Plasma power: Our renewable advantage

Australia is truly the lucky country when it comes to endowments of renewable energy resources. We have more sunlit, windswept land than virtually any other country.

And now that solar and wind electric power generation have become cost-competitive, investors are starting to propose large-scale power generation facilities (for example, the Sun Cable project) that will be capable of producing all the electricity we need and much more. 

It’s time to start thinking about how we can build on existing capabilities to develop a leading edge in renewable energy compatible technologies to export our excess energy, power hard-to-abate long-haul transport, and create new value-added products. 

Power to X (P2X) and particularly plasma power to X (PP2X) technologies are an attractive proposition that we should seriously consider prioritising.

Power to X (P2X) refers to processes and technologies that convert renewable energy and sustainable materials into power fuels and clean chemicals.

Plasma is the fourth state of matter (beyond solids, liquids and gases), formed when further energy is given to a gas so that it becomes ionized to contain significant numbers of positively and negatively charged particles, such as ions and electrons.

The energies of the species in plasma makes them highly reactive and improved selectivity of reactions can be provided by employing catalysts to enhance the rates of desired reaction pathways.

Plasma is most effectively created by direct coupling of electrical power so plasma P2X can easily follow the variations inherent in renewable energy generation.

Among the key hurdles in developing a hydrogen economy, hydrogen storage and transportation has always been challenging issues because of safety and cost.

A cost-effective alternative pathway to store hydrogen in the form of an energy carrier that can be transported and exported using existing infrastructure will be a game changer.

There are several possible energy carriers, including methane, methanol, other liquid organics, and ammonia. Methane, methanol and liquid organics can be produced by reacting H2 with CO2, giving the possibility of a carbon-neutral fuel cycle, with the carbon produced when burning the carrier being balanced by the carbon captured in its production.

Methane can be injected into the natural gas grid as a universal energy carrier – compressed natural gas (CNG) for cars and buses, CNG/liquified natural gas (LNG) for trucks, ships and industry.

Ammonia can be produced from a range of feedstocks, including H2 and N2, and H2O and air. In the latter case, the energy required to separate H2 from H2O and N2 from air is saved.

Existing thermal processes used to produce these fuels need ramping up and ramping down and are poorly adapted to the intermittent nature of renewable energy sources. Hence the attraction of plasma processes.

Plasma power to methane (CH4) is an emerging technology that can convert hydrogen and CO2 at ambient conditions without additional heating and compression, which saves significant energy.

As this process is not constrained by the thermodynamics of the methanation process, it has the potential to surpass the thermal process’s energy efficiency.

Most importantly, the plasma can be easily turned on and off without ramping, allowing alignment with the intermittent nature of the renewable energy source.

Green methane pipeline injection is much easier than hydrogen pipeline injection. The latter has a 10 per cent injection upper limit, while green methane injection has no upper limit.

Japan has a target of 90 per cent renewable CH4 in the gas grid by 2050, while Europe has a target of 75 per cent.

Japan cannot source the renewable methane locally and aims to import it from Australia through their LNG portals here and has been actively involved in the green methane projects in Australia to prepare themselves for the import.

Australian gas suppliers are also monitoring global interest in green CH4. The gas pipeline industry is actively pushing the momentum behind the scenes. If a 50 per cent target is set for 2050, equivalent to 18 million tonnes per year, or 900 PJ (900 trillion joules), a huge green methane market is available both domestically and overseas.

CO2 conversion to methanol, which is a liquid that can be transported as a fuel substitute or chemical feedstock for high-value chemicals, has attracted significant industrial attention in recent years.

Conventional methanol synthesis by CO2 hydrogenation through thermal heterogeneous catalysis requires high pressure (50–100 bar) and a temperature of 200–400 °C, which results in increased energy costs because of the need for heating and compression.

The thermal process is further constrained by kinetic and thermodynamic limitations, with the maximum CO2 conversion being less than 30 per cent. Low conversion requires further post-reaction processing to increase the product purity, inevitably increasing the production cost and product carbon intensity.

Very recent work demonstrated 21.2 per cent CO2 conversion and methanol selectivity of 53.7 per cent in the plasma process at atmospheric pressure and room temperature, while no reaction occurred at these conditions without using plasma.

The energy consumption for methanol production under plasma when a catalyst was employed was more than 20 times lower than in the plasma-only process.

Ammonia is usually produced by the Haber-Bosch process, a thermal catalysis process that requires high temperature (~500°C) and pressure (~100 bar). While the Haber-Bosch process has excellent energy efficiency, it is, in common with other thermal catalysis processes, not compatible with intermittent renewable energy sources. 

A range of plasma processes has been used to produce ammonia. The most investigated use H2 and N2 as the precursors. The plasma is usually combined with a catalyst, which increases the conversion to ammonia (NH3) . The main challenge is obtaining energy efficiencies that are competitive with Haber-Bosch.

