Quite a misleading article. They say it has the potential to be "highly efficient" in the intro. But later say it can achieve 64% of it's Carnot efficiency. If we assume their max 21C temp differential is from 20C to 41C, the Carnot efficiency is only 6.7%. Taking 64% of that, and you're looking at 4.3% efficient. That is a pretty far cry from the 300% or more that we expect from conventional refrigerant based systems.