Use of Low/Mid-Temperature Solar Heat for Thermochemical Upgrading of Energy, With Application to a Novel Chemically-Recuperated Gas-Turbine Power Generation (SOLRGT) System

This paper presents the concept of indirect thermochemical upgrading of low/mid temperature solar heat, and demonstration of its integration into a high efficiency novel hybrid power generation system. The proposed system consists of an intercooled chemically recuperated gas turbine (SOLRGT) cycle, in which the solar thermal energy collected at about 220°C is first transformed into the latent heat of vapor supplied to a reformer and then via the reforming reactions to the produced syngas chemical exergy. The produced syngas is burned to provide high temperature working fluid to a gas turbine. The solar-driven steam production helps to improve both the chemical and thermal recuperation in the system. Using well established technologies including steam reforming and low/mid temperature solar heat collection, the hybrid system exhibits promising performance: the net solar-to-electricity efficiency, based on the gross solar thermal energy incident on the collector, was predicted to be 25–30%, and it can reach up to 35% when the solar share is reduced. In comparison to conventional CRGT system, 30% of fossil fuel saving is feasible with the solar thermal share of 26%, and the system overall efficiency reaches 51.2% to 53.6% when the solar thermal share is increased from 11 to 28.8%. The overall efficiency is about 5.7%-points higher than that of a comparable intercooled CRGT system without solar assist. Due to the introduction of steam into the combustion chamber, production of NO_x is near zero, and the reduction of fossil fuel use results in a commensurate 23% reduction of CO₂ emissions as compared with the comparable intercooled CRGT system without solar assist.