Monitoring and control of a hydrogen production and storage system consisting of water electrolysis and metal hydrides

Renewable energy sources such as wind turbines and solar photovoltaic are energy sources that cannot generate continuous electric power. The seasonal storage of solar or wind energy in the form of hydrogen can provide the basis for a completely renewable energy system. In this way, water electrolysis is a convenient method for converting electrical energy into a chemical form. The power required for hydrogen generation can be supplied through a photovoltaic array. Hydrogen can be stored as metal hydrides and can be converted back into electricity using a fuel cell. The elements of these systems, i.e. the photovoltaic array, electrolyzer, fuel cell and hydrogen storage system in the form of metal hydrides, need a control and monitoring system for optimal operation. This work has been performed within a Research and Development contract on Hydrogen Production granted by Solar Iniciativas Tecnológicas, S.L. (SITEC), to the Politechnic University of Valencia and to the AIJU, and deals with the development of a system to control and monitor the operation parameters of an electrolyzer and a metal hydride storage system that allow to get a continuous production of hydrogen.     

Life cycle assessment of an alkaline fuel cell CHP system

A life cycle assessment (LCA) of an alkaline fuel cell based domestic combined heat and power (CHP) system is presented. Literature on non-noble, monopolar cell design and stack construction was reviewed, and used to produce a life cycle inventory for the construction of a 1 kW stack. Inventories for the ancillary components of other commercial fuel cell products were consulted, and combined with information on the fuel processing requirements of alkaline cells to suggest a hypothetical balance of plant that would be required to produce AC electricity and domestic grade heat from natural gas and air.     

Ag and Ag–Mn nanowire catalysts for alkaline fuel cells

Low loadings of Ag and Ag–Mn nanowire catalysts were applied to the surface of a CNT-base electrode. The catalyzed electrodes had a 60 mV larger onset potential and promoted the ORR via the direct 4 electron pathway. The Ag/CNT, Ag–Mn/CNT, and CNT samples produced a Tafel slope of about 70 mV/decade which confirmed the ORR activation was limited by the migration of oxygen molecules to active surface sites. The catalytic performance of the Ag and Ag–Mn nanowires was also comparable to that of a bulk catalyst but at a much lower loading. Electrochemical test results showed that the Ag and Ag–Mn catalysts exhibited similar performance. The Ag–Mn nanowire catalysts were synthesized using a unique electroless deposition procedure to co-deposit Ag and Mn. ICP confirmed that 2 to 9 at% Mn was present in the nanowires. XPS and XRD analysis showed that the Ag–Mn nanowires were composed of Mn in solid solution with Ag and a thin surface layer containing MnO and MnO₂. The Ag–Mn nanowires were expected to be the most active. The equivalent performance between Ag and Ag–Mn samples was attributed to the presence of inactive MnO and low concentrations of MnO₂ in the nanowires. Although MnO₂ is known to be active towards the ORR, the dominant Mn species in the nanowires was MnO.     

Pd nanoparticles supported on PDDA-functionalized carbon black with enhanced ORR activity in alkaline medium

Pd/C catalyst with small particle size, high dispersion and high wt.% of metal was in situ synthesized by a simple aqueous phase reduction method. Poly(diallyldimethylammonium chloride) PDDA-functionalized carbon black was used as a support material for the in situ deposition of Pd nanoparticles by means of electrostatic attraction. The catalysts were characterized by transmission electron microscopy, X-ray diffractometry and X-ray photoelectron spectroscopy, cyclic voltammetry and rotating disc electrode test. The results indicated that Pd nanoparticles with an average size of 2.09 nm were uniformly dispersed onto the carbon black with a metal weight percentage of ∼30 wt.%. The prepared Pd/C catalyst has showed remarkably larger electrochemical surface area and higher and more stable ORR activity as compared to commercial Pd/C catalyst and commercial Pt/C catalyst in alkaline media, which was believed to be a promising alternative to Pt-based catalyst used in alkaline fuel cell.     

