When we flip a light switch and nothing happens due to a power failure, what do we turn to for electricity? We typically use battery-powered flashlights and lamps. Other portable devices, such as cell phones, watches, and hearing aids, require the use of ever smaller and longer-lasting, reliable batteries. This chapter starts by discussing the electron transfer that takes place in different types of batteries. What is the difference between a rechargeable battery and one that must be discarded after it "runs down"? What are fuel cells, and how can they be used to produce electricity? Hydrogen is one of the fuels used in fuel cells. And so the chapter continues by considering hydrogen, a non-fossil fuel. After being obtained from a variety of possible sources, hydrogen can either be burned as a fuel or used to generate electricity in a fuel cell. The discussion of fuel cells leads to a related section on powering many modern devices, including the so-called zero emission electric vehicles (ZEVs). Although electric cars are now commercially available, questions about them remain: Why have them? How do they operate? How do they compare to gasoline-powered vehicles? Are electric vehicles competitive in the marketplace? Are people using them? We will address all these questions in this chapter, as well as discuss other electric vehicle technologies.

In the long run, the most promising alternate technology for generating electricity could well be photovoltaic cells, devices that convert the Sun's radiation directly into electricity. The principles governing semiconductors in photovoltaic cells, their operation, and their current and potential applications are discussed. The chapter ends with an assessment of future trends in developing energy sources from electron transfer.