[Brometheus]

Yeah, but you can't since the energy produced is in form of heat and radiation and not electricity.

That is like using lasers to start a fire and then saying: Look the fire is producing energy in the form of heat! But the heat has to be turned to electricity to power the lasers. And then the fire better produce enough heat to produce enough electricity to power the lasers...

[marssaxman]

So far as I am aware, coal, oil, gas, and nuclear power stations all generate electricity by producing heat, boiling water, and using the steam to spin a turbine. Once you have heat, the rest seems like well-understood industrial technology. Is there something unique about fusion power which makes its heat more difficult to employ?

[Brometheus]

Yes, the fusion needs "huge" amounts of electrical energy input to happen, be it in the form of lasers like here or in the form of magnetic fields like in iter.

In this experiment 2.1 units of input energy produced 2.5 units of output energy. That energy has to be converted to electricity. Conversion looses like 40% of energy (escapes unsused) – so you have produced 1.5 units of electricity from 2.1 units of electricity input.

[marssaxman]

Sure, that's always been the challenge with fusion. I mistook you to be implying that there was something uniquely difficult about generating electricity from heat produced by fusion, but now I suppose you were simply describing the overhead involved.

[zardo]

It's energy_out/energy_in, but the energy_in is not the total energy used by the experiment, it's the fraction that is transferred to the fusion fuel.

[greggarious]

>In this experiment 2.1 units of input energy produced 2.5 units of output energy. That energy has to be converted to electricity. Conversion looses like 40% of energy (escapes unsused) – so you have produced 1.5 units of electricity from 2.1 units of electricity input.

Thanks for distilling this into one three simple sentences, I know from my brief career in science policy how hard that can be. (You should write 1 pagers for the US Congress :-))

To get back on topic:

So basically, if I'm understanding you correctly: this is an increase in efficiency but not one such that it makes sense economically to generate power in this way?

Is this a large jump in efficiency from previous attempts?

The reason I ask is that I know physics can be incremental, so I don't want to detract from the contributions of the authors... and by all means, it's the type of thing I'd expect to see on HN if so and I'm glad it was shared.

I was just surprised to see many more mainstream sites, geared towards a more general audience, running stories about what I'd expect to be more of a niche discovery.

(Possibly as more of a geopolitics thing -- much like if someone is arrested no one recalls with equal vigor when the charges are dropped, a PR-y article about a minor but important discovery can influence public opinion and be a tool of geopolitics.)

[Symmetry]

It's not that it's difficult, its just that it's not perfectly efficient. So once you include the inefficiencies of the heat engine it not necessarily producing energy on net.

But there are also some engineering challenges to work out in employing heat generated like this to drive a heat engine, at least with somethings decent like 30% efficiency.

[greggarious]

Is ~30% what other sources achieve?

[Symmetry]

Other sources can do better but the problem of transferring heat from plasma erupting in a vacuum chamber lined with mirrors seems really hard to me compared to the problem you have in a natural gas power plant, say, so I'd expect even a well developed laser pulse fusion power plant to have a lower efficiency.