I don't think anyone is talking about painting the desert with this stuff, so it isn't geohacking in any real sense.

What you CAN do with this stuff is paint your roof and external walls with it, which will reduce the need for active cooling in your building. This both saves money for the purchaser (making it commercially viable) and reduces energy usage, which in turn reduces fossil fuel usage.

Seems like it would be a lot quicker / easier to pick up a few large sunshades? Coolaroo makes roller shades up to 10ft / 3m wide which are easy to mount under eaves (no association, except I installed one on a west-facing balcony and it works nicely), if your structure has a roof with those. Then you can block solar heat in the summer, but let it do what it can for you in the winter.

Putting a shade under the eaves is great for shading a wall, but putting one over your roof is going to be an absolute pain to clean.

Not to mention that your roof and walls may need paint _anyway_ depending on the material, so for new builds using it this is no added messing around.

All of which reduce the Heat Island Effect.

While your comment is interesting discussion, I'm not sure the posted video is arguing for geohacking. I watched it last night and got more of a "here's a cool physics trick that seems like it has some real-world applications outside of a lab, and I did a lot of work to make it achievable outside of a research lab."

I think you may have skipped the article and assumed it was about e.g. sun-shading