Seawater Activated Power System (SWAPS): Energy for Deep Water Detection, ocean platforms, buoys, surface craft and submersibles

A Seawater Activated Power System (SWAPS) has most recently been tested for providing all electrical power for a US Navy Deep Water Detection System (DWADS). DWADS requires 40 kW bursts of power to produce acoustic pulses that are detected by submerged receivers whose signals are transmitted to and analyzed by ship or shore based operators. SWAPS, a proprietary technology developed by Mil3, Inc., is a portable, modular, economical, non-polluting and safe power source utilizing the reaction of a proprietary magnesium alloy with seawater to produce hydrogen. This hydrogen is converted to DC electrical power in proton exchange membrane (PEM) fuel cells at an efficiency of about 50%. Because the hydrogen is extracted from seawater, the on-board mass of the system is reduced, contributing to increased energy per unit mass. Consequently, with a remarkable energy density of 1.4 kWh/kg, SWAPS requires about 12-15 times less mass and volume than the best lithium ion batteries, 35-50 times less than marine gel cell batteries, and with investment/operating costs of only 2% to 20% the cost of any rechargeable batteries. Recent advances in PEM fuel cells, supported by Mil3, are significantly reducing size and cost. SWAPS is also far smaller and inexpensive than photovoltaic, wind turbine and wave energy systems and SWAPS is not affected by weather or time of day. For DWADS, SWAPS must compete with a diesel engine generator charging a battery storage unit. Short duration, high power-requirement missions are the one area where SWAPS can be challenged, but only by engine gensets. SWAPS is slightly smaller, with no moving parts and minimal control, requires less power conditioning, and offers quieter, cooler performance. Together with partner Falmouth Scientific, Mil3 has successfully developed and demonstrated a prototype unit for DWADS - see Figure 1. This unit continuously provides 4 kW for a duration of 48 hours to charge a custom designed 2 kWh LiFePO₄ battery that - an produce the 40kW, 20 second bursts of power utilized by the sonar system. By July 2011, this prototype will have been further demonstrated in shallow ocean water on the North Carolina coast, with planned assistance by the US Coast Guard. SWAPS has also been demonstrated for potentially applying all electrical power for instrumentation and communications on meteorological buoys and for propulsion and electronics on a station-keeping buoy (Gatekeeper) - see Figures 2 and 3. For a Navy met buoy, the performance of 720 pounds of conventional batteries and a solar PV panel was surpassed by a 24 pond SWAPS unit. For Gatekeeper, SWAPS held the buoy position in currents up to 1.5 knots. Additionally, SWAPS is an ideal primary or auxiliary power source for navigation buoys, motor and sailing yachts, surface remotely operated vehicles, SCUBA and manned underwater vehicles, ocean and coastal floating platforms, piers, and in coastal emergencies such as tsunamis. SWAPS can be extended to submersibles and sea floor operations using a compressed oxygen supply. Mil3 is also examining the used of novel liquid-gas contactor membranes for sufficient dissolved oxygen extraction in the deep ocean.