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 Navys 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.
Benefit: With support from private investors and charitable foundations (e.g. the Thiel Foundation's Breakout Labs; Schmidt Marine Technology Partners) Seatrec continues to pursue commercial development of a compact modular S2L thermal engine (TREC2 0x9D ) for integration with profiling floats, profiling moorings, and underwater gliders. A commercial prototype is presently under development and demonstration trials are expected in late 2017. Seatrec is presently partnering with Sea-Bird Scientific (Seattle, WA) to bring this product to market and we expect to leverage their global marketing and distribution network. We have identified several initial customers in the academic research market and have engaged in preliminary discussions with representatives of the Naval Oceanographic Office, one of the largest operators of profiling floats and underwater gliders and a potential benefactor of Seatrec technology. In addition to possibly supplanting our existing S2L technologies due to their expected size, weight, and performance advantages, the L2G thermal engines to be developed as part of this Phase II effort have the potential to positively impact a number of ongoing and future Navy programs. We have identified support of UUV operations (and particularly tactical and persistent UUV operations; e.g. oceanography, MCM, CN3, and ISR missions) as a prime target for our new thermal engine technologies -- and this has been reinforced by ONR program management through this Phase II RFP. Both our cyclic and continuous L2G thermal engines have the potential to contribute to extending the endurance and utility of UUV-based operations either through onboard energy harvesting (cyclic) or fixed/mobile UUV recharging stations (continuous). The proposed continuous systems could also power other persistent underwater sensor or communication networks that require high power and extreme endurance. Over the past 18 months Seatrec has engaged in informal discussions with a number of major defense contractors working in relevant topical areas (especially persistent UUV networks) to improve our understanding of this application space and to acquaint ourselves with current development activities. We anticipate that interactions with our ONR TPOC as part of this Phase II effort will lead to greater clarity regarding power and form-factor requirements for specific naval applications and result in support for continued development and future commercial opportunities. Given the potentially large generating capability and the expected relative ease of integration, we anticipate that a continuous L2G thermal engine mated to a subsurface mooring would be among the earliest of commercial products to result from this effort. A very preliminary estimate suggests that such a system could retail for around $50,000 per unit. Potential customers include academic researchers, the oil and gas industry, government-sponsored environmental monitoring programs, and major defense contractors engaged in development of persistent UUV networks. We hope to partner with a larger, more experienced company, ideally in the defense space, to bring this product to market and provide Seatrec access to customers, marketing resources and distribution channels. Following completion of this Phase II effort we anticipate an additional investment on the order of $2-3M would be required to refine a commercial product, facilitate the necessary partnerships, and complete an appropriate technology demonstration and validation program. Seatrecs thermal engines provide a unique capability: unlimited power in the ocean. The operational flexibility resulting from unlimited power has a price -- and to date this price has been higher than the cost of incrementally increasing the volume of batteries carried by a vehicle or platform. Thus forms of stored energy (traditional batteries, seawater batteries, fuel cells) have been the most important competitors to Seatrecs thermal engine technologies. As UUV missions become more complex, widespread, and interdependent the penalty for running out of energy will increase as will the cost of operations and maintenance for expansive UUV arrays or sensor networks. As these systems mature and multiply the ability to deploy a platform or vehicle for indefinite duration becomes a key operational and economic advantage made possible by the energy harvesting technologies proposed herein.
Keywords: Energy Harvesting, Unmanned Underwater Vehicles, underwater power station, Ocean Thermal Energy Conversion, Thermal Engines
