Metal Hydride Canisters Research Articles

Heat pipe for thermally coupled fuel cell and metal hydride as well as for cooling metal hydride hydrogen charging

ABSTRACT In this paper, a metal hydride (MH) canister and a PEM fuel cell are coupled using heat pipes to study the minimum number of heat pipes required, the operating range of the fuel cell, and the temperature change patterns of the MH. We account for temperature difference limitations between the fuel cell and the MH (∆T = 35–55 K) on the heat pipe dynamics, which has been neglected in previous similar studies. Since the hydrogen absorption rate of the MH canisters exhibits an initial increase followed by a decrease with increasing temperature, an analysis was conducted to select the appropriate heat pipe under different hydrogen filling pressures. This analysis ensured that the MH canisters remained at the optimal charging temperature (326 K) and achieved the maximum charging rate (6.64 slpm).

Assembly and Testing of a Hydrogen Fuel Cell System to Power an Airship

An airship, or dirigible balloon, is an aircraft that gains its lift from a gas less dense than air, like helium. For traction, airships have two or more propellers normally attached to a gondola that is suspended under the balloon. At present, they are used for hovering long times without the need for a high speed, like for aerial observation, advertising, or as camera platforms. In our laboratory, the airship is being used as a platform for testing hydrogen fuel cell systems for aerial applications.The airship used in this communication is a 3 m3 polyurethane's inflatable zeppelin, with radio control, and three electrical propellers (Fig. 1a). A hydrogen fuel cell system has been developed and integrated with the gondola for powering the propellers and electronics. The fuel cell is a 15 W PEMFC stack prototype able to work fully under passive feeding conditions (Fig. 1b). In addition, three supercapacitors have been implemented, that are recharged by the fuel cell, for eventual larger power demands up to 40 W. Hydrogen is stored in two metal hydride canisters with 2g capacity to provide 30 W h energy enough for a few hours autonomy. In addition, for fuel cell parameters monitoring, different sensors have been implemented that provide voltages of the individual cells, current, and temperatures. The sensors are connected to Arduino board, and measurements are continuously monitored by a Labview software with wifi. Boost dc-dc conversion provides 7V voltage power to feed the motors.The stack prototype allows for different testing configurations, using cells in series and parallel connection to change power characteristics with different voltage and current. Results of the testing are provided in this communication.Acknowledgement: The work is partially financed by the ELHYPORT project (PID2019−110896RB-I00), Spanish Ministry of Science and Innovation. Figure 1

An experimental study of employing organic phase change material for thermal management of metal hydride hydrogen storage

This paper presents the details of an experimental study of using a phase change material (PCM), made of 4.56 kg RT28HC paraffin wax, for self-contained thermal management of an 800 NL metal hydride (MH) hydrogen canister (MmNiMnCo). Thermal behaviour and charging/discharging performances of this innovative arrangement were investigated by considering the impacts of the operating parameters including hydrogen pressure, hydrogen flow rates, and effective thermal conductivity of PCM. Introducing PCM for thermal management of MH offered a possibility to store the heat released during hydrogen charging mode and transfer it back to the canister during discharging. The test results suggest that the total amount of hydrogen being utilised, while MH absorption/release rates being maintained at desired levels, is improved by two times after employing PCM for its thermal management. However, the maximum accumulative amount of hydrogen absorbed/released by the MH was still only up to 26 % of its total storage capacity with hydrogen charging rate dropped gradually after being started from 1.1 slpm. Recognising the low thermally conductivity of the PCM as the root cause of this shortfall, 10 PPI copper metal foam (MF) with 96 % porosity was embedded in the PCM. By introducing this MF, the full capacity of the MH canister could be utilised at continuous charging and discharging rates of 1.1 slpm and 1.5 slpm, respectively.

