Adaptive real-time optimal energy management strategy based on equivalent factors optimization for hybrid fuel cell system

Fuel cell, a new kind of energy supply equipment, has several advantages such as high efficiency, low noise, and no emission. Proton exchange membrane fuel cell (PEMFC) is considered to have the potential to take the place of the conventional engine on unmanned underwater vehicle (UUV). Besides the power sources in the hybrid power system, the energy management system (EMS) is crucial to operating performance. In this paper, an on-line adaptive equivalent hydrogen consumption minimization strategy (ECMS) is proposed to solve the problem of prior knowledge demand and poor adaptability of current energy management algorithms. In this presented method, a battery state of charge (SOC) constituted penalty term is designed to calculate the equivalent factor (EF), and then the equivalent factor obtained by optimization is substituted into the original objective equation to realize the real-time energy regulation. In this paper, a typical UUV load curve is used to verify the control effect under different working conditions, and the performance is compared with three conventional algorithms’. Simulation results show that the hydrogen consumption of proposed algorithm is close to the optimal solution obtained in offline environment, and it is reduced by more than 3.79% compared with the traditional online methods.     

One-pot synthesis of Pt/CeO2/C catalyst for improving the ORR activity and durability of PEMFC

Oxygen reduction reaction (ORR) activity and durability of Pt catalysts should be both valued for successful commercialization of proton exchange membrane fuel cells (PEMFCs). We offer a facile one-pot synthesis method to prepare Pt/CeO₂/C composite catalysts. CeO₂ nanoparticles, with high Ce³⁺ concentration ranging from 30.9% to 50.6%, offers the very defective surface where Pt nanoparticles preferentially nuclear and growth. The Pt nanoparticles are observed sitting on the CeO₂ surface, increasing the PtCeO₂ interface. The high concentration of oxygen vacancies on CeO₂ surface and large PtCeO₂ interface lead to the strong PtCeO₂ interaction, effectively improving the ORR activity and durability. The mass activity is increased by up to 50%, from 36.44 mA mg^?1 of Pt/C to 52.09 mA mg^?1 of Pt/CeO₂/C containing 20 wt.% CeO₂. Pt/CeO₂/C composite catalysts containing 10–30 wt.% CeO₂ loss about 80% electrochemical surface area after 10,000 cycles, which is a fivefold enhancement in durability, compared to Pt/C losing 79% electrochemical surface area after 2000 cycles.     

Development of a fast empirical design model for PEM stacks

A simple and fast empirical design model for a 5 kW proton exchange membrane (PEM) stack is presented in this paper. The performance analysis of the PEM stack operating on a membrane humidifying method is made through a series of experiments, including current–voltage–power characteristics, uniformity of cell unit voltages, gas pressure impact and air flux impact. Based on the above analysis, an empirical predicted model for the PEM stack has been developed by the combination of mechanistic and empirical modeling approaches to characterize and predict the voltage–current characteristics without examining in depth all physical/chemical phenomena. The good agreement between the predicted and experimental results covering a range of optimal operating conditions shows that the proposed model provides an accurate representation of the behavior for the PEM stack.     

Osmium–ruthenium carbonyl clusters as methanol tolerant electrocatalysts for oxygen reduction

This work presents the synthesis and the structural and electrochemical characterization of novel mixed Os_xRu_y(CO)_n electrocatalysts for oxygen reduction in 0.5 mol L⁻¹ H₂SO₄; their monometallic Os_x(CO)_n and Ru_y(CO)_n counterparts were synthesized as well, for comparison purposes. The catalysts were obtained by thermolysis of Ru₃(CO)₁₂ and Os₃(CO)₁₂ (either alone or mixed) in three organic solvents: 1,2-dichlorobenzene (b.p. 178–180 °C), n-nonane (b.p. 150–151 °C) and o-xylene (b.p. 143–145 °C), under reflux conditions. The products were characterized by FT-IR spectroscopy and scanning electronic microscopy, and their chemical composition obtained by energy-dispersive X-ray spectroscopy. The electrocatalytic activity of the new materials was evaluated by room temperature RDE measurements, using the cyclic and linear sweep voltammetry techniques; all of them are methanol tolerant ORR catalysts, however, the bimetallic clusters, in general, show more favorable characteristics to perform this reaction than their monometallic analogues. On this basis, the novel catalysts can be considered as potential candidates to be used as cathodes in PEMFCs and DMFCs.     

