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.

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 previous step, taking into account that the stack internal temperature behavior 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.

The design of Solid Oxide Fuel Cell (SOFC) Hybrid Systems (HS) is usually based on the use of natural gas as fuel. However, the possibility of using other fuels such as biomass gasification, pyrolysis, fermentation, and coal gasification could potentially increase the market for SOFC Hybrid Systems. In this paper, the influence of fuel composition on both HS layout and performance is investigated. The analysis is based on a layout and a detailed simulation model of a Hybrid System based on Rolls-Royce Integrated Planar SOFC (IP-SOFC) technology fed with natural gas, previously developed by the authors. Particular attention has been given to the thermal management of the stack, the anode flow recirculation design and the turbine-compressor redesign, including safe surge margin operation conditions.

Rolls-Royce Fuel Cell Systems Limited in the last few years has been developing a low cost hybrid system for electricity production based on planar SOFCs (Solide Oxide Fuel Cells). The novel cycle is based on the recycle of cathodic off-gas to pre-heat the oxidant flow, using ejectors. On the anode side, ejectors are used to recycle steam-rich off-gas to the reforming reactor. This paper describes the analysis process carried out to optimize the ejector geometry, from the preliminary sizing of lengths and sections, to the flow path optimisation. Further study has been carried out in order to evaluate the influence of altered geometries on the ejector performance varying the nozzle position relative to the ejector body. An extensive and successful use of CFD (Computational Fluid Dynamics) combined with experimental results allowed the validation of the basic design tools and the optimisation of the ejector performance.

The inherently clean and efficient nature of fuel cell systems makes them highly attractive for electrical power generation applications, subject to overcoming their disadvantage of high initial cost. Rolls Royce has been working for 10 years to create a fuel cell stack design of much lower cost, having a structure both tolerant to sharp changes in operating temperature and fully durable when used in load-following applications requiring moderate cycling of stack conditions. The effort was launched as a company supported research initiative but has also attracted substantial European Commission funding, with emphasis on developing low manufacture cost stack technologies. This paper describes how chemical and physical features of the stack, and the technologies selected for the integrated plant system, have achieved major strides in cost reduction. The design and development of the system using this technology has been transitioned to an European/USA industry development team whose goal is commercialization of the product within five years. Manufacture will use both European and USA facilities. Market opportunities for fuel cell hybrids are briefly discussed.