• Energy Research

Abstract This paper reports the numerical investigation of the effect of different phase change materials (PCMs) on the metal hydride (MH) behaviour in a reactor bed during the absorption process. The feasibility of integrating metal foams (MFs) into the phase change materials to improve the hydrogen storage performance of the system was also evaluated. A two-dimensional model for a LaNi5 hydride reactor equipped with different phase change materials has been developed. The selection of five different PCMs having a high latent heat of fusion and a range of melting temperatures were investigated. In addition, the effect of the mass and volume of the different PCMs on the hydrogen performance of the MH reactor was studied. It was found that LiNO3·3H2O PCM shown better performance than the other PCMs, its loading time is faster, and its mass within the reactor is enough to absorb the total heat generated from the MH during hydrogenation. Three different metals foam with three different porosities were integrated into the most suitable PCM with the appropriate dimension of a cylindrical reactor that shows the optimum performance. The obtained results indicated that the integration of the metal foams into the PCM show better heat transfer performance than the case of MH-PCM without metal foams. Two different configurations cylindrical and spherical MH reactors were investigated. The obtained results indicated that the two configurations have very similar behaviours. So, both configurations are good for the hydriding process within an MH reactor.

Metal hydride (MH), considered a promising hydrogen storage material, has received wide attention. As an efficient device for hydrogen energy utilization, a proton exchange membrane fuel cell (PEMFC) generates power and releases waste heat. MH tank can supply hydrogen for PEMFC, and the waste heat produced by PEMFC can be applied to heat the MH bed for dehydriding reaction. Thermal management between MH tank and PEMFC has been studied in this work. A lumped parameter model for the PEMFC-MH system has been developed and validated. The performance of the PEMFC-MH system has been predicted, the results show that it is feasible to use waste heat produced by PEMFC for heating the MH bed. The effect of the valve's opening degree on system performance has been investigated. The performance of the PEMFC-MH system with various output powers has been studied. The hydrogen supply rate from the MH bed to PEMFC can be adjusted based on different power requirements. The valve's opening degree can be considered an effective control measure in thermal management to improve the energy efficiency of the PEMFC-MH system.

Abstract Thermodynamic analyses for a hydriding-dehydriding cycle process of a hydrogen storage system are carried out. Assuming the mass flow rate and the mass source term are both constant, the analytical solutions for lumped temperature in the metal hydride hydrogen storage tank are obtained in the absorption, dormancy and desorption processes. The analytical solution is important to understand the hydriding-dehydriding process, which can be used as a benchmark to validate lumped/distributed parameter models for further study. A lumped parameter numerical model is developed on the Matlab/Simulink software platform. The numerical solutions of this model with constant source term coincide with the analytical solutions. Different analytical solutions are solved with various combinations of the hydrogen inflow/outflow temperature. The analytical solution in present work is compared with the reduced model in the reference, and shows more accurate than the reduced model. The variable source term is applied to the validated lumped parameter model. The results of parametric study show that the source term of metal hydride is roughly constant when the hydrogen storage capacity is not beyond about 90% of its limited capacity.

Thermal runaway (TR) of lithium-ion batteries has always been a topic of concern, and the safety of batteries is closely related to the operating temperature. An overheated battery can significantly impact the surrounding batteries, increasing the risk of fire and explosion. To improve the safety of battery modules and prevent TR, we focus on the characteristics of temperature distribution and thermal spread of battery modules under overheating conditions. The heat transfer characteristics of battery modules under different battery thermal management systems (BTMSs) are assessed. In addition, the effects of abnormal heat generation rate, abnormal heat generation location, and ambient temperature on the temperature distribution and thermal spread of battery modules are also studied. The results indicate that the BTMS consisting of flat heat pipes (FHPs) and bottom and side liquid cooling plates can effectively suppress thermal spread and improve the safety of the battery module.