Cobalt oxyphosphide as oxygen reduction electrocatalyst in proton exchange membrane fuel cell

The cobalt oxyphosphides supported on carbon black were prepared using incipient wetness method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The possibility of their application as the electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC) was investigated and the electrocatalytic activities were evaluated by the electrochemical measurements and single cell test, respectively. The electrocatalyst presents attractive catalytic activity towards ORR and good stability in acid media and exhibits an onset potential for oxygen reduction as high as 0.69 V (RHE) in H₂SO₄ solution. The maximum power density obtained in a H₂/O₂ PEMFC is 57 mW cm⁻² with Co₄P₂O₉/C loading of 1.13 mg cm⁻². No significant performance degradation is observed over 50 h of continuous fuel cell operation. The combination of heteroatom P with nanostructured oxides with high stability, excellent functionality and low cost which are prerequisites for large-scale applications, probably provide a new solution for the critical challenge of finding effective cathode materials for PEMFC.     

Development of a proton exchange membrane fuel cell cogeneration system

A proton exchange membrane fuel cell (PEMFC) cogeneration system that provides high-quality electricity and hot water has been developed. A specially designed thermal management system together with a microcontroller embedded with appropriate control algorithm is integrated into a PEM fuel cell system. The thermal management system does not only control the fuel cell operation temperature but also recover the heat dissipated by FC stack. The dynamic behaviors of thermal and electrical characteristics are presented to verify the stability of the fuel cell cogeneration system. In addition, the reliability of the fuel cell cogeneration system is proved by one-day demonstration that deals with the daily power demand in a typical family. Finally, the effects of external loads on the efficiencies of the fuel cell cogeneration system are examined. Results reveal that the maximum system efficiency was as high as 81% when combining heat and power.     

Multivariable robust control of a proton exchange membrane fuel cell system

This paper applies multivariable robust control strategies to a proton exchange membrane fuel cell (PEMFC) system. From the system point of view, a PEMFC can be modeled as a two-input-two-output system, where the inputs are air and hydrogen flow rates and the outputs are cell voltage and current. By fixing the output resistance, we aimed to control the cell voltage output by regulating the air and hydrogen flow rates. Due to the nonlinear characteristics of this system, multivariable robust controllers were designed to provide robust performance and to reduce the hydrogen consumption of this system. The study was carried out in three parts. Firstly, the PEMFC system was modeled as multivariable transfer function matrices using identification techniques, with the un-modeled dynamics treated as system uncertainties and disturbances. Secondly, robust control algorithms were utilized to design multivariable H_∞ controllers to deal with system uncertainty and performance requirements. Finally, the designed robust controllers were implemented to control the air and hydrogen flow rates. From the experimental results, multivariable robust control is shown to provide steady output responses and significantly reduce hydrogen consumption.     

A novel approach on the determination of the minimal operating efficiency of a PEM fuel cell

In this article, a novel mathematical approach is proposed to determine the minimal proton exchange membrane fuel cell efficiency below which it is not recommended to operate the fuel cell. The objective of this proposal is to minimize the annual fuel cost and the electricity cost of a proton exchange membrane (PEM) fuel cell since both terms are efficiency dependent. A new concept developed in this article might be used as a valuable mathematical tool to determine the minimal efficiency required to operate a fuel cell in a reasonable fashion in order to make the fuel cell system technically and economically feasible. Two dimensionless mathematical criteria J₁ and J₂ were proposed for the annual fuel cost and electricity cost, respectively. A minimum fuel cell efficiency of was obtained with J₁ and J₂ values of 2.7 and 0.026, respectively.     

An overview: Current progress on hydrogen fuel cell vehicles

The harmful consequences of pollutants emitted by conventional fuel cars have prompted vehicle manufacturers to shift towards alternative energy sources. Currently, fuel cells (FCs) are commonly regarded as highly efficient and non-polluting power sources capable of delivering far greater energy densities and energy efficiency than conventional technologies. Proton exchange membrane fuel cells (PEMFC) are viewed as promising in transportation sectors because of their ability to start at cold temperatures and minimal emissions. PEMFC is an electrochemical device that converts hydrogen and oxidants into electricity, water, and heat at various temperatures. The pros and cons of the technology are discussed in this article. Various fuel cell types and their applications in the portable, automobile, and stationary sectors are discussed. Additionally, recent issues associated with existing fuel cell technology in the automobile sector are reviewed.