1,721,042 research outputs found
Renewable Energy Storage System via coal hydrogasification with co-production of electricity and synthetic natural gas
No full textDesigning and analyzing an electric energy storage system based on reversible solid oxide cells
No full textThe Reversible Solid Oxide Cell (ReSOC), operating under electrolysis and fuel cell modes, is a promising
technology that, thanks to high efficiency and fuel flexibility, can be applied in the development of Electric
Energy Storage (EES) systems.
Several critical issues are required to be addressed, which are specific to ReSOC, such as oxidant electrode
performance and reversibility, set of materials, cell/stack design and operating parameters suitable for reversible
operation. Moreover, the optimal system design, to demonstrate the feasibility of the technology as well as the
Balance of Plant (BoP) components at high operating temperatures, are also challenging factors.
Therefore, the objective of this work is to propose an HEES (Hydrogen-based Electric Energy Storage) system
for distributed scale energy storage applications (100–200 kW) by taking into account some of these challenging
issues. The proposed system consists of (i) the BoP section needed for the energy storage, (ii) the ReSOC module
operating in reversible mode, (iii) the BoP section needed for the energy production.
In order to guarantee a competitive roundtrip efficiency, the design of the solid oxide cell unit and of the
supporting auxiliary systems (BoP components) has been performed without external heat sources for the
heating of feeding streams and for the thermal requirements of the ReSOC during its operation in the electrolysis
mode.
The study has been carried out by developing a steady-state thermo-electrochemical model that has been built
with a modular architecture. The model, validated by means of experimental data, has been used to assist the
system designing and the thermal management optimization to ensure high performances from electric and
thermal points of view.
Results highlight that the proposed system is able to store and use the renewable energy with a roundtrip
efficiency of 60%. Moreover, thanks to the optimized thermal integration, additional heat is available for cogeneration
purpose, with a cogeneration efficiency of 91%
Performance of a polymer electrolyte membrane fuel cell system fueled with hydrogen generated by a fuel processor
No full textCombined hydrogen, heat and electricity generation via biogas reforming: Energy and economic assessments
No full textPolygeneration systems, designed for providing multiple energy services like hydrogen, heat and electricity, represent a possible solution for the transition to sustainable low-carbon energy systems, thanks to a substantial increase in the overall efficiency. A further step to reach zero-carbon energy systems can be done by using renewables as primary sources.In this study a biogas-based polygeneration system for the combined hydrogen, heat and electricity production is designed and analyzed from energy and economic points of view.The system consists of four sections: a biogas processing unit consisting in an autothermal reactor and a water gas shift reactor, an SOFC power unit, a hydrogen separation unit and a hydrogen compression/storage unit. The syngas generated in the autothermal reforming reactor is split in two fluxes: the first one is sent to the SOFC power unit for generating electricity and heat, the second one is sent to the water gas shift reactor to increase the hydrogen content. The hydrogen rich gas exiting the shifter, purified in the hydrogen separation unit (hydrogen quality is equal to 99.995%), is then compressed up to 820 bars and stored.The system behavior and the energy performances have been investigated by using the numerical simulation based on thermo-electrochemical models. Four operating conditions, related to different SOFC loads (from 30% to 100%), have been analyzed. The evaluated overall efficiencies range from 68.5% to 72.3% and the energy saving, calculated with respect to the separate production of hydrogen, heat and electricity, ranges from about 8% to 26%.The economic assessment, carried out by estimating the total capital investment and the plant profitability, has been performed by analyzing different management strategies (Base Load, Peaker, Ancillary Service and Mobility) and accounting for different technological development levels and market scenarios. Results show that the hydrogen production is the main contributor to the system economic sustainability thanks to the highest prices of hydrogen with respect to the electricity ones. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
SOFC and MCFC system level modeling for hybrid plants performance prediction
No full textIn this paper a generalized model, based on system-level approach, for predicting the High Temperature Fuel Cells (HTFCs) behavior and performance is presented.
The system-level model allows to forecast the HTFC performance under different operating conditions (cell temperature, anode off-gas recirculation, reactants tempera- tures, fuel and oxidant utilization factors, etc.) and cell design (tubular and planar con- figurations and with co-flow, counter-flow and cross-flow arrangements).
Mass and energy balances are solved by considering both the electrochemical (i.e. electro-oxidation of hydrogen) and thermochemical reactions (i.e. reforming and shifting reactions) which occur in the anode and cathode sides and by applying different equations systems to take into account the type of fuel cell (MCFC or SOFC).
The ability of the proposed model in the HTFCs performance prediction is pointed out by the model validation carried out by using experimental data and by analyzing the impact of the model calibration parameters on the cell voltage calculation carried out by means of a sensitivity analysis.
