Performances of a micro-CHP system fed with bio-ethanol based on fluidized bed membrane reactor and PEM fuel cells

• Assessment of membrane reactor fueled by bioethanol into a micro-CHP system.
• Impact of membrane reactor operating conditions on the system performances.
• Thermal integration between membrane reactor and PEM fuel cells stack.
• Investigation of membrane permeate side options on performances and membrane area.
• Net electric efficiency above 40% with sweep gas configuration.

A 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.