The Solar Cell
|Solar cells are made almost entirely out of silicon, with other metallic elements added.||Most leaves are made from silicon, phosphorus, chlorine, sulphur, potassium and calcium.|
|Efficiency||The current record holding efficient solar cell was about 42% efficient. However, these ultra efficient solar cells are extraordinarily expensive, and therefore not practical for general use. Most common solar cells are only 13-16% efficient, even less efficient than fossil fuel power generation.||According to some estimates photosynthesis absorbs about three to six percent of all solar radiation that hits Earth. In reality photosynthesis is not overly efficient. If it was one hundred percent efficient leaves would appear black in color. Instead only a small fraction of needed energy is absorbed.|
|Operation||The semiconducting silicone absorbs photons, creating extra electrons. The design of the solar cells forces these electrons to flow in one direction, creating a direct current through the solar cell.||The molecule chlorophyll absorbs a photon and looses an electron, causing a chain reaction that breaks apart water, releasing the chemical energy and a molecule of oxygen. At the same time the chemical reaction is used to break apart carbon dioxide, releasing the oxygen and using the extra carbon to create sugars.|
|Price||Produced using amorphous silicone, which is expensive to isolate and work with. Although the cost of solar cells falls each year, the most efficient solar cells are still inconveniently expensive.||Completely free. Millions are grown each day by trees around the world. A full grown tree can regrow thousands of leaves each spring.|
|Scientific Date||The first working solar cell was created in 1883 by Charles Fritts. It was made from selenium coated with gold.||Science has studied photosynthesis since the 1600's, but it was not until the late 1800's that the first chemical description of photosynthesis was attempted.|
|Environmental Impact||Creating solar cells involves the use of lead, mercury, cadmium and other toxic heavy metals. It also produces carbon dioxide, which contributes to global warming. Solar cells are nevertheless touted as a replacement for fossil fuel consumption.||Leaves are grown using water, sunlight, carbon dioxide, and various soil nutrients. Leave decompose by themselves, contributing to soil richness. There are no heavy metal pollutants released in the process. Another interesting side effect of leaves is that they can be eaten by animals.|
A Replacement for Leaves?
In 2008 a Japanese firm created the first prototype of an organic solar cell that is not only flexible, but also leaf shaped. The result is interesting, and slightly artistic, but hardly a replacement for real leaves operating by photosynthesis.
However, it is possible that solar cells such as this could be used as one way of making solar power more attractive. No one wants to see fields of traditional solar arrays. A comparable field of green solar cell leaves would appear more natural, though. In fact, a careful design could use these solar cells as natural looking blades on a field of small wind powered generators.
Finally a design that combines efficiency, art, and natural power could become a possibility.
But in the meantime the simple leaf, with its photosynthetic power, will always be many times better than anything science can create.