# Generators and alternators

Machines that turn rotation into electricity in almost every power plant.

Source page: https://www.materialinsights.org/energy/e_generators/

Conversion and use · Conversion devices · No. 99

- Conversion and use
 Conversion and use · Conversion devices · Foundation · Energy

The world's biggest generator turns 99% of its spin into electricity, yet still sheds enough heat to warm thousands of homes.

Chart: Illustration: Generators and alternators

##### Where it comes from

Chart: Map of where it comes from

Moving a magnetic field past copper coils induces a voltage, Faraday's law, which every coal, gas, nuclear and most hydro plant relies on.

##### Three things to know

1. Generators are not heat engines, so no Carnot limit applies; losses are only resistance, magnetic and friction effects.
2. Very large units are cooled with hydrogen, about one fourteenth as dense as air (calculated), to cut drag and carry heat away.
3. Each 0.1 point of efficiency on a big unit is worth about USD 0.4 million a year (calculated).

##### The journey

1. 1 **Turbine**Steam, gas, water or wind spins
2. 2 **Rotor**Spinning electromagnet carries the field
3. 3 **Stator**Copper coils feel a changing field
4. 4 **Induction**Voltage appears, 18-27 kV at terminals
5. 5 **Grid**Transformers step it up for transmission

##### Go deeper pick a tab to open it in full

## Other sections

- [Overview](https://www.materialinsights.org/energy/e_generators/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_generators/correlation/index.md)
- [Science and limits](https://www.materialinsights.org/energy/e_generators/science/index.md)
- [Value chain](https://www.materialinsights.org/energy/e_generators/valuechain/index.md)
- [Unit economics](https://www.materialinsights.org/energy/e_generators/economics/index.md)
- [Engineering methods](https://www.materialinsights.org/energy/e_generators/methods/index.md)
- [Equipment and suppliers](https://www.materialinsights.org/energy/e_generators/equipment/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_generators/links/index.md)