D.1 Introduction

In general, 10–30% of the total volume in a portable electronic application is used by its power source. This percentage is increasing in newer applications, where the electronics size is decreasing and the quest for more power and energy is increasing. This makes the power source an important component influencing a great deal of the application's form.

Usually a power source is chosen at the very end of the design process (usually called off the shelf) instead of at the beginning of the conceptualization phase of the design process. Most industrial design engineers operate in the concept phase, and almost 80% of the product is defined in this phase. Based on first assumptions the industrial design engineer wants to size the application, which leads to important and sometimes irreversible choices. The industrial designer engineer makes use of experience from past projects, knowledge deve-loped at school and university, expert knowledge, or mother wit. When it comes to power sources, no tools are commonly used that support the industrial designer.

Therefore, in this case a review is given of tools and methods that give conceptual designers a first estimate of the issues they have to deal with when designing the power source. Section D.3.1 provides a first approach to a second-order model and method that should produce an optimized volumetric design of the fuel cell (FC) hybrid, being used in the concept phase of design.

Also in this case we will show a tool that has been developed for choosing and sizing the right power source combination for a portable electronic application during the concept phase of design. A literature review on tools and methods is also executed, described in detail in Section D.2.

In Section D.3 a first approach toward a new algorithm for a power source selection tool is presented. For this tool, different transfer functions have to be developed. In Section D.3.2, a simple analytical model for the direct methanol fuel cell (DMFC) hybrid system is presented. This model is evaluated by designing a FC-powered MP3 player (Flipsen, 2007, 2009) as presented in Section D.3.3. The simple model was found not to be sufficient in the design of an FC hybrid system, and is updated based on the redesign, in Sections D.3.4 and D.3.5.