Ken Baldwin | Nuclear fusion is unlikely to be the climate change saviour

Nuclear fusion - the process that powers the sun - creates energy by colliding nuclei, the core, of hydrogen isotopes (deuterium and tritium) at high speed, which then fuse and produce helium nuclei and neutrons.

Helium is inert, does not contribute to greenhouse gas emissions and is not radioactive, so fusion is environmentally friendly and has virtually endless amounts of fuel to provide almost unlimited energy.

By contrast, nuclear fission as the name implies releases energy by the splitting of heavy nuclei (chiefly finite supplies of uranium), leaving byproducts that are radioactive.

While the technology exists to contain and store them, it is an added complication in an already expensive technology compared to zero-carbon alternatives such as wind and solar.

But now the joke is over: nuclear fusion - the holy grail of physics for decades - has become a reality.

A team at the Lawrence Livermore Laboratory in the US has recently demonstrated that they can produce more energy from a fusion reaction than the energy put into it - exceeding the breakeven threshold. But what next?

There are two main routes to nuclear fusion. The first is inertial confinement fusion that uses high power lasers to blast together nuclei in a microscopic hydrogen bomb, as pursued at the Lawrence Livermore Laboratory (LLL).

The second is magnetic confinement fusion that contains extremely high temperature nuclei in a magnetic bottle.

A consortium of major nations has combined efforts to build the world's largest experiment - the International Thermonuclear Experimental Reactor - that aims to demonstrate breakeven using magnetic confinement in the early 2030s.

In the past, both approaches have come close to energy breakeven, but now LLL has done this for the first time - a truly groundbreaking achievement.

In reality though, the amount of energy released was tiny - just over a megajoule, or enough to boil a few jugs of water. And it doesn't take into account the huge amount of electrical energy needed to produce the laser pulse, which results in a low wall-plug efficiency.

This is a long way from realising a fusion power station. Even if the number of LLL laser pulses can be increased from a few a day to 10 per second and operated constantly, this would only yield 10 megawatts of average thermal power - or about one hundredth the electrical output of a conventional fossil fuel or nuclear fission thermal power station.

So huge improvements in fusion yield or repetition rates would be needed to create a fusion electricity generator with the high wall-plug efficiency required to generate significant net amounts of electricity. This might take decades - perhaps leading to a new, 21^st century fusion joke.

For this reason, it's unlikely that fusion power will save us from climate change.

All the heavy lifting for the energy transition will be done by existing energy sources.

Renewable energy (solar, wind and hydro) plus existing nuclear fission power (in those countries unlike Australia that allow it) will replace fossil fuel technologies to eliminate greenhouse gas emission.

So nuclear fusion at commercial scale is unlikely to be available until well after the 2050 deadline needed to keep global warming below 2 degrees.

But beyond that, fusion might provide limitless energy for centuries to come.

What opportunity does this present for Australia?

Australia has a long history in fusion research, starting with Mark Oliphant's partnership with New Zealand's Ernest Rutherford in the first fusing of deuterium into helium, plus his discovery of the other key isotope, tritium. When it comes to fusion power research, Australian-born Peter Thonemann was also leader of the ZETA (Zero Energy Thermonuclear Assembly) project in the UK back in the 1950s.

Experimental and theoretical fusion research contributions from a number of Australian institutions (including The Australian National University) led earlier to the creation of the Australian ITER forum, and ultimately to engagement with ITER via a cooperation agreement signed in 2016 by the Australian Nuclear Science and Technology Organisation (ANSTO) on behalf of the Australian fusion research community.

But should fusion power be realised, a change in the law would be required to allow nuclear fusion to be employed in Australia. Under the Environment Protection and Biodiversity Conservation Act 1999, Section 140A(1)(b): "The Minister must not approve an action consisting of or involving the construction or operation of a .... nuclear power plant."

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This Act would need to be changed if nuclear fusion were to be available to power Australia in future decades.

However, Australia has abundant renewables, and in recent years has led the world's energy transition as the fastest installer of wind and solar per capita. Australia also has the highest percentage of households with rooftop solar. Renewables are becoming even cheaper, so would fusion power be needed in the distant future given that it represents an expensive and complex technology?

Perhaps it might, because decarbonising the last few percent of electricity is very difficult and expensive using intermittent renewables alone. Even then, it might still be cheaper to overbuild solar and wind, as well add more electricity storage and transmission.

However, in a future decarbonised world, Australia also has the opportunity to add value to its vast mineral reserves and export clean iron, steel, aluminium and other metals using clean energy. This would require clean energy installations at vast scale - but again, would renewables outcompete the prospect of fusion power?

Whatever future energy scenario plays out, the LLL achievement might now place another clean energy option on the table - albeit beyond the timescale required to address climate change. That challenge will be addressed globally by renewables and nuclear fission, with a practical nuclear fusion option perhaps - once again - 30 years away.