Virtually all hydrogen used today is produced from fossil fuels, primarily through the highly energy intensive steam reforming of methane, the principal component of natural gas. While this is likely to remain the technology of choice for some time, the role of hydrogen as a clean fuel of the future is predicated on new production routes with low or zero greenhouse gas emissions.
Solar thermal reforming of natural gas is regarded as a promising transitional technology to produce hydrogen with reduced carbon intensity. In this process, the reforming reaction is carried out using thermal energy supplied from concentrated solar energy rather than the combustion of fossil fuels. Besides reducing the carbon intensity of the product hydrogen, the process provides a viable means for storage of solar energy in the chemical bonds of a transportable product, overcoming many of the limitations of solar energy.
This article summarizes the key thermochemistry and thermodynamics of conventional methane reforming, and addresses the issue of how solar energy can be used to drive the process. Various reactor concepts are reviewed and discussed, and past and current research activities are reviewed to identify where future work on this topic should be focused.