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Direct methanol fuel cells (DMFCs) employing proton exchange membrane
electrolytes have emerged as a major contender for power sources
of many electronic applications, most recently as a supplement
or even replacement for current rechargeable battery packs for
notebooks.
For the system operation, dilute methanol solution of a specified
concentration enters the stack. Methanol in a fuel cell delivers
power most efficiently when it is mixed with water in a 3 percent
to 6 percent concentration. Since water is generated in the process
itself, methanol sensor is required for monitoring and controlling
the fuel concentration in DMFC. The dielectric constants of water
and methanol differ by a factor of 2.4 allowing it to determine
the exact ratio from measurements provided by the fluid sensor
developed by CMT.
Until recently the small optimum concentration of water meant
that the fuel tank would have been simply too large for portable
equipment. However, in most recent fuel cells the methanol is
diluted by water directly produced in the power generation process.
This process controlled by methanol sensors allows the methanol
be stored at a much higher concentration, allowing the size of
the fuel tank to shrink to only 10 % of the size previously needed.
Communicating with the computer the methanol sensors can even
tell users when it is time to change the cartridge. |
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