Introduction
The initial chapter of this work is devoted to a discussion of the various factors involved in the "energy crisis"; surveying various sources of energy, considering the ecological consequences of their usage; and indicating the potential of a solar cell driven solar-electric energy system. Chapter П provides insight into the amount of energy available in sunlight as a function of the site location on the earth’s surface, the weather and the time of year. This second chapter also includes preliminary information on the ways and means of manipulating and concentrating sunlight. The third chapter is devoted to a brief review of solid state physics, semiconductor materials and those phenomena of importance when considering solar cells. The interaction of light and semiconductors, including reflection, transmission and photon absorption is examined in Chapter IV. A general model for estimating the energy that can, potentially, be converted from optical form (sunlight) to electrical nature is developed in this chapter.
In the fifth chapter, methods for separating and collecting the hole – electron pairs generated by the incoming photons are discussed. An expression for the electrical power delivered to a matched external resistive load by a solar cell, in terms of the parameters of that cell, is derived. Chapter VI is concerned with specifying the properties of a semiconductor solar cell in terms of the methods used in its construction and the optical orientation of the solar cell. The seventh chapter investigates the effects of temperature and optical concentration on the performance of a solar cell. Chapter VIII studies additional advanced techniques including techniques for altering the input photon spectrum such as dichroic mirrors and thermophotovoltaic systems.
To a great extent, the material covered in Chapters I and П is introductory in nature, concerning energy as a general field as well as solar energy in particular. The third through eighth chapters are devoted to solar cells constructed of single crystal semiconductors—both in theory and practice. The ninth chapter, expands our viewpoint by examining solar cells constructed with polyciystalline and amorphous semiconductors. Because the theory of operation for such solar cells is not, as yet, thoroughly grounded, Chapter IX is primarily one of example, discussing the observed performance of recent amorphous and polycrystalline solar cells.
As intimated in the preceding chapters, there remains considerable research and engineering development to be done before we can consider the solar cell to be as a routine a device to construct and use as a rectifier diode. It is not even certain whether single crystal, polycrystalline, or amorphous material orientations would be preferable, or even which semiconductor would be most desirable. Rather than spend additional time on other solar cell optical orientations, other materials, special heat sinking schemes (all of which would be variations on the various technologies and designs considered to date) let us spend what space remains in this work on some of the system aspects of solar energy.
We cannot simply "plunk" down a solar cell, attach a load and expect a completely satisfactory energy production scenario. We need to consider the economics of fabrication (of the solar cells and of the other portions of the solar cell modules, including such items as a solar tracking systems) and of assembly (taking individual solar cells and placing them in electrical circuits, installing the circuits in modules or collections of solar cells, and placing the modules in physical structures that protect the cells from ambient conditions, allowing for electrical and thermal conduction and enabling the solar cells to follow the motion of the sun). We also must consider the cost of solar cell system operation. (Do the solar cell systems require energy to enable them to move to face the sun, is cleaning of the solar cells required, and is some of the obtained solar energy required for other operating purposes?)
Furthermore, sunlight is not available on a twenty-four hour basis (we are considering solar cell systems installed on the earth’s surface, as opposed to those employed in various artificial satellite operations) so that we need to give thought and commit resources to storing this solar – derived energy against periods of darkness and inclement weather. We should also give some consideration to potential future developments in photovoltaic energy production and storage. We begin this final survey of solar cells and solar cell systems by considering the economics of solar cell power production.
