Electrical energy from plants - green power plants

The direct transformation of light energy into electrical energy underlies the operation of generators containing chlorophyll. Chlorophyll can give and attach electrons when exposed to light.

In 1972, M. Calvin put forward the idea of ​​creating a solar cell, in which chlorophyll would serve as a source of electric current, capable of taking away electrons from certain specific substances under illumination and transfer them to others.

Calvin used zinc oxide as a conductor in contact with chlorophyll. When illuminating this system, an electric current with a density of 0.1 microamperes per square centimeter appeared in it.

This photocell did not function for long, since chlorophyll quickly lost its ability to donate electrons. To extend the duration of the photocell, an additional electron source, hydroquinone, was used. In the new system, green pigment gave away not only its own, but also the hydroquinone electrons.

Calculations show that such a 10-square-meter photocell can have a power of about kilowatts.

Japanese professor Fujio Takahashi used chlorophyll extracted from spinach leaves to generate electricity. The transistor receiver to which the solar panel was connected worked successfully.

In addition, studies are underway in Japan to convert solar energy into electrical energy using cyanobacteria grown in a nutrient medium. A thin layer of them is applied to a transparent electrode of zinc oxide and, together with the counter electrode, immersed in a buffer solution. If the bacteria are now illuminated, an electric current will appear in the circuit.

In 1973, the Americans W. Stockenius and D. Osterhelt described an unusual protein from the membranes of violet bacteria that live in the salt lakes of the California deserts. It was called bacteriorhodopsin.

It is interesting to note that bacteriorhodopsin appears in the membranes of halobacteria with a lack of oxygen. Oxygen deficiency in water bodies occurs in the case of intensive development of halobacteria.

Using bacteriorhodopsin, bacteria absorb the energy of the sun, thereby compensating for the energy deficit resulting from the cessation of breathing.

Bacteriorhodopsin can be isolated from halobacteria by placing these salt-loving creatures that feel great in a saturated solution of sodium chloride in water. Immediately they overflow with water and burst, while their contents are mixed with the environment. And only membranes containing bacteriorhodopsin are not destroyed due to the strong “packing” of pigment molecules that form protein crystals (without knowing the structure, scientists called them purple plaques).

In them, the bacteriorhodopsin molecules are combined into triads, and the triads into regular hexagons. Since plaques are significantly larger than all other halobacterial components, they can be easily isolated by centrifugation. After washing the centrifuge, a pasty mass of violet color is obtained. 75 percent of it consists of bacteriorhodopsin and 25 percent of phospholipids filling the gaps between the protein molecules.

Phospholipids are fat molecules in combination with phosphoric acid residues. There are no other substances in the centrifuge, which creates favorable conditions for experimenting with bacteriorhodopsin.

In addition, this complex compound is very resistant to environmental factors. It does not lose activity when heated to 100 ° C and can be stored in the refrigerator for years. Bacteriorhodopsin is resistant to acids and various oxidizing agents.

The reason for its high stability is due to the fact that these halobacteria live in extremely harsh conditions - in saturated saline solutions, which, in essence, are the waters of some lakes in the area of ​​deserts burnt by tropical heat.

In such an extremely salty, and also overheated environment, organisms that have ordinary membranes cannot exist. This fact is of great interest in connection with the possibility of using bacteriorhodopsin as a transformer of light energy into electrical energy.

If bacteriorhodopsin precipitated under the influence of calcium ions is illuminated, then using a voltmeter it is possible to detect the presence of an electric potential on the membranes. If you turn off the light, it disappears. Thus, scientists have proven that bacteriorhodopsin can function as an electric current generator.

In the laboratory of the famous scientist, specialist in the field of bioenergy V.P. Skulachev, the process of incorporating bacteriorhodopsin into a flat membrane and the conditions for its functioning as a light-dependent electric current generator were carefully studied.

Later, in the same laboratory, electrical elements were created in which protein generators of electric current were used. These elements had membrane filters impregnated with phospholipids with bacteriorhodopsin and chlorophyll. Scientists believe that similar filters with protein generators, connected in series, can serve as an electric battery.

Research on the use of protein generators in the laboratory of V.P. Skulachev attracted the close attention of scientists. At the University of California, they created the same battery that, when used for one and a half hours, made the light bulb glow.

The experimental results give hope that photo cells based on bacteriorhodopsin and chlorophyll will be used as generators of electrical energy. The conducted experiments are the first stage in the creation of new types of photovoltaic and fuel cells capable of transforming light energy with great efficiency.

See also: Other alternative energy sources