No abstract

Rolls-Royce Fuel Cell Systems (RRFCS) is developing a 1MW fuel cell hybrid system package, supported by a prototype demonstration of a 250kW generator module in 2006. The ongoing design process has been focused from the early stages towards simplicity as a key to achieve the demanding cost targets for an effective market entry. This paper describes how the specifically designed components are being integrated as a system. A description of the progress against the demonstration plan is provided. The baseline plant is expected to provide excellent part-load performance in an extensive range of operating conditions, while a modular architecture guarantees availability and reliability. Finally, opportunities for further increases in efficiency and power density are discussed, as the technology evolves towards a next generation product.

Composite electrodes are of great interest in the field of solid oxide fuel cells because their use can improve the performance of these cells. However, an important correlation exists between composition, microstructure, and thickness of an electrode and its performance. This correlation has been investigated in this work using a theoretical model. The model, in order to consider all the losses occurring in an electrode, includes Ohm’s law for ionic and electronic charge transport, and the Butler-Volmer equation to evaluate the activation polarizations, and mass transport equations, taking into account diffusion through porous media, to evaluate the concentration losses. The model shows that the best electrode performance is a trade-off between activation and concentration losses. This is because a decrease in the dimensions of the particles or an increase in its thickness result, on the one hand, in a reduction of the activation polarizations, because of a larger active area for the electrochemical reaction, and, on the other hand, in an increase in the concentration losses due to a more difficult gas diffusion. In particular, in order to understand the impact of concentration losses on the performance of composite electrodes, the simulations have been run with two models, one including and the other one neglecting the mass transport equations. The results show that concentration losses play a role only with thick electrodes composed of small particles, operating at high fuel utilization.

In this paper the design point definition of a pressurised hybrid system based on the Rolls-Royce Integrated Planar-Solid Oxide Fuel Cells (IP-SOFCs) is presented and discussed. The hybrid system size is about 2 MWe and the design point analysis has been carried out using two different IP-SOFC models developed by Thermochemical Power Group (TPG) at the University of Genoa: (i) a generic one, where the transport and balance equations of the mass, energy and electrical charges are solved in a lumped volume at constant temperature; (ii) a detailed model where all the equations are solved in a finite difference approach inside the single cell. The first model has been used to define the hybrid system lay out and the characteristics of the main devices of the plant such as the recuperator, the compressor, the expander, etc. The second model has been used to verify the design point defined in the preview step, taking into account that the stack internal temperature behaviour are now available and must be carefully considered. Apt modifications of the preliminary design point have been suggested using the detailed IP-SOFC system to obtain a feasible solution. In the second part of the paper some off-design performance of the Hybrid System carried out using detailed SOFC model are presented and discussed. In particular the influence of ambient conditions is shown, together with the possible part load operations at fixed and variable gas turbine speed. Some considerations on the compressor surge margin modification are reported.

Progress at Rolls-Royce Fuel Cell Systems (RRFCS) continues towards demonstration of a 250 kW generator module for launch of a 1 MW pressurized SOFC hybrid system for stationary power generation. This paper describes recent progress on demonstration of the SOFC system, both as individual components - core cell and stack technology, the turbogenerator, packaging, and, crucially, the progress on building these components together into a functional hybrid Generator Module and system. The establishment of a truly global engineering team with skills and experience across the range of technologies required has been crucial to the development of the overall system with a view to cost effective manufacture, system simplicity and realistic fuel availability. Efficiency and key system components are discussed, together with design evolution as the technology moves towards a commercial product.