In my previous posts, I gave an overview about the composition of a solar cell, what it is made of and how it is used to transform sunlight into electric energy. In this article, I will illustrate the inside anatomy of a cell and how it really works.

In the last post, I explained the concept of a solar cell with two separate pieces of silicon, that were electrically neutral. However, it becomes much more interesting when you put them together. This is because without an electric field, the cell wouldn’t work; the field is formed when the N-type and P-type silicon come into contact. This makes the free electrons on the N side to rush to the openings on the P side.

Silicon is commonly used to make solar cells due to its special chemical properties. A silicon atom has 14 electrons that are arranged in three different shells.

The first two shells which have two and eight electrons each are completely full. However, the outer shell is only half full as it only has four electrons. Thus a silicon atom is always on a look out for ways to fill up its last shell.

In order to do this, it will have to share electrons with four nearby atoms to gain stability. It is just as if each atom has joined four hands to four neighbors. This is what forms the crystalline structure, leading to the formation of a PV cell.

We have all seen calculators with solar cells, that enable the device to work without any batteries, and can be used for unlimited time period as long as there’s enough light.

These solar cells that are present in calculators and many other devices are also called photovoltaic (PV) cells. As the name depicts, these cells have the capability of converting sunlight directly into electricity.

A group of cells can also be connected together electrically, fitted into a frame to form a solar panel. Moreover, these solar panels can be combined together to form larger solar arrays, similar to the ones operating at Nellis Air Force Base in Nevada.

Human’s curiosity leads towards invention, like utilizing energy from sun and generating electricity. This is a renewable form of energy and is an unlimited resource unlike other resources to generate electricity. This discovery further leads  to invention of appliances and instruments that uses sun rays to generate electricity and when applied  to a large scale  it results in creation of solar power plants.

What is a solar power plant?

A solar power plant captures the sun rays and convert photons into electricity. A solar semi-conductor possess electrons and the  sun ray contains photons. As a  photons  enter  this semi-conductor, these photons are captured and the electrons are transformed into electricity. This mechanism depends on the nature of material being used as semi-conductor.

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Silicon, used to make some of the earliest photovoltaic (PV) devices—is still the most popular material for solar cells.Silicon must be refined to a purity of 99.9999%. In single-crystal silicon, the molecular structure—which is the arrangement of atoms in the material—is uniform, because the entire structure is grown from the same crystal. This uniformity is ideal for transferring electrons efficiently through the material.

To make an effective PV cell, however, silicon has to be “doped” with other elements to make it N-type and P-type. The crystalline of a material indicates how perfectly ordered the atoms are in the crystal structure. Silicon, as well as other solar cell semiconductor materials, can come in various forms: single-crystalline, multi crystalline, polycrystalline, or amorphous. In a single-crystal material, the atoms making up the framework of the crystal are repeated in a very regular, orderly manner from layer to layer.

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Having dished out plenty of solar power info, I got to think whether or not the majority of people are even unaware of the brains behind the project, the Solar Panel? Whatever the metaphor, lets familiarize us with the photovoltaic physical workings of this super hero enigma.

How They Do And What They Do?

As mentioned, the principles of photovoltaic physics are used to convert the energy of the sun in to electricity rather than just heat. Now the impressive scientific stuff has been duly noted, let me paint a much simpler picture.

Solar cells are not made using pure silicon but instead have impurities added to it. Why? Because pure silicon crystals are non reactive in a stable state, which is not good as the electrons need some form of instability to be productive. So in this context some impurities must be required.

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Silicon is electrically neutral and on that the extra protons in the phosphorus balance out electrons, the missing protons in the boron balance out the missing electrons holes. That neutrality is disrupted when the holes and electrons mix at the junction between N-type and P-type silicon. Its not like that free electrons fill all the free holes if that happened then whole arrangement wouldn’t be very useful. However they mix when they form a barrier at the junction, because of that it becomes harder for electrons on the N side to cross to the P side. Occurring in due course, equilibrium is reached, and an electric field separating the two sides.

