Passive Fuel Cell Heat Recovery Using Heat Pipes to Enhance Metal Hydride Canisters Hydrogen Discharge Rate: An Experimental Simulation (original) (raw)
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Thermal integration of a metal hydride storage unit and a PEM fuel cell stack
International Journal of Hydrogen Energy, 2009
A metal hydride (MH) storage unit and a polymer electrolyte membrane (PEM) fuel cell (FC) stack were thermally integrated through a common water circulation loop. The low temperature waste heat dissipated from the fuel cell stack was used to enhance and ensure the release of hydrogen from the storage unit. A water-heated MH-tank can be made more compact than an air-heated MH-tank with external heating fins, due to more direct heat transfer between MH-alloy and heating/cooling media. A water-heated MH-tank will therefore have the potential for better kinetics for absorption and desorption of hydrogen.
Energy Procedia, 2012
A proper thermal management strategy is needed to maintain uniform temperature distribution and derive optimal performance in high temperature proton exchange membrane fuel cells (HT-PEMFC). In HT-PEMFCs, more than half of the chemical energy is converted into thermal energy during the electrochemical generation of electrical power. We investigate the viability of three heat removal strategies: (a) using cooling plates through which cathode air is passed in excess of stoichiometric requirement for the purpose of heat removal, (b) using forced convection partly in conjunction with cooling plates, and (c) using forced convection alone for heat removal. Calculations, partly done using computational fluid dynamics simulations, for a 1 kWe HT-PEMFC stack, which is suitable for scooter type of transport applications, show that a combination of excess stoichiometric factor and forced draft appears to provide the optimal strategy for thermal management of high temperature PEM fuel cells. With proper cooling strategy, the temperature variations within the cell may be reduced to about 20 K over most of the cell and to about 50 K in isolated spots.
Energy Conversion and Management, 2019
A fuel cell power system integrating proton-exchange-membrane fuel cell (PEMFC) and metal hydride (MH)based hydrogen storage tank presents great potential in transportation applications. The embedded PEMFC and MH tank are thermally coupled through a heat ex-changer and control system. The hydrogen generating and supplying rate from the MH tank to PEMFC is strongly influenced by the transferred heat, which affects the performance of long-term operation as well. In this work, the dynamic behavior of the fuel cell system is simulated with a mathematical model set and validated using a database from the real operation vehicles. Thanks to the heat ex-changer combined by fan, radiator and circulation water, the hydrogen flow rate from MH tank to PEMFC is well controlled to meet the requirement of power load. The simulated model describes the response of each component including the power and heat generated by PEMFC, the hydrogen desorption kinetics and the heat transfer in the system. A thermal management strategy with a PID controller is proposed to reduce the degradation and extend the lifespan of PEMFC. The results demonstrate that an optimized performance of PEMFC after 1000 h is realized. In spite of the MH tank degradation rate has been raised 0.3%, 2.5% of voltage degradation of PEMFC is reduced. Meanwhile, for the integration fuel cell system, more than 3% of fuel efficiency and 10% of fuel economy is saved.
Hydrogen, Fuel Cell & Energy Storage, 2019
PEMFC heat generation was utilized to desorb hydrogen from a LaNi 5 fi lled MH-Hydrogen Storage tank. Heat pipes were used to transfer heat from the FC to the MH-tank. The study was conducted using CFD simulation. Results showed that the increase of initial pressure of the MH tank and the cooling temperature of 303 K led to a rise in the hydrogen adsorption performance.After 4000 s in the desorption stage, 5.39 g of hydrogen was purged from the hydride tank. Additionally, results demonstrated that a total hydrogen discharge rate of 0.304 slpm was achieved only at the expense of 7.36 W of the total 23.43 W generated heat in the fuel cell. Furthermore, the hydrogen desorption fl ow rate gained 45% for the presented geometry compared to a similar system. Moreover, a very good agreement was found between the present work simulation results and the literature data.
Thermal management of edge-cooled 1 kW portable proton exchange membrane fuel cell stack
• Lumped model and real-time transient CFD model are compared during a load profile. • Influence of bipolar plate material on temperature is determined. • Influence of operating delta pressure on relative humidity inside the stack. • Significant influence of cooling fin redesign on heat transfer is outlined. • Heat transfer between the stack and metal hydride tank is analyzed.
