Development of Ocean Thermal Energy Harvesting Systems

Despite continual increases in battery energy density, unmanned underwater vehicle (UUV) design and mission capabilities continue to be strongly influenced by onboard energy storage limitations. Primary and rechargeable lithium-chemistry batteries constrain operational endurance, require high initial investment and significant ongoing operations and maintenance costs, and are associated with both safety hazards and negative environmental impacts. Environmental energy harvesting provides a means to transcend the limitations of onboard energy storage, maximize operational flexibility and safety, and enable underwater platforms and vehicles to contribute their full potential to the Navy’s mission. The objective of this Phase II effort is to design, characterize, and prototype novel ocean thermal energy harvesting systems with the potential to support tactical and persistent UUV operations (e.g. oceanography, MCM, CN3, and ISR missions). Two distinct design concepts will be considered: Cyclic systems suitable as integrated onboard UUV power subsystems, and continuous systems suitable for moored or mobile power stations for UUV recharging or persistent underwater sensor or communication networks. The performance of these systems will be quantitatively assessed, first in a laboratory environment and then in the ocean, with specific emphasis on their ability to exploit the minimal and/or variable environmental temperature differentials relevant to global naval operations.