Aakash Ahuja: Electricity Generation from Photosynthesis Using Carbon Nanotubes

As humans scour the Earth for energy, venturing farther offshore and deeper underground, a new study suggests the answer has been under our noses all along. Rather than chasing finite fossils like oil and coal, it focuses on Earth's original power plants: plants.

Plants use energy from the Sun through photosynthesis, and humans use energy from the Sun through things like solar panels. A new technique created by researchers at the University of Georgia allows humans to get electricity from plants by breaking the Process of photosynthesis. This research could someday lead to some very literal power plants.

Solar panels seem to be a good option for generating electricity, but the reality of the situation is that they’re terribly inefficient at generating power from sunlight. Thanks to eons of evolution, most plants operate at 100 percent quantum efficiency, They convert nearly 100 percent of the photons they capture from sunlight into electrons, which go through a series of reactions on the pathway to generating sugars, the team behind the technology explained. meaning they produce an equal number of electrons for every photon of sunlight they capture in photosynthesis. An average coal-fired power plant, meanwhile, only operates at about 28 percent efficiency, and it carries extra baggage like mercury and carbon dioxide emissions. Even our best large-scale imitations of photosynthesis — photovoltaic solar panels — typically operate at efficiency levels of just 12 to 17 percent. Plants divide water molecules into hydrogen and oxygen through photosynthesis, and when this split occurs, electrons are generated. Typically, these electrons are used by the plants to create sugar used to grow and reproduce. The team at the University of Georgia have developed a way to use carbon nanotubes to capture those electrons before they’re used by the plant. This isn’t the first experiment that’s used plants to generate electricity, but it’s at least two orders or magnitude more electrical current than earlier work. It’s going to take more research before this is a commercially viable technology, and at the moment it’s best suited for powering things like remote sensors and portable electronics. One of the researchers, Ramaraja Ramasamy, compares his work to hydrogen fuel cells, saying, “The electrical output we see now is modest, but only about 30 years ago, hydrogen fuel cells were in their infancy, and now they can power cars, buses and even buildings.”Photosynthesis is arguably one of the most important natural processes in the entire world. Experts say that it is mainly to praise for the development of a breathable atmosphere. Basically, it's constituted from a range of complex chemical reactions, which see the conversion of carbon dioxide (CO2) and water into glucose (energy) and oxygen (O2), all in the presence of visible light. While the initial atmosphere surrounding our planet was laden with volcano-produced carbon, the earliest plants did a monumental job at clearing the air for the more complex lifeforms that followed.
The secret lies in thylakoids, the membrane-bound sacs inside a plant's chloroplasts (pictured at bottom) that capture and store energy from sunlight. By manipulating the proteins inside thylakoids, Ramasamy and his colleagues can interrupt the flow of electrons produced during photosynthesis. They can then restrain the modified thylakoids in a specially designed backing of carbon nanotubes, which captures the plant's electrons and serves as an electrical conductor, sending them along a wire to be used elsewhere. He and his colleagues do this by extracting the plant machinery that drives the photosynthetic reaction called thylakoids and immobilizing them on a bed of carbon nanotubes, which act as an electrical conductor, capturing the electrons and sending them along a wire.

"That way, you have a continuous flow of electrons when the light is falling on the photosynthetic machinery from the plant," Ramasamy said, adding that the energy conversion technology is similar to a fuel cell, only in this case the fuel is sunlight. Similar systems have been developed before, but Ramasamy's has so far generated significantly stronger electrical currents, measuring two orders of magnitude larger than previous methods. It's still far too little power for most commercial uses, he points out, but his team is already working to boost its output and stability. Although carbon nanotubes are key to this method of harnessing sunlight, they can also have a dark side. The tiny cylinders, which are nearly 50,000 times finer than a human hair, have been implicated as potential health risks for anyone who inhales them, since they can become lodged in the lungs much like asbestos, a known carcinogen. But recent redesigns have reduced their harmful effects on lungs, based on research that shows shorter nanotubes produce less lung irritation than longer fibers do. Ramasamy says of his study. "The electrical output we see now is modest, but only about 30 years ago, hydrogen fuel cells were in their infancy, and now they can power cars, buses and even buildings."

"What we are trying to do is interrupt the pathway of natural photosynthesis and then trying to deal with those electrons," Ramaraja Ramasamy, an electrochemist at the University of Georgia, told NBC News.The efficiency of the system has the potential to be much greater than solar panels, which convert between 12 and 17 percent of the sunlight that hits them into electricity. First, though, more work needs to be done to improve the stability of the system. Currently, taking the thylakoids out of a plant is akin to taking the heart out of a human — it is not stable for very long, Ramasamy noted. But plants have a mechanism to replenish their photosynthetic machinery. It may be possible, he said, to genetically engineer this machinery for long-term stability.

"That's the direction this has to be explored in much more detail," he said.If successful, potential applications for the technology, at least in the near to medium term, include use as a power source for sensors used in remote locations, eliminating the need for batteries. Ramasamy and colleagues recently described a proof-of-concept device in the journal Energy and Environmental Science. "It is green energy, 100 percent clean, it has the potential to operate at really high efficiency, if we can continue to improve on this," Ramasamy said.

In the new achievement, French scientists at the Centre de Recherche Paul Pascal (CNRS) developed a new type of biofuel cell, that functions based on the two compounds that result following natural photo photosynthesis, and namely glucose and oxygen. The system's design is very basic, as it is composed of two electrodes, that have been altered using enzymes. What's also amazing is the fact that the team managed to insert one such cell into the leaf, or spike, of a living cactus, and then watch the chemical reaction take place in vivo – which means that they observed it while the plant was alive. The discovery could also be used in botanical research, so that experts working in this area can better understand how photosynthesis acts. In their observation, the CNRS experts also noticed the variable levels of glucose that were produced as light struck the biofuel cells. This is the first time such an observation is conducted, they say. It was additionally revealed that a single one of the new cells, inserted in a cactus leaf, could produce as much as 9 Watts of electricity per square centimeter. But one of the main applications for the new cells is as power source for medical devices, as they are able to function in live subjects. Placed under the skin, they could benefit from enough light to produce the necessary amounts of electricity to power up a variety of medical implants. olar power could transform the energy landscape in the United States, reducing the nation's reliance on coal and natural gas for electricity. Today, however, solar power remains more expensive on average than fossil fuels.

"You may think that the sun is abundant, but traditional photovoltaics require rare-earth elements, and a lot of them are imported from areas that have wars or where it is difficult to extract, which raises the cost," says Margaret Cheung, Assistant Professor of Physics at the University of Houston. She notes that if we learn from plants, which use only common elements—hydrogen, nitrogen, carbon, oxygen and some others—to convert sunlight into energy, then we’ll be able to bring down the cost of solar power. This is why researchers are looking at bio-inspired materials as possible resources for solar energy.

Study co-author and UGA engineering professor Ramaraja Ramasamy says in a press release. "Clean energy is the need of the century. This approach may one day transform our ability to generate cleaner power from sunlight using plant-based systems."