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Use of sensor systems in water bodies has applications that range from environmental and oceanographic research to port
and homeland security. Power sources are often the limiting component for further reduction of sensor system size and
weight. We present recent investigations of metal-anode water-activated galvanic cells, specifically water-activated Alcells
using inorganic alkali peroxides and solid organic oxidizers (heterocyclic halamines), in a semi-fuel cell
configuration (i.e., with cathode species generated in situ and flow-through cells). The oxidizers utilized are inexpensive
solid materials that are generally (1) safer to handle than liquid solutions or gases, (2) have inherently higher current and
energy capacity (as they are not dissolved), and, (3) if appropriately packaged, will not degrade over time. The specific
energy (S.E.) of Al-alkali peroxide was found to be 230 Wh/kg (460 Wh/kg, considering only active materials) in a
seven-gram cell. Interestingly, when the cell size was increased (making more area of the catalytic cathode electrode
available), the results from a single addition of water in an Al-organic oxidizer cell (weighing ~18 grams) showed an
S.E. of about 200 Wh/kg. This scalability characteristic suggests that values in excess of 400 Wh/kg could be obtained in
a semi-fuel-cell-like system. In this paper, we also present design considerations that take into account the energy
requirements of the pumping devices and show that the proposed oxidizers, and the possible control of the chemical
equilibrium of these cathodes in solution, may help reduce this power requirement and hence enhance the overall
energetic balance.
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