Electric Power Generation

In high school the physics teacher showed us a nail wrapped with an insulated wire. When he turned on the power, the nail became a magnet and could pick up other nails. He also said if you grab onto a wire your thumb pointing forward, then the magnetic field around this wire is in the direction of your fingers. Thus electricity and magnetism are related, as one can cause the other.
So they wind a wire around something and make this go around and around in a strong horsehoe magnet and this will cause electricity to go through the wire, thus generating electric power. What makes the wound hub go around is you boil some water,using coal or atomic energy, and then direct the steam so it forces this wound hub to go around, or else you can use Niagara Falls or the Hoover Dam or wind, etc.
Now the question is is this right? And also, is electric power still generated a lot by boiling water into the steam?
And hows do you get the electrons off the wound up coil that they are running in?

I believe most all fossil fuel electric plants use steam turbines to run the generators.

You don’t need to get the electrons to flow off the wire, just through a wire. Moving a magnetic field over a conductor induces electrons to flow and vice-versa. Remember that a generator is just a motor in reverse. Some have electric contact to the spinning coil with brushes contacting commutators - AC/DC universal motors - and some don’t need a connection to those coils - AC only induction motors.

Incidentally, every nuclear plant design that I know of uses steam power to drive the turbines.

Nearly all coal, oil, and nuclear plants use steam turbines to generate electricity.

Some natural gas plants operate as gas boilers, which generate steam to use in a steam turbine. The vast majority of natural gas plants are gas turbines, which are essentially stationary jet engines. These use the combustion of the gas directly to turn a turbine, which is then connected to a generator to generate electricity.

There are some oil plants that operate as gas turbines, but they are not very common, nor do they account for much of the electric output.

And for how you get the electrons off of the coil, there is usually a ring of metal on the part that rotates and a metal contact that rides along its surface attached to the stationary part of the generator.

That last is not really the true picture so I’d better explain.

Modern generators consist of two main parts, the rotor with its windings and the stator with its windings.

The rotor is supplied with current which produces a magnetic field, which in turn induces a much larger current in the stator or field windings.

This much larger current is dependant on the turning force of the prime mover, which is what drives the rotor around, and the excitation current, which is what is fed to the main generator rotor windings.

The excitation current is taken from the excitor, which is another smaller generator on the same shaft as the main generator. The excitor has a voltage supplied to its field windings from a voltage regulator whose job is to vary this current which in turn alters the final voltage from the main stator.

The current generated in the excitor rotor windings is rectified using diodes built onto the main shaft and it is this rectified current that is fed to the rotor of the main generator.

Hence it is called a brushless generator.

There are variations on this, on smaller generators the excitor has a multipole magnetic rotor whose magnetic field causes current to be produced in the static excitor field windings, now this has to be rectified so it goes through the voltage regulator and is finally fed to the main rotor windings using slip rings.
The contact riding on the slip rings is called a brush and is usually made of a high metal content carbon mix.

In both cases the power is taken from the fixed main generator windings, this is because you can construct far heavier duty windings than could be mounted on a rotating shaft, they are easier to supply with a cooling medium, you can use better insulating materials, since weight is no longer an issue, and so generate at higher voltages, and finally there is only a certain amount of current per square inch that can be taken from a brush which would make them impracticly large.

I think the OP is correct insofar as a typical fossil fuel (or nuclear) power plant operates.

However, I can think of at least one other way where electricity can be generated without the use of magnets and that’s via the use of thermocouples.

Basically, if you have a place where two different metals meet (i.e. iron and copper) and heat that spot you will generate an electric current. This method of electric generation is used in some satellites (ones that are flying to the outer edges of our solar system since they’re too far away from the sun for solar panels to be effective). In this case they may use a radioactive source to provide the heat (and the radioactive source can do its thing for a long time).

Given the nature and special needs of a satellite I suppose this makes sense. I would guess that this is not as efficient as using a heat source to boil water to make steam to spin a turbine else we’d probably see thermocouple power plants instead of steam power plants.

Anthracite wrote

“Nearly all … oil … plants use steam turbines to generate electricity” but “There are some oil plants that operate as gas turbines”

“The vast majority of natural gas plants are gas turbines” but “Some natural gas plants operate as gas boilers”

Presumably the majority of these plants do it the most efficient way, but why the exceptions? Were these oil and gas plants formerly gas and oil plants respectively, which were retrofitted, or what?

The newer gas plants are combined cycle plants. They use gas to run turbines. They then use the extra heat from the gas turbines to boil water to run steam turbines.

First a definition. Gas turbine plants are typically seen in two different configurations.

Simple Cycle: The gas is burned in a combustor that is similar to a jet engine, and the engine drives a generator.

Combined Cycle: The gas is burned in the same way as in Simple Cycle, but the exhaust (which is very hot) is then passed through a boiler to generate steam, which is used to turn a steam turbine. Sometimes there is additional gas burned in the exhaust duct to provide extra heat…but we won’t go there right now.

Whereas a gas boiler typically burns gas in a furnace, which heats water into steam and uses that steam to turn a turbine.

There are a few reasons that most all new gas plants are gas turbines. The first is technology - gas turbine technology made leaps and bounds from the pre-1970’s era to the 1980’s. Thus, most all gas plants built in the 1980’s to present are gas turbines. That option was not quite as practical when many of the previous gas boilers were built.

Gas turbines have very high efficiencies - a CC gas turbine has an efficiency that is the higest of any commonly-installed fossil fuel plant. Tokyo General Electric claims more than 60% (net) efficiency on some of their installations, as opposed to a good gas boiler which is about 30% (net) efficient, or even a really good coal plant which is about 36% (net) efficient.

Gas turbines are easy to install on-site, and require a very small footprint. A Westinghouse 501D 110 MW gas turbine and its related controls take up a building about the size of a double-wide trailer. A 110 MW gas plant takes up an area the size of a school building. A 110 MW coal plant takes up an area the size of a Community college (especially if they do something insane like a 90-day pile…but I digress). Gas turbines can be installed anywhere where the gas pipeline infrastructure can support them, just like gas boilers can.

They also have a quick install time. That 110 MW gas turbine mentioned above could be installed and running in 9-12 months from start to finish - compared to 1-1.5 years for a gas boiler, or 2-3 years for the coal plant.

So basically…those are some reasons why gas turbines are chosen over gas boilers.