Comment on Inconvenient truths about energy policy by David L. Hagen

wade
good question. The commercially important conversion is from 2 CO2 to 2 CO + O2 – See Sandia’s Sunlight to Petrol program.
It appears to need a little lower energy than 2 H2O to 2H2 + O2.
The cost of the solar collectors at $300/m2 is the primary barrier!