Energy storage onboard zero-emission two-wheelers: Challenges and technical solutions

The two-wheelers powered by battery, hydrogen fuel cell, or a combination of these two power sources are the potential candidates for the greenhouse gas emission reduction strategy in the future although they have been running into difficulties relating to the onboard energy storage technology. Therefore, the main aim of this review paper is to present the existing challenges and technical solutions to the energy storage of two-wheelers. Indeed, exchanging batteries and swapping metal hydrides hydrogen storage canisters were found to be the appropriate solutions, in which fuel cell and the metal hydride canister could constitute a cogeneration system that the heat needed for hydrogen desorption from the metal hydride canister could be recycled from the waste heat of fuel cell stacks or stored in phase change material during the uptake process. Furthermore, powertrain layouts of the fuel cell two-wheelers and the fuel cell-battery hybrid two-wheelers based on the traditional two-wheeler platforms were also suggested in this paper. More importantly, a novel concept associated with the “zero-emission two-wheeler-building” polygeneration system was also suggested to improve the global energy conversion efficiency. Finally, the energy system of two-wheelers powered by battery, fuel cell, and fuel cell-battery hybrid was thoroughly analyzed and compared.

Thermal coupling of an open-cathode proton exchange membrane fuel cell with metal hydride canisters: An experimental study

In this paper, the impacts of utilising the heat generated by a 2.5-kW open-cathode proton exchange membrane fuel cell (PEMFC) on enhancing the hydrogen release rate of nine 800 NL AB5 metal hydride (MH) canisters were experimentally investigated. Thermal coupling of MH canisters with PEMFC offers a potential to improve the hydrogen discharge rate of MH canisters by utilising its waste heat. However, the added complexity for implementing this idea remains to be a barrier. Open-cathode fuel cells with hot air exiting the cathode side offer an opportunity to simplify its thermal coupling arrangement with MH canisters. The set-up was designed with minimum added parts with just a ducting system to direct the hot exit air from the fuel cell passing over the MH canisters. The experimental results showed that the heat required by the MH canisters to supply enough hydrogen to the fuel cell at 500 W, 1000 W and 2000 W operating points accounts for around 40%, 36.5%, and 32% of the total heat removal from the stack, respectively. The arrangement proved to be feasible for serving its purpose and could eliminate the need for oversizing the MH hydrogen storage system that is normally practised to guarantee the right rate of hydrogen supply at higher power outputs.

A Simplified Optimization Model for Sizing Proton-Exchange Membrane Fuel Cells

The fluctuations in the cost of energy coupled with the gradual decrease in natural resources (i.e., oil, natural gas, coal) and the environmental issues caused by the extensive use of fossil fuels, demand the urgent need for the development of advanced and clean energy systems. The European Union has requested new measures to target climate and energy deterioration by developing renewable energy sources by 2030. The stochastic character of the energy sources and the fluctuation in demand for the energy systems poses a hindrance to achieving these targets. In this direction, hydrogen technology, that can be produced by electrolysis carried out in the presence of electricity from renewable energy systems can contribute as an energy carrier. It does not emit hazardous gasses and can be stored in the metal hydride canisters for future use via fuel cells (FCs). Modeling these systems is important for achieving their optimal size and to increase the penetration of renewable energy. They are beneficial both from the energy and economic point of view. For the accurate understanding of the hydrogen systems and especially FCs, it is important to understand the thermodynamic and electrochemical operating principles. In the present study, an integrated mathematical model is proposed concerning the electrical and thermal behavior of the FC. The model developed can simulate the operation of an FC by using the FC’s technical specifications. The reliability of the model was validated under three different hydrogen flow patterns applied in the experimental configuration (NEXA 1.2 kW). The proposed model was applied to a specific case study for the optimum sizing of an FC in terms of maximum hydrogen absorption. A hydrogen production pattern from electrolysis was used, and the excess energy from a wind park installed in an autonomous grid island network was utilized.