Enhancement of hydrogen charging in metal hydride-based storage systems using heat pipe
International Journal of Hydrogen Energy, 2018
Heat transfer in metal hydride bed significantly affects the performance of metal hydride reactors (MHRs). Enhancing heat transfer within the reaction bed improves the hydriding rate. This study presents performance analysis in terms of storage capacity and time of three different cylindrical MHR configurations using storage media LaNi 5 : a) reactor cooled with natural convection, b) reactor with a heat pipe on the central axis, c) reactor with finned heat pipe. This study shows the impact of using heat pipes and fins for enhancing heat transfer in MHRs at varying hydrogen supply pressures (2e15 bar). At any absorption temperature, hydrogen absorption rate and hydrogen storage capacity increase with the supply pressure. Results show that using a heat pipe improves hydrogen absorption rate. It was found that finned heat pipe has a significant effect on the hydrogen charge time, which reduced by approximately 75% at 10 bar hydrogen supply pressure.
Journal of International Council on Electrical Engineering, 2013
A Totalized Hydrogen Energy Utilization System (THEUS) is proposed for load leveling and stabilizing the grid. The THEUS is a novel unitized regenerative fuel cell system that achieves high overall efficiency through optimized heat utilization. In this paper, a metal hydride tank (MHT) is chosen as hydrogen storage. In the MHT, the heating and cooling from adsorption/desorption processes is used to produced heated and chilled water for building ventilation systems. A new horizontal type MHT was developed to enhance the recovery rate of the reaction heat. This tank has a double coil heat exchanger and contained 50kg of AB5 metal hydride. The experimental results were compared with the results which were developed previously at AIST. The new tank results showed an improvement for the heat recovery rate which is the ratio of recovered energy to the entire reaction heat of the metal hydride. The reaction heat recovery was improved due to the decrease of the thermal capacity of the tank.
2012
A proper thermal management strategy is needed to maintain uniform temperature distribution and derive optimal performance in high temperature proton exchange membrane fuel cells (HT-PEMFC). In HT-PEMFCs, more than half of the chemical energy is converted into thermal energy during the electrochemical generation of electrical power. We investigate the viability of three heat removal strategies: (a) using cooling plates through which cathode air is passed in excess of stoichiometric requirement for the purpose of heat removal, (b) using forced convection partly in conjunction with cooling plates, and (c) using forced convection alone for heat removal. Calculations, partly done using computational fluid dynamics simulations, for a 1 kWe HT-PEMFC stack, which is suitable for scooter type of transport applications, show that a combination of excess stoichiometric factor and forced draft appears to provide the optimal strategy for thermal management of high temperature PEM fuel cells. With proper cooling strategy, the temperature variations within the cell may be reduced to about 20 K over most of the cell and to about 50 K in isolated spots.
International Journal of Hydrogen Energy, 2016
Recent work in hydrogen storage is mainly focused on implementing metal hydrides. Metal hydrides well demonstrated their high capacity for hydrogen storage within reasonable and safe pressures and temperatures. One of the effecting parameters on the performance of a reactor in a metal hydride hydrogen storage system is its design and configuration. There are a number of technical issues which need to be considered in designing a reactor. Some of these parameters are reactor configuration, thermal management, hydrogen transfer and mechanical strength. The current work is concentrated on the problem of thermal management while focusing on reactor and heat exchanger configurations. In this paper, different reactors and heat exchangers in metal hydride hydrogen storage systems are studied, categorized and compared. This classification helps the reader to find the best option for any specific application. However, for an optimum design of the reactor, in addition to the above noted parameters, other factors like coupling process of porous flow and reaction kinetics should be taken into account as well.
Cooling Mechanisms and Contribution Analysis of an Experimental PEM Fuel Cell System
Proc. of the 2nd Engineering Conference (ENCON) 2010,Malaysia, 2010
Thermal engineering is an important aspect of a hydrogen fuel cell system that directly affects the overall power output of the system. Generated heat from the electrochemical reactions of a fuel cell needs to be removed from the cells to inhibit a drastic rise in cell temperature. Theoretically, active cooling systems of a Polymer Electrolyte Membrane (PEM) fuel cell are required to dissipate at least 90% of the total cooling load. Passive cooling mechanisms consist of free convection, radiation, as well as some heat carried out by the reactants. Experiments were performed on a water-cooled PEM fuel cell system with the objective of identifying the actual heat generation and cooling contributions of active and passive cooling mechanisms during operation. Steady-state active cooling is within the range of 54% to 67% cooling effectiveness, where optimum cooling occurs when the cooling water inlet temperature is less than 60 o C. Passive cooling is significant only at high surface temperatures, providing between 14% to 23% of cooling contribution. The cooling characteristics from these analysis provides a platform for further improvement of the fuel cell thermal system design.