Interesting, functional, concrete with German efficiency !!
However I did not find the final yield of the process, photovoltaic-electrolysis-giving H2 combined with CO2 to give methane CH4, used in a car with tank at 200 Bars, in my opinion a few% to compare to that of nature photosynthesis algae or forest, quite close, but very different in investment, nature doing this spontaneously ?????
http://www.eubia.org/uploads/media/1._F ... terner.pdf
In my opinion
store concentrated solar heat at 300 ° C and above, underground (on a large volume of large solar thermal concentrating plant), to use 24h on 24 and 365 days a year, to make electricity, risk to have a much better return, (that of Carnot real 20 to 30%) with far fewer steps at poor performance.