16 What are the different methods for converting fusion energy to useful energy?
Description
This article is from the Fusion FAQ, by Robert F. Heeter heeter1@llnl.gov with numerous contributions by others.
16 What are the different methods for converting fusion energy to useful energy?
Generally it is expected that fusion energy will be converted to
electrical energy. However, one might want to make lots of heat
to drive chemical reactions, perhaps to make hydrogen as a fuel.
The easiest method to convert fusion energy to electricity is to
collect the fusion energy as heat, use the heat to boil water,
and then drive a good 'ol steam turbine. Alternatives use something
besides water as the heat transfer fluid (say liquid metal, or helium)
and something besides water as the turbine driver (such as helium).
These more advanced turbines are somewhat more efficient. (Steam
turbines have a conversion efficiency of about 35%, and advanced
turbines can get up to about 50%.)
In principle, energy can also be extracted from a fusion reactor
in the form of charged reaction-product particles (such as p-B11
or D-He3). In this case one can use magnetohydrodynamic conversion
(or direct conversion) to convert the motion of the energetic
reaction products directly to electrical energy. This conversion
can be up to 95% efficient. However, direct conversion is only
useful on the fraction of the energy which is in the form of charged
particles. The D-T fuel cycle generates most of its energy in the
form of neutrons, so the thermal cycles described above must be
used. The advanced, aneutronic fuels are more suitable for
direct conversion.
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