Integration of solar gasification with conventional fuel production: The roles of storage and hybridization

The use of concentrated solar radiation as the source of process heat to drive biomass gasification offers potential increases in yield and efficiency over conventional approaches to gasification but requires that temporal variations in output be alleviated with thermal storage or hybridization. The impacts of thermal storage and degree of hybridization on the efficiency, specific yield, and variation in output of a solar gasification facility are explored through parametric simulations of a generalized 100 MWth solar receiver facility. Nominal syngas yield rates from 1.5 to 50 tonnes/h are considered along with molten carbonate salt storage volumes from 200 to 6500 m3. High solar fractions (95%) result in a maximum thermal efficiency of 79% and specific syngas yield of 139 GJ/ha while low solar fractions (10%) for highly hybridized facilities reduce the thermal efficiency to 72% and specific yield to 88 GJ/ha, akin to conventional gasification processes. Solar fractions greater than 95% result in large variation in synthesis gas yield rate, varying as much as 30:1 throughout the year. This variation can be reduced to below a 4:1 ratio, more acceptable for downstream processes, through either hybridization to achieve solar fractions less than 50% with little to no thermal storage, or alternately the use of 5600 m³ of molten carbonate salt to allow for solar fractions up to 87%.