Umm.. so the article was focused on the abstract idea of increasing efficiency of thermoelectric generators. The practical idea (and even the article title) was about how it might be able to power a car more efficiently. But yet you focus right in on how it's never going to work. (Why yes, I DO understand the carnot limit of heat engines).
The article never talked about massive gains in heat efficiency for power plants, just scavenging waste heat. Right now we have massive cooling towers at power plants to get rid of waste heat, which sometimes provides problems for increased temperatures of waterways. If you could make an efficient thermoelectric device like this you might be able to take some of that waste heat and turn it into usable electricity, reducing your cooling needs and producing power at the same time. A 600MW coal plant going from a 33% efficient to 34% would produce an additional 18MW. That's not bad. At
So no, there's nothing really to "debunk" here, since no claims are really made about large gains in efficiency.