Power Generation 6/25/20

Science with Richard Bleil

Let’s get away from politics for a moment. I want to talk about science for a bit, specifically, how electricity is generated. Frankly, electrical generation fascinates me. It’s a remarkably simple concept, with incredibly complex manifestations.

First, let’s discuss the relationship between electricity and magnetism. In 1873, James Clerk Maxwell developed his unified theory of electricity and magnetism, known as the “Maxwell Equations” which related, for the first time, electricity and magnetism showing their interconnectedness. His equations basically demonstrated that electric current and magnetism occur at right angles to one another.

Experimentally, this can be demonstrated in a variety of ways. For example, an electromagnet is a magnetic field, potentially a very strong magnetic field, that is generated by the flow of electricity in a highly controlled and well-organized system such that the current supports and builds on itself. My father used this same principle to magnetize many of his tools, by wrapping them with wire in a tight coil and running electricity through it. The current aligned the magnetic dipoles in the ferromagnetic metal which were maintained for significant time, long enough to be considered “permanently” magnetized.

That you can generate a magnetic field from electrical current implies that the converse must also be true, specifically, that it is possible to generate electricity from a magnetic field. In principle, it’s an easy thing to do; with a fixed magnetic field, you will have electron flow (that is, electrical current) by moving wire within the field.

This is how electrical generators in electric power plants work. With two huge “C” shaped powerful magnets with the ends facing one another, a magnetic field exists between them. Wires are wound around a core that is free to rotate. This core rotates at a rate of 60 revolutions per second, or 120 Hz. The voltage is controlled by the number of coils in the wire. Cutting the magnetic field in one direction on the up-swing, and in the opposite in the down and you push the electrons first one direction, then the other along the wire creating what is colloquially referred to as “alternating current”. It’s because of the shape of the magnets that these power generators are often circular.

Direct current, on the other hand, has the electrons always flowing in the same direction. Typically, DC current is associated with batteries, where chemical reactions within the battery drives electrons to flow from the anode (the negative side of the batter) to the cathode (the positive side) and always in the same direction. Once the chemical reactions have been sufficiently completed, the battery voltage drops, and the battery is dead. Some batteries are rechargeable, meaning that if you force current to flow through the battery in the opposite direction, the chemical reactions will reverse, and the battery will recharge. Unfortunately, some batteries use chemical reactions that will not run in reverse the same way, creating hydrogen gas which creates pressure and can ignite creating an explosion. This is why it is dangerous to try to recharge batteries that were not specifically designed for it.

The difficulty in electrical power plants, then, is simply keeping the wires on that core rotating. This takes incredible amounts of power and force. Typically, this is done through a closed high-pressure vapor system. Water is boiled and used to generate high-pressure steam. The steam travels through pipes and pushes turbine blades attached to the wire core causing it to rotate.

All of that technology is simply to boil water. Coal, oil or gas “boilers” are used in more old-fashioned power plants, while nuclear power plants use nuclear energy, but the concept is the same. The nuclear core is controlled with lead “control rods” that are inserted into holes in the nuclear core keep the reaction in check. When the reaction is going too fast, they are inserted slower to slow it down, and they are pulled out to speed the reaction up. The nuclear reaction generates a great deal of heat, which creates high-pressure super heated steam, and that steam, again, turn the turbines.

“Clean” energy uses the same turbines to generate electricity. Hydroelectric plants run water through a dam under high pressure, opening and closing control valves to keep the pressure and velocity in check, but this water turns the turbine blades to generate electricity in a very similar generator. Wind turbines work exactly the same way but with smaller and more compact generators. None the less, the turning turbine blades are rotating the wire coils in the generator housed in the top unit.

Solar power is a different beast altogether. First it generates direct, rather than alternating, current. Light is absorbed, and the energy moves electrons from a lower energy to a higher energy band. These electrons then flow through the circuitry back to the original band creating a constant flow of electrons in the same direction. To make this current compatible with the alternating current system, it has to do though a DC to AC converter. This is the opposite of what your computer system uses. With a built in battery, it must have direct current to recharge and operate, so the power going into your system goes through an AC to DC converter.

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