Direct Energy, 2018a

8 1.2 Preview of Topics
drodynamic device converts kinetic energy of a conducting material in the
presence of a magnetic eld into electricity.
Optical devices are discussed in Chapters 6 and 7. These chapters discuss
devices made from diode-like pn junctions such as solar cells, LEDs,
and semiconductor lasers as well as other types of devices such as incandescent
lamps and gas lasers. Thermoelectric devices convert a temperature
dierential into electricity [3, p. 146]. They are also made from junctions
of materials in which heat and charges ow at dierent rates, and they are
discussed in Chapter 8. Batteries and fuel cells are discussed in Chapter 9.
A battery is a device which stores energy as a chemical potential. Batteries
range in size from tiny hearing aid button sized batteries which store tens
of milliamp-hours of charge to large car batteries which can store 10,000
times as much energy. A fuel cell is a device which converts chemical energy
to electrical energy through the oxidation of a fuel [3]. During battery
operation, the electrodes are consumed, and during fuel cell operation, the
fuel and oxidizer are consumed instead. A variety of resistor-like energy
conversion devices, among other devices, are discussed briey in Chapter
10.
Chapters 11 - 14 comprise the second part of this book. These chapters
are more theoretical, and they establish a mathematical framework for understanding
energy conversion. This mathematics allows relationships to
be studied between energy conversion devices built by electrical engineers,
mechanical engineers, chemists, and scientists of other disciplines. Chapters
11 and 12 introduce the idea of calculus of variations and apply it to
a wide variety of energy conversion processes. Chapter 13 applies the idea
of calculus of variations to energy conversion within an individual atom.
Chapter 14 shows how a study of the symmetries of the equations produced
from calculus of variations can provide further insights into energy
conversion processes.