Chapter one of the study was used to introduce the topics under consideration, provide a statement of the problem, the purpose and importance of the study, as well as its scope and rationale. Chapter two provides a critical review of the relevant and peer-reviewed literature, and chapter three more fully describes the study's methodology, including a description of the study approach, the data-gathering method and the database of study consulted. Chapter four is comprised of an analysis of the data developed during the research process and chapter five presents the study's conclusions, a summary of the research and recommendations for improvements to the device prototyped and envisioned herein.
Chapter 2: Review of Related Literature
It is reasonable to suggest that all battery-powered handheld device users have experienced battery failure at a critical juncture, whether it is making an important or even emergency call on a cell phone, uploading an assignment to school, or downloading critically important corporate data on a personal digital assistance, tablet computer or similar devices. In this regard, Clinton and Kantrakirschner ask, "Why is it that more and more we find ourselves pushing the 'on' button and watching the sad spectacle of nothing going on?" (2004, p. 58). The reason for this failure, of course, is the limited amount of power that conventional batteries are capable of providing, with some of the more power-hungry devices such as multifunction cell phones, laptop and notebook computers that require battery replacements after just an hour's use (Clinton & Kantrakirschner 2004). As an example of such energy-intensive devices, Clinton and Kantrakirschner cite the Nokia 7700 which provides the following features:
1. A 65,546-color touch screen with 640x320-pixel resolution,
2. A Web browser;
3. Audio and video playback;
4. FM radio;
5. Built-in camera;
6. Voice recording;
7. Bluetooth connectivity;
8. Personal-information-management software, word processing, spreadsheet and presentation viewers.
This veritable "Swiss army knife" of mobile devices was engineered to provide between just 3 and 4 hours of telephone use only, and this performance is severely diminished if any of the other features are used (Clinton & Kantrakirschner 2004). According to a senior analyst for the technology consulting firm IDC, "Everybody wants more in the way of functionality, everybody wants more in the way of capabilities. They wish their iPod had a color screen. Vendors are trying to pack in more processing power; better, brighter, deeper displays; better audio capability; 3-D accelerators for graphics; more storage. And the reality is, battery life is extremely limited" (quoted in Clinton & Kantrakirschner 2004, at p. 60). Not surprisingly, researchers have been actively involved in seeking improvements in conventional battery design and performance, as well as reducing the energy requirements for existing devices. To date, at least some progress has been made as can be seen from the power requirements needed for three-megapixel digital camera model shown in Figure 5 below.
Figure 5. Average Power Requirements for 3MP Digicams: 2002-2004
Source: Based on tabular data in Clinton & Kantrakirschner 2004, p. 60
Other improvements in performance have also been developed in screen displays and hard drives for mobile computers, but the fact remains that while this research continues, the marketplace is being flooded with other multi-feature devices that remain energy-intensive and require frequent battery replacements. For instance, a recent report from Denison (2011) emphasizes that, "As the technology built into battery powered devices like laptops and cell phones advances, so does their demand for power. it's great that your cell phone can now act as a fully functional GPS device and HD video player, but it starts looking a lot less attractive when its battery life is knocked out in a matter of minutes" (p. 2).
While these multi-feature devices continue to be improved in their performance, the constant addition of yet more functionalities has created a Catch-22 cycle wherein researchers have been more efficient in incorporating additional features in hand-held mobile devices than they have in the battery technology that is required to power them (Yildiz 2009). According to this authority, "The critical long-term solution should therefore be independent of the limited energy available during the functioning or operating of such devices" (Yildiz 2009, p. 4). There are some potentially long-term solutions available, though, and Table 1 below compares the estimated power and challenges of various ambient energy sources in a recent study by Yildiz, Zhu, Pecen, and Guo (2007).
Table 1
Comparison of Power Density of Energy Harvesting Methods
Energy Source
Power Density & Performance
Source of Information
Acoustic Noise
0.003 ?W/
0.96 ?W/
(Rabaey, Ammer, Da Silva Jr.,
Patel, & Roundy, 2000)
Temperature Variation
10 ?W/cm3
(Roundy, Steingart, Frechette,
Wright, Rabaey, 2004)
Ambient Radio Frequency
1 ?W/cm2
(Yeatman, 2004)
Ambient Light
100 mW/cm2 (direct sun)
100 _W/cm2 (illuminated office)
(Yildiz 2009)
Thermoelectric
60 _W/cm2
(Stevens,...
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