on cultivating other inherent technical qualities of such systems. Based on an analysis of their use within energy markets, these inherent qualities include (1) an ability to vary their electrical load rapidly, (2) an ability to vary their heat to power ratio during operation, and (3) an ability to deliver their waste heat to a useful thermal sink. This article focuses on the last of three design objectives: effectively capturing heat from a CHP FCS. This article (1) delineates the design specifications for a 6 kWe CHP FCS, (2) analyses four possible cooling loop configurations for this system, and (3) concludes which one of these provides the optimal heat recovery performance.

Solid Oxide Fuel Cell Systems for Power Generation Applications

Solid oxide fuel cell (SOFC) systems are being developed for a number of power generation applications. The SOFC technology under development at General Electric is based on a planar design that incorporates thin-electrolyte anode-supported cells fabricated by tape calendering and thin-foil metallic interconnects. For 5-kW systems based on this technology, the projected cost for the system when fully developed is below $400/kW. Current activities have been focused on system design and analysis, stack technology development including design, performance and life improvements, fuel processing assessment and evaluation, and thermal management and control subsystem development. This paper describes the system design concept and summarizes certain selected results obtained to date in the development of 5-kW SOFC power systems.