Examples of sets of energy conversions in machines

For instance, a coal-fired power plant involves these power transfers:

1. Chemical energy in the coal converted to thermal energy
2. Thermal energy converted to kinetic energy in steam
3. Kinetic energy converted to mechanical energy in the turbine
4. Mechanical energy of the turbine converted to electrical energy, which is the ultimate output

In such a system, the last step is almost perfectly efficient, the first and second steps are fairly efficient, but the third step is relatively inefficient. The most efficient gas-fired electrical power stations can achieve 50% conversion efficiency. Oil and coal fired stations achieve less.

In a conventional automobile, these power transfers are involved:

1. Potential energy in the fuel converted to kinetic energy of expanding gas via combustion
2. Kinetic energy of expanding gas converted to linear piston movement
3. Linear piston movement converted to rotary crankshaft movement
4. Rotary crankshaft movement passed into transmission assembly
5. Rotary movement passed out of transmission assembly
6. Rotary movement passed through differential
7. Rotary movement passed out of differential to drive wheels
8. Rotary movement of drive wheels converted to linear motion of the vehicle.

There are many different machines and transducers that convert one energy form into another. A short list of examples follows:

• Thermoelectric (Heat → Electricity)
• Geothermal power (Heat→ Electricity)
• Heat engines, such as the internal combustion engine used in cars, or the steam engine (Heat → Mechanical energy)
• Ocean thermal power (Heat → Electricity)
• Hydroelectric dams (Gravitational potential energy → Electricity)
• Electric generator (Kinetic energy or Mechanical work → Electricity)
• Fuel cells (Chemical energy → Electricity)
• Battery (electricity) (Chemical energy → Electricity)
• Fire (Chemical energy → Heat and Light)
• Electric lamp (Electricity → Heat and Light)
• Microphone (Sound → Electricity)
• Wave power (Mechanical energy → Electricity)
• Windmills (Wind energy → Electricity or Mechanical energy)
• Piezoelectrics (Strain → Electricity)
• Acoustoelectrics (Sound → Electricity)
• Friction (Kinetic energy → Heat)