Solar-energy project works towards 'clean' fuel production

The SolarCAP project is a multi-disciplinary effort that involves physicists who manipulate the behaviour of photons and harvest them; chemists to utilise these photons for fuel generation; and, eventually, engineers to scale up the process.

‘I think the public tends to think of hydrogen-powered cars as being very green and I don’t think there’s a widespread understanding that all that hydrogen is currently coming from fossil-fuel sources,’ Prof Wendy Flavell of Manchester University told The Engineer.

One of the SolarCAP research groups recently demonstrated the splitting of water to form hydrogen using an indium phosphide (InP) nanocrystal array with an external light source.

However, Flavell believes there may be too much emphasis on achieving a hydrogen economy given the difficulty in storing and transporting the gas in fuel form. She said the ‘holy grail’ would be solar activation of alkanes such as methane into methanol, for which there is a very ‘mature technology’ in terms of utilisation in devices such as fuel cells. This process would also release carbon monoxide as a byproduct, which is a widely used feedstock for the chemical industry.  

‘The reason why we’d like to generate liquids, specifically, is that they are easy to ship. If you’re embedding this technology in a part of the world that’s remote where there’s a lot of sunlight, it may well be easier to think of actually shipping fuel rather than electricity or indeed hydrogen.’

Flavell is primarily a physicist and her work centres around producing so-called quantum dots to effectively absorb and harvest light for use in chemical reactions through a process called multiple exciton generation (MEG).

‘If we can use this phenomenon and that buys us, say, an extra 10 per cent efficiency in light harvesting — which it looks as though it will — that’s a clever bit of quantum engineering.’

While Flavell admitted that her fundamental research is some way away from the real engineering required to make such processes a commercial reality, she said solar technologies are moving so quickly that aspects of their work should be easily integrated with existing technologies by the time they are ready.

The SolarCAP collaborators are the universities of Manchester, York, East Anglia and Nottingham, along with industrial expertise from NANOCO Technologies and funding from EPSRC.