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Power Generators

The Evolution of Power Generators

Though the Greek Philosopher, Thales of Miletus, wrote of the electrostatic effect of rubbing amber in 600 BC, it was 2 400 years later that electricity was first harnessed to perform useful work. Nevertheless, humans have never ceased to find new ways to harness energy for their own purposes. Though no wires or electrons were involved, the earliest power generators were the beasts of burden that hauled the heavy loads their owners were unable to carry. Later, mankind learned to exploit the kinetic energy of the river to turn the water wheels, which in turn, operated the millstones to grind corn into flour, a task later made possible with the windmill.

To create the first machine that was capable of generating electricity required the marriage of motion and magnetism. The first person to achieve this was the British scientist, Michael Faraday, in 1821. His invention, however, did not produce electricity, but was a motor driven by it. Further experiments revealed that the process was reversible. Rotating the motor manually caused an output of electric current through a principle known as electromagnetic induction. This became the mechanism employed by the majority of future electrical power generators.

When rotating a magnetic field around a coil of copper wire or vice versa, a flow of electrons is induced in the coil. This results in an opposite flow of electrical current, which may then be used to power various external devices. Adding a suitable engine to perform that rotation led, first, to the dynamo, with its direct current (DC) output and, later, to the alternator, which produced the alternating current (AC) that, in time, would become the standard in most countries. Early applications were directed mainly at street lighting following the establishment of the first commercial generating stations in the US.

Domestic electricity from power generators was the inevitable spinoff of the industrial revolution, and early steam-driven units were soon joined by models driven by internal combustion engines fuelled either by petrol, diesel oil or, more recently, by natural gas or LPG. Even before current concerns about the environmental consequences of burning fossil fuels and their limited reserves, a combination of economics and geography drove the development of hydroelectric schemes. In a more sophisticated version of the ancient water wheel, the head of water created by constructing a dam is used to drive turbines in order to provide the rotational energy required for electromagnetic induction.

In practice, hydroelectric schemes are not the only power generators whose modus operandi is based on updated ancient technology. Today, rows of gigantic three-bladed windmills have become a common sight in most countries. Described as wind farms, they are the latest addition to the genre. Instead of milling corn, these slimmer, modern descendants leverage the power of the wind to supply consumers with vital kilowatts.

Up until relatively recently, the physical property of electromagnetic induction formed the sole basis for producing usable electricity. That constraint has since been lifted with the development of the photovoltaic cell. With no engine or moving parts, its action is chemical rather than physical, and relies on the ability of photons in sunlight to displace electrons from a suitably treated semiconducting material, such as silicon. Arrays of solar panels have become the new silent power generators and are now to be seen adorning the rooftops of suburban dwellings across South Africa. On a much larger scale, massive ground-level arrays of solar panels are now also being utilised, in a manner similar to the wind farm, for the production of electricity on a commercial scale.

On the local scene, continuity of supply remains an issue, as Eskom’s failing infrastructure and generating capacity continues to necessitate the parastatal’s policy of load shedding, and drives the need for industrial, commercial, and even residential consumers to acquire their own power generators to cope with the outages that have become a feature of South African life.