Adjusted method to calculate an electric wheelchair power cycle: fuel cell implementation example

Abstract The implementation of lighter and smaller power sources requires the estimation of power demand under different driving conditions, which are not available for portable assistive technology such as electric or power wheelchairs. Power demand estimated through power and driving cycles is a common methodology in the automotive industry and critical for sizing the power sources. This study determines power and driving cycles in simulated standard outdoor conditions adapting the microtrip methodology. Power consumption and distance travelled were calculated for five different tasks (longitudinal slopes, cross slopes and a flat surface). A “typical” wheelchair journey is presented as a suggested representative drive cycle. A numerical estimation of the power cycle is compared to the experimental results. The difference between numerical and experimental mean and maximum power is 7.58% and 1.07% respectively. Ascending longitudinal slopes were characterized by significantly higher mean power consumption compared to cross slopes and the flat surface. A theoretical fuel cell implementation is presented. The powertrain has a 160 W fuel cell and 470 W battery with a 27 gH2 metal hydride canister that increases the 30 km original range of the deep-cycle lead acid batteries of the electric wheelchair to 521 km.

Open-cathode PEMFC heat utilisation to enhance hydrogen supply rate of metal hydride canisters

In this paper, the hydrogen supply to an open-cathode PEM fuel cell (FC) by using metal hydride (MH) storage and thermal coupling between these two components are investigated theoretically. One of the challenges in using MH hydrogen storage canisters is their limited hydrogen supply rate as the hydrogen release from MH is an endothermic reaction. Therefore, in order to meet the required hydrogen supply rate, high amounts of MH should be employed that usually suggests storage of hydrogen to be higher than necessary for the application, adding to the size, weight and cost of the system. On the other hand, the exhaust heat (i.e. that is usually wasted if not utilised for this purpose) from open-cathode FCs is a low-grade heat. However, this heat can be transferred to MH canisters through convection to heat them up and increase their hydrogen release rate. A mathematical model is used to simulate the heat transfer between PEMFC exhaust heat and MH storage. This enables the prediction of the required MH for different FC power levels with and without heat supply to the MH storage. A 2.5-kW open-cathode FC is used to measure the exhaust air temperature at different output powers. It was found that in the absence of heat supply from the FC to the MH canisters, significantly higher number of MH canisters are required to achieve the required rate of hydrogen supply to the FC for sustained operation (specially at high power outputs). However, using the exhaust hot air from the FC to supply heat to the MH storage, can reduce the number of the MH canisters required by around 40% to 70% for power output levels ranging from 500 W to 2000 W.

Study of a thermal bridging approach using heat pipes for simultaneous fuel cell cooling and metal hydride hydrogen discharge rate enhancement

Low hydrogen discharge rate of Metal Hydride (MH) hydrogen canisters is a common challenge for this type of storage when used to supply hydrogen to Proton Exchange Membrane (PEM) fuel cells. The present paper investigates the use of fuel cell heat, transferred using heat pipes, to enhance the hydrogen release rate of MH canisters. Both the theoretical models and the experimental study on a 130-W PEM fuel cell supplied by an 800-sl MH canister (used as a case study), confirmed that ∼30% of the fuel cell cooling load is sufficient to maintained the temperature of the canister at ∼25 °C, required for the MH canister to supply hydrogen at 1.7 slpm (as demanded by the fuel cell for operation at 130 W). Using additional heat pipes (i.e. to remove the remaining ∼70% the fuel cell cooling load), the temperature of the fuel cell could be maintained at ∼60 °C. The study also confirmed that this thermal management system can deliver relatively uniform temperature distributions across the stack and the MH canister with less than 5 °C of temperature gradient across these components.

