Making electricity is easy. You take a coil of wire, you spin it near a strong magnet and you get electricity. Getting the coil to spin is, oddly, the more challenging part. I’ll explain this below, but first let’s talk about my childhood.
When I was a kid my favorite toy was a race track with little electric cars. The track was made of plastic with two lanes. Each lane had two thin metal rails and a groove down the middle. The cars had a pin in the front to go into the groove and two metal skids to slide along the rails. When you switched it on there was a small voltage applied across the rails. If you’ve never see one before, here is a picture.
It was pretty much the perfect toy for a young engineer. You could put the track together in multiple configurations and you had to be adept at repairs and maintenance to make it work, fixing electrical connections, replacing broking pins, cleaning the rails and skids for good electrical contacts, aligning little plastic gears, etc.
Under the plastic lid of the little cars is everything you need to learn about how electricity is produced. Inside the car are two curved magnets (like little half moons) surrounding a coil of wire on a disk. When you turn on the track, electricity flows from the two little rails, through the skids, and through the coil. Running electricity through a coil of wire makes an electromagnet. Below is a picture of about the simplest possible electromagnet. The battery makes electricity flow through the wire turning the coil into a magnet. Try it!
If you have ever played with magnets, you know that you can make one magnet spin with the other magnet if you move them properly. In the case of our little electric car engine, the coil is connected to the power in our house which uses alternating current (AC). Every second, the current in the circuit changes direction 60 times. This makes the polarity of the little electromagnetic coil in the car switch back and forth 60 times every second. Since the polarity in the little coil keeps switching while is sits in the magnetic field of the two stationary half moon magnets, the little coil spins. The spinning coil is connected to a shaft which drives the wheels of the car. (I think this is about my 50th revision of this paragraph so I really hope that made sense.)
Before we continue on to talk about electricity production, I need to explain one additional item. In the car we run electricity through the coil, to make the coil into an electromagnet, which spins under the influence of the stationary magnets. The spinning coil is connected to a shaft which makes the wheels of the car turn. To product electricity you run this process in reverse. You spin the coil next to the magnet using mechanical force. Spinning the coil near the magnets induces electricity to flow in the coil which is how electricity if produced.
In electric power plant you take the coil of wire and attach it to a shaft. On the other end of the shaft you put a turbine. (See the picture at the top of the blog for an example). A turbine is really just a fancy sort of a fan. Then you make high-pressure steam; let the steam flow through the turbine, which spins the turbine, which spins the coil near a large magnet, which makes the electricity.
Now the only trick is to make some steam. Around the world, we generally do this by burning coal to heat water. The burning of coal results in the release of tremendous amounts of carbon dioxide making electricity generation a key contributor to Global Warming.
Nuclear and geothermal power work in the same basic way as a coal-fired power plant. For nuclear power you run a controlled nuclear fission process in a bath of heat transfer fluid. The heat transfer fluid gets really, really hot and it is used to boil water to make the steam to spin. For geothermal you make steam using heat tapped from underground. Geothermal sounds great when you first learn about it but economically it is not competitive.
Hydroelectric and wind power work by spinning the coil directly rather than making steam to flow through a turbine. For a hydroelectric plant the falling water from a dam is directed through the turbine. For wind power the large propellers themselves serve as the turbine. Since neither of these approaches burn hydrocarbons, neither contribute directly to global warming. Bear in mind, however, that both of these technologies have significant drawbacks. Discussion of these will need to wait for future blogs.
The only noteworthy electricity generating system which is not based on a spinning coil of wire is solar power from photovoltaic cells. Solar cells can convert sunlight into electricity directly with no moving parts. I gave a review of this technology in “Local Deal: 60% Off Hot Water
The next time you flip on a light, turn on your radio, or hear your air conditioning kick in, remember that the electricity for this comes from spinning a coil of wire next to some magnets. Mostly we spin the coil by burning coal to make steam. The environment would be much better off if we could convert primarily to the other methods I described. Unfortunately, that will be a lot harder than it sounds. Look for future blog entries on the challenges of converting to a world not driven on fossil fuels. In the mean time, buy your kids some toys they can take apart, fix, and maintain. The future is going to need more engineers.
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