Eileen Tortora

Analysis of an integrated PEMFC/ORC power system using ammonia for hydrogen storage

The present work deals with a high temperature proton exchange membrane (SPEEK-type) fuel cell (HT-PEMFC) energy system fuelled with hydrogen obtained by reforming of ammonia (NH3) and coupled with a bottoming Organic Rankine Cycle (ORC) energy system. This system was designed for distributed electric power generation, mainly for production of electric power systems with potential future applications in smart-grid.The use of ammonia as hydrogen rich gas source allows to avoid hydrogen tanking with metal hydrides, giving the opportunity to lighten and simplify the storage section of the system with respect to the pure hydrogen fed systems.The hybrid fuel cell/ORC configuration allows to increase the efficiency of standard power generation technologies. In other words, the ORC subset represents the most appropriate solution, in terms of sustainability, for extracting the excess heat produced during the H2 combustion maintaining the PEMFC working temperature at 120°C and for reducing the temperature of the exhausts.The objective of the work is to optimize the electric output of the system (PEMFC + ORC), thus improving the overall efficiency. To this end, a numerical model is implemented and tested. A validation of the numerical scheme is carried out comparing the prediction of the reforming phase with experimental results obtained by the authors. The thermal and electrical energy balance is also assessed. Furthermore, the operation conditions of the reformer are studied in detail to determine the settlements leading to a proper ammonia cracking to produce nitrogen and hydrogen. Furthermore, the calculations take into account also the auxiliary equipments such as pumps, compressors and heat exchangers.© 2012 ASME

Experimental and Numerical Analysis of Steam-Oxygen Fluidized Gasifier Feeding a Combined SOFC/ORC Power Plant

The aim of this work is to experimentally and numerically analyze the performance of a combined power plant, composed by a steam oxygen fluidized bed biomass gasifier fed by woods, a Solid Oxide Fuel Cell (SOFC) and an Organic Rankine Cycle (ORC). The gasifier model is developed and validated by means of experimental activities carried out with a bench scale gasifier in our lab. Different compounds (Benzene, Toluene, Naphthalene, Phenols) were chosen to analyze the tar evolution in the gaseous stream during the gasification process. Hot gas cleaning (based on catalytic ceramic filter candles inserted in the freeboard of the gasifier - UNIQUE concept) is adopted to remove tar and particulate at high temperature from the fuel gas stream. The numerical analysis is carried out by means of the software Aspen Plus®. In particular, the SOFC and the gasifier are modelled using proper developed Fortran subroutines interfaced to the basic software. The adopted SOFC model was already validated by the authors in previous works. Finally, a realistic ORC is modelled. Different moisture contents in the range of 10–30 % (i.e. in a deviation of 10% around the usual wood moisture content of 20%) are investigated in the simulations, as also the degree of purity of the oxygen used in the power plant (between 25 and 95%, rest N2). The power requirement for the production of pure oxygen for this kind of gasification technology leads to a reduction of the electrical efficiency of the whole power plant. For this reason a sensitivity analysis was conducted to find the optimal operation conditions in order to maximise the syngas content in the produced gas (H2, CO) maintaining a high overall electrical efficiency.Copyright