Every
day, every living thing on the surface of planet Earth receives free
energy from one of the most elegant of chemical transformations, the
energy of the stars. It’s called fusion, the combining of two light
nuclei to produce a heavier one of slightly lower mass than the sum
of the two, with a concurrent release of energy in accordance with
Einstein’s equation E=mc2
Nuclei
of deuterium and tritium combine under great heat and pressure to
yield helium plus 3.5 MeV and a neutron plus 14.1 MeV......an
enormous energy output.
Of
course, in stars, fusion doesn’t stop there.... additional fusion
takes place up the periodic table to iron, following which the
remaining elements are produced by fission. All the material in the
universe was provided by exploded stars.
The
hydrogen isotopes, deuterium and tritium, are the same as used in
fusion bombs which were developed in the 1950’s. Setting off a
fusion bomb, though, is an instantaneous release of energy, useless
for power generation. In a hydrogen bomb ignition is initiated by a
fission bomb, configured to compress and heat the hydrogen isotopes
to a region where fusion will occur.
Since
the 1950’s there has been an avid interest in many nations to
create on Earth an artificial means to tap into this prodigious
energy source. Billions have been spent in this quest, following two
main ideas on how to achieve controlled fusion.
One
idea is magnetic containment of the plasma. Thermal energy must be
added either by the fusion products or by electricity generated by
the reactor. The goal is to produce more energy than is necessary to
sustain the reaction.
The
U.S program began in 1951 when Lyman Spitzer began work on
magnetically confined plasmas. His work led to creation of the
Princeton Plasma Physics Laboratory, where magnetically confined
plasmas are still studied. Other major universities began to
undertake theoretical studies and experimental work.
Theoretical
work in the Soviet Union during 1950-1951 by I.E. Tann and Andrei
Sakarov led to construction of the first tokamak.(a Russian word
meaning “a toroidal device for producing controlled nuclear fusion
by means of confinement in a magnetic field) and first demonstrated
the feasibility of a continuous nuclear fusion reaction.
In
1997 the largest joint experiment was the Joint European Torus (JET).
In that year a test run produced a peak of 16.1 MW of fusion power,
with a sustained power of 10 MW over a period of 5 seconds. Not much,
and the output of this experiment was only sixty-five per cent of the
power put into it.
But
bigger plans were afoot with the formation of ITER
(InternationalThermonuclear Experimental Reactor), and the funding of
an entirely different approach to achieving fusion in the National
Ignition Laboratory at Lawrence Livermore Laboratories. That method
seeks to obtain ignition by focusing powerful lasers on a raindrop
sized capsule filled with deuterium and tritium. Scientists at
Lawrence Livermore hope to produce a powerful enough implosion of the
capsule to achieve ignition.
ITER
was proposed to President Reagan by Gorbachev in the 1980’s. The
United States initiated the project, putting together a consortium of
participating nations, but later withdrew. and still later decided to
participate in a limited role. That largely takes place via the
Princeton Plasma Laboratories, funded by the Department of Energy at
about 175 million dollars annually. The United States, then, has work
underway on the two main approaches to fusion energy.
ITER
continued under French leadership. The experimental laboratories for
ITER are located in Cadarache, France and headquarters is located in
Barcelona, Spain.
The National Ignition Laboratory
(www.theatlantic.com/infocus/2014/01/the-national-ignition-facility)
funding exceeds eight billion dollars. Budget for ITER was
established at fifteen billion dollars in 2008 and is certain to be
exceeded. Billions more will have to be invested if either concept
demonstrates economic and operating feasibility, to produce reliable
and safe means of extracting the energy to produce electricity. That
appears to be years in the future.
But
here’s the rub: We are already benefitting from a limitless source
of fusion energy. Why go to the enormous cost and effort to make it
on Earth? It’s called the sun, a safe 93 million miles from Earth.
It is free, there are no waste products, and it is reliable. 174
petawatts of radiated energy arrive daily at the upper atmosphere.
World energy consumption is about 25 terrawatts. It remains only to
apply ingenuity in devising systems to collect it and convert it to
electricity. Significantly, we are already doing it, capturing it via
photo-voltaic and solar thermal collectors and wind (yes the wind is
solar energy. Available wind energy alone is 335 terrawatts).
The
twenty five or so billion dollars being spent on laboratory
demonstration of fusion power could have been spent to produce 25
gigawatts of fusion power that is already available from the sun, or
advancing the technology for doing so.
What
are we thinking? Admittedly, the research efforts produce technology
advancements in computational technique, materials science and
processing. But
it
may not be a sufficient justification for all the spending.
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