The sperm whale is the largest of the toothed whales and the largest toothed predator. They can dive to 2,250 metres, ranking to be the third deepest diving mammal.

Sperm whaling was a major industry in the 19th century. The whaling is mainly targeting for spermaceti (sperm oil), which was used for illumination making oil lamps, lubricants, and candles. The spermaceti is also a typical Phase Changing Material (PCM), melts in high temperature and solidifies in low temperature. During the phase changing process, the volume changes, which is suspected to help adjust the whale's buoyancy.

In this research, we are aiming to develop a self-sustainable underwater glider, using PCM to convert thermal energy in the ocean to drive the underwater vehicles diving and surfacing. We are going to design a new tyoe of large capacity thermal buoyancy engine (Patent applied) for this kind of operation and a new kind of dual purpose rotor which can be both used as a turbine for energy harvesting and as a propeller for propulsion.