This is really interesting. That said, it looks pretty straightforward to build; looks like there are no novel materials or equipment needed to make this happen, from my reading of it. Given that, why don't we have a full-scale prototype of this, at the very least? Is it just the money, or is there something non-trivial about this? I feel like I'm missing some reason why this is non-viable in practice.

I actually worked in the lab with Louis' team this past summer (completely unrelated projects.)

If the wind was going faster than a couple miles per hour, they couldn't even turn their prototype on to run their tests. I think the biggest problem they're having with going big-picture with this is doing the due-diligence to prove it's not a tornado machine.

Say more about "couldn't even turn [it] on"? Because it didn't work then (not a good sign)? Or because they, or somebody, thought the vortex would detach and go rogue?

It was less of an immediate safety concern and more a case of trying to limit the variables. They were only doing tests under ideal conditions, rather than testing in all conditions. I imagine the plan involves testing in all conditions eventually, but they need to fine-tune their equipment in ideal conditions to make sure they know what "good" and "bad" look like before potentially feeding some atmospheric action that they didn't anticipate.

How about doing it somewhere remote? Say, on a remote pacific island with no inhabitants? Or is there even the fear that it could emit a hurricane (which would probably happen anyways, but if it's your machine that starts it, all (media) hell breaks loose)?

http://en.wikipedia.org/wiki/Energy_tower_(downdraft) Downdraft tower seems similar. In theory could produce 400MW in a small area and solve our energy problems.

The difference between the vortex engine and the downdraft or solar tower is that you don't have to build a 1000 meter high tower. I'm not a believer in it but it's important to realise the difference.