A team of biologists and chemists from the Israel Institute of Technology is completing an avant-garde project in the energy field aimed at creating a biological solar cell installed on a succulent plant. The intention is to supply homes with clean energy through houseplants. In recent years, the “biological” component in solar research has carved out an ever greater space for itself, with the aim of providing an energy solution that can be ecological and economical at the same time. Over time we have moved from organic cells with plant pigments to devices capable of replicating photosynthesis. Bio-photovoltaic belongs to this scientific trend, a technology that exploits solar energy using microorganisms engineered in the laboratory.
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Scientists at the Israel Institute of Technology, however, have gone one step further. The study reported on Acs Applied Materials & Interfaces demonstrates the creation of a special biological solar cell made directly on a succulent plant. The work, as well as others in the field, harnessed the natural chemical process of photosynthesis to generate a current. In fact, during photosynthesis, light converts CO2 and metabolic water into oxygen and sugar generating a flow of electrons that can, in theory, be carried away from the cell as a “photocurrent” and used to power an external circuit. Until now, the system for collecting electrical energy from biological photosynthesis systems took place by immersing the system in an electrolytic solution. Research eliminates this step: the particular tissues of succulent plants are able to contain and retain large quantities of water which replace the classic electrolytic solution used in the past. With this mechanism, in fact, a living photovoltaic cell is created.
In practice, the researchers have created a biological solar cell using the succulent Corpuscularia lehmannii, also called “ice plant”. They inserted an iron anode and a platinum cathode into one of the leaves of the plant and thus discovered that its voltage was 0.28V. By connecting it to a circuit and exposing it to light, the plant produced up to 20 µA/cm2 of photocurrent density. Continuing to generate electricity over 24 hours. While these numbers are lower than a traditional alkaline battery, they are representative of only one leaf. Previous studies of similar organic devices suggest that connecting multiple leaves in series could increase the voltage.
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The team specifically designed the living solar cell so that protons in the leaf’s internal solution could combine to form hydrogen gas at the cathode, which could be harvested and used in other applications. According to the researchers, their method could enable the development of future sustainable and multifunctional green energy technologies. Perhaps by combining cells based on succulents with cells based on algae. Scientists from the Biochemistry department of the University of Cambridge have in fact developed a bio-photovoltaic system that contains algae capable of storing sunlight and producing energy through photosynthesis. For the system to work, it only needs to be powered by electricity and water. Even before succulent plants and algae, however, bacteria opened the doors to living photovoltaics. Some researchers from the Federal Polytechnic School of Lausanne (École Polytechnique Fédérale de Lausanne), in Switzerland, in collaboration with colleagues from the University of Salento and the Sapienza University of Rome, have managed to insert carbon nanotubes inside some photosynthetic bacteria , increasing their ability to generate electricity when illuminated. The application also has direct implications in the solar sector.