A techno-economic model for SOFC power systems

The combination of specified operating and performance parameters for an SO FC system, such as fuel flow rates, operating voltage and power density, af fects capital and operating costs. Additional components of the cost of ele ctricity are attributable to finance costs and system maintenance costs. Wh ile computing the cost of electricity from a given set of conditions is fai rly straightforward, minimization of the cost of electricity generated from a solid oxide fuel cell power system requires development of functional re lationships between the various design and operating parameters. Such a set of relationships is developed for a simple cycle natural gas-fueled SOFC p ower system. This work builds on the analysis methodology developed previou sly by the authors for SOFC operation on natural gas to include capital and operating cost maps. Relationships between fuel flow rates, stack resistan ce and operating voltage were defined in a closed form parametric model to predict power density, fuel utilization and efficiency at a specified opera ting point. The stack performance model was coupled via mass and energy bal ances with design equations to size system components such as heat exchange rs and insulation. Estimated component costs, based on the required size of each component, are used to obtain an estimate of total system capital cos t. The cost of electricity for some typical operating conditions is then ca lculated. The cost framework provides a useful tool for determining opportu nities for cost minimization. The overall strategy employed in developing s uch a model is described and illustrated with various examples. This cost f ramework can be extended to SOFC power systems involving gas turbine combin ed cycles as well. (C) 2000 Elsevier Science B.V. All rights reserved.