Energy: beware of con fusion

By Richard North - December 13, 2022

As I peer out of my office window at the frozen wasteland that the immediate streetscape has become, totting up the days to bankruptcy as the central heating performs its minimalistic function of preventing the condensation on the inside of the windows from freezing, there could be no better news than the prospect of “near limitless energy” from the miracle of nuclear fusion.

Now, according to the Guardian, that prospect has edged a little bit closer with a report of a “breakthrough” National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California.

In the breathless tones of the newspaper, we are told that it seems the Rubicon has been crossed, as the test reactor in a recent experiment has released 2.5 MJ of energy after using just 2.1 MJ to heat the fuel with lasers which drive the system.

Cited in ebullient terms is Dr Robbie Scott, of the Science and Technology Facilities Council’s (STFC) Central Laser Facility (CLF) Plasma Physics Group, who contributed to this research. He describes the results as a “momentous achievement”.

“Fusion”, he says, “has the potential to provide a near-limitless, safe, clean, source of carbon-free baseload energy”, going on to say that: “This seminal result from the National Ignition Facility is the first laboratory demonstration of fusion ‘energy-gain’ – where more fusion energy is output than input by the laser beams”.

Thus does Dr Scott roundly declare that: “The scale of the breakthrough for laser fusion research cannot be overstated”. But, if we are to take a sanguine look at the claims being made, it would appear that the importance of this development is indeed being “overstated”.

Nothing of this comes over in the Guardian though, nor in the source of this paper’s report, an article in the Financial Times. Here, one sees “two of the people with knowledge of the results” telling us that the energy output had been greater than expected, which had damaged some diagnostic equipment, complicating the analysis.

Nevertheless, we are informed, “the breakthrough was already being widely discussed by scientists” and, if confirmed, Dr Arthur Turrell tells us that “we are witnessing a moment of history”.

Turrell, though, does have his own dog in the fight. He is a plasma physicist and author of a book, The Star Builders, which charts the effort to achieve fusion power. “Scientists have struggled to show that fusion can release more energy than is put in since the 1950s”, he says, “and the researchers at Lawrence Livermore seem to have finally and absolutely smashed this decades-old goal”.

However, a small insight into what is being measured comes in the FT’s next paragraph which tells us a little bit about the $3.5 billion National Ignition Facility. It was, it seems, primarily designed to test nuclear weapons by simulating explosions but has since been used to advance fusion energy research.

So far, we are told, “it came the closest in the world to net energy gain last year when it produced 1.37 megajoules from a fusion reaction, which was about 70 percent of the energy in the lasers on that occasion”.

To gain a better insight into what is going on, it is worth investing the ten minutes or so in time it takes to watch the YouTube video by Sabine Hossenfelder. She introduces us to some of the terminology which puts the current claims in context.

Crucial to the understanding is the term “Q” which is used to describe the ratio of energy input to output, technically known as the “fusion energy gain factor”. A breakeven ratio where the amount of energy put in matches the amount produced is expressed as one. Any figure of less than one signifies an energy deficit, while a surplus of energy produced delivers a figure greater than one.

As any afficionado of James Bond films will tell you, though, there is more than one “Q”. In this context, we need to be aware of two iterations: Q-plasma and Q-total. In the former case, this measures the ratio of energy produced from the plasma activity.

The problem, though, is that to produce the plasma which is central to the reaction takes an enormous amount of power. Then, to turn the heat produced into usable energy (usually electricity) involves energy loss: it would be optimistic to expect an efficiency of 50 percent.

This is where Q-total comes into play – the measure of the total amount of energy put into the system compared with the amount of usable power delivered. This is obviously rather less than Q-plasma.

Generally, as a rule of thumb, a Q-plasma of at least 5 is needed before the reaction becomes self-sustaining and it must be much higher before any useable power is delivered.

What we are seeing reported though, without it being explicitly stated, is a breakthrough not in Q-total, but in Q-plasma. Exact Q-total performance figures are hard to get, but I have seen a figure of 0.01 for the NIF’s reactor.

Putting it more graphically is an article in Science Insider. It tells us that the NIF’s laser input of 1.8 MJ is roughly the same as the kinetic energy of a 2-tonne truck traveling at 160 km/h (100 mph).

On the other hand, the output of the reaction – 14 kJ – is equivalent to the kinetic energy of a baseball traveling at half that speed. Numerically speaking, the gain is 0.0077. The experiment, says Michael Campbell, a former director of NIF, “is a good and necessary step, but there is a long way to go before you have energy for mankind”.

Addressing the hype in the British Scientific press is the New Scientist which asks: “Has there been a breakthrough and what will it mean?”

Unfortunately, rather than prick the bubble of inflated expectation, it cites Gianluca Sarri at Queen’s University Belfast saying that the result from the NIF, if verified, represent “a huge milestone”. “This was not a given, it was not obvious that this could be done,” he says. “We know that now we can get fusion on Earth”.

Only then are we allowed a tiny glimpse of reality. While an energy output higher than that of the lasers that power NIF’s reactor would be extremely positive, the NS says, “there is still much more work to be done”.

For a reactor to be generally useful, it adds, “it would have to produce more energy than was initially put into the lasers”. Inefficiencies involved in producing laser light from electricity mean that is currently not the case – Sarri estimates that if 2.1 MJ of energy was output by the laser then NIF would have had to draw “tens” of megajoules from the electricity grid to achieve it.

Interestingly, in referring to the confusion between Q-plasma and Q-total (convenient, if not deliberate on the part of some scientists), Sabine Hossenfelder mentions a 1988 report by the European Parliament on the criteria for the assessment of European Fusion Research.

Back then, it warned that a framework for the evaluation of fusion power was necessary. This, it stated, ought to replace the generalised statements about the inherent advantages of fusion as a potential energy source with a set of criteria which are consistent with market-related economic assessments. “Correcting this lack of a recognisable framework is, we believe, more important as an objective than any other matter at this juncture”, it added.

Clearly, the core of that framework is an evaluation of the progress towards delivering useable power, as measured by Q-total. Yet, more than 30 years on, we are no further forward in reporting sensibly on a technology which has in over 70 years of research, has delivered remarkably little and is as far as ever from providing a solution to our energy needs.