E.1 Introduction

Photovoltaic (PV) cells have been introduced to consumer products since as early as the mid-1980s and have found many applications in consumer products since that time, for example calculators and wristwatches. A large percentage of the PV products presently available on the market, however, do not function properly or have shortcomings that make them noncompetitive with their conventionally powered counterparts (Kan, Van Beers, and Brezet, 2004). In addition, the present knowledge base on systems powered by small PV units does not cover the knowledge necessary for suitable consumer product designs (Veefkind, 2004). This may result in poor energetic performance, which users perceive as inappropriate, especially for PV-powered devices.

To investigate industrial design processes with regard to technical engineering solutions, we selected a test product: the solar-powered wireless mouse (SPM) (Alsema et al., 2005). The choice for this SPM fulfilled our aim to tackle the many problems frequently encountered by PV product designers. The key issue – to select a challenging product case – was fulfilled to such an extent that it was initially unclear whether an SPM product could be a feasible product concept at all. Variations of device use patterns and available irradiation lead to uncertain energy balances. In the case of heavy device use and little irradiation, it may not be possible to power an SPM on a solely PV-generated charge. Furthermore, the hand of the user will have to touch the SPM cover with the solar cells directly underneath, thereby shading the solar cells and reducing the amount of generated charge. Moreover, the uncertainty of the energy balance poses the question of how far users are willing to sunbathe their PV-powered mouse. The energy balance is thus one, if not the most critical, issue for an SPM product type. Integrating solar cells into a wireless computer mouse in an aesthetically pleasing and energetically acceptable way poses yet another challenge.

In this case study, we will present technical engineering solutions in combination with correlated industrial design processes, which are required to build a wireless computer mouse equipped with solar cells (Reich et al., 2009). First, we aim to distinguish different design concepts of computer mice that are to be equipped with PV. Therefore, in Section E.3 we will analyze the product and design criteria of this kind of product. The design process itself also comprises research on and analysis of user requirements and desires, and a preliminary assessment of suspected energy balances. Second, in Section E.4 we aim to identify one optimized design concept that is related to both technical aspects and design aesthetics. Here, the selection and dimensioning of the required secondary battery type and size are discussed together with required charge controller electronics. Also the selection of appropriate solar cell types, especially with respect to appropriate low-light performances of the various PV technologies that might be used, will be presented.

The integrated approach, especially the cooperation of PV and industrial design experts, contributes to improving the product design process of PV-powered devices, which might help to open up further markets for solar cell applications.