Human-Generated Power for Mobile Electronics

Since the 1990’s, mobile computing has transformed its penetration from niche markets and early prototypes to ubiquity. Personal Digital Assistants (PDAs) evolved from GRiD’s PalmPad and Apple’s Newton in 1993 to the Palm, Handspring, and Microsoft-based models that support the multi-billion dollar industry today. While BellSouth/IBM’s Simon may have been the only mobile phone to offer e-mail connectivity in 1994, almost every modern mobile phone provides data services today. Portable digital music players have replaced cassette and CD-based systems, and these “MP3 players” are evolving into portable repositories for music videos, movies, photos, and personal information such as e-mail. Laptops, which were massive and inconvenient briefcase devices in the late 1980’s, now outsell desktops. Yet all these devices still have a common, difficult problem to overcome: power. This chapter will review trends in mobile computing over the past decade and describe how batteries affect design tradeoffs for mobile device manufacturers. This analysis leads to an interesting question: is there an alternative to batteries? Although the answer has many components that range from power management through energy storage [142], the bulk of this chapter will overview the history and state-of-the-art in harvesting power from the user to support body-worn mobile electronics.