Today at the Small Fuel Cells Conference in Washington, D.C., Neah Power Systems revealed it has reached a major milestone in the development of its micro fuel cell technology. The company recently demonstrated a fully integrated, multi-cell “stack” functioning as the core engine of a fuel cell based on the company’s silicon engine. The results verify the potential of the proprietary silicon-based architecture, which differs from the popular approach of the proton exchange membrane (PEM) direct methanol fuel cell (DMFC) system.
The fuel cell stack just demonstrated in the company’s laboratory consisted of three individual fuel cells connected in series to produce approximately 1.2 W to 1.3 W of output. Each cell in the string produces 0.3 V to 0.5 V at about 1 A. Fed by an external benchtop source of methanol, the fuel cell stack provided stable power output for approximately 1 hr, indicating the robustness of the company’s all-liquid silicon-based system. Power density levels exceeding 80 mW/cm² at room temperature were achieved.
This system differs from the convention DMFC in that it does not contain a PEM. Instead, Neah Power Systems’ fuel cell uses liquid electrolyte and silicon-based electrodes. With its finely etched pores, the silicon electrode structure provides a 3D reaction zone that is said to increase the overall power density and efficiency of the fuel cell when compared with PEM-based DMFC systems.
The recently demonstrated fuel cell stack is less than one-third the size of the company’s first fuel cell stack prototype, which was demonstrated in 2003. To reduce the size of the stack, the company has optimized the electrode structure by doping the electrodes with new catalysts and conductive materials.
The company now is working to combine the fuel cell stack with a pump and power conversion circuitry to create a complete fuel cell prototype. The company expects to complete this prototype by the end of the year.
The military is said to be one of the likely first adopters of this fuel cell technology. Existing military radio systems now use a primary lithium battery, the BA-5590, for power. Weighing 1 kg and occupying a volume of 883 cc, this battery offers a capacity of 210 Wh. The corresponding energy density for this battery is 238 Wh/l and 206 Wh/kg.
Neah Power Systems intends to produce a fuel cell with power capability like that of the BA-5590, but with a weight of just 483 g and a volume of 286 cc. With the approximately 600 cc of remaining battery space used for fuel, the fuel cell will be able to deliver 9 W of output for 72 hr, or 648 Wh of capacity—three times that of the lithium battery. The company plans to produce qualification units for this fuel cell by 2006 and commercially ship units in volume the following year.
For more information, visit www.neahpower.com.