Effects of thermocline on performance of underwater glider’s power system propelled by ocean thermal energy

Frontiers of Energy and Power Engineering in China 12/2009; 3(4):472-479. DOI: 10.1007/s11708-009-0052-7

ABSTRACT The thermal glider’s changeable volume produces propelling force to power the glider’s descending and ascending through the
thermocline. The different depth, thickness, and intensity of the thermocline at different seasons and locations affect the
working processes of the glider’s power system. Based on the enthalpy method, a mathematical model of the underwater glider’s
power system was established and the time efficiency of operation was introduced, so that the effects of different thermoclines
on the underwater glider’s power system were analyzed theoretically. The simulation result shows that the thermocline affects
the transition time of the phase change processes of working fluids within the thermal engine tubes. There exist the threshold
values of the thermocline’s depth and upper thickness for the power system’s operation. A depth or upper thickness of the
thermocline less than the corresponding threshold leads the power system to work abnormally. To keep the power system working
efficiently, a glider must be kept in warm surface water for a certain period before it moves through cold water, so that
the time efficiency of operation is reduced. A less time efficiency of operation is unfavorable to the thermal glider to penetrate
through the ocean currents.

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