Quasi-static model of a thermal driven volumetric pump for an underwater glider

Underwater gliders enable an increase of human presence in the oceans. A particularly interesting solution lies in the use of the thermal gradient of the ocean as a means to provide energy to the vehicle. These type of gliders - thermal gliders - may remain years underwater collecting and transmitting data to seashore. A key element of these vehicles is the thermal driven volumetric pump that enables energy harvesting. In this paper a new quasi-static model of a thermal driven volumetric pump, for use in underwater gliders, is presented. The system considered includes a Phase Change Material (PCM) to convert thermal to mechanical energy and a hydraulic accumulator to store retrieved energy. The model allows the description of the quasi-static behaviour of the PCM coupled to the hydraulic system. The full thermodynamic cycle of the system can thus be simulated so that, in future works, the parameters of the system can be tuned for optimal performance.