You want us to dump our knowledge into you.
That will not be easy because most of us have read thousands of books and spent many years in colleges and universities to get what we know today.
Nevertheless, I will try to give you some knowledge that though it is basic, it is very important and it is what you need at this time. So read this carefully and let it sink in.
Start with OHM'S Law.

By following Ohm's law, you will see that WATTS (Power) equals voltage multiplied by amperage.
For example:
120 volts at 4 amps = 480 watts
48 volts at 10 amps = 480 watts
12 volts at 40 amps = 480 watts
With lower voltage, you need higher amperage to get the same power (WATTS)
The higher the amperage flowing through a wire, the thicker the wire has to be. If you use a thin wire to conduct a high current (AMPS) though it, the wire will get very hot and could burn up. There are tables that show the current ratings of different wire gauges.
How does an alternator produces power?
First, let me explain the difference between an alternator and a generator. A very simple way to define it is this:
An alternator is composed of a number of magnets and a number of coils. As the magnets pass over the coils, it generates voltage (AC voltage)
A generator is exactly the same thing as an alternator. The difference is that to convert it to a generator, we add a rectifier to the output of the alternator. The rectifier converts the AC voltage to DC voltage.
The voltage that an alternator produces depends of these five things:
1 - The number of magnets (poles)
2 - The magnetic strength of the magnets
3 - The number of coils
4 - The number of turns of wire in the coils
5 - The speed of the magnets passing over the coils
Let's say that an alternator with 50 turns of wire in the coils produces 20 volts when is turning at 100 RPM.
If you want to double the voltage, to get 40 volts, you can do it by either doubling the speed to 200 RPM or by doubling the number of turns in the coils to 100 turns.
If you double both, the speed (RPM) and the number of turns in the coils, you will get the alternator to output 80 volts.
I think that it is great when people get interested in alternative ways to generate power and start experimenting.
But it is important to learn basic electricity first. When you do that, the outcome of your experiments will be more predictable and satisfying. When you see good results, you get excited and you are likely to continue to experiment until you are successful. Without knowing the basics, the outcome of your experiments will be disappointing. That could cause you to get discouraged and give up. I hate to see that happen.
I hope this is helpful.
Ed