Passive Fuel Cell Heat Recovery Using Heat Pipes to Enhance Metal Hydride Canisters Hydrogen Discharge Rate: An Experimental Simulation

This paper reports on an experimental investigation of a passive thermal coupling arrangement between a Proton Exchange Membrane (PEM) fuel cell and a Metal Hydride (MH) hydrogen storage canister using heat pipes for enhancing the release rate of hydrogen. The performance of this arrangement was measured by inserting the evaporator sections of the heat pipes into an aluminum plate mimicking one out of five cooling plates of a 500-W fuel cell (that is a 100 W section of the stack). Thermal pads were attached on both sides of the plate to represent the fuel cell heat to be supplied to a 660-sl MH canister. The results showed that the operating temperature of the fuel cell can be maintained in the desired range of 60–80 °C. A complementary experimental study was also conducted on an 800-sl MH canister supplying hydrogen to a 130-W fuel cell stack (a slightly scaled-up setup compared to the first experiment). The study confirmed the findings of an earlier theoretical study by the authors that by supplying about 20% of the total cooling load of the stack to a MH canister, its maximum sustainable hydrogen supply rate increased by 70%, allowing for continuous operation of the stack at its rated power.

Mathematical modeling, numerical simulation and experimental comparison of the desorption process in a metal hydride hydrogen storage system

A two-dimensional axisymmetric model is developed to study the hydrogen desorption reaction and its subsequent discharge in a metal hydride canister. Experimental tests are performed on an in-house fabricated setup. An extensive study on the effects of the metal properties and boundary conditions on discharging performance is carried out through non-destructive testing (NDT). Results show that the desorption process is more effective if the activation energy for desorption (Ed) and the reaction enthalpy (ΔH) decrease, and when the desorption rate coefficient (Cd) and the external convection heat transfer coefficient when the bottle is being heated (h) increase. Furthermore, porosity (ε) can be useful for the design of hydrogen storage systems, with a trade-off between charge/discharge time and storage capacity. Numerical and experimental results are compared achieving a good agreement. These results can be used to select metal hydride materials and also for the future evaluation of metal hydride degradation.

Effect of metal hydride properties in hydrogen absorption through 2D-axisymmetric modeling and experimental testing in storage canisters

A two-dimensional axisymmetric model is developed to study the hydrogen absorption reaction and resultant mass and heat transport phenomena inside a metal hydride canister. The model is compared against published literature and experimental data. Experimental tests are performed on an in-house fabricated setup using different cooling scenarios. An extensive study on the effects of the metal properties on charging performance is carried out through non-destructive testing (NDT). Results show that the properties that most influence the charging performance are: absorption rate constant (Ca), activation energy (Ea) and thermal conductivity (km). A Higher porosity (ε) reduces charging time and amount of hydrogen stored while a higher cooling level produces a faster charging process. These results can be used to select metal hydride materials but also to estimate the metal hydride internal state and the process can be used for future evaluation of metal hydride degradation.

Development of a Portable Polymer Electrolyte Membrane Fuel Cell System Using Metal Hydride as the Hydrogen Storage Medium

This paper describes a Portable Polymer Electrolyte Membrane Fuel Cell (PEMFC) System developed at HySA Systems, UWC. The system has a rated maximum output power of 130 W at 240 VAC and 5 VDC USB output port. Hydrogen is supplied to the PEMFC using Metal Hydride (MH) on the basis of a multi-component AB2 – type hydrogen storage alloy (A=Ti,Zr; B=Mn,Fe,Cr,Ni; Ti:Zr=0.55:0.45). The stainless steel MH canister with external aluminium fins was developed in-house. The heat transfer performance was optimized by utilizing external fins and compacting thermal expanded graphite (TEG) with the MH powder to form pellets. The MH canister has a maximum hydrogen storage capacity of 90 NL H2. It is well-known that the endothermic desorption of H2 from MH results in the significant cooling, which decrease H2 supply flow rate. To overcome this problem and improve the dynamic performance, the MH canister was placed in front of the fuel cell exhaust to utilise the waste heat generated by PEMFC. By utilisation of the PEMFC waste heat in combination with external fins and MH / TEG compacts, the MH canister allowed for >40 minutes-long stable operation at the stack power of 130 W (225 W/kg(MH)) with the utilisation of >90% of the stored H2. Figure 1 illustrates the MH storage unit integrated with 200 W PEMFC stack, Figure 2 shows the rated power of the PEMFC and temperature of the MH canister at different loads connected to the system. Figure 1

