An artificial photosynthesis system that is both compact and complete has been developed by scientists from the Forschungszentrum Juelich Institute of Energy and Climate Research. This is a pivotal step towards applying the technology in commercial applications. The concept is flexible in respect of both the size of the system and the materials used.
The majority of our energy will in the near future be supplied by the sun and wind. As these renewable energy sources are by nature inconsistent, research on efficient storage technologies is a major focus of research in this area. Technologies developed should be both affordable and environmentally friendly. Direct photo electrochemical water splitting is an artificial photosynthesis process that employs a combination of electrolyzers and solar cells. This method in particular meets the affordability and environmentally friendly criteria. Solar energy can be directly converted into the universal storage medium of hydrogen using this process. Although the process was first examined in the 1970s, it has only in recent year been attracting increased attention. Researchers have thus far focused on materials science for new catalysts and absorber materials in an effort to improve efficiency.
One aspect that has been largely neglected so far is to develop a realistic design that can take the technology from laboratories and apply it in practical applications. Juelich solar cell researchers Bugra Turan and Jan-Philipp Becker are however changing this. Turan explains that photo electrochemical water splitting has only ever been done in a laboratory. Although the individual materials and components have been enhanced through previous research, not one person has actually tried to manufacture a real application.
The new design developed by the two specialist is undoubtedly different from the usual laboratory experiments. Turan and Becker have created a self-contained, compact system – manufactured completely from low-cost materials that are readily available instead of using the individual components the size of a finger nail that are normally used.
The component still appear relatively small having a surface area of only 64 square cm, but the flexible design is what makes the difference. It is possible to fabricate systems that are several square meters in size simply by continuously duplicating the basic unit. This unit consists of a number of solar cells that are connected to each other by using an unusual laser technique. Becker explains that this connection in series means that each unit reaches the 1.8 volt required for hydrogen production. Doing things this way results in greater efficiency when compared to the techniques usually used for scaling up in laboratory experiments.
The prototype currently has a solar-to-hydrogen efficiency of 3.9%. Turan points out that although this does not sound like much, natural photosynthesis only achieves an efficiency of 1% and since they have only created the first draft for a complete facility, there is still plenty of room for improvement. Becker thinks that the Jülich design could be increased to about 10% efficiency within a short time simply by using conventional solar cell materials. There are however also other approaches that could be explored, for example using perovskites, a novel class of hybrid materials. By using these, it should be possible to achieve efficiencies of up to 14%.
One huge advantage of the new design is that it enables the two main components to be optimized independently. An electrochemical component uses electricity for water splitting while a photovoltaic component produces the required electricity from solar energy. Becker notes that they have patented the concept, which can also be applied for various types of electrolyzer and most types of thin-film photovoltaic technology. The team feels that they have created a solid basis from which a market launch is the next logical step.