Plant energy may power machines of the future

Scientists in Arizona have taken a key step towards creating an artificial plant which could power miniature machines of the future, using the same process as photosynthesis.

The team at Arizona State University has developed a chemical system which, like plants, takes light energy and transforms it into electrical potential which can be used later to power other processes.

"The process of plant photosynthesis is like a solar-powered hydro-electric station," said Tom Moore, at the university's department of Chemistry and Biochemistry.

If the team succeeds, it might be able to produce more efficient solar energy systems. Present photovoltaic cells, which generate electricity directly from the sun, struggle to turn more than 20 per cent of the solar energy falling on them into power. They also cannot store the energy, except at remote sites.

Photosynthesis is a complex yet highly efficient process, converting more than 60 per cent of incoming solar rays into energy. Researchers have tried to mimic this in the laboratory for more than 100 years. It occurs within plants cells, in structures called chloroplasts, which absorb light and use a combination of enzymes and chemicals to shunt electrons and protons (hydrogen nuclei) in different directions across an internal membrane.

This creates an electrical potential across the membrane. That stored energy is then released, and used by another enzyme to create a molecule called adenosine triphosphate (ATP) - the prime source of energy for cell processes. "In a sense, ATP is the gasoline of life," said Professor Moore.

The Arizona system, reported in today's issue of the science journal Nature, uses chemicals to absorb light energy and use it to shuttle both electrons and protons in different directions across a membrane, just as the chloroplasts do.