Gasification of German oil shale and coal using concentrated solar energy as a heat source is studied in a fixed bed reactor under an argon atmosphere. The reactor allows direct absorption of irradiation resulting in high rates of temperature increase and hence in simultaneous decomposition of organic matter and carbonates present in the shale. Synthesis gases are produced consisting of H-2, CO, CH4, and CO2. Basic considerations on stoichiometrics of shale gasification are presented. A macrokinetic modeling of the shale reaction rate based on conversion is established and verified experimentally. Further experiments are carried out with different irradiation times, shale-particle sizes, gasification temperatures and water contents of the raw shale and coal.