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Power Generators of Past and Present

While there are still many who believe that pictograms discovered in the tombs of ancient Egyptians strongly resemble batteries and filament light bulbs, the only form of power generators known, for certain, to have existed in those times were electric eels, some species of catfish, and manta rays. Interestingly, the physicians of that period made use of this curious natural ability as a means to treat muscle pain. The application of electric current to various parts of the body, although produced by more scientific means, is still used to provide pain relief by physiotherapists today.

Man cannot take credit for inventing electricity, which, of course, is a natural phenomenon, and one whose potential is clearly demonstrated in the lightning strike. Instead, the role played by humans has been to find ways in which to produce it artificially with the aid of power generators in one form or another, as well as to employ the current produced to perform various useful tasks.

Lightning is an example of static electricity, and occurs when the heavier negatively charged particles in a cloud sink to the bottom, creating a difference of potential energy between these and the lighter positively charged particles left behind. When that difference is large enough, the static discharge known as lightning occurs. In practice, static electricity can also be produced simply by rubbing various materials together, by applying pressure as in the piezoelectric effect, and even by applying heat to some materials.

However, while these properties have been widely applied to create machines capable of producing huge voltages, in this form, the output of power generators has little practical use, because the movement of the charged particles produced is completely random. To operate an electrical device, such as a lamp or a radio, a steady flow of electrons is required.

Thus, while the work of physicists, such as Holtz and Wimshurst during the mid-1800s served to reveal a lot about the nature and behaviour of matter, it was the phenomenon known as electromagnetic induction, revealed by the experiments of Michael Faraday, that would eventually lead to a more practical form of machine capable of powering lighting and the many other applications of electricity that were to follow.

Almost all modern power generators employ the principle of electromagnetic induction in which the interaction between a moving magnetic field and a metal coil is used to induce a flow of electrons in the latter. The main difference between the various types of machines now in use is the means employed to create the relative movement between the magnetic and the coil components. Most commonly, it is an internal combustion engine that provides the necessary mechanical rotation, and these differ both in their size and the various fuels used to drive them. These include diesel, petroleum, LPG, and natural gas for most industrial, commercial, and residential purposes, while most of Eskom’s power stations depend on burning coal to produce steam in order to rotate turbines.

Concerns for the environment have led to the development of alternative power generators. Although hydroelectric schemes have been operating for decades, more recently, their output is being supplemented by wind farms and tidal barrage schemes, both of which also make use of natural forces to drive their turbines. Such schemes are costly and tend to be accessible only to utility companies, while another renewable energy option has been gaining growing attention from industrial, commercial, and domestic users worldwide.

Solar energy promises to be the most eco-friendly source of electricity to date. Both the warmth and the light of the sun can be harnessed for various tasks. While the former is largely limited to the production of hot water, the latter has led to a new breed of power generators that have no moving magnetic field, but which rely, instead, on the photovoltaic effect to convert the energy from photons into direct electric current.