70 | SCIENCE ILLUSTRATED
ground to slowly seep up from the hole. The
vapour was more than 450 degrees hot – a
new world record for a geothermal well and
much warmer than the about 300 degrees of
a typical geothermal well.
The scientists behind the project made
measurements of the energy potential of the
red-hot well and got extremely promising
results: the well could generate 36
megawatts of electricity – more than half of
the Krafla plant’s 33 holes combined. At
Krafla, scientists were surprised that the drill
reached into a magma chamber. And when
the well was to be linked with the Krafla
plant, a valve broke, forcing scientists to stop
their work to seal the hole.
The people behind the IDDP decided to try
again in the Reykjanes region in South-
Western Iceland. This time, the well was to be
5 km deep to get both the high temperatures
of the Krafla drilling and ensure high pressure.
At temperatures above 374 degrees and a
pressure of 220+ bar, water does not only
turn into vapour, but rather into supercritical
fluid, which becomes much more high-energy
at rising temperatures than if ordinary water
vapour were heated further.
This is due to the laws of thermo-
dynamics. When water is 100+ hot, all other
heat is used to convert water into vapour
(boiling). At a higher pressure, the boiling
point increases, and the water will not bubble
until at a higher temperature. On the other
hand, less energy is lost in the boiling process
and in the transition from water into vapour.
When the temperature exceeds the critical
point, and the pressure is sufficiently high,
the water will no longer boil, but rather be
converted from water into vapour without
any energy consumption. In this state, the
water is known as super-critical vapour.
Due to its qualities, supercritical fluid
includes more energy per drop than
subcritical vapour. One litre of supercritical
fluid of 400 degrees under a pressure of 250
bar contains five times as much energy as
ordinary vapour of 225 degrees.
In a geothermal power plant, the
difference is key. The more energy the vapour
contains, the more it can make a power-
generating turbine move, before the vapour
cools and condensates.BRIGHT FUTURE
Now that the IDDP drilling has been
completed, a period of about two years of
efficiency studies follows. Scientists must
find out how the supercritical fluid affectsDrill workers spent about
six months drilling the some
5-km-deep hole down
to the magma chamber.THE DRILL
HAS A 22 CM
DIAMETER.the stainless steel, nickel, titanium, and
concrete which make up the well and the
plug at the bottom. Supercritical fluid is
highly corrosive, i.e. it breaks down other
materials in the same way as acid, etc.
Moreover, scientists have not yet powered a
turbine by supercritical fluid. So, a turbine
which can efficiently convert the extreme
vapour into energy must be developed.
Once the different challenges have been
solved, the future potential is huge. Iceland
has almost covered its own electricity
requirement, but scientists are trying to find
out, if it is possible to place a live cable on the
ocean floor to carry surplus electricity to
Scotland or Scandinavia, where it can be
distributed via local electricity grids.
Geothermal energy researchers are
optimistic concerning the future of
geothermal heat. Right now it provides just
1% of the world’s energy demand, but
according to scientists, it could rise to as
much as 20% by 2050.IDDP/HS ORKAGeothermal
energy could
provide 20 per cent of the
world's power by 2050.TECHNOLOGY ENERGY