So, the self filling water bottles don't work because of the energy required to extract H2O out of the air is excessive (think how much electricity is required for your dehumidifier) ... Extracting carbon from the CO2 in the air is going to need a heap more, I would have thought.

I'm not a physicist though, would be glad to be proven wrong.

It does sound very much like a "solar freaking roadways" type effort though.