Hydrogen purification is an important part of hydrogen energy utilization. This study aimed to perform hydrogen purification of multi-component gas (H2/CO2/CH4/CO/N2 = 0.79/0.17/0.021/0.012/0.007) by one-column vacuum pressure swing adsorption (VPSA) and pressure swing adsorption (PSA). AC5-KS was selected as the adsorbent for hydrogen purification due to its greater adsorption capacity compared to R2030. Furthermore, VPSA and PSA 10-step cycle models were established to simulate the hydrogen purification process using the Aspen Adsorption platform. The simulation results showed that the hydrogen purification performance of VPSA is better than that of PSA on AC5-KS adsorbent. The effects of feeding time and purging time on hydrogen purity and recovery were also discussed. Results showed that feeding time has a negative effect on hydrogen purity and a positive effect on hydrogen recovery, while purging time has a positive effect on hydrogen purity and a negative effect on hydrogen recovery. By using an artificial neural network (ANN), the relationship between the inputs (feeding time and purging time) and outputs (hydrogen purity and recovery) was established. Based on the ANN, the interior point method was applied to optimize hydrogen purification performance. Considering two optimization cases, the optimized feeding time and purging time were obtained. The optimization results showed that the maximum hydrogen recovery reached 88.65% when the feeding time was 223 s and the purging time was 96 s. The maximum hydrogen purity reached 99.33% when the feeding time was 100 s and the purging time was 45 s.

Currently, most of the vehicles make use of fossil fuels for operations, resulting in one of the largest sources of carbon dioxide emissions. The need to cut our dependency on these fossil fuels has led to an increased use of renewable energy sources (RESs) for mobility purposes. A technical and economic analysis of a one-stop charging station for battery electric vehicles (BEV) and fuel cell electric vehicles (FCEV) is investigated in this paper. The hybrid optimization model for electric renewables (HOMER) software and the heavy-duty refueling station analysis model (HDRSAM) are used to conduct the case study for a one-stop charging station at Technical University of Denmark (DTU)-Risø campus. Using HOMER, a total of 42 charging station scenarios are analyzed by considering two systems (a grid-connected system and an off-grid connected system). For each system three different charging station designs (design A-hydrogen load; design B-an electrical load, and design C-an integrated system consisting of both hydrogen and electrical load) are set up for analysis. Furthermore, seven potential wind turbines with different capacity are selected from HOMER database for each system. Using HDRSAM, a total 18 scenarios are analyzed with variation in hydrogen delivery option, production volume, hydrogen dispensing option and hydrogen dispensing option. The optimal solution from HOMER for a lifespan of twenty-five years is integrated into design C with the grid-connected system whose cost was $986,065. For HDRSAM, the optimal solution design consists of tube trailer as hydrogen delivery with cascade dispensing option at 350 bar together with high production volume and the cost of the system was $452,148. The results from the two simulation tools are integrated and the overall cost of the one-stop charging station is achieved which was $2,833,465. The analysis demonstrated that the one-stop charging station with a grid connection is able to fulfil the charging demand cost-effectively and environmentally friendly for an integrated energy system with RESs in the investigated locations.

Abstract The heat transfer analysis in the filling process of compressed on-board hydrogen storage tank has been the focus of hydrogen storage research. The initial conditions, mass flow rate and heat transfer coefficient have certain influence on the hydrogen filling performance. In this paper, the effects of mass flow rate and heat transfer coefficient on hydrogen filling performance are mainly studied. A thermodynamic model of the compressed hydrogen storage tank was established by Matlab/Simulink. This 0D model is utilized to predict the hydrogen temperature, hydrogen pressure, tank wall temperature and SOC (State of Charge) during filling process. Comparing the simulated results with the experimental data, the practicability of the model can be verified. The simulated results have certain meaning for improving the hydrogenation parameters in real filling process. And the model has a great significance to the study of hydrogen filling and purification.

Abstract Based on the analytical solution of a lumped parameter model for fast filling of hydrogen storage tank, the final hydrogen temperature under final pressures of 35 MPa and 70 MPa are both fitted very well with the reference data through curve and surface fittings. The results show effects of ambient temperature, initial pressure and filling rate on the final hydrogen temperature. Reducing the rate of hydrogen filling, reducing the ambient temperature or increasing the initial pressure can effectively reduce the final hydrogen temperature in the tank. We suppose this study not only helps to know the relationship between the final hydrogen temperature and refueling condition, but also lets us learn how to control refueling processes.