Berlin, Sep 13 Scientists in Germany have developed the first complete and compact artificial photosynthesis system that uses solar power to split water and produce hydrogen fuel.
Solar energy can be directly converted into the universal storage medium of hydrogen.
This process was first investigated in the 1970s, but has only begun to attract increasing attention in recent years.
Research has focused on materials science for new absorber materials and catalysts to further improve efficiency.
Scientists at Forschungszentrum Juelich, a German research centre, are concentrating on an aspect that has so far largely been neglected - a realistic design that can take this technology from the scientists' laboratories and put it into practical applications.
"To date, photoelectrochemical water splitting has only ever been tested on a laboratory scale," said Burga Turan, from Forschungszentrum Juelich.
"The individual components and materials have been improved, but nobody has actually tried to achieve a real application," said Turan.
The new design is different from the usual laboratory experiments. Instead of individual components the size of a finger nail that are connected by wires, the researchers have developed a compact, self-contained system - constructed completely of low-cost, readily available materials.
With a surface area of 64 square centimetre, their component still appears relatively small.
However, by continuously repeating the basic unit, it will in future even be possible to fabricate systems that are several square metres in size.
The basic unit itself consists of several solar cells connected to each other by a special laser technique.
"This series connection means that each unit reaches the voltage of 1.8 volt necessary for hydrogen production," said Jan-Philipp Becker from Forschungszentrum Juelich.
"This method permits greater efficiency in contrast to the concepts usually applied in laboratory experiments for scaling up," Becker said. At the moment, the solar-to-hydrogen efficiency of the prototype is 3.9 per cent.
"This is only the first draft for a complete facility. There's still plenty of room for improvement," said Turan.
Natural photosynthesis only achieves an efficiency of one per cent, researchers said. According to Becker, the design could be increased to around 10 per cent efficiency using conventional solar cell materials.
There are also other approaches, such as using perovskites, a novel class of hybrid materials, with which it is already possible to achieve efficiencies of up to 14 per cent. The research was published in the journal Nature Communications.