IN AN electrifying first, American scientists have plugged into algae cells and harnessed a tiny electric current. They found it at the very source of energy production – photosynthesis, a plant’s method of converting sunlight to chemical energy.
The Stanford University team suggest it may be a first step toward generating “high-efficiency” bioelectricity that doesn’t give off carbon-dioxide as a byproduct.
“We believe we are the first to extract electrons out of living plant cells,” said WonHyoung Ryu, one of the researchers.
The team developed a unique, ultra-sharp nanoelectrode made of gold, specially designed for probing inside cells. They gently pushed it through the algal cell membranes, which sealed around it, and the cell stayed alive. From the photosynthesising cells, the electrode collected electrons that had been energised by light and the researchers generated a tiny electric current.
Ryu said: “We’re still in the scientific stages of the research. We were dealing with single cells to prove we can harvest the electrons.”
Plants use photosynthesis to convert light energy to chemical energy, which is stored in the bonds of sugars they use for food. The process takes place in chloroplasts, the cellular powerhouses that make sugars and give leaves and algae their green colour.
In the chloroplasts, water is split into oxygen, protons and electrons. Sunlight penetrates the chloroplast and zaps the electrons to a high energy level and a protein promptly grabs them.
The electrons are passed down a series of proteins which successively capture more and more of the electrons’ energy to synthesise sugars until all the electrons’ energy is spent.
In this experiment, the researchers intercepted the electrons just after they had been excited by light and were at their highest energy levels. They placed the gold electrodes in the chloroplasts of algae cells and siphoned off the electrons to generate the tiny electrical current. The result, the researchers say, is electricity production that doesn’t release carbon into the atmosphere. The only byproducts of photosynthesis are protons and oxygen.
“This is potentially one of the cleanest energy sources for energy generation,” Ryu said.
“But the question is, is it economically feasible?”
Ryu said they were able to draw from each cell just one picoampere, an amount of electricity so tiny that they would need a trillion cells photosynthesising for one hour just to equal the amount of energy stored in an AA battery.
In addition, the cells die after an hour.
That perhaps provides a measure of just how huge the challenge to get power out of plant cells really is.