What Makes Open Water’s Technology Different?

Open Water’s technology is different from other aluminum-based power systems developed at MIT and elsewhere.  A progression of three increasingly advanced aluminum-based systems have been developed at MIT as part of an ongoing collaboration between Lincoln Lab and a senior design course at MIT.  Open Water Power’s founders were a part of the development of all three systems, which built upon the large body of work done previously by others in this field.  Open Water’s direct fuel cell chemistry is the final evolution of decades of research done at MIT, elsewhere in the US, and around the globe by talented researchers across a number of disciplines.
TableOfEnergies
Aluminum has enormous potential as an energy source for underwater use, as shown in the table above.  At 47 MJ/L when oxidized by water, it stores more energy per volume than any other metal fuel.  The various technologies developed at MIT and elsewhere attempt to harvest that energy in different ways.  A timeline of our work is depicted in the graphic below, followed by a detailed description of these various approaches.
ComparisonWithoutLogos-WithTransparency
Type #1: Aluminum as a Heat Source.  This earliest type of system uses the Al-H2O reaction to generate heat, which in turn is used to drive a heat engine (e.g. a Stirling cycle engine) and/or  thermoelectric generators.  Projects taking this approach include ARL/Penn State’s aluminum combustor[1] and the first aluminum system developed by the Lincoln Lab / MIT collaboration.  This technology is still being developed at MIT for niche applications that require a lot of heat or gas, but it is infeasible as an electrical power system for UUVs and sensors.  The activation of aluminum with gallium that was developed for this category laid the groundwork for the two more advanced types of systems that have been developed since.
Type #2: Aluminum as a Hydrogen Source.  The next type of system uses the Al-H2O reaction as a hydrogen gas source, combined with a complementary system for oxygen storage. The two gases are used to drive a proton exchange membrane (PEM) fuel cell. Projects taking this approach include the General Atomics & Infinity “ALPS” system being developed for the LDUUV program[2], as well as the second aluminum system developed by the Lincoln Lab / MIT collaboration.  Unfortunately, the oxygen storage components (whether compressed gas, chemical storage, or liquid oxygen) limit the achievable energy density and can pose significant safety hazards.  This type of system can practically store between one and three times as much energy as a Lithium-ion system[3] at large scales like the LDUUV, but the balance of plant systems scale down poorly, making this type of system infeasible for small and mid-sized UUVs.
Type #3: Direct Electricity Generation.  This most recent and most advanced type of aluminum power system generates electricity directly from the Al-H2O reaction.  This is done by splitting the reaction into two half-reactions to create a fuel cell.  This is the technology Open Water is commercializing.  It builds upon decades of aluminum anode research[4], including aluminum-air fuel cells and aluminum-seawater corrosion batteries.  This technology can practically store ten times as much energy as a lithium-ion system, can dynamically provide small and large amounts of power, and can do all of this far more safely than any of the alternatives.
When Open Water spun out of MIT, the Type 1 & 2 systems were left behind so that  students could continue using them as class projects for educational purposes.  Those systems have not been spun out as companies by others because they were not deemed to be commercially viable, but they remain active class projects at MIT because they are academically interesting.  Open Water is exclusively commercializing the Type 3 direct Al-H2O fuel cell.  Open Water’s co-founders are the inventors on the pending patent applications, and Open Water holds the exclusive rights to them.  We have great confidence—and the data to back it up—that this technology is the future of underwater power.

 


[1] Miller, T.F., Walter, J.L., Kiely, D.H., “A next generation AUV energy system based on aluminum-seawater combustion,” Workshop on Underwater Vehicles, June 20-21, 2002.
[2] http://fuelcellseminar.com/wp-content/uploads/b2b32-2-1.pdf Accessed April 5th 2015
[3] Mendez, Alejandro, Teresa J. Leo, and Miguel A. Herreros. “Current State of Technology of Fuel Cell Power Systems for Autonomous Underwater Vehicles.” Energies 7.7 (2014): 4676-4693.
[4] Li, Qingfeng, and Niels J. Bjerrum. “Aluminum as anode for energy storage and conversion: a review.” Journal of Power Sources 110.1 (2002): 1-10.