Question: How is power harvested from Nuclear Fusion, and typically, how much power/energy is generated from the process compared to fossil fules?

David Armstrong answered on 13 Jun 2011:

Currently there are no fusion power plants which generate electricity. All the devices currently being used, such as JET in the UK, are really about developing the technology and physics to control the plasma which is where the reaction takes place. They don’t generate any electricity yet.

In the reaction in the plasma two isotopes of hydrogen (tritium and deuterium) are “fused” together to form helium and a neutron is ejected. In a future fusion device which produces electricity the neutron will hit the wall of the vessel which contains the plasma. This causes the wall to heat up. By passing pipes with water in though the wall the water can be heated and converted to steam to drive a generator and produce electricity. The neutrons hitting the wall will also be used to “breed” tritium from lithium. This is important as while deuterium is found in sea water, tritium does not naturally occur and breeding it will be important for the commercial operation of a reactor.

While the neutrons are important for energy generation and tritium breeding they also damage the material the vessel is made of. Understanding what damage this does is part of the work I am involved with.

It is hoped that a commercial power plant will produce 2Gigawatts of power, similar to a fossil fuel power plant