Development and Experience of a Practical, Pressure-Tolerant, Lithium Battery for Underwater Use
For a number of years, lithium-ion batteries have promised energy and power densities that make them an attractive alternative to the silver-zinc batteries historically used in underwater vehicles. For AUV (Autonomous Underwater Vehicle) application, polymer-electrolyte cells offer the promise of pressure tolerance; this key attribute impacts vehicle design and operational logistics in a number of ways. Primarily, it facilitates the design of arbitrarily large battery packs by obviating many of the problems associated with large, heavy and expensive pressure vessels that would have been otherwise required to house batteries at depth. This allows a single AUV operator to recover the vehicle and remove and replace the batteries in minutes without the down time associated with servicing o-rings and seals. In a military context, this new operational paradigm has made back to back search and classify missions a practical reality. As with all new technologies there is a hiatus between availability, practical implementation and adoption. Many fundamental, logistical and practical engineering problems in design and manufacture have been solved in the past 5 years leading to a range of commercially available batteries with power densities exceeding 100Wh per neutrally buoyant Kg. This paper will explore these challenges, examining specific solutions derived from experience gained through the pressure testing of over 20,000 cells
Hybrid, high density energy storage for AUVs
This paper forwards a concept for a hypothetical hybrid, internal combustion-electric power generation system that can be used to increase the energy density of an AUV. Though the system is hypothetical, it consists of subsystems that are mature technologies with long histories of successful commercial use. The use of hydrocarbon based fuels as a primary source of energy within an AUV has the advantage of a 350% increase in energy density over the PEM fuel cell based technologies currently being researched.
Autonomous Buoyancy-Driven Underwater Gliders
A class of small (50 kg, 2 m length), reusable autonomous underwater vehicles capable of operating at speeds cm/s with ranges several thousand kilometers and durations of months has been developed and tested. The vehicles, autonomous profiling floats with wings, execute sawtooth patterns between the surface, where they are located and com to shore, and depths of O(1000 m). These vehicles are commanded remotely and report results to shore in near real tim ent approaches to the various design issues are embodied in the vehicles Spray, Seaglider and Slocum models desc including batteryand thermal-powered propulsion, different depth and speed capabilities, diverse hydrodynamic appro reducing drag and gliding control, various communication schemes, and a range of sensors. These approaches are des examples of completed scientific missions are given. l., e st els. h ic es rs s, ing ult g, em cg on the ive is cles an be an eing ean urand the lidin