A research team led by the University of Tokyo won a €5 million European Union prize this month for coming up with a novel way to make abundant and cheap fuel from sunlight.
In the scramble to find alternatives to fossil fuels, the EU competition aimed to accelerate development of one of the most promising new technologies – artificial photosynthesis – in a spirit of fostering international collaboration over the most promising clean-energy paths.
The technology mimics natural photosynthesis in which plants use rays from the sun to transform water into oxygen and carbon dioxide into chemical energy in the form of glucose.
Artificial photosynthesis uses sunlight to split water into oxygen and hydrogen. Oxygen is released into the atmosphere and hydrogen can be used as fuel.
‘Artificial photosynthesis has the potential to provide a huge amount of green fuel,’ Professor Kazunari Domen, the winning team’s coordinator, said in an interview after the European Commission announced the award on 5 December in Brussels.
Composed of scientists from the University of Tokyo and Japanese energy company INPEX, the team was among 22 applicants for the Fuel from the Sun prize and made it on to a shortlist of three finalists before emerging victorious. The two runners-up were from France and Britain.
The contest took place in the framework of a global initiative called Mission Innovation, which brings together 24 countries and is spurring research activities and investments in a bid to make clean energy universally accessible and affordable.
Artificial photosynthesis has the potential to provide a huge amount of green fuel.
‘The prize was awarded to the winning team for the high degree of professional engineering and integration,’ said the Commission.
If artificial photosynthesis can be done cheaply enough, it could replace oil, natural gas and coal for all sorts of vehicles, machines and industries including chemicals that cannot be powered by renewable electricity alone.
Although sunlight is abundant and free, many of the methods for converting it into fuel are too expensive - or too difficult to scale up - to compete with fossil fuels.
The winners’ prototype has the potential to be both cheap and easily scalable.
Contestants had to develop a device that used artificial photosynthesis to create enough fuel to power a small engine. The devices were run outdoors and tested for the amount of fuel they produced, its composition and its ability to power the engine.
The winning system used photocatalysts in contact with pure water.
Photocatalysts are ultrafine particles that absorb the sun’s energy and trigger the water to split. The resulting hydrogen was then combined with carbon dioxide to produce methane, which was used to run the engine.
A solar fuel (methane) production system constructed at Ispra, Italy for the EIC Horizon Prize 'Fuel from the Sun: Artificial Photosynthesis'. © Kazunari Domen and Taro Yamada
Because photocatalysts are a simple way to convert sunlight into chemical energy, they hold out the hope of making low-cost green hydrogen, said Prof Domen, a professor at the University of Tokyo and Shinshu University.
The challenge of the contest was to build a fully functional prototype of an artificial photosynthesis-based system that can produce a useable synthetic fuel.
‘Our project has so far targeted the production of hydrogen, but thanks to this competition we gained important insights into the synthesis of green fuels like methane that are more favourable for storage and transport,’ Prof Domen said.
The hydrogen produced in the winning system can be deemed green, he said.
Today green hydrogen, made with renewable energy including solar and wind, accounts for less than 1% of total hydrogen produced, according to the International Energy Agency.
The current cost of producing green hydrogen is so high that the activity is unprofitable without government support, according to Prof Domen.
His team’s priority now is to find a more effective photocatalyst.
The winning device achieved about 0.6% efficiency – meaning that around 99% of the energy was lost. To make such a fuel commercially viable, the catalyst will need to deliver at least 5% efficiency, said Prof Domen.
‘We have already found several candidate materials which can deliver efficiency of 5% or even 10%,’ he said. ‘So I believe that we can do that in the near future.’
If successful, the team should be able to overcome the remaining barriers to commercialisation within years - rather than decades - in collaboration with industry partners, he said.
One hurdle that Prof Domen is confident of clearing is regulatory.
While the combination of hydrogen and oxygen is ‘explosive’, he said, ‘we know how to handle the mixture safely.’
Another obstacle is developing cheap reactors and improving the separation of the hydrogen from the mix.
If successful, the final production plants will comprise very thin containers of water and photocatalysts, which are exposed to sunlight.
About 10 000 plants, each covering 25 square kilometres, would need to be built by 2050 to meet one third of the world’s energy needs, according to Prof Domen.
‘Many industry people told me that if they can make money, then 10 000 plants is not impossible,’ he said. ‘It really depends on whether they can make money or not.’
Meanwhile, as his team races to find a more effective photocatalyst, Prof Domen says the Fuel from the Sun prize will help turn sceptics of the method into proponents of it.
‘Most people don’t believe photocatalysts would work,’ he said.
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Fuel from the Sun finalists
The two runners-up for the “Fuel from the Sun” prize were the France-based Atomic Energy and Alternative Energies Commission, also known as CEA, and the University of Cambridge in the UK.
Following are comments made by representatives of two contestants at the 5 December award ceremony:
‘We are very happy to have been a part of this very exciting project related to the environmental crisis.’
‘I would like to congratulate the other contestants and, of course, the winner of the prize. We are really impatient to discover more about the technology you developed and we are, of course, open for collaboration. And we have young researchers that are open to opportunities too in these topics.’
University of Cambridge
‘It really pushed us to develop these technologies much faster than we would have done otherwise.’
‘Many congratulations to the Japanese team, a very well-deserved winner. We have all been following their work for many, many years – it’s very impressive. But also the French team many congratulations. We are very pleased to have been in the boat with you and battle for the prize.’
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