While solar cells and wind turbines are the devices many people will think of for off-grid electricity production, the development of practical artificial photosynthesis for the creation of hydrogen via solar-powered water splitting could radically alter the way we produce energy locally. As part of the on-going pursuit of this goal, researchers from Forschungszentrum Jülich claim to have created a working, compact, self-contained artificial photosynthesis system that could form the basis for practical commercial devices.
Photosynthesis in plants and certain types of algae is the process where light energy is transformed into chemical energy to synthesize simple carbohydrates from carbon dioxide and water. In artificial photosynthesis, or photoelectrochemical water splitting, solar energy is used to split hydrogen molecules from water (or even further refine it into methane in some systems).
In this latest system, as in most other artificial photosynthesis devices, the amalgamation of a solar cell and an electrolyzer is used to capture solar energy to split water into hydrogen. A technique employed since the 1970s, most research has concentrated on increasing efficiency by developing new absorber materials and catalysts. The Jülich system, however, does not seek to improve the components used but instead concentrates on bringing all of the material and experimental knowledge together to produce a practical working unit.
"To date, photoelectrochemical water splitting has only ever been tested on a laboratory scale," said Burga Turan one of the researchers on the project. "The individual components and materials have been improved, but nobody has actually tried to achieve a real application."
Created by Turan and his colleague Jan-Philipp Becker at Jülich's Institute of Energy and Climate Research, the team has created a small, self-contained unit with a surface area of around 64 cm2 (9.9 in2), and built entirely from inexpensive, commercially available materials. Though each unit is individually diminutive, the team points out that by connecting a set of basic units, future commercial production will make it possible to create a photoelectrochemical system many square meters in size.
"This series connection means that each unit reaches the voltage of 1.8 volt necessary for hydrogen production," said Jan-Philipp Becker. "This method permits greater efficiency in contrast to the concepts usually applied in laboratory experiments for scaling up."
According to the researchers natural photosynthesis conversion of sunlight to energy tops out at only about 1 percent (and other artificial systems top out at about 3 percent), so the conversion efficiency of solar input to hydrogen production in the prototype at around 3.9 percent could be considered high in comparison but, in practical terms, really isn't.
"That doesn't sound like much," said Bugra Turan. "But naturally this is only the first draft for a complete facility. There's still plenty of room for improvement."
Given more efficient solar cell materials, the researchers believe that the conversion effectiveness could reach up to 10 percent, and with the use of perovskite materials it may be possible to achieve efficiencies of 14 percent or more.
"This is one of the big advantages of the new design, which enables the two main components to be optimized separately: the photovoltaic part that produces electricity from solar energy and the electrochemical part that uses this electricity for water splitting," said Becker.
The system has been patented by the researchers, and they believe it could be used with various types of thin-film photovoltaic technologies and a diverse range of electrolyzers, making the unit relatively easy and practical to commercialize.
"For the first time, we are working towards a market launch", said Becker. "We have created the basis to make this reality."
The results of this research were recently published in the journal Nature Communications.
The video below shows the system in action.
Source: Forschungszentrum Jülich
