Author | Jia Haonan
Smart car reference | public account AI4Auto
Major progress in new energy comes suddenly:
For the first time, humans have achieved a net energy gain in a fusion reaction.
It means that in the controllable nuclear fusion device, the output energy is greater than the input energy for the first time. The “artificial sun” takes its first step toward commercialization.
How important is it?
Musk has pursued cheap and clean energy all his life, and has exhausted almost all means: solar roofs, lithium battery storage stations, pure electric vehicles, recyclable rockets…
Everything he does always revolves around one theme: to improve the scale and efficiency of energy utilization by human civilization.
The general consensus in the academic and industrial circles is that the ultimate answer to the energy problem is controllable nuclear fusion.
Once commercialized, all mankind will have cheap and inexhaustible energy.
Significant progress in artificial sun
The research results come from Lawrence Livermore National Laboratory (LLNL).
Go directly to the result:
On December 5th, a new experiment at LLNL with an input energy of 2.05 megajoules (MJ) and an output energy of about 3.15 MJ after a nuclear fusion reaction.
The energy gain is as high as about 150%.
The 3.15 megajoules of energy output by the reactor is roughly enough to boil 20 pots of water.
It doesn’t seem like much, but the significance is that the energy to maintain a controllable nuclear fusion reaction is less than the energy output by nuclear fusion for the first time.
The basic conditions for the positive cycle are met, and the basis for continuing to reduce the cost of controllable nuclear fusion and improve efficiency in the future is also established.
It has been a total of 90 years since human beings recognized nuclear fusion until today (humans discovered the nuclear fusion program in 1932).
Why is it so difficult?
Nuclear fusion, the reaction in which light atomic nuclei (such as deuterium and tritium) combine to form heavier nuclei (such as helium) with the release of enormous amounts of energy.
Taking deuterium-tritium fusion as an example, the relative atomic mass of a free proton is 1.007; the relative atomic mass of a free neutron is 1.0084; is 4.0026.
And 4.0026<2*(1.007+1.0084)=4.0308, the missing mass in the equation is transformed into energy, which satisfies the law of mass-energy conservation.
1 kg of deuterium-tritium fusion is equivalent to 80544.9 tons of TNT equivalent, this efficiency far exceeds any energy source that humans have ever used.
But the difficulty is that the conditions for nuclear fusion to occur are harsh, requiring extremely high pressure and high temperature, and once it starts, it will release energy instantaneously, which is difficult to control.
Therefore, the first application of human nuclear fusion is the hydrogen bomb.
The problem to be solved for the artificial sun is to adopt suitable means to control the nuclear fusion process.
One of the controllable nuclear fusion devices with certain feasibility is called tokamak. In the center is a circular vacuum chamber with coils wound around it. When the tokamak is powered on, a huge spiral magnetic field will be generated inside the tokamak, which will heat the plasma in it to a very high temperature to achieve the purpose of nuclear fusion.
After the reaction starts, the tokamak uses magnetic confinement to achieve controlled nuclear fusion.
The problem is—to maintain the reaction in the tokamak, it needs to continuously input energy, which is far greater than the energy produced by the nuclear fusion of the device.
Another technical route is laser nuclear fusion, which has made significant progress this time.
How does the “positive cycle” of the artificial sun come true?
The so-called laser nuclear fusion is inertial confinement nuclear fusion that uses a high-power laser as a driver to irradiate a nuclear fuel target.
Laser-based reactors, which allow nuclear fusion to occur in a fraction of the time, have now somewhat crossed the threshold for net energy gain.
The so-called “inertia”, in simple terms, is to increase the temperature and pressurize the plasma formed in the fusion reaction in a very short time, and use the inertia of the internal atomic nuclei to allow them to overcome the static electricity between each other before they expand and dissipate around. Repulsion completes the fusion.
The specific process is: use a laser to irradiate a nuclear fuel target, and under the action of the beam heating, the target container such as particles will explode outward.
During the explosion, except for the surface of the container, the rest of the reaction force will accelerate it inward and compress the fuel inside.
In addition, the process generates a massive shock wave that compresses and heats the fuel in the center, thereby enabling nuclear fusion to occur.
But if fusion reactors are to be used commercially to generate electricity, the lasers would need to heat the target at least 10 times per second. This is not impossible, but from an engineering point of view, it is very difficult.
LLNL’s breakthrough method is to use the National Ignition Facility (NIF) in the United States, the world’s most powerful laser ignition device, to irradiate the cavity (hohlraum) in a radiation equilibrium state with as many as 192 laser beams. ), that is, pinhead-sized spherical particles surrounded by deuterium and tritium.
Through laser action, a mixture of deuterium and tritium forms an ultrahot hydrogen plasma.
Plus, during the reaction, the X-rays produced blasted away the original particles, and the fuel layer imploded, creating the conditions for nuclear fusion to happen.
In the end, with the support of NIF, enough heat was generated in this experiment, and the heat spread through the fuel fast enough that the energy output exceeded the input.
△NIF has cost 3.5 billion US dollars
The result of this experiment is actually a kind of “miracle with great effort”.
How far is it from commercial use?
Zhihu user @树树 gave such an estimate:
At a cost of US$1 million, 20 pots of water were boiled (not counting the US$3.5 billion facility cost), and the cost is still horribly high.
But the outlook is optimistic.
What does musk think
Musk has long had a view:
Cool and workable, but unnecessary.
Because there has always been an inexhaustible nuclear fusion reactor above our heads – the sun.
Therefore, Academician Ma believes that the best ultimate solution to the energy problem is to use solar energy (wind energy is also a type of solar energy), rather than building an artificial sun regardless of cost.
Therefore, Musk has invested in solar energy, lithium batteries, new energy vehicles, aerospace, urban transportation, brain-computer interfaces… ． Only no investment in nuclear fusion.
Finally, return to the new energy vehicles we are concerned about.
Regardless of whether Musk is optimistic or not, the commercialization of controllable nuclear fusion is still of great significance.
To be clear, the commercialization of controlled nuclear fusion is unlikely to be a small reactor device installed in the vehicle itself, which is technically difficult and does not conform to the attributes of the car itself as a consumer product.
The real significance is that controllable nuclear fusion makes electric energy inexhaustible, the cost is extremely low, and it is completely zero-carbon and zero-emission. The cost of using a car is almost negligible.
What humans have to do is to build a reasonable energy storage and transportation system – such as the lithium battery energy storage station that Musk is working on.
(Disclaimer: This article only represents the author’s point of view, not the position of Sina.com.)
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