This electric field works as a diode, which allow electrons to flow from the P side to the N side, but not to other way around. Its function is just like a hill that electrons can easily go down the hill (to the N side), but cant climbs it (to the P side).

Now we got an electric field working as diode in that electrons can only move in one direction.

When light in form of photons hit the solar cell, its energy frees electron hole pairs.

Every photon with enough energy normally will free one electron, and result in free hole as well. If that happen so near to the electric field, or free electron and free hole happen wander into its range of influence, then the field will send the electron to the N side and the hole to the P side. This will cause further disruption in electrical neutrality, and if we provide an external current path then electrons will flow through the path to their original side (the P side) to unite with holes that the electric field sent there, and that will work along the way. Flow of electrons provides current and cell’s electric field causes a voltage. With combination of both we gets power and that’s generated by two.

There are few more steps before we use our solar cell. Silicon is a very shining material means it’s so much reflective. Because of that photons are reflected and can’t be used by the cell. For that antireflective coating is applied at the top of the cell to reduce reflection losses to less than 5%.

On final step glass cover plate is placed on it to protect the cell from the elements. By connecting several cells (usually 36) in series and parallel PV modules are made to achieve useful levels of voltage and current, and putting then in an strongly built frame complete with a glass cover and positive and negative terminals on the back.

A PV cell absorb sunlight at most 25% but usually that’s 15% or less.

Electric generator is a device or machines that covert the mechanical energy into electrical energy. It’s based on the principal of electromagnetic induction that is scientific law, which was discovered by British scientist Michael Faraday and American scientist Joseph Henry in 1831.

According to this scientific principle an electric conductor such as copper wire moving through a magnetic field, electric current will flow through the conductor. The moving wire’s mechanical energy is converted into electrical energy. Faraday and Henry found that when a magnet is moved in a coil of wire, electric current is generated.

According to Faraday’s law of induction a moving magnetic field will cause electrons to move. Generators create electron movement in the copper wire coils contained within by moving them through a magnetic field.

Faraday was the one who built the first electromagnetic generator “Faraday disc”; it was a simple copper disc rotating between the poles of a horseshoe magnet. That generator produced a small DC voltage and large amounts of current that was inefficient, but that was good start for future generators.

Solar energy takes benefit from the sun radiations to produce of the sun’s rays to generate electrical energy or power. It is a natural source of energy and unique for its capacity to produce energy in a calm, clean, and reliable way.

How Do Solar Photovoltaic Cells Work?

Photovoltaic cells consist of a semiconductor substance like silicon. In addition, other components are the phosphorous and boron which produce conductivity within the cell and enables the movement of electrons. The electrons pass across the cell when activated by the sunlight’s energy into the electrical circuit.

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In this post, you will be taught about something called circuit. Electrons do not work in air to get attracted by positive charged atoms. There is a medium in between which helps link the electrons to the positive charged atoms. The link is what that connects the negative area with the positive area. This is the link or the bridge in between them called as ‘circuit’.

So, circuit is important for the passage of electrons towards the positive charged atoms. The electrons movements, high or slow, depend on the resistance of material. If the circuit is not carefully observed, the number of electrons moving fast at one time can damage the circuit in the process. In our previous post, we learned that there is a strong attraction between the opposite charges and  also we have learned  that  how we can build a circuit between the opposite charges.

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Panasonic has publicizing its fuel-cell technology as a new  and innovative way to provide homes with electricity and cut their consumption of mains-sourced power, claiming that every home should have one.The company declared that it will start the production of  home-use polymer electrolyte fuel cell (PEFC) system in June. According to the company, the power pack can run for 40,000 hours and 4,000 start-stop cycles that is enough for a ten-year operational lifespan.

Working Of PEFC

The PEFC, i.e. the polymer electrolyte fuel cell, works in the usual way. It takes the hydrogen from the fuel which is combined with the oxygen from the air across a pair of electrodes separated by an electrolyte. The electrons produced by the reacting hydrogen and oxygen are forced by the electrolyte to travel around a circuit as a current. Heat and water are also generated in this process.

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