It's a fancy 'swamp cooler', is what it is. You can buy swamp cooler A/C units now, and lots of people do; most of them use a wheel coated with silica gel (ie DO NOT EAT THROW AWAY PACKET) that rotates through the incoming / outgoing air streams so it theoretically doesn't get saturated. The efficiency of these things is always pretty low, and they tend to grow mildew -- hence the name 'swamp cooler'.
This guy's system appears to be more physically complex, and it uses a more exotic dessicant than silica gel. There's a vague mumble about drying the dessicant out again when it gets saturated. He seems to think you can do that with waste heat or solar heat, and maybe you can, but:
- This system basically throws away water. If you're talking about using it on lots of commercial buildings, your city is going to be throwing away a lot of water, and I'm not sure you can use gray water in a situation like this because you'd be contaminating your air.
- You can't use the cooler and re-dry out the dessicant at the same time. So you need a lot of extra cooling capacity. Standard dehumidifiers have this same kind of problem, where they have to stop dehumidifying to run a cycle where they reset their coil temperatures and drain off water accumulated as frost.
I don't see this as likely being terribly efficient in practice. The advantage of using evaporation in cooling is the energy you get to give away 'for free' in the phase-change where the water turns to vapor. It's just an extra coolant that you don't have to recapture, pump, condense, etc. You just let it steam away outside, and it takes heat energy with it. This is why lots of really big A/C systems have a pool of water outside somewhere that the pipes run through, like the famous reflection pool at the Christian Science Center in Boston.
But you don't keep that water inside the building. You want it to take the heat away with it, and you don't want to put humidity back into your inside air. Evaporative cooling is used a lot in non-industrialized settings, but always where the water vapor escapes like that. Take a terra cotta flower pot, line the inside with damp sand, nest a smaller terra cotta pot in there, dampen the sand a little more, and put a cover on it -- put that in a hot dry market, and anything inside the inner pot will stay cool because of the water evaporating through the outer pot. But it doesn't work well indoors, and the water vapor just winds up inside to annoy you.
Eh. Who knows. Maybe there's a hidden efficiency boost in this guy's system, and the article just doesn't explain it. But it's not very likely.