Another approach has recently been developed. In this case, a plasma (without a catalyst) is used to convert air, or other mixtures of N2 and O2, to NOx (nitrous oxide). The NOx is then reacted with water in an electrocatalytic process to produce ammonia.

This approach saves the large amount of energy required to separate hydrogen from water. Initial techno-economic analyses suggest that the process could be competitive with Haber-Bosch for ammonia production using renewable energy.

The nitrous oxide can also be reacted with water to form HNO3 (nitric acid), which is a precursor for fertiliser production.

Plasma catalysis for P2X applications is an emerging area that has undergone rapid development over the last 5-8 years.

The applications provide the opportunity for cost-effective production of energy carriers to promote renewable energy uptake and a hydrogen economy.

Plasma P2X aligns closely with Australia’s energy landscape and has the potential to create new local manufacturing industries.

Australia has a long history of research in plasma physics, with the first programs established by Mark Oliphant at the ANU in 1958, and by Charles Watson-Munro at the University of Sydney in 1961.

Initially the focus of this research was in space plasma physics and nuclear fusion.

Research into the use of plasma for manufacturing, such as thin film coatings, later emerged, leading to the establishment of the Gaseous Electronics Meetings series which continues to be the Australian conference for plasma science and technology.

The first meeting was organised by John Lowke and Richard Morrow of CSIRO in 1980 and meetings have run every two years since then.

Today there is internationally renowned research activity in plasma science addressing many application areas across many Australian institutions including CSIRO, the University of Sydney, ANU, University of South Australia, James Cook University, QUT, Curtin, Swinburne, Griffith, and the University of Western Australia.

P2X is a relatively new area of research in Australia. Efforts are still relatively small scale but are growing.

The plasma power to ammonia and fertiliser is the most advanced, with the recent launch of the PlasmaLeap company and a field trial in the Clare Valley, and strong research support from at least four research institutions.

Investment in other technologies has commenced and is growing. Plasma P2X is an area in which Australia could easily reach a leadership position in the medium term if investment is secured since a number of local research groups are already performing world-class R&D.

In terms of science, appropriate funding schemes could encourage cross-disciplinary collaboration, including with international leaders, and attract talented researchers to Australia.

Incentives for collaboration between Australian researchers to form a unified P2X group would be valuable.

In terms of applications and technology development, flexible collaboration environments are needed to allow early testing of inventions, with seed funding provided for testing and improvement of emerging technologies, with the aim of increasing the TRL.

A possible approach would be developing a testing platform with a range of power supplies and characterisation equipment that could be accessed by researchers – this would reduce duplication and allow the optimum approaches to be determined.

Ideally, incentives should be provided for industry to be involved at an early stage to ensure the take-up of promising processes.

This is an emerging area, and we would expect new IP and, eventually, new manufacturing industries to be developed.

Australia is particularly rich in renewable energy sources. It also has a huge investment in the export of LNG. Decarbonisation of energy exports demands technologies to convert renewable energy and sustainable resources into green fuel products.

Australia’s geographical location and extensive LNG portals place it in an ideal position to export fuels to regional customers, particularly Japan. Plasma P2X processes are important candidate technologies, likely to be the optimum approach in some cases.

A coordinated scheme to develop and evaluate these and other P2X technologies, including scale-up to pilot or demonstration plant scale, would be valuable.

Some large and small companies are willing to invest, and government assistance (financial and/or through a technology plan) would encourage more substantial investment and progress.

Professor Marcela Bilek has expertise in fundamental science and practical applications of materials physics and engineering, plasma processing, and biointerfaces. Honours include Physical Scientist of the Year; ARC Federation Fellowship; Australian Academy of Science Pawsey Medal; and ARC Laureate Fellowship; as well as election to the Fellowships of the American Physical Society (APS), the IEEE; AVS and the Australian Academy of Science. She was recognised as a Member of the Order of Australia (AM) for significant service to physics and biomedical engineering.

Dr Yunxia Yang is a Senior Research Scientist in CSIRO’s Energy Business Unit. She has extensive expertise in heterogeneous catalysis, particularly novel materials for H2 and CO2 utilisation. Her research goals are to develop or improve materials as well as technology solutions to increase process efficiency. She has led a number of international collaborations with universities in Australia, China and Europe, on plasma-assisted green fuel production from CO2 and H2.

Dr Tony Murphy is a Chief Research Scientist in CSIRO’s Manufacturing Business Unit. He has extensive experience in development and computational modelling of plasma processes including waste treatment, arc welding and wire-arc additive manufacturing, and has worked with clients including General Motors, Boeing, LS Electric and several SMEs. His awards include the Pawsey Medal of the Australian Academy of Science, the Harrie Massey Medal of the Australian and UK Institutes of Physics, and the Plasma Chemistry Award of the International Plasma Chemistry Society. He is Editor-in-Chief of the journal Plasma Chemistry and Plasma Processing.

Do you know more? Contact James Riley via Email.

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