Fusion Still Unready To Save Us

Update 12-19-2022:  An edited version of this appeared in the Sunday 12-18-2022 Waco "Tribune-Herald" paper as a board-of-contributors column.  

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With scientists achieving “breakeven” at the national ignition facility,  their press release has been ballyhooed into notions that fusion is here to save us immediately from energy shortages and climate change.  Wrong!

Excerpted from an NBC News release 12-13-2022:

“While the Livermore team achieved what researchers call a scientific break-even or energy gain, it did not achieve an engineering break-even: The inefficient lasers used in the experiment required about 300 megajoules of energy to fire just 2 megajoules of energy into the experiment. The reaction produced about 3 megajoules of energy.”

and

“Scientists must now find ways to reduce inefficiencies, burn a larger portion of available fuel during the reaction and harness the energy for use as electricity, said Troy Carter, a professor in UCLA’s department of physics and astronomy and the director of the Plasma Science and Technology Institute.”

And here is an image of the target bay: 

My take on it:

Figured as output/input,  the scientists are comparing fusion energy released (as heat) to the incident laser light energy on the fuel pellet that compressed it:  3 megajoules/2 megajoules = 1.5,  which is greater than 1,  indicating they got more fusion-derived heat energy out,  than they put in as laser light energy (or magnetic confinement energy,  or whatever type of energy the experiment used). 

That definition of the ratio is termed “scientific breakeven”,  and this is the first time that ratio has ever exceeded 1 in anybody’s experiment!  That is quite the significant achievement!  However,  bear in mind that many experimenters have been trying to do that ever since the early 1950’s (some 7 decades ago).

That achievement says getting energy from fusion is actually theoretically possible.  But it ignores the efficiency of producing the input laser (or other) energy,  and it ignores the efficiency of utilizing the output heat to make usable electricity.  The second quoted paragraph above says exactly that,  but without any numbers to “calibrate” the notions.  Allow me to “calibrate” it for you:

Per the quoted data in the first quoted paragraph,  the efficiency of producing those 2 megajoules of laser energy is 2 megajoules/300 megajoules = 0.67%,  which is really,  really low! 

A heat engine is required to produce electricity from the released heat of fusion.  The best of those that we have,  are the steam-powered generators at power plants,  which are limited by the laws of thermodynamics to efficiencies in the range of 25-50%.  I will use that value range for illustration.

What all that really says,  from the viewpoint of any engineer actually tasked to build a powerplant,  is that the output should be the producible electricity,  say 25-50% x 3 megajoules,  or 0.75-1.5 megajoules.  The input is the energy required to actually produce the laser energy in this case,  which is the 300 megajoules quoted. 

Looked at that way,  the ratio is 0.75-1.5 megajoules/300 megajoules,  or about 0.25-0.50%,  and very likely lower than that.  And yet THAT is the ratio that really needs to be greater than 1 for a real-world powerplant design to work!  That would be “engineering breakeven”. 

It took 7 decades to achieve “scientific breakeven”.  It is unrealistic to expect that reaching “engineering breakeven” won’t require a similar number of decades.

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What we face:

We face a shortfall of grid capacity as the population increases and as motor fleet electrification proceeds,  plus we face a climate disaster already in progress.  For our energy and climate needs,  it is obviously wiser to count on techniques that we already have operational. Those are fossil fuels,  hydroelectric,  nuclear fission,  solar,  and wind.  Nothing else is operational.

How we can face it:

All the fossil fuels produce greenhouse gas emissions,  and the technologies to reduce or prevent that are simply not operational.  Of the fossil fuels,  the one cleanest of both ordinary pollution and greenhouse gas emissions is natural gas.  But you must pay careful attention to stopping the leaks from,  and the freezing of,  those pipelines and distribution infrastructure.  We know how to do that,  but we have yet to make those into regulatory requirements.  So,  change that lack!

Hydroelectric capacity cannot be expanded much further:  we have already dammed all the dammable rivers in the US.

Solar and wind are already 20+% of the Texas grid capacity,  but because of their intermittent nature and long-distance transmission losses,  they cannot be much more than that percentage,  until “grid-scale” energy storage is operational.  It is not yet operational.

That leaves nuclear fission,  which is free of conventional pollution and free of greenhouse emissions,  but does incur radioactive wastes and risks!  It has to be done “right”,  which prioritizes safety over profit,  which the US Navy has long-demonstrated really works.  It also needs a short-term and a long-term solution for dealing with the nuclear waste stream. 

The short-term nuclear waste solution is using the Yucca Mountain disposal facility already constructed in Nevada,  but so far never used.  Long-term,  we need to re-process spent nuclear fuel,  which might reduce the waste stream amounts,  by a factor approaching 10.

Just cut the red tape (while maintaining and enforcing the safety requirements) and get on with building nuclear plants as rapidly as we can!  We already know how.  No,  it’s not the cheapest source of electricity,  but it alone meets all the steady generation-capacity and emissions requirements.

My recommendations in a nutshell: