Environmental Engineering Reference
Each year the sun radiates 1.5 quintillion kilowatt hours of energy towards the earth.
The atmosphere swallows up around 30% of this energy but over one quintillion
kilowatt hours are still able to reach the earth's surface. Our current primary energy
needs are around 125 trillion kilowatt hours worldwide. By the way, a quintillion
is a 1 with 18 zeros, and a trillion has 12 zeros. Therefore, the amount of energy
that reaches the earth's surface from the sun each year is 8000 times more than the
total primary energy requirement of the world. So we only need to use about one
hour's worth of the solar energy that reaches the earth's surface in order to cover
the energy needs of the whole of mankind for a whole year.
Natural occurrences convert some of the sun's energy into other renewable forms
of energy, such as wind, biomass and hydropower. In addition to these energy forms,
we are also able to use the natural heat of the earth as well as tidal power derived
from the motion of the moon in conjunction with other planets. All sources of
renewable energy combined exceed the total fossil and nuclear fuels available on
earth many times over (Figure 4.7). In less than one day the sun radiates more energy
to the earth's surface than we could ever use if we were to burn all the oil reserves
available on earth.
Figure 4.7 Comparison of annual renewable energy available and global primary energy
requirement with the total existing conventional energy sources on earth.
In discussions on climate, some critics question whether renewable energies are
even able to cover our energy requirements. But a brief glance at the facts just
mentioned shows that these doubts can safely be cast aside. The variety of possible
uses of renewable energies is enormous. A number of different types of power plants
can provide almost any amount of electricity, heating or fuel desired (Figure 4.8).
The following chapters of this topic will present in detail the key technologies for
using renewable energies.