For me personally, this is one of the most promising aspects of solar that I hope to see in the future. There are many, many things we could do but currently do not because the energy cost is not worth it. Push the energy cost to zero, or even below, and it will be interesting to see what new things become abundant.
CO2 capture from the atmosphere, turning it into hydrocarbons. All the solar panels/wind farms combined have quite large surface that might be useful for the capture. Just need to figure out the mechanism to do it. Easy-peasy, right? :-)
