Optimization of a hybrid solar-fossil fuel plant: Solar steam reforming of methane in a combined cycle

In this article, an analysis of solar reforming as the solar integration method for a hybrid solar-fossil fuel cycle is presented. The solar reformer is integrated with a solar tower and steam reforming of methane is studied. The tower reformer system is integrated with a standard combined cycle, and the design and operation of the hybrid cycle are optimized for highest annual work output for a fixed fuel input and solar collector area. A heuristic two step procedure is used for the optimization: first, both the design and operation of the plant is optimized for every hour and then in the second step, the design is fixed at the average value determined by the first step and the operation of the plant is again optimized for every hour. The optimization results indicate that the tower reforming integration method is a promising integration option in that this type of hybrid cycle yields high incremental solar efficiencies compared to alternatives. Moreover, the analyzed hybrid cycle has a higher efficiency for a fixed CO2 emissions compared to a linear combination of solar only and fossil fuel only cycles of comparable complexity.