Designing Microfuel Cells for Portable Electronics

Abstract

The main driving force in the developments of consumer electronics, such as cell phones and laptop computers, is longer run times and more functionality. In this quest for higher energy densities, battery characteristics improve at a constant pace. Fuel cells seem to be the next big technology breakthrough improving energy density with a factor of 3–10 compared with current lithium-ion batteries. In particular, the direct methanol fuel cell (DMFC) is an interesting opportunity because of the high energy capacity of methanol and the handling of the fuel making “charging” easy, safe, and fast. To get information on the different aspects that determine the boundaries of the DMFC power source, a power source for an MP3 player, the Samsung YP-Z5F, is designed. This design is based on a DMFC plus battery (DMFC hybrid) and utilizes standard available components [Flipsen, 2007, “Design Challenges for a Fuel Cell Powered MP3 Player,” International Power Sources Symposium, Bath, Great Britain]. The design of a DMFC hybrid power source in a conventional way (standard practice engineering) will not result in a smaller power source for this particular application. The design has a power and energy densities of lower than the currently available lithium-polymer battery, mainly because of the low fuel-efficiency of the cell at low temperatures, the use of commercially available but still too bulky components, and a large amount of dead space (≈34%). There are three ways to increase the power and energy densities of the system. First is by increasing the fuel-efficiency of the cells membrane. Second is by scaling down the system components to the right proportions and third is by improving the systems architecture diminishing empty space. This paper presents the design of a DMFC hybrid with scaled-down components. A literature study is done on the efficiency improvements of DMFC cells. The results are presented in a computer aided design (CAD) model and evaluated, comparing the “improved design” with “standard practice” design and the current lithium-polymer battery. The energy density of the redesigned fuel cell system is still low compared with the used lithium-polymer battery but an improvement to the preliminary design.