What's green and makes electricity? An artificial leaf
Photosynthesis is nearly the sole source of energy for the creatures inhabiting our planet, include the two-legged variety. For billions of years, since the appearance of the first vegetable cell, plants and bacteria have converted sunlight into energy-rich compounds. That is how all petroleum and coal reserves were created. Unfortunately, about 200 years of post-Industrial Revolution activity has wiped out most of these, and today's vegetation cannot take up the slack.
Photovoltaic cells made of silicon can convert solar energy to electricity, but due to their extremely high price, it costs four times more to generate power this way than with coal or petroleum. Now, researchers from Tel Aviv University (TAU) claim to have created a prototype of a photovoltaic cell by genetically engineering proteins that produce energy using photosynthesis. If successful, this would enable energy production on a commercial scale through the construction of "artificial leaves." The cells would even appear green, because of the wavelength of the light that they collect.
The new technology, developed by a team headed by TAU biochemist Prof. Chanoch Carmeli, will be presented tomorrow at an international conference, Renewable Energy and Beyond, that opens today at the university's Ramat Aviv campus. Former U.S. vice president Al Gore is to attend the conference.
The new photovoltaic device is based on a genetically engineered dry protein, photosystem I (PS I), created from bacteria that carry out photosynthesis.
"On its own, nature creates for us materials that collect the sun's energy, and all we need to do is extract them from the bacteria and use them," said Prof. Abraham Kribus, TAU's coordinator for renewable energy. "These materials do exactly the same thing as silicon-based photovoltaic cells - they collect sunlight and create an electrical charge."
The project draws from several different branches of the sciences. In the first stage, the researchers grew cells that can produce large quantities of the PS I protein. "We introduced genetic changes into bacteria so that the proteins they create can bond to a substrate bottom metal and be suited for use," Carmeli explained. The most complex stage involved placing the protein molecules on the substrate, all facing the same direction. Next, the surface was coated with a suitable conducting material. Electrical wires were then connected to the cells, which produced an electrical charge when exposed to light.
The research team includes Carmeli's son, Dr. Itai Carmeli, an expert in nanotechnology, as well as Dr. Shachar Richter and Prof. Yossi Rosenwaks. The research is still in its early stages, and so far the team has only created a microscopic cell that produces a tiny amount of energy. Kribus said it is too early to talk about the total cost of producing electricity on a commercial scale using the new method. "Creating a complete cell will require processing stages that will require more time to develop," he said.