You've probably heard by now that the Department of Energy will announce tomorrow that one of their fusion machines has achieved the holy grail: net energy production. That is, the energy coming out will be greater than the energy going in.
Not to put a damper on the whole thing, but there's a little less here than meets the eye. Here's a very rough block diagram of the energy flow in the National Ignition Facility:
The very final stage, where lasers heat up the fusion fuel, does indeed produce a net energy gain. This is known as Q, and in this example equals 1.25, which is about what we're expecting DOE to announce tomorrow.
But the wall-to-wall energy consumption is quite different: Taken as a whole, the system is likely to produce about 1-2% of the energy initially used to charge the capacitors that drive the lasers. This is nowhere close to net energy gain.
There's no deception here. At least, I assume there won't be when DOE makes the official announcement. The name of the lab, after all, is the National Ignition Facility, and ignition refers specifically to creating a self-sustaining fusion reaction, not to producing a net energy gain. This was the original goal of the NIF, which is used for nuclear bomb research and is by no means state of the art in fusion energy production.
Achieving ignition is a landmark, and it certainly deserves a bit of hoopla. But net energy gain in a commercial reactor is still a very long way away.
Thanks for the sanity check. Not being an energy expert myself, but being someone who remembers the original false announcement 30 years ago that cold fusion had been achieved, I was, to say the least, skeptical. It's good to hear from someone who has actually had the time to do a bit of research into what exactly was achieved.
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I feel like you grabbed this information from 2021. It is, isn't it? That's why you don't have links.
Wake me up when the reaction sustains for tens of seconds. Still not useful, but would make eventual usefulness conceivable, which, today, it still isn't.
That's an unimportant metric, especially for the way NIF works.
All that matters is the ultimate energy that comes out; how long the reaction lasts (even in the case of plasma, which is what you are thinking about, as opposed to inertial confinement) is a means to an end, it's not an end in itself.
If pseudo-confinement methods (utilizing both magnetic and inertial confinement) or hohlraum techniques ever become practical, they will complicate the issue further in terms of multiple timescales that govern different aspects of the problem.
Remember, Kevin hates fusion. So he will always cast things in the worst light.
Ok but the fusion people are pretty guilty of optimistic marketing. Bordering on deliberately misleading
It’s like saying “all the ingredients of a Big Mac cost $0.99. And we sell for $1. Let’s open for business!” Like we can just wish it into being
I’ve seen articles like “can fusion energy solve the climate crisis?” Not just premature, but pretty ridiculous. You know this and so do I, but the average person thinks this breakthrough is all it took to have a fusion energy toaster in their kitchen
If you insist on putting it that way, well, yeah. For good reason. That whole 'promise of fusion' bit is a product of the nuclear rocket punk era. It didn't help that a lot our best and brightest were brought up on a steady diet of bang-bang sf.
That's what some folks were pointing out on Twitter. They'd realistically have to get far more out of the same amount of input power just to truly break-even, and it's not clear how they'd do it. Either the lasers would have to become far more efficient, or they'd have to fuse larger pellets - or both.
I’m pretty sure that formula was copied directly from the label my morning energy drink…
So my presumption is this is an important step because in theory, if they can maintain a stable fusion reaction, if the final output step exceed the penultimate laser input energy input (ie Q is positive) then they system could begin an output to input loop that is net energy positive. So the initial input energy would end up unimportant as a one time ignition input. The problem is we cannot maintain a long term stable fusion reaction of that nature. Is this anywhere near right?
No, because the way the NIF is setup you cannot just take the energy from one experiment and drive the next one. You have to convert it to the laser energy (plus preparation of the hohlraum and other overhead) to drive the next cycle.
thanks.
This is sobering:
https://mobile.twitter.com/elidourado/status/1602331689182810113
The noise about this "milestone" is really completely unjustified.
They (physicists) haven't learned anything new from this experiment, except some minor improvments in the design of the bits of their system.
Since the actual figures are 2 MJ in, 3 MJ out, I divided everything by 10 to get a rough idea of what this really means. I get about 7-ish % of the total input power.
BUT a megajoule sounds impressive because, you know, it has that mega there. But a megajoule is about the amount of caloric energy in a jelly doughnut. Or released in the fire you get from lighting a piece of kindling. Even taking the claims at face value, this is peanuts. What is more important than the total energy produced is the rate at which it is produced. If the device were able to fire a million shots a day, it would produce about 11 megawatts. That's getting into the neighborhood of a small gas fired plant.
A million shots each day is about 10 shots each second. That's a lot. It would be challenging to get capacitors at the input power stage that could recharge that fast. But even if you could, this particular device is never going to do it. All those lasers and conversion steps involve huge chunks of glass that require hours to cool down before the next shot.
I don't expect to see fusion power plants for the next 50 years, if ever.
The very few articles that mention exactly HOW fusion energy will be used all speak of using it to ... wait for it ... BOIL WATER so as to drive a steam engine.
Are they serious?? Look, we've used the energy of fluid motions - wind and water - for centuries to drive mechanical systems, so as to grind grains, pump water, saw wood, and more recently, turn turbines that produce electricity. Electricity is the common coin these days; the more efficiently it can be produced, the better.
Solar photovoltaics turn sunlight directly into electricity! And if you just want heat, solar thermal is great, by virtue of concentrating it via focused mirrors, etc. You don't need to fuse nuclei or split them to get that.
Boiling water to power a steam engine that drives a turbine that makes electricity? Come on. Surely, in the 21st century, engineers can be more creative than that, can't they?
Its actually much worse than that
The energy OUT is heat
The energy IN is high level energy
You NEED to get three times as much energy out as HEAT to replace the high level energy going in
And that would be just to break even