You want a better alternative? Here's one that's actually (technically) a Carbohydrate; Ethylene Glycol. Among other things, it's primary use is as radiator coolant in modern society, which when you get right down to it sounds like the kind of thing you would expect a phase change material to be doing.
On top of that, it's also a primary ingredient for some 'smart' PSMs, like your Germanium based one.
There's only one catch; it's toxic to humans. Very toxic actually. What that means is that there would have to be a biochemistry substantially different to human physiology in place for this stuff to function inside a living body, but it's more likely to happen than your Germanium one for several reasons;
1) Availability of the elements
One of the reasons that earth life is carbon based is because there is a lot of carbon, hydrogen, oxygen, nitrogen, iron, etc. in the universe. Because they're common elements, if life can form in the universe, it's far more likely to be carbon based than (say) silicon or germanium based. That means that ethylene glycol (as a CHO compound) is more likely to exist or form naturally on another planet than a compound that includes Germanium, especially in quantities that can sustain a large and thriving biomass.
2) Compounds V. Elements
Put simply, you can do a hell of a lot more in terms of materials diversity if you focus on compounds rather than introducing new elements. If you take a look at most drugs and other substances that have a material impact on our health and / or behaviour, quite a lot of them are CHNO compounds, or some subset thereof. This is because our physiology already uses these elements in various compound formations so the drugs or other substances are designed to interact with our internal chemistry already. Introducing new elements into a carbon based life form only works if those elements can interact with CHNO compounds to create something even newer.
So; what you're suggesting may work, and in fact could be an energy extraction system on a planet where no photosynthesis exists. In such a case, your creature needs energy and may actually be able to directly draw it from a hot planet's atmosphere. In such a case, the physiology may not even be chemical energy based in the conventional form, but may have an internal exothermic reaction that extracts the heat from the ethylene glycol, meaning that it only needs 'food' for nutrition, not for energy.
As such, I can see such a creature existing on the surface of Venus for instance, where the heat and pressure could kill a conventional plant but such a creature as this could exist higher in the stratosphere, converting the heat energy around it to internal body energy and then consuming any nutrition it needs from that same cloud formation.