How does fusion release energy?

Answer 1

In the case of the sun, we get the energy by radiation. In man-made fusion, which has not been achieved yet except for a very brief moment in an experimental facility, it is hoped to get the energy which will be emitted by the gaseous plasma. Theoretically, more energy should be released than is put in to start the plasma reaction. However the actual design of a working plant is not as far as I know established yet.

Answer 2

When light element nuclei fuse to give a heavier nucleus, energy is released. This is a consequence of the fact that the nuclear binding energy per nucleon is a maximum for elements iron and nickel. For elements lighter than those, the binding energy falls away becoming a minimum for isotopes of hydrogen. Thus if two hydrogen isotopes fuse together, some nuclear mass is destroyed in forming the helium nucleus and this appears as a release of energy, E = mc2. At the opposite end of the nuclear mass scale, it is the splitting of heavier nuclei like U235 which releases energy, but for the same reason, as the resulting lighter nuclei have greater binding energy per nucleon.

You can see the relation between binding energy and Atomic Mass number in the graph in the link below

Answer 3

Fusion releases energy because the binding energy curve per nucleon is increasing up to iron-56. As a result, the total binding energy for light nuclides, such as tritium and deuteruim, is greater than the binding energy required for the product, helium.

As the total binding energy for light nuclides, such as helium, is less than the sum of the binding energy for tritium and deuterium, the excess energy is released to the system in the form of energy and particles (radiation).

Unfortunately, we do not yet have an effective way to produce a fusion reaction, except in an uncontrolled reaction such as a hydrogen bomb. We are working on this problem, but we do not expect success for another 50 to 100 years.

For further information, please see the Related Link below.