1,721,373 research outputs found
Thermodynamic analysis of PEM fuel cell units fuelled by humid ethanol processed within innovative membrane reactors
No full textInvestigation of a 5 kW micro-CHP PEM fuel cell based system integrated with membrane reactor under diverse EU natural gas quality
Full text linkThis work investigates the techno-economic assessment of a 5 kW micro-cogeneration system based on membrane reactor and PEM fuel cell flexible towards different natural gas qualities. The flexibility of the system is evaluated for four typical natural gas compositions from different European countries featuring an average condition and three extreme cases. The optimal system design conditions are determined together with performance variation as function of NG composition and load. The sweep gas and vacuum pump are explored as options to reduce the membrane surface area, outlining the efficiency advantages of the former (41.21% vs. 39.24%). Simulations at partial load show that the electric efficiency increases until 60â70% of the load in both cases, then quickly drops. Micro-CHP performance are used as input to determine the specific system target cost (â¬/kW) based on a yearly energy and economic analysis. The first reveals that the primary energy savings is always positive outlining the environmental benefit of FERRET system application respect to the reference separated production. The target cost considering its application to two dwellings is around 2000 â¬/kW
Hydrogen production from ethanol steam reforming: energy efficiency analysis of traditional and membrane processes
No full textThe ethanol steam reforming reaction has been considered for producing pure hydrogen to be used for feeding a PEM fuel cell of power 4 kW. As an innovative technology, Pd-Ag thin wall membranes are proposed for building membrane reactors: accordingly, the energy efficiency analysis of the processes producing hydrogen from the ethanol steam reforming has been carried out and, particularly, the comparison among a traditional process and different membrane processes is reported.
The traditional process studied consists of an ethanol reformer followed by two water gas shift reactors operating at high and low temperature, respectively: the final hydrogen purification is carried out by a preferential oxidizer in order to reduce the CO concentration below 10 ppm before feeding the PEM fuel cell.
Then two membrane processes using Pd-Ag tubes and operating with a feed H2O/ethanol have been considered. The first one uses a traditional ethanol reformer and a Pd-Ag membrane reactor where the water gas shift reaction and the hydrogen separation take simultaneously place: the pure hydrogen recovered in the permeate side of the membrane reactor is sent to the PEM anode. In the second membrane process, one Pd-Ag membrane reactor performs both the ethanol steam reforming and the hydrogen separation: also in this case, the pure hydrogen recovered in the permeate side of the membrane reactor is directly sent to the PEM anode.
The analysis showed that the highest values of the energy efficiency have been attained by the process using one membrane reformer: this process has a net electric efficiency higher than the traditional one by 10 %.
Finally, an efficiency field-to-wheel analysis has been also carried out: a conventional application of the pure bio-ethanol in a reciprocating engine has been compared to a membrane system processing humid bio-ethanol and fuelling a PEM driven electrical engine. As a result, the membrane process presents a higher energy efficiency up to 50% and mainly as a consequence of the direct use of water-ethanol mixtures: in fact, in this case the distillation and dehydration of the bio-ethanol is avoided thus increasing the energy efficiency
Performances of a micro-CHP system fed with bio-ethanol based on fluidized bed membrane reactor and PEM fuel cells
No full textA micro-CHP system, rated at 5 kWel, based on membrane reactor and PEM fuel cells is simulated in the present work. Bio-ethanol is used as feedstock and converted into hydrogen inside the innovative fuel processor: a membrane-assisted fluidized-bed auto-thermal reforming reactor. The pure hydrogen separated by the Pd-based membranes inside the reactor is fed to a low-temperature PEM fuel cells stack. Heat is recovered to produce low temperature water. Two different reactor configurations are investigated: the first one adopts a sweep-gas stream, the second one a vacuum pump. Parametric analysis is performed for both cases evaluating the impact of feed composition (water-to-ethanol ratio) and operative conditions of the membrane reactor (temperature and feed/permeate pressures) on performances and design parameters. Optimal conditions are defined as a trade-off between efficiency and Pd-membranes area. For the sweep-gas layout, net electric efficiency higher than 40% can be achieved for a wide range of operative conditions, but large Pd-membranes area is required (≈0.4 m2); for the vacuum pump layout efficiency is lower (down to 39%), but Pd-membranes area is lower too (≈0.2 m2). Future work is the economic evaluation of the system for off-grid installations
Co-production of Hydrogen and Electricity from Autothermal Reforming of Natural Gas by means of Pd-Ag Membranes
No full textAbstractIn this paper, the use of two Water Gas Shift (WGS) Hydrogen Separator Membrane Reactors (HSMRs) is proposed downstream of a natural gas Autothermal Reformer (ATR), for hydrogen and electricity co-production with low carbon dioxide emissions. Starting from an advanced ATR plant based on state-of-the-art technologies with carbon capture, a novel configuration is proposed. Application of HSMRs allows a significant layout simplification and the reduction of the number of components.Hydrogen separation by means of membrane reactors allows carbon capture higher than 99% compared to 87% of the reference case. Simulation results show that the membrane based power plant achieves higher equivalent fuel conversion efficiency even with a significant amount of electricity produced. Moreover, the innovative solution allows to produce electricity and hydrogen at different ratio without affecting the overall performances
An innovative hybrid combined cycle using MCFCs for the application to CO2 capture
No full textEFC09-1711
PEM fuel cell stack protection from CO poisoning in a m-CHP system with membrane reformer
No full textComparison of different physical models for PV power output prediction
Full text linkThe electricity produced from renewable energy, in particular from wind and photovoltaic plants, has seen exponential rise in the last decade. Consequently, the prediction of power produced from these plants is fundamental for the reliability, safety and stability of the grid. This paper compares three physical models describing the PV cell (corresponding to three-, four- and five-parameter equivalent electric circuit) and two thermal models for the cell temperature estimation (NOCT and Sandia). The models were calibrated and tested towards ten monocrystalline and eight polycrystalline modules installed at SolarTechLab at Politecnico di Milano. The hourly error of the forecasted power output is usually lower than 15Wh, while NMAE% and WMAE% are in the range of 0.5% and 10%. Low errors, calculated with actual weather conditions, suggest that the implemented models are accurate, but they cannot be directly compared with other approaches which adopt weather forecasts. Results show that there is no clear advantage of using complex models, but the data used for the model calibration mostly affect the model accuracy. It was found that forecasted power output are more accurate using experimental data and Sandia's thermal model in monocrystalline cells type, while for the polycrystalline the data from the manufacturer and NOCT have lower errors
Membrane Reformer PEMFC Cogeneration Systems for Residential Applications - Part B: Techno-Economic
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