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Abstract: In the last decade, production of biogas from biomass degradation has attracted the attention of several research groups. The interest on this hydrogen source is focused on the potential use of this gas as raw material to supply high temperature fuel cells (HTFC). This paper reports a wide research investigation carried out at CNR-ITAE on biogas reforming processes (steam reforming, autothermal reforming and partial oxidation). A mathematical model was developed, in Aspen Plus, and an experimental validation was made in order to confirm model results. Simulations were performed to determine the reformed gas composition and the system energy balance as a function of process temperature and pressure. The value of Gas Hour Space Velocity (GHSV) was selected for calculating compositions at full equilibrium, as it is expected in operative large scale plant. To obtain a realistic evaluation of the reforming processes efficiency, the energy balance for each examined process was developed as available energy of outlet syngas on inlet required energy ratio. The comparison between values of efficiency process gives useful indication about their reliability to be integrate with fuel cell systems. [Copyright &y& Elsevier]

Abstract: In many visions and roadmaps, there is a broad agreement that fuel cells – both for stationary and mobile applications – are the key technology to allow the development of a hydrogen infrastructure. Furthermore, this development is generally thought to be based on a gradual, decentralised evolution. Nevertheless, in this paper it is argued that, taking into account the entire hydrogen chain (production, transport, storage, distribution and end-use), this decentralised fuel-cell based philosophy shows some serious flaws. Therefore, a new hydrogen-transition approach was pushed forward: mixing in of hydrogen into the natural-gas bulk. Using Flanders – the Northern part of Belgium – as a case study, the development of a transitory hydrogen infrastructure has been studied, taking into account the entire hydrogen chain and its dynamics, from production to end use. In a next step, this transition is being quantified. An optimisation model has been developed using Matlab and the commercial solvers GAMS and CPLEX. Following a mixed-integer linear-programming approach, this model is able to determine the economically optimal hydrogen-production mix and operational behaviour of each hydrogen-production plant separately. The model then allows gaining valuable insights in the importance of storage and the influence of fuel prices and carbon taxes with regard to the development of an early hydrogen economy. [Copyright &y& Elsevier]

Abstract: This paper employs societal lifetime cost for evaluating hydrogen fuel cell vehicles (FCVs) from a societal welfare perspective as compared to conventional gasoline vehicles. We employ a learning-curve model for fuel-cell system cost estimates over time. The delivered hydrogen fuel cost is estimated using the UC Davis SSCHISM hydrogen supply pathway model, and most vehicle costs are estimated using the Advanced Vehicle Cost and Energy-Use Model (AVCEM). To estimate external costs, we use AVCEM and the Lifecycle Emissions Model (LEM). We examine hydrogen transition costs for a range of market penetration rates, externality evaluations, technology assumptions, and oil prices. Our results show that although the cost difference between FCVs and gasoline vehicles is initially very large, FCVs eventually become lifetime cost competitive with gasoline vehicles as their production volume increases, even without accounting for externalities. High valuation of externalities and high oil price could reduce the buy-down cost (the cumulative investment needed to bring hydrogen FCVs to lifetime cost parity with gasoline vehicles) by $10 billion relative to our reference case. [ABSTRACT FROM AUTHOR]

Abstract: A simple and fast empirical design model for a 5kW 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. [Copyright &y& Elsevier]

Abstract: The objective of this paper is to mathematically model a stand-alone renewable power system, referred to as “Photovoltaic–Fuel Cell (PVFC) hybrid system”, which maximizes the use of a renewable energy source. It comprises a photovoltaic generator (PV), a water electrolyzer, a hydrogen tank, and a proton exchange membrane (PEM) fuel cell generator. A multi-domain simulation platform Simplorer is employed to model the PVFC hybrid systems. Electrical power from the PV generator meets the user loads when there is sufficient solar radiation. The excess power from the PV generator is then used for water electrolysis to produce hydrogen. The fuel cell generator works as a backup generator to supplement the load demands when the PV energy is deficient during a period of low solar radiation, which keeps the system''s reliability at the same level as for the conventional system. Case studies using the present model have shown that the present hybrid system has successfully tracked the daily power consumption in a typical family. It also verifies the effectiveness of the proposed management approach for operation of a stand-alone hybrid system, which is essential for determining a control strategy to ensure efficient and reliable operation of each part of the hybrid system. The present model scheme can be helpful in the design and performance analysis of a complex hybrid-power system prior to practical realization. [Copyright &y& Elsevier]