Intro to Power, Part 1: Power Generation
Magnet Inside a Power Generator
I’d like to start off with something so important, but so invisible, in our everyday lives. We all know by now that energy and power generation is the hot topic that’s moving us forward, with talk about global climate change, renewable energy, and “green” technology.
I’ll kick off the blog with a special 4-part series about energy and power generation. Let’s start with reintroducing the concept of energy and the basic ideas used by nearly all power stations today. It is at least a little bit scary that, with all the talk in the media about how we must reinvent the energy sector today, very few people actually know where we need to reinvent from. What are our current means of producing electricity? How do we make the energy we need to light today’s highly electrified infrastructure?
With the exception of photovoltaic cells (which atomically converts sunlight into electricity) and maybe batteries (even hydrogen fuel cells are essentially just chemical batteries), pretty much all the energy we use today is generated by something spinning or turning, from chemical to kinetic to electric energy conversion. It all starts with magnets and electric wire. Fundamentally, the electric generator consists of a bar magnet spinning inside a stationary coil of wire (called it the stator). As it spins, the magnetic field the wire experiences from the magnet changes, and this change induces an electric current in the wire. By winding a large number of turns of wire into a ring or doughnut, the end-result is a much more powerful current. It’s this single principle that’s what lights our homes and and power our computers. That’s it!
In actuality, however, a simple permanent magnet isn’t strong enough, at least in the past. Today’s permenant magnets have gotten strong enough to perform the way we need them to work. Otherwise, we need to beef it up by making it an electromagnet. (An electromagnet is magnetized by electricity flowing to another set of coil s of wire wound around the magnet itself.) This might be a sort of Catch-22. For the generator to function in any real capacity, this electromagnet needs to be powered. Otherwise, we can have all the kinetic and chemical energy we want with no way of converting it to usable, electrical energy.
Basically, we need energy to make energy. (Keep in mind there are other components in the system that needs to be powered too, like motors, pumps, and lights. We’ll get to those things next time.) The simplest way to get this energy is to draw it from the energy from the plant itself. And surely enough, that’s what we do. But what happens if the plant is cold, i.e. completely offline? Well, then, we’ll need the help of the others connected to the “grid” or use an auxilary generator, which is smaller and whose sole purpose is to start up a power plant. Component by component, the plant comes online.
Here’s our goal: To get this magnet to spin really fast. Simple, isn’t it?
Wind Turbine in England
All the coal plants, natural gas plants, fuel oil plants, nuclear plants, biomass plants, geothermal plants, solar thermal plants, wind farms, hydroelectric dams, and tidal-powered systems are merely ways to get this magnet to spin. Remember, a spinning magnet relative to a stationary coil of wire creates electricity.
Now, it gets a little complicated. We all understand we need electricity. There is no way around it. Where the problems and controversy lies is how to do it. Believe it or not, all the types of power plants I listed above, except the last three, can be grouped together—they function essentially the same. We’ll refer to them as steam turbine power plants.
Next time, we’ll take a step-by-step look into how steam turbine power plants (the most popular “style” of power generation) get this magnet spinning.
If you have any questions so far, definitely leave a comment below.
(Power Generator image from Alternative Energy Blog. Wind Turbine image from Flickr.)
You say to generate electricity you need to spin a magnet around a coil of wire. Can you also spin a coil in a magnetic field creating electricity?
Also how would would start an electromagnet (simple coil around a piece of metal) in a generator that already requires mechnical energy to convert to electrical energy.
@ Abdul Kohistany
The idea is to have a CHANGING magnetic field in a coil. The rate of change is what decides how much power comes out of the generator. It does not matter whether the magnet is moving and the coil is stationnary or vice-versa. The magnet can be a permanent or electro magnet : its only purpose is to create a magnetic field.
In fact, motion is not even required : in a transformer, a constantly varying current is sent to an electromagnet creating a constantly varying mag field near another coil. The constantly varying mag field will induce current in the second coil (called “secondary” for this reason). We cannot use transformers to produce electricity however since they need electricity to produce the mag field : there is no net gain.
Starting an electromagnet in a generator is no problem neither since, even if the rotor is magnetised by coils, there is always a (maybe weak) mag field remaining in the ferromaterial of the rotor even when there is no current in the coils. So, starting it turning will create a weak current in the stator’s coils which can be used to increase the mag field of the rotor, creating more current in the stator which can be used to increase the mag field of the rotor, creating more current in the stator, which can be used to… until the desired output is obtained, which takes usually just a few seconds. At starting, the rotor can also be magnetised by a current from a battery : this is exactly how car alternators operate. The energy from the rotating movement then induces more current in the stator then is needed in the rotor, resulting in a net current gain at the expanse of mechanical rotational energy.
So, the only real problem is turning the rotor. And one thing to remember is that, when the alternator (or generator) produces current which is used by an external load, this current puts a brake on the rotation of the rotor, making it more difficult to turn. This is a consequence of the law of conservation of energy : you won’t get more energy out of a generator than what you put in. Or, to say it in bussinessmen’s terms : TANSTAAFL : Thar Ain’t No Such Thing As A Free Lunch.
@ Kevin C
Maybe there is an obvious link somewhere and I didn’t see it, so this may be a “duh?” question, but how do we go to part 2?