Energy exists in many forms. Common energy forms include mechanical, thermal, or chemical energy. One of the most wonderful properties of the universe is that energy can be transformed from one type to another and transferred from one object to another. Humans have created various energy conversion devices for these purposes. These devices are, for example:
- Heat engines, such as the internal combustion engine used in cars, or the steam engine (Heat → Mechanical energy)
- Electric generator (Kinetic energy or Mechanical work → Electrical energy)
- Electric motor (Electrical energy → Mechanical work)
- Battery (electricity) (Chemical energy → Electrical energy)
- Electric heater (Electric energy → Heat)
- Fire (Chemical energy → Heat and Light)
For example, burning gasoline to power cars is an energy conversion process we rely on. The chemical energy in gasoline is converted to thermal energy, then converted to mechanical energy that makes the car move. The mechanical energy has been converted to kinetic energy. When we use the brakes to stop a car, that kinetic energy is converted by friction back to heat or thermal energy.
But nothing is perfect. One Joule in thermal energy is not the same as one Joule in kinetic energy. All these energy conversions are associated with energy losses. For example, a typical gasoline automotive engine operates at around 25% to 30% thermal efficiency. About 70-75% is rejected as waste heat without being converted into useful work, i.e., work delivered to wheels. This inefficiency is caused predominantly by the Second law of thermodynamics.
If not necessary, we want to say that the transformation of energies is always associated with losses. For example, compare CNG and hydrogen-powered vehicles with an internal combustion engine. Note that most hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas with the efficiency of process about 65% to 75%. In the case of hydrogen-powered vehicles, you must multiply inefficiencies associated with natural gas-to-hydrogen conversion (about 0.7) since the other inefficiencies are similar. The solution, of course, is to produce hydrogen using renewable or sustainable sources.
The efficiency of motors – Combustion Motor vs. Electric Motor
[/su_heading]The efficiency of an electric motor is significantly higher than the efficiency of a combustion engine. In the case of an electric motor, however, it is necessary to consider from which sources the electricity is produced.
