Devices, systems, and methods relating to providing a portable, rechargeable vessel for collecting, storing, and recovering thermal energy are provided. In one aspect, vessel includes a structure defining a well and an open-top portion at the top of the well; a phase-change material, wherein the phase-change material is disposed in the well, the phase-change material being configured to change phase at temperature in the range of 110-700° C.; one or more thermally-conductive fins interleaved in the phase-change material; and a thermally-conductive heat transfer plate disposed at and substantially covering the open-top portion of the structure, in direct thermal contact with the one or more fins, thereby allowing the transfer plate to directly exchange thermal energy with the phase change material.