[DmitriRavinoff]

The only problem with that is you can't think of cold as something you can generate. Cold is the absence of heat, and so the only way to make it in a place where there is already heat is to move the heat somewhere else.

If you keep it inside the vessel, then you're faced with containing a zone of steadily increasing heat (and thus steadily decreasing efficiency of your heat pump). If you try to dissipate it outside of the vessel, you run into further engineering problems (the heat conduit has to pass through the hull at some point, which creates a weak spot for pressure and a potential heat leak to the rest of your hull).