Researchers find electricity-plant link

April 21, 2010, 1:03 a.m.

A team of Stanford engineers has managed to harness electrical energy directly from algae cells. The researchers believe that this result represents the first step toward generating “high efficiency” electricity from living plants.

The research team, headed by WonHyoung Ryu and Stanford mechanical engineering professor Fritz Prinz, published its findings in the March issue of Nano Letters.

Researchers find electricity-plant link
Stanford scientists worked on a study that intercepted electrons in plant cells once they had been excited by sunlight and before the proteins began to use energy to synthesize sugars, which holds promise for research on efficient energy. (JIN ZHU/The Stanford Daily)

The researchers generated an electrical current by inserting tiny gold nanoprobes into individual living algae cells, extracting electrons that the cells had produced during photosynthesis.

During photosynthesis, plants convert sunlight to chemical energy in the plant’s chloroplast. This chemical energy is stored in the form of sugar bonds. Plants generate electrons when their chloroplasts break water into oxygen, protons and electrons.

When sunlight reaches the chloroplast, these electrons are excited and are subsequently picked up by proteins, which use the electrons’ energy to synthesize sugars.

The Stanford team intercepted the electrons once they had been excited by sunlight and before the proteins had begun to use their energy to synthesize sugars.

According to the study, harvesting electrons directly from plant cells “potentially reduces energy losses associated with the multistep transformation of solar energy into products used for the production of biodiesel and bioelectricity.”

While biofuel combustion typically only yields three to six percent of a plant’s stored solar energy, the Stanford study’s electron harvest yielded 20 percent. Electron harvesting could theoretically occur with 100 percent efficiency, Ryu said in an interview with the Stanford News Service.

And unlike burning biofuels or biomass, there is no carbon released in electron harvesting, making the process not only efficient but also green.

But the team’s research is still in its infancy. Practical implementation of their research, if it is possible, is still years away.

The research is still “in its very early scientific stage and many things need to be understood,” Ryu said in an e-mail to The Daily.

Gary Brudvig, a professor of molecular biophysics and biochemistry at Yale, predicted in an e-mail to The Daily that most in the scientific community “would feel that this is an interesting result that may never have practical applications.”

“I feel that the work is a proof of concept,” said Arthur Grossman, one of the paper’s authors and a researcher in the Department of Plant Biology at the Carnegie Institution and the Department of Biology at Stanford, in an e-mail to The Daily. “There is still a lot that would need to be done to develop this work more in order to make it practical… so we are only at the very beginning of the development of this concept.”

WonHyoung Ryu, now a professor at Yonsei University in Seoul carried out the study while a research associate for Prinz, who was unavailable for comment while stuck in Europe this week because of grounded flights.

The project received funding from the Global Climate and Energy Project at Stanford and from the Yonsei University Research Fund of 2009.

The research team also includes Seoung-Jai Bai, Tibor Fabian, Rainer J. Fasching, Zubin Huang and Joong Sun Park, all researchers at the Rapid Prototyping Laboratory for Energy and Biology at Stanford; and Arthur R. Grossman and Jeffrey Moseley, both researchers in the Department of Plant Biology at the Carnegie Institution and Department of Biological Sciences at Stanford.

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