Bio-solar battery made from vegetables

Along with the exhaustion of fossil fuel sources such as oil and coal, renewable energy has been increasingly concerned in recent years. The infinite source of sunlight is an important goal of solar cell systems or artificial photosynthesis.

However, the latest inventions are still limited due to low performance: with conventional solar panels, the actual performance is only about 12% (20% in experimental conditions) and the photomultiplier The most effective creation has been made by Panasonic and only 0.2%. Therefore, while not yet exploring the secrets of nature, the best way is that humans should imitate what it operates.

Summary of PS1 photosynthetic protein in plants

For more than 40 years, scientists have focused on a protein involved in photosynthesis in plants called Photosystem 1 (PS1) . PS1 has an important feature that it retains its ability even when it is extracted from the plant. Furthermore, this protein has a valuable property that it can convert light into electrical energy with an efficiency close to 100%. Therefore, scientists have tried to take advantage of PS1's ability to create bio-hybrid photovoltaic cells with higher energy conversion rates.

As we know, silicon materials themselves have extremely low photovoltaic performance. Therefore, in order to increase the efficiency of energy metabolism, a small amount of rare earth must be added to the material. It will not be a problem if the amount of rare earth is exploited and the price is low. However, these elements are often difficult to obtain in nature and the cost to exploit them is very high. In addition, major solar cell producing countries such as Germany, Japan, and the United States have no large reserves or many operating mines, while China is tightening export volume, which pushes up prices. half. With PS1, humans have an extremely rich supply of plants. Studies are currently underway to extract large amounts of vegetables and Kudzu (a legume).

The problem with using PS1 is that it uses any method to separate them easily and preserve them so that they will not be damaged in the long run.

Principle of operation of biological solar cells using PS1

When the PS1 protein is illuminated, it absorbs energy and supplies valence electrons (electrons linked to atoms) to convert it into free electrons. If the electron leaves a certain position, it will leave a local positively charged hole there. Because of the electric field, electrons and holes will travel to different sides of the PS1 protein.

On the leaves, PS1 is arranged in an orderly manner so that the protein parts with many electrons (negatively charged) will be on the same side and the head of the multi-hole protein (positively charged) will be on the other side. However, on bio-batteries, due to uncontrollability during the introduction of silicon, this protein will orient itself freely. Then an inevitable effect is that the previous negative and positive charges will cancel each other out. As a result, the resulting current will be much smaller.

The plan of scientists at Valderbilt

Thanks to a special technique, researchers can extract PS1 from the cabbage, and keep it for 9 months without being damaged. They mixed this protein with a water-based solvent and poured it on the face of a p-type silicon battery (empty solar cell). Then the entire substrate will be introduced into the vacuum chamber and evaporate the steam to obtain film plates of protein batteries. Tests show that film thickness at 1 micrometer will give optimal performance, which is equivalent to 100 overlapping PS1 molecules. Thanks to p-type semiconductors, electrons will move into the outer circuit in the same direction. Although this arrangement is not as perfect as on the leaves, it will also increase the current intensity quickly.

Result

The graph produces electricity on a cubic centimeter of a solar cell

Measures on new materials show that every square centimeter of film will produce an electric current of 80 microampe (microA) at a voltage of 0.3 volts. A 0.6m long battery will produce 100mA current at 1 Volt voltage, enough to run a small electronic device. Although still low, such electrical parameters were 2.5 times the previously generated bioelectric cells with a greater efficiency of 1,000 times.

It is expected that scientists will continue to develop their research to bring this invention into a true commercial product in three years.

Reference: Gizmag