Recreating the sun’s power from tiny fuel

As scientists hope to harvest the star-like energy released from fusion, they focus the world’s largest lasers to manipulate atoms.

 
This view from the bottom of the NIF target chamber shows the target positioner being inserted. Pulses from NIF’s high-powered lasers race toward the Target Bay at the speed of light. They arrive at the center of the target chamber within a few trillionths of a second of each other, aligned to the accuracy of the diameter of a human hair. (Philip Saltonstall/Lawrence Livermore National Laboratory.)

Putting aside the political and environmental problems of the world’s energy supply, burning fossil fuels is just a ridiculously inefficient process. Fusion energy hopes to be far more effective at producing power with none of the problematic byproducts of carbon fuels.

As stated in the previous blog, scientists at the National Ignition Facility (NIF) near San Franscisco have announced they are closing in on ‘ignition’ in their attempt to produce energy through inertial laser fusion.

Ignition is the Holy Grail of fusion research and would prove that a controlled fusion reaction can produce a significant net energy gain, the first stepping stone to a new form of commercial energy.

While nothing in science is certain until it is proven, Penrose C. Albright, incoming director of the Lawrence Livermore National Laboratory, which houses the LIF, has said ignition should happen in the next fiscal year. To a physicist, the technical advantage of fusion over fossil fuels is the effectiveness of a thermodynamic versus a chemical process. It’s been estimated that one kilogram of fusion fuel can provide the same amount of energy as 10 million kilograms of fossil fuel.

Dr. Allan Offenberger is a retired professor of electrical and computer engineering at the University of Alberta and has been an active advocate of the potential of laser fusion. He explains that when compared with fusion, burning fossil fuels is chemically inefficient because it only creates power from the low energy electrons around the hydrogen nucleus.

“When I introduce a fusion event, another nucleus coming in with another nucleus core, I’m dealing with the internal dynamics of the fundamentally strong forces of matter—they happen to have a much higher energy base than the weak electrons that rotate around the core.”

Of course, we know that tearing apart the nuclei of atoms releases enormous amounts of energy as when a nuclear device is detonated or when fission occurs in a nuclear plant. The difference with fusion is that it is a much more controlled event that, according to experts, does not generate dangerous amounts of radioactivity. As well, there is no chance of a runaway ‘meltdown’ reaction since the reaction is not self-propelling.

The process of fusion refers to the fusing of different elements into an entirely new state. At the LIF, 192 high-powered lasers are focused evenly on a tiny target pellet composed of tritium and deuterium. In theory, the heat and pressure from the lasers should evenly collapse the pellet in on itself. As the target is suddenly heated to 100 million kelvins  (10 times hotter than the sun) the extreme pressure conditions in the atom’s central core are stressed as the nuclei of the elements fuse together. At that point the basic nature of the atoms change which sends out shockwaves and enormous amounts of heat.

But there are difficulties involved in achieving the ignition goal. One is the ability to compress the pellet uniformly so that there is enough force concentrated to produce an efficient ignition event.

Another problem is the massive amount of fuel required to carry out the testing. To create ignition scientists destroy the pellets in a chamber, measuring the energy produced and refining the experiment. Each of these ‘shots’ produces a fusion event and these take place at a pace of about two a week.

But for commercial fusion to work, a number of processes still have to be created. For instance millions of these pellets will have to be prepared and destroyed, the residue cleared and the chamber made ready again to allow the next pellet in a constant stream. This means the flow of fuel must be continuous to produce constant power—a problem that is being addressed but a solution for which is still years away.

Even after that, going from proving ignition to producing a commercial energy supply will take yet more time. Next post, we will investigate the groundwork being laid for a new form of power for the world.

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