Intermittent nature of solar energy and solution strategies for steam methane reforming reaction powered by concentrated solar energy over Ni/mullite and Pd/CeO2/mullite catalysts were demonstrated. The solar concentration was achieved using a parabolic mirror with a 70 cm, delivering concentrated solar flux onto a focal area that is approximately 3 cm in diameter. The solar field tests conducted on monolithic catalyst support structures were compared with the laboratory scale measurements on powdered catalysts. Despite the fluctuations in solar irradiation, CH4 conversions higher than 90% could be obtained. Coke deposition was observed over the 15%Ni/Mullite monolith. On the 1%Pd/20%CeO2/Mullite monolith, the oxidative nature of the catalyst resulted in oxidation reactions with local temperatures exceeding 1700 degrees C, inferred through the melting point of mullite. Numerical simulations revealed temperature gradients as large as 500 degrees C, over the refractory monoliths. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.