Basic chemistry

How efficient are solar cells?

Solar cells development

Solar cells development and efficiency :

Solar cells development and efficiency is discussed here. You must have seen before one of these photovoltaic calculators, which do not need a battery or a solar cell in one of the roads on lighting poles or on the roof of a house, but have you ever wondered how those solar cells work?

Well follow us to know the answer to that question.

Solar cells work unlike  other methods that depend on heat and turbines, these cells, which are called “photovoltaic cells or photovoltaic cells”, depend on converting light directly into electricity, where they convert photons (light particles) into electrons with an electrical charge and then generate the electric current.

What are solar cells made of?

solar cells
solar cells construction

Solar cells are made of semiconducting materials such as silicon, whose atoms are distinguished by the presence of four electrons in the outer energy orbit, so each atom is bound to four other neighboring atoms as shown in the figure:

 

When a photon collides with sufficient energy with one of these atoms, one of these electrons is released, leaving a positive charge gap in its place.

But when adding impurities to the silicon such as phosphorous, which has five electrons in its outer orbit, the number of free electrons increases in the formed alloy, while when adding atoms of boron, which has only three electrons in its outer path, the alloy will contain many positive gaps.

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When the two subatens are affixed together, some electrons and gaps move toward the opposite alloy at the point of convergence, forming an electric field between the two ends.

The more electrons and gaps travel from one alloy to another, the stronger the electric field, making it difficult to transfer more electrons and gaps.

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When a photon collides with a specific photoelectric cell, it causes the release of an additional electron (also leaving an additional gap). If this free electron coincides with the electric field at the convergence point, it moves, affected by this field, in the positive direction, which increases the number of free electrons in the negative alloy and the number of positive gaps in the positive alloy, creating the difference in voltage between the ends of the cell.

When an external path is added between the two ends, the electrons move through it, creating an electrical current.

We use an effective solar cell to form a large array of those small cells to reach the voltage and current to the required levels.

The cell is also coated with special materials to reduce light reflection from the surface of the silicon. The glass is used to protect the outer surface of the cell from weather and other factors.

solar cells efficiency :

Efficiency is the biggest problem facing solar cells. For example, in 2006 the energy efficiency of most used solar cells ranged between 12 and 18%, and now newer and better efficiency of these solar cells is about 40%.

But why can’t we get better efficiency?

Sunlight is characterized by a mixture of different light waves at different frequencies and wavelengths, therefore different energy levels, and since the electrons need a specific amount of energy to be freed from their own energy orbits, any photon that does not carry the appropriate energy if its energy is more or less than the required level will cross Through the solar cell directly as if it did not exist.

Knowing that the electrical resistance of the semiconductors from which the solar cell is made is relatively high, but metal conductors must be placed to cover parts of the cell in order to provide paths to the electric current, but certainly adding these dark conductors will cause a loss of part of the light energy, so the conductive materials are distributed With a grid image to better conduct current and reduce optical loss, some transparent conductors are also used to conduct current in some solar cells.

Can solar cells be used to generate household energy?

Certainly, solar energy can be used in homes when installed in the right direction and at a suitable angle of inclination so that it faces the sun in most of the daytime periods, which makes it produce the largest amount of energy possible.

However, it should be noted that the resulting energy is only during the day and therefore work must be made to provide alternative sources of energy in times when there is not enough sunlight to provide energy.

To achieve this, additional sources such as fuel generators or the rechargeable batteries of solar cells can be used and reused as needed.

Also, connecting the house to the public electricity network will allow it to be used when needed. Indeed, the excess of solar energy production can be sold to the electricity company during the day, but this requires a lot of devices to match the electricity produced by the house with that produced by the electricity delivery company.

In all cases, the house needs to connect several devices to connect the solar energy to operate household appliances, such as the charging unit in the case of using the battery, and the constant current unit for alternating current, that unit can also be used to connect the electricity produced to the public network, and is used in the protection and automatic conversion between the internal network And the public network.

Is solar energy free?

The energy from the sun is free, but converting it to electricity is of course not free. The costs of installing and maintaining solar cells are not small at all, but certainly areas that have stronger and continuous solar brightness for a long time, with increasing cell size contribute to reducing the cost per kilowatt hour.

But some governments provide assistance to people and companies who want to use solar energy, and the actual costs decrease over time with the development of solar cell technology.

Therefore, before taking the step of converting the house to use solar energy, all calculations must be done accurately to determine the feasibility of this step.

Solar cells development:

Companies are now working to produce cost-effective solar cells per kilowatt. To achieve this, researchers are working on three different ideas: thin-film technology, multi-link cells, and solar light technology.

Thin-film technology uses materials that are different from the traditional cells made of impurity-revised silicon crystals. In fact, materials such as the silicon element are used, but not in the form of a crystal (i.e. not all silicon atoms bond to four adjacent atoms) and it is called (Amorphous Silicon) also uses gallium arsenide Gallium Arsenide and other materials.

These materials work as solar cells with less efficiency, but due to their ease of manufacture and low price, they may be a suitable option for development.

Some companies also developed solar cells consisting of layers of different materials, each of which works on photons that have different energy levels, thereby raising the efficiency of the cell.

This type of cell is called “multi-link cells”. The upper layers work on photons with high energy, while the lower layers exploit photons The least energy and thus the largest possible use of photons.

While some companies use mirrors and lenses to focus light from large areas in solar cells with a small area, which increases the efficiency of the optical cell itself, as it is exposed to a greater amount of concentrated light than an area larger than its original area.

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