Technical and cost analysis of Medis’ micro fuel cell


By Fréderic Breussin, Yole Développement

The ‘energy gap’ in portable electronics makes micro fuel cells increasingly attractive. However, the technology adaptation has been delayed due to high costs, lack of standards, and low reliability. Over the last year, tremendous improvements have been made to the technology in terms of reliability and miniaturization. To enter the market, many players are developing fuel cell chargers for electronic devices such as mobile phones and PDAs. Among the current major players in this field (MTI, Angstrom, Toshiba, and others), Medis Technologies is the first company to launch a consumer product in the market, while others are not expected before the end of 2008.

Figure 1 gives an overview of some power devices available on the market or under development. Note that UltraCell developed a device specific to military applications that is extremely robust and can deliver relatively high power, but it is not well-suited to portable consumer applications due to its size and weight.

Figure 1: Fuel cell chargers availabe or under development
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The interest in the Medis Technologies Power Pack application (bottom-left of Fig.1) resides in the compactness of the energetic solution, which is very easy to use. In fact, this self-powered fuel cell can be used without external gases except the oxygen in the air. Consequently, this solution can be adapted to many potential markets. This device is not refillable, which means that it has to be disposed after use and has therefore must be low-cost. It has a power capacity of 20Wh and is able to perform up to 15 cell-phone charging operations, which is equivalent to 20 AA batteries, for half their weight and approximately the same volume occupation.

Figure 2: Medis Power Pack.
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To better understand how Medis Technology has been able to put a consumer product on the market more than a year earlier than its competitors, we proceeded together with SYSTEMPlus Consulting to a complete technical and cost analysis of this product. This analysis provides answer to the following questions:

  • How does the Medis fuel cell works, and what does it contain?
  • How can Medis Technologies provide a low-cost disposable fuel cell charger?
  • How does this technology compare to the competing products under development?
  • Is the technology safe and reliable?
  • How could this technology be improved in the future?

The Medis Fuel Cell is an alkaline borohydride fuel cell that includes three tanks (Figure 2): one filled with water, one with KOH electrolyte, and the third with a gel mixing NaBH4 and KOH. The working principle of an alkaline fuel cell is illustrated in Figure 3. In this particular case, the sodium borohydride NaBH4 breaks down on contact with water according to the following reaction:

NaBH4 + 2H2O -> NaBO2 + 4H2

This reaction enables creation of H2 gas for the catalytic reaction on the anode level. Reaction at the cathode level occurs with oxygen coming from ambient air.

The design relies on cheap materials and an optimized manufacturing line. The result is an estimated manufacturing cost near US$5, with 40% for the electrodes, 20% for the fluids, 20% for the plastic parts and connections, and 20% for assembly.

Figure 3: Alkaline fuel cell principle.
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Further information is published in a Yole Développement study, “Medis Power Pack: Micro fuel cell technical and cost analysis,” which provides an overview of the competitive landscape of fuel cell chargers, and a complete description of the technology, including working principle, technical analysis and pictures of the main parts, with chemical analyses of the different fluids used, as well as the material analyses of the electrodes. The report also includes a detailed cost analysis of the product (quoting electronics (PCB and connectors), liquids and gel, electrodes, plastic parts, and assembly), and an overview of the advantages and limitations of the product, with suggestions to improve its performance.

Fréderic Breussin started his career as project leader in the power industry. In 2004 he became business developer at TNL (NL) with special attention to microfluidic devices, micro reactors, sensors, and precision instruments. He joined Yole Développement in 2007 as project manager, microfluidics.