Steven Chu: Fuel from Sunshine and Air

“Can we design something that begins to replicate what a plant does?… in principle, we can design something better….. Can we go from water, to oxygen, hydrogen, carbon dioxide, to hydrocarbon fuel?”

Steven Chu’s description at the National Press Club of exciting new prospects for creating carbon neutral, or maybe even carbon negative(?) fuel using sophisticated solar processes. The invaluable Greencarcongress has a diagram of the emerging technology.

A team from Caltech, ETH Zürich and the Paul Scherrer Institute have devised a solar reactor for the two-step, solar-driven thermochemical production of fuels. In a paper published in the journal Science, they report stable and rapid generation of fuel over 500 cycles. They achieved solar-to-fuel efficiencies of 0.7 to 0.8%, and showed that the efficiency was largely limited by system scale and design, rather than by its chemistry.

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Given that, the team anticipates that reactor optimization and system integration will result in substantial increases in both efficiency and fuel production rates. Furthermore, they note, the abundance of cerium, which is comparable to that of copper, is such that the approach is applicable at scales relevant to global energy consumption.

Here’s the abstract of the paper, published in Science. –

Because solar energy is available in large excess relative to current rates of energy consumption, effective conversion of this renewable yet intermittent resource into a transportable and dispatchable chemical fuel may ensure the goal of a sustainable energy future. However, low conversion efficiencies, particularly with CO₂ reduction, as well as utilization of precious materials have limited the practical generation of solar fuels. By using a solar cavity-receiver reactor, we combined the oxygen uptake and release capacity of cerium oxide and facile catalysis at elevated temperatures to thermochemically dissociate CO₂ and H₂O, yielding CO and H₂, respectively. Stable and rapid generation of fuel was demonstrated over 500 cycles. Solar-to-fuel efficiencies of 0.7 to 0.8% were achieved and shown to be largely limited by the system scale and design rather than by chemistry.