Development of a Portable Polymer Electrolyte Membrane Fuel Cell System Using Metal Hydride as the Hydrogen Storage Medium

This paper describes the development of a Portable Polymer Electrolyte Membrane Fuel Cell / PEMFC system that was developed at HySA Systems Competence Centre. The system has a rated peak output power of 130W at 240Vac and 5Vdc USB output power. Hydrogen is supplied from Metal Hydride (MH) hydrogen storage canister which uses multi-component AB2 – type hydrogen storage hydride alloy. The in-house developed MH canister was made up of stainless steel tube with external aluminium fins and had a maximum hydrogen storage capacity of 90 NLH2. The improvement of H2 discharge dynamic performance of the MH bed, which is cooled down in the course of H2 desorption, was achieved by the placement of the MH canister in front of exhaust of air cooling system of the PEMFC stack. By the utilisation of the PEMFC waste heat, in combination with the external fins (increase of heat exchange area) and compacting the MH material with Thermal Expanded Graphite / TEG (improvement of the effective thermal conductivity in the MH bed), the MH canister allowed for >40 minutes-long stable operation at the stack power of 130 W (225 W/kg(MH)) with the utilisation of >90% of the stored H2.

An economic evaluation on the purification and storage of waste hydrogen for the use of fuel cell scooters

ABSTRACTSafe and reliable metal hydride canisters (MHCs) for the use of hydrogen storage at low pressure can be applied to supply small fuel cell vehicles or scooters with hydrogen fuel. However, greater cost-effectiveness of hydrogen gas is obviously necessary to the successful promotion of hydrogen fuel cell scooters in the market. In this study, we use the net present value (NPV) method to evaluate the feasibility of an investment project on the supply of purified hydrogen in a pulp company at Hualien, Taiwan. The purified hydrogen can be separated from waste hydrogen by using pressure swing adsorption (PSA) technology and then be stored in MHCs. Under some assumptions of improved parameters about hydrogen production cost and hydrogen gas price, the discounted payback period of hydrogen purification and storage project in our study can be less than 10 years and the unit cost of hydrogen gas can be close to the price of gasoline. Moreover, the unit cost of hydrogen gas in our study can be lower than the cost from other sources of hydrogen.

Evaluation of Electrical Load Following Capability of Fuel Cell System Fueled by High‐Purity Hydrogen

SUMMARYThis paper describes the electrical response in the load change in a fuel cell system fueled by high‐purity hydrogen. The purpose of this study is to use the fuel cell system to make up for the unstable electrical output of a photovoltaic system utilized as a renewable energy source. As an alternative method instead of a secondary battery, the fuel cell system, which is able to continuously generate power as long as fuel is supplied, is expected to provide better power with higher reliability and stability. To evaluate the load‐following capability of a polymer electrolyte fuel cell (PEFC) system, an experimental setup was constructed with a 200‐W PEFC stack (number of cells: 20; cell area: 20 cm2), which was supplied with hydrogen from a compressed hydrogen cylinder and a metal hydride canister. We measured the transient phenomena in the current and cell voltage when the PEFC stack was given step‐up current loads that changed in the range of 0 to 300 mA/cm2. It was found that PEFC systems with both hydrogen supply sources are able to respond with a time constant of 6.6 to 11.6 µs in the presence of an adequate oxygen supply and at a load below the PEFC rated power. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(4): 37–47, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22353

