There are a number of stories about this, and for most of them the technical explanation starts and ends with “The structure works similarly to a magnifying glass that intensifies light from the sun — except in this case, the lens intensifies wind flow” or something similar. Which is really frustrating. This story doesn’t, and even provides a link to the university web site, so perhaps we can glean additional information from that.
OK, it looks like this “lens” is a venturi of sorts. I’m neither a fluid mechanic nor an aeronautical engineer; I imagine the compressibility of the air makes this a little different for air than for water. But when you restrict the area of flow, the speed increases. Put another way, by funneling/focusing you increase the energy density of the air, so more energy is present within the area of the turbine and you can extract more energy without making the blades bigger. That much I get. I’m not sure if this accounts for all of the increased efficiency or if there are other effects as well, like improved efficiency by generally having higher speeds. It certainly doesn’t look like you are tripling the capture area from the pictures.
The stories tout this as being great, but I notice that the turbines are ~1 kW, as opposed to commercial turbines which are MW-ish beasts, and the researchers do not say how far this effect will scale up, and in fact caution that it will not. The bits about how these might be less objectionable on aesthetic grounds don’t sway me — there’s no justification that these will look pretty to those who disapprove of regular turbines. So I’m not seeing these as “farms” and >100 m diameters would seem to exclude them as being put up in your yard.