Numerical results show that the model allows to characterize the behavior of the HTFCs with a good approximation so, thanks to the simplicity of the simulation procedure and to the small computational time efforts, it can be a useful tool for predicting the performance of hybrid power plants or more complex systems in which the fuel cell is one of the main components
Green hydrogen production plants via biogas steam and autothermal reforming processes: energy and exergy analyses
No full textThe use of biogas to produce “green hydrogen” represents an interesting solution for assuring sustainability in the energy and mobility sectors with lower costs and a continuous production. In this study, two hydrogen production plants using biogas as primary source, are studied and compared by applying the energy and exergy analyses for both the overall plant and components. The plants are designed as polygeneration systems able to produce high-pressure hydrogen, heat, and electricity for self-sustaining the energy consumption for purification, compression, and storage of the produced hydrogen. In this sense, these plants are proposed as on-site hydrogen production plants for the development of novel refueling stations. The two proposed plants differ for the hydrogen production process: i) a biogas-to-hydrogen plant through steam reforming, ii) a biogas-to-hydrogen plant through autothermal reforming. The results of the study have highlighted that the steam reforming-based configuration allows for achieving the best performance in terms of hydrogen production energy-based efficiency (59.8%) and hydrogen production exergy-based efficiency (59.4%). Moreover, the steam reforming-based configuration represents the best solution also considering the co-production of heat and hydrogen (energy-based efficiency 73.5% and exergy-based efficiency 64.4%), while the ATR-based layout, globally more exothermic, can be adopted when a larger local heat demand exists (energy-based efficiency 73.9% and exergy-based efficiency 54.8%)
Assessment of design and operating parameters for a small compressed air energy storage system integrated with a stand-alone renewable power plant
No full textThe renewable energy systems promotion in the field of the distributed generation is linked to the development of efficient energy storage systems. This study analyzes the behavior and the performance of a photovoltaic power system that, integrated with an adiabatic CAES (compressed air energy storage) unit, supplies electric power to a small scale off-grid BTS (base transceiver station) using only a renewable resource. The adiabatic condition of the CAES system is assured by realizing a TES (thermal energy storage) unit that recovers the heat from the inter-cooling compression for satisfying the inter-heating expansion without using additional fossil fuels. The power system is also designed to obtain a cooling effect from the cold air (3C) at the outlet of the turbine, useful for the refrigeration of the telecommunications equipment.
The aim of this study is to assess the optimal plant operating parameters, in terms of average storage pressure and operating pressure range of the air tank, considering the plant installation in three different climatic zones.
The analysis has been carried out by introducing some performance parameters such as the system storage efficiency, the energy supply factor and the cooling supply factor.
Results have highlighted that the best performance can be obtained by choosing both the lowest average pressure and the highest operating pressure range of the air tank
Realization of 0- π states in superconductor/ferromagnetic insulator/superconductor Josephson junctions: The role of spin-orbit interaction and lattice impurities
No full textJosephson devices with ferromagnetic barriers have been widely studied. Much less is known when the ferromagnetic layer is insulating. In this paper we investigate the transport properties of superconductor/ferromagnetic insulator/superconductor (SFIS) junctions with particular attention paid to the temperature behavior of the critical current that may be used as a fingerprint of the junction. We investigate the specific role of impurities as well as of possible spin-mixing mechanisms due to the spin-orbit coupling. The transition between the 0 and the π phases can be properly tuned, thus achieving stable π junctions over the entire temperature range that may be possibly employed in superconducting quantum circuits
Fluid dynamic investigation of channel design in high temperature PEM fuel cells
No full textIn this paper we analyze the three-dimensional flow field in anode and cathode gas channels of polymer electrolyte membrane (PEM) fuel cells operating at high temperature (T > 100 °C). Different gas flow channel designs (pin-type, parallel channels, comb-tipe and multiple serpentine), as well as different channel sections (squared, trapezoidal and rounded with different curvature radii) are evaluated in function of some relevant parameters. The analysis is performed accounting for overall pressure losses, gas distribution over the electrode area and residence time with focus on channel hydraulic diameter, active surface ratio, gas path. Differences with low temperature (LT) PEM fuel cell design are also adressed. The investigation is conducted by means of 3D-CFD softwares and the results of our simulations are compared to experimental data in literature. © 2012 American Society of Mechanical Engineers
From Waste to Electricity through Integrated Plasma Gasification/Fuel Cell (IPGFC) System
No full textThe waste management is become a very crucial issue in many countries, due to the ever- increasing amount of waste material, both domiciliary and industrial, generated.
The main strategies for the waste management are the increase of material recovery (MR), which can reduce the landfill disposal, the improvement of energy recovery (ER) from waste and the minimization of the environmental impact.
These two last objectives can be achieved by introducing a novel technology for waste treat- ment based on a plasma torch gasification system integrated with a high efficiency energy conversion system, such as combined cycle power plant or high-temperature fuel cells.
This work aims to evaluate the performance of an Integrated Plasma Gasification/Fuel Cell system (IPGFC) in order to establish its energy suitability and environmental feature.
The performance analysis of this system has been carried out by using a numerical model properly defined and implemented in Aspen Plus" code environment. The model is based on the combination of a thermochemical model of the plasma gasification unit, previously developed by the authors (the so-called EquiPlasmaJet model), and an electrochemical model for the SOFC fuel cell stack simulation.
The EPJ model has been employed to predict the syngas composition and the energy balance of an RDF (Refuse Derived Fuel) plasma arc gasifier (that uses air as plasma gas), whereas the SOFC electrochemical model, that is a system-level model, has allowed to forecast the stack performance in terms of electrical power and efficiency.
Results point out that the IPGFC system is able to produce a net power of 4.2 MW per kg of RDF with an electric efficiency of about 33%. This efficiency is high in comparison with those reached by conventional technologies based on RDF incineration (20%)
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