江苏某低品位蓝晶石矿分选试验

对江苏某低品位难选蓝晶石矿采用脱泥-磁选-碱性介质浮选工艺流程进行了分选试验研究,探索了磨矿、脱泥、磁选及浮选的适宜工艺条件,以此为基础拟定的磨矿-脱泥-强磁选-1粗4精浮选闭路流程处理该矿石,最终获得了Al₂O₃品位为55.13%的蓝晶石精矿。     

Effects of property variation and ideal solution assumption on the calculation of the limiting current density condition of alkaline fuel cells

A computational study of the electrochemical hydrodynamic process in an alkaline fuel cell was conducted. The computation relaxed the ideal solution assumption, accounted for thermodynamic solubility of the reactants, and allowed for property variations due to temperature and concentration effects. The results showed that the ideal solution assumption is not adequate for calculation of the transport process of the concentrated electrolyte considered, 7 M. The ideal solution formulation resulted in a lower limiting current density condition by about 50% than that predicted by the non-ideal solution formulation. The study also showed that the thermal condition is important to the calculation of the limiting current density condition. The calculated limiting current density increased by about 30% when the boundary condition was changed from isothermal to adiabatic. The computational results suggest that maintaining a uniform KOH concentration in the electrolyte (for example, at design point of 7 M) be an effective measure to increase the limiting current density condition.     

In-situ measurement of ethanol tolerance in an operating fuel cell

Ethanol is seen as an attractive option as a fuel for direct ethanol fuel cells and as a source for on-demand production of hydrogen in portable applications. While the effect of ethanol on in-situ electrode behavior has been studied previously, these efforts have mostly been limited to qualitative analysis. In alkaline fuel cells, several cathode catalysts, including Pt, Cu triazole, and Ag can be used. Here, we apply a methodology using a microfluidic fuel cell to analyze in-situ the performance of these cathodes as well as Pt anodes in the presence of ethanol and acetic acid, a common side product from ethanol oxidation. For a given concentration of ethanol (or acetic acid), the best cathode catalyst can be determined and the kinetic losses due to the presence of ethanol (or acetic acid) can be quantified. These experiments also yield information about power density losses from the presence of contaminants such as ethanol or acetic acid in an alkaline fuel cell. The methodology demonstrated in these experiments will enable in-situ screening of new cathodes with respect to contaminant tolerance and determining optimal operational conditions for alkaline ethanol fuel cells.     

MEA for alkaline direct ethanol fuel cell with alkali doped PBI membrane and non-platinum electrodes

This paper reports on the fabrication of MEA for alkaline direct ethanol fuel cell (ADEFC). The MEA was fabricated using non-platinum electrocatalysts and a membrane of alkali doped polybenzimidazole (PBI). The employed oxygen reduction catalyst was prepared by pyrolysis of 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine cobalt(II) supported on XC72 carbon. This catalyst is tolerant to ethanol. Electrocatalyst at the anode was RuV alloy supported on XC72 carbon. It was synthesized by reduction of respective salts at elevated temperature. Single cell power density of 100 mW cm⁻² at U = 0.4 V was achieved at 80 °C using air at ambient pressure and 3 M KOH + 2 M EtOH anode feed. The developed MEA is considered viable for use in emergency power supply units and in power sources for portable electronic equipment.     

Modeling,control and simulation of a photovoltaic /hydrogen/ supercapacitor hybrid power generation system for grid-connected applications

Hybrid renewable energy systems (HRES) should be designed appropriately with an adequate combination of different renewable sources and various energy storage methods to overcome the problem of intermittency of renewable energy resources. Focusing on the inevitable impact on the grid caused by strong randomicity and apparent intermittency of photovoltaic (PV) generation system, modeling and control strategy of pure green and grid-friendly hybrid power generation system based on hydrogen energy storage and supercapacitor (SC) is proposed in this paper. Aiming at smoothing grid-connected power fluctuations of PV and meeting load demand, the alkaline electrolyzer (AE) and proton exchange membrane fuel cell (PEMFC) and SC are connected to DC bus of photovoltaic grid-connected generation system. Through coordinated control and power management of PV, AE, PEMFC and SC, hybrid power generation system friendliness and active grid-connection are realized. The validity and correctness of modeling and control strategies referred in this paper are verified through simulation results based on PSCAD/EMTDC software platform.     

A new analysis of two phase flow on hydrogen production from water electrolysis

It is clear that the entire world have to research, develop, demonstrate and plan for alternative energy systems for shorter term and also longer term. As a clean energy carrier, hydrogen has become increasingly important. It owes its prestige to the increase within the energy costs as a result of the equivocalness in the future availability. Two phase flow and hydrogen gas flow dynamics effect on performance of water electrolysis. Hydrogen bubbles are recognized to influence energy and mass transfer in gas-evolving electrodes. The movement of hydrogen bubbles on the electrodes in alkaline electrolysis is known to affect the reaction efficiency. Within the scope of this research, a physical modeling for the alkaline electrolysis is determined and the studies about the two-phase flow model are carried out for this model. Internal and external forces acting on the resulting bubbles are also determined. In this research, the analytical solution of two-phase flow analysis of hydrogen in the electrolysis is analyzed.