The solar chemical reactor technology for the steam-gasification of petcoke is presented. The reactor features a continuous vortex flow of steam laden with petcoke particles confined to a cavity receiver and directly exposed to concentrated solar radiation. A 5 kW prototype reactor tested in a high-flux solar furnace in the range 1300-1800 K yielded up to 87% petcoke conversion in a single pass of 1 s residence time. The solar-to-chemical energy conversion efficiency attained 9% without accounting for the product's sensible heat, and 20% when the sensible heat is recovered for steam generation and pre-heating. A steady-state process model that couples radiative heat transfer with the reaction kinetics is validated with experimental data and used for optimization and scale-up of the reactor design. (c) 2005 Intemational Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.