Evolution of Energy Sources
Economic and technological development is linked with shifts in sources
of energy. The tendency has been the adoption sources that have a higher
energy content, as the shift from coal (solid) to oil (liquid) and natural
gas (gas) indicates. This shift can be simplified into five major phases,
one about the future being speculative:
- From the beginning of history up to the industrial revolution
(18th century), mankind's use of energy relied only on muscular
and biomass sources. Most work was provided by manual labor and
animals, while the biomass (mainly firewood) provided for heating and
cooking energy needs. Other sources of energy, such as windmills
and watermills were present but their overall contribution was marginal.
- By the mid 19th century, the industrial revolution brought a
major shift in energy sources with the usage of coal, mainly for
steam engines, but increasingly for power plants.
- As the 20th century began, the major reliance was on coal, but
a gradual shift towards higher energy content sources like oil began.
This second major shift inaugurated the era of the internal combustion
engine and of oil-powered ships.
- In the late 20th century, the emphasis on petroleum products
as the main provider of energy reached the point where the world
economy highly depends on the internal combustion engine and its
supporting industries. As its level of technical expertise increased,
mankind was able to tap on more efficient sources of fossil fuels,
mainly natural gas, and energy released by matter itself (nuclear
- The 21st century will be characterized by major shifts in energy
sources with a gradual obsolescence of fossil fuels, like coal and
oil, for more efficient fossil fuels such as natural gas. There
may also be a substantial clean coal technology potential. Advances
in biotechnologies let anticipate the growing usage of biofuels.
Nuclear energy, particularly if nuclear fusion becomes commercially
possible, may also play a significant role. A very important change
in energy sources is likely to be the usage of hydrogen, mainly
for fuel cells powering vehicles, small energy generators and numerous