Thermodynamic evaluation of small-scale systems with biomass gasifiers, solid oxide fuel cells with Ni/GDC anodes and gas turbines

Thermodynamic calculations were carried out to evaluate the performance of small-scale gasifier-SOFC-GT systems of the order of 100 kW. Solid Oxide Fuel Cells (SOFCs) with Nickel/Gadolinia Doped Ceria (Ni/GDC) anodes were considered. High system electrical efficiencies above 50% are achievable with these systems. The results obtained indicate that when gas cleaning is carried out at temperatures lower than gasification temperature, additional steam may have to be added to biosyngas in order to avoid carbon deposition. To analyze the influence of gas cleaning at lower temperatures and steam addition on system efficiency, additional system calculations were carried out. It is observed that steam addition does not have significant impact on system electrical efficiency. However, generation of additional steam using heat from gas turbine outlet decreases the thermal energy and exergy available at the system outlet thereby decreasing total system efficiency. With the gas cleaning at atmospheric temperature, there is a decrease in the electrical efficiency of the order of 4-5% when compared to the efficiency of the systems working with intermediate to high gas-cleaning temperatures.