The obvious question
The obvious question—assuming that light is being trapped, internally reflected and ultimately turned to heat— seems to be: could this be the basis of an efficient solar heating system? No doubt it's so obvious that everyone and his penguin has thought of it. I'm a little intrigued by the notion of black-faced capillary tubes turning incident solar radiation directly into hot liquid, self-circulating through a baby turbogenerator for useful power ... but I wonder what the use case would be compared with the big, typically desert-based solar furnace systems that concentrate acres of sunlight into a boiler. Perhaps too niche and small-scale?