fusion

[claymore]

If,or when we get a fusion reactor up and running will it still take more energy to run it than what it will put out?

[ChuckFickens]

Assuming you are not talking about experimental reactors then why would anyone bother to get one up and running unless it could produce energy.

[vascop]

Have a look here:
http://www.inference....ir/c24/page_172.shtml

[vascop]

and follow on to page 173 as well

[R1Geezer]

Fusion has been up and running for years, it is not yet at a stage where there is a poitive energy output and where the reaction is sustainable. Until those two reuirements are accomplished there will be no commercial fusion rectors.

[jake-the-peg]

The first sustained fusion burn happened at JET in Oxfordshire in 1997 - in was 0.5 seconds long.

http://www.jet.efda.org/faq/about-jet/

This took more energy than it produced because JET was an experimental device never designed to do so.

Currently ITER (JET's sucessor) is under construction in France. This will be able to generate more energy than it creates but will not be a commercial powerstation.

http://www.jet.efda.o.../iter-and-the-future/

ITER's task is to sort out some of the engineering (as opposed to science) problems before DEMO can be built, probably in Japan which would be the first demonstration fusion power plant.


http://en.wikipedia.org/wiki/DEMO

Timelines in above link

[claymore]

Jake, I was under the impression that you cannot get more energy from a device than what is put into that device. Correct me if i am wrong, but doesn`t the law of conservation of energy back this up?

[jake-the-peg]

This is E=Mc²

Energy and mass are equivilent You can distroy mass and get energy or vice versa.

c, the speed of light is a very big number you don't have to distroy much mass to get a lot of Energy.

In effect you actually have the conservation of mass/energy - they have to be considered together in nuclear reactions.

When you bang light atoms together the heavier atom that is produced contains less mass than the sum of the parts so you get energy out.

It's the opposite to fission where heavier atoms are split to make lighter ones.

This is because there is something called binding energy that holds it together and if you look at how the binding energy as you go up from lighter to heavier atoms it looks like this:

http://hyperphysics.p...cene/imgnuk/bcurv.gif

See that going from a very light element to a slightly heavier one generates a lot of energy (left hand side)

Incidently Iron is in the middle, it is the most stable, you can't get energy by splitting it or by fusing it