How to generate Electricity
What is Electricity?
Essentially, there are two kinds of Electricity: Static Electricity and Current Electricity. Both depend on electrons, the tiny charged particles that orbit the nucleus of an atom.
Static Electricity has been known about since earliest times, though it was not properly understood until the discovery of subatomic particles a little over a hundred years ago.
Static Electricity on a large scale causes lightning and on a much smaller scale can give you an annoying shock when you step out of a car. You can generate it simply by combing your hair with a nylon comb. The electrical charge transferred to the comb will cause it to attract the hair, or, if you like, to pick up little scraps of paper to entertain the kids.
Though interesting, static electricity is of limited practical use. For the remainder of this hub, we'll concentrate on current electricity which is a flow of electrons through a conductor (usually a copper cable).
A Little Science
First, we need to talk a bit about Energy. In Physics, Energy is defined as the ability to do Work. (Everyday examples of Work are: climbing stairs, loading a truck. anything that involves moving mass).
Some of the common types of energy are: heat, light, kinetic energy (movement), chemical energy, gravitational energy and of course. electrical energy.
In Physics, the Law of Conservation of Energy says that energy cannot be created or destroyed. It can only be transformed from one type to another. This means that to generate electricity, we have to use another kind of energy to fuel the process - in this World you don't get something for nothing!
In the 19th Century, Michael Faraday carried out the pioneering work that linked Electricity and Magnetism. In particular, he showed that an electrical current is generated in a conductor moving in a magnetic field.
The effect is greatly magnified if the conductor is replaced with a coil or coils of copper wire. If these coils are mounted on a rotating shaft or armature, continuous rotation will produce a continuous alternating electrical current. This is how nearly all electricity is generated today.
Now that we have a device (the generator, or alternator) that converts mechanical energy (rotation) into electrical energy, the next problem is how to obtain the mechanical energy to keep the alternator spinning. Here is a brief summary of some of the viable ways of generating electricity on a commercial scale.
The Modern Alternator
Faraday's electrical machines were laboratory experiments. Technology has developed his ideas dramatically. The modern alternator does not use permanent magnets but an energised coil instead, to produce the magnetic field. Also, his invention has been turned inside out, with the field coils mounted on the armature (now called the rotor) and the electrical current induced on the stationary coils (the stator). There are normally three stationary windings in the stator, spaced 120° apart, to produce 3-phase alternating current, the modern standard for distribution.
The Commercial Options
In a coal or oil fired power station, the fuel is burned (converting its chemical energy into heat) and the heat used to convert water into steam at very high temperature and pressure. This then drives a steam turbine, a device which harnesses the energy in the steam (heat and pressure) to produce rotational movement (mechanical energy). The rotating shaft of the steam turbine is coupled to the armature of the alternator, so the final result is electricity.
Windmills have been around for centuries and all have harnessed the energy of moving air (wind!) through rotating sails or fan blades. Traditionally, the mechanical energy was used directly, to turn a mill wheel. A modern wind turbine simply couples the rotating shaft to an alternator armature. The last link in the chain is always the same - electricity from mechanical rotation.
Hydro Electric Power
Here, the source energy (there always has to be one!) is gravitational potential energy. A mountain stream is dammed in a high place, to create an artificial lake or reservoir. Farther down the mountain, the power station is equipped with water turbines. These are simply highly efficient versions of the old fashioned water-wheel; effectively they harness the kinetic energy of a carefully channelled waterfall to produce mechanical rotation. The rest you know.
Tidal Power and Wave Power
These new technologies extract energy from the long-term bulk movement of water in a tidal estuary and from the short-term wave motion of the surface. The principle remains the same, to harness the 'free' natural energy in moving water to drive a mechanical turbine.
Solar Power - local
In a sense. all energy on Earth is solar energy, as even fossil fuels are chemical 'memories' of ancient sunshine. But we're talking here about generating electricity from solar energy, and strangely enough, it's not very easy. The problem is that you can't easily convert sunshine into mechanical rotation to drive alternators on a commercial scale. Solar panels have no moving parts, and so the electricity they produce is 'DC' or direct current. This is like the electricity from a battery. It's great for local use, e.g. running a small irrigation pump, but the big problem with DC is that it is hard to distribute. (No time to explain that now - maybe another hub!)
Solar Power - commercial
Photovoltaic units, as described above, are best suited to localised applications like space or water heating. However, commercial-scale solar power plants, though still expensive to build, are becoming viable, the more so as the price of fossil fuels increases.
No single design for commercial solar power has yet won through, but all are based on the same idea - a large array of reflectors to collect the sun's rays and focus them onto a receiver which is effectively pipe-work containing a heat-absorbing fluid. Technologies are already well developed to store the collected energy as heat and to convert it to electricity using steam or gas turbines at a steady rate, night and day. The biggest problem is that the sun moves (OK, the Earth rotates!) and so ingenious tracking mechanisms are needed to make the reflectors follow the sun through the daylight hours.
Ironically, the part of the world best suited for deploying this technology is the part that least needs it - the oil rich deserts of the Middle East.
This is another underdeveloped source. If you drill down into the Earth's crust, at first the temperature drops, because the sun's warmth can't penetrate. But deeper, the temperature rises. Volcanoes are evidence of this - molten lava is pretty hot! That well of energy is there to be tapped. As always, the final conversion process is the familiar steam turbine. And, like solar energy, it is environmentally friendly, provided you don't accidentally trigger a local volcano! But it is not as simple as it seems. The process of taking heat from a hot rock cools the rock locally. There's plenty more heat surrounding it, but can it flow quickly enough to your collectors? Again, it's another technology whose time will come, but not a panacaea.
This is the controversial one. Nuclear fission is a process in which unstable (radioactive) atomic nuclei break down, releasing energy in the form of radiation (escaping particles). By concentrating these nuclei together, a controlled chain recation is produced releasing huge amounts of energy which is used to convert water into steam. The process of generating electricity in a nuclear power plant is simply by steam turbine, exactly the same as in a fossil fuel plant. The public fear of nuclear power is twofold: the risk of meltdown - an uncontrolled nuclear reactor is not very different from an 'atomic' bomb; also the by-product, radioactive nuclear waste, is none too pleasant.
As an aside - Nuclear energy does not obey the classical Physics law of conservation of Energy. It does however obey the Modern Physics law of conservation of Mass-Energy which allows for interconversion of matter and energy according to Einstein's famous equation E=mc² This fundamental difference means that Nuclear Energy is potentially the most fruitful source of all. It is important that proper scientific research & development into nuclear energy, and Nuclear Fusion in particular, should be allowed to continue.