Environmental Engineering Reference
In-Depth Information
approach was tried in the
s in a Department of
Energy funded program, and failed; the
fluid became
contaminated with corrosive material, and getting the
right conditions in the rock underground proved too
dif
cult. It is being tried again in Australia, Europe, and
the United States.
The key to making this work is the condition of the
rock between the injection and extraction wells. It has to
be appropriately fractured so that the water has many
paths between the two that are spread out so that heat
can be obtained from a large volume of rock. Remember
that rock is a poor conductor of heat and if there were
only a few paths the rock near those would quickly cool
and little energy could be extracted in the long run. Even
if the rock is well fractured there is the danger of what are
called short circuits where in the midst of all the little
cracks there are a few big ones that connect the two wells.
In this case most of the water rushes through the short
circuits, again limiting the amount of energy that can be
economically extracted. There are two reports that are
worth looking at if you are interested in more details. One
is a
s
Idaho National Laboratory that looked at the potential
of EGS energy [
study by MIT commissioned by the DOE
'
find this report to be an excellent
primer on the technology, but too optimistic about the
ease of overcoming the technical obstacles to large-scale
deployment. The other is a
]. I
analysis by the DOE
itself of the MIT report that reviews the MIT assump-
tions [
].
is from the MIT report and I include it to
give an idea of the scale of EGS plants. The table gives the
surface area required for a plant of a given electrical
Table
.
