Gas phase change systems in practice are up to about 60% efficiency (relative to an idealized carnot cycle), magnetocaloric systems in labs have been something like 70%, and elastocaloric 80%.

Edit: And just for reference peltier devices are usually 10-15% efficiency on this scale. So I suppose this new one is somewhere in the 20-30% range.

Probably very applicable, this video from Ben

https://www.youtube.com/watch?v=lfmrvxB154w