Experimental tests of an air-cooling hydrogen fuel cell hybrid electric scooter

A system integration of a novel proton exchange membrane fuel cell (PEMFC)-powered hybrid scooter was conducted to assess its performance. The fuel cell/lithium ion battery hybrid electric scooter system was composed of an air-cooled and self-humidified 2.3 kW PEMFC stack, a lithium ion battery, a low-pressure metal hydride canister set, a quick connector, a DC–DC converter, a hub motor, and an electronic control unit. PEMFCs have the benefit of a rapid start-up, low operating temperatures, and high power densities, making them ideal power sources for electric vehicles. Most recent fuel cell vehicle designs have used fuel cell hybrids architectures because of their enhanced fuel economy, superior performance at cold starts, ability to capture regenerative braking energy, and reduced system costs. Similarly, this study configured a lithium ion battery as the secondary energy source because of its rapid discharge capability. The PEMFC provided the scooter with a continuous electricity supply, and a 9.2 A h and 48.92–50.05 V lithium ion battery powered the scooter when a sudden burst of electric energy was required for stepping out, speeding up, or climbing. However, the hybrid system presented a unique challenge for the multiple energy sources to work together effectively. A modified ECE40 test and a USABC dynamic stress test were conducted to assess the performance of the hybrid scooter. Besides, in the dyno test, the maximum speed of the scooter was 53.2 km/h, and the distance between refueling was 63.5 km when the scooter's speed was fixed at 30 km/h. In the future, the main objectives are to extend the range, reduce the weight of the scooter, and increase the hydrogen use of the fuel cell.

Performance evaluation of a polymer electrolyte membrane fuel cell system for powering portable freezer

A polymer electrolyte membrane fuel cell (PEMFC) powered portable freezer has been developed. The PEMFC system is composed of an air-cooled fuel cell stack module with combined oxidant and coolant flow, a fuel supply subsystem with two metal hydride canisters, a power management subsystem with a DC–DC converter and a lead acid battery, and a control electronics subsystem. The vapor compression refrigeration cycle has been adopted for refrigerating. The control logic for fuel cell stack operation, cabinet temperature maintenance and fuel canister replacement has been designed for a stable system operation. To estimate PEMFC system performance, the stack power output, parasitic loss and battery charging power are measured for various external loads. The PEMFC system provides a rated power output of 200.5W at 13.4V with balance-of-plant (BOP) efficiency of 72%. The maximum system efficiency based on lower heating value (LHV) is 37% at 120.7W. The PEMFC powered freezer stably operates with the continuous replacement of hydrogen canisters, and the cabinet temperature drops to −21.8°C when the ambient temperature is 26.6°C.

System Modelling, Simulation and Feasibility Study for Seawater to Hydrogen Offshore Solar Harvesting System

Solar hydrogen harvesting system converts solar energy and stored them in the form of hydrogen gas instead of charges in batteries. Furthermore, oxygen released during the electrolysis process is a non-polluting element. This paper presents the feasibility study of solar hydrogen harvesting system using seawater instead of clean water to produce hydrogen. Besides, the system is proposed to operate on offshore to avoid deforestation. In this system, solar irradiance collected by the Photovoltaic (PV) panel is firstly used to pump the seawater into the distillation tank. The distillation process of seawater takes place with direct sunlight via evaporation. Clean water obtained will be directed into electrolysis chamber and process into hydrogen, which will be stored in metal hydride canister. The system model, overall process flow chart and total system efficiency had been studied and described. Results from the study showed that the total system efficiency is about 5%. From the efficiency, the feasibility of the system is studied, which shows a slow return of about 50 years. The finding could be premature, since the motivation by the PV technology where high efficient and low cost PV modules are possible to be produced.

Development of Proton Exchange Membrane Fuel Cell System for Portable Refrigerator

A proton exchange membrane (PEM) fuel cell system for powering a portable refrigerator is developed. The PEM fuel cell system consists of an air-cooled stack with combined oxidant and coolant flow, a hydrogen supply subsystem with two metal hydride canisters, a power management subsystem with a DC-DC converter and a rechargeable battery, and a control electronics subsystem. To analyze the performance of the PEM fuel cell system, the stack power output, the balance-of-plant (BOP) power consumption and the battery charging power are measured at various external loading conditions. The BOP system shows low efficiency of 20.7% under no-load condition, while it increases to 72.3% at 200.5 W system power output.