Environmental Engineering Reference
In-Depth Information
so, in places where peak demand is in the summer as it is in
most of the United States, solar electricity has a potentially
large role to play.
.
Geothermal
The Earth has at its center an iron core compressed by
the weight of
miles of rock above it, and at a tem-
perature somewhere between
C and
C(
Fto
F). The high temperature was originally
generated by the accumulation of all the material that
makes up our planet, and the temperature is maintained
today by the heat from the decay of radioactive uranium,
thorium, and potassium that were in the primordial
material that came together
billion years ago. The
heat from the interior of our planet leaks slowly to
the surface, slowed by the insulating properties of the
.
miles of material to be gotten through.
At the surface the heat
flow from the interior is less than
one
five-thousandth of the heat from sunlight, and is negli-
gible in determining the temperature of the surface. There
are places where the very hot interior material comes close
to or even on to the surface, and there we have hot springs
or volcanoes emitting rivers of molten rock. Hydrothermal
systems in these areas have been used for millennia for
heat and in the past
years for electricity production.
If you go far enough below the surface the temperature
rises even where there is no volcanism, and if you go deep
enough it becomes high enough to be used for energy
production. The potential of this second geothermal
source is only now beginning to be explored by what are
called enhanced geothermal systems (EGS).
