Solar Cell
Solar Cell
Why waste our time digging for oil or shoveling coal when there’s a gigantic power station high above us that is sending out free and clean energy? The Sun as a burning nucleus, has enough fuel to supply power to our Solar System for five billion more years. Solar panels can transform this energy into an inexhaustible power source.
Although solar power might appear futuristic or strange but it’s actually quite common. A solar-powered watch or calculator for your pocket might be at your fingertips. Many gardeners are equipped with solar-powered lighting. Solar panels are often seen on spacecrafts and satellites. NASA an American NASA space agency has even created an aircraft powered by solar energy. Global warming is threatening our environment and it seems certain that solar power will become an increasingly important source of renewable energy. How do they work?
What is the maximum amount of solar power we can get from the Sun?
It is incredible how solar power functions. Each square meter on Earth receives an average 163 watts of solar energy. This figure will be discussed in greater detail later. This means that you could put the power of a table lamp that is 150 watts on every square meter of Earth and utilize the sun’s energy to illuminate the entire planet. Another way to put it, If we could cover just 1% of the Sahara desert with solar panels, we could create enough electricity to solar power the entire planet. The great aspect of solar energy is that it has a large amount of it, much more than we could ever need.
There’s a down side. The Sun’s energy is the result of heat and light. Both are vital. The light is what makes plants grow, and also provides food for us. The heat keeps us comfortable enough to live. However, we are not able to use the Sun’s light or heat directly to power a TV or car. It is essential to convert solar energy into another form of energy that can be used more efficiently like electricity. That’s precisely the job solar cells perform.
In summary:
- The cell’s surface is illuminated by sunlight
- Photons transport energy through cells’ layers.
- Photons transfer their energy to electrons that reside in lower layers
- This energy is utilized by electrons to let electrons escape the circuit and then jump back to the top layers.
- The power of devices is supplied by the electrons that flow around the circuit.
What are solar cells?
A solar cell is an electronic device which absorbs sunlight and converts it into electric energy. It’s about similar to an adult’s hand, octagonal in form, and colored bluish-black. A variety of solar cells can be bundled together to create bigger units, also known as modules. They are then joined to form larger units referred to as solar panels. (The black- or blue-tinted tiles that you see on your homes typically have hundreds of individual solar cells on top of the roof) Or chopped into chips (to power small gadgets like digital watches and small calculators in pockets).
The cells in solar panels work the same manner as batteries do. However, in contrast to battery’s cells which produce electricity through chemical reactions the cells of solar panels absorb sunlight and generate electricity. Photovoltaic cells (PV) is a term used to describe solar cells that make electricity from sunlight (photo is derived directly from Greek word that means light). The term “voltaic” however, is a reference to Alessandro Volta (1745-1827), an Italian electric pioneer.
Light is described as tiny particles, called photons. A beam of sunlight is similar to a huge white firehose, which shoots trillions upon trillions. A solar cell can be placed on the path of these photons to capture them and then transform them into electric current. Each cell produces some volts, and the function of the solar panel is to combine the energy produced by many cells to produce an appropriate amount of electric energy and voltage. The solar cells of today are nearly all composed of pieces of silicon (one the most common chemical elements{ found|| that are found} on Earth and is found in sand). However, as we’ll see, other materials may also be possible. The sunlight’s energy blasts electrons out of a solar cell when it is exposed to sunlight. These electrons can later be used to power any electrical device powered by electricity.
How are solar cells made?
Silicon is the substance that microchips’ transistors (tiny switches) are created. Solar cells work in a similar way. It is also a type of material. Conductors are substances that permit electricity to flow smoothly through them, like metals.
Other materials, such as plastics and wood, aren’t able to permit electric current to pass through; they are called insulation. Semiconductors such as silicon are not conductors or insulators. However, we can make them conduct electricity in certain conditions.
Solar cells made up consisting of two different layers of silicon, each one of them being treated or doped so that electricity can move throughout it in a particular way. The lower layer has slightly less electrons because it is doped. The layer is known as p-type, or positive-type silicon. It has too many electrons, which is why it is negatively charged. To provide the layer with an excess of electrons, it is doped in the opposite direction. This is known as negative-type and n-type silicon. (Read more about doping and semiconductors in our articles on transistors and integrated circuits.
A barrier is formed by the interplay between two layers of n type and silica p-type. This is the vital boundary where both kinds of silicon meet. It is unaccessible to electrons. Therefore, even if the silicon sandwich is connected to a flashlight it won’t be able to flow current and the light bulb won’t switch on. But, if you shine light onto the sandwich, it will create an amazing effect. The light is described as{ a|| an evaporation} flow as well as “light particles”, which are energetic, referred to as photons. Photons entering the sandwich transfer their energy to silicon atoms when they move through. The incoming energy is able to knock electrons away from the lower layer, which is p type. They then leap across and over the wall to the n-type layer above and flow around the circuit. The greater the amount of light the greater chance that electrons will rise and more current will flow.
How efficient are Solar Panels?
The law of conservation energy is a basic principle of physics, says that energy can’t be made or dissolved in the air. We can only transform it from one type of energy to another. A solar cell is unable to produce more electricity than it receives in light each second. As we will see, the majority of solar cells convert 10 to 20 percent of energy that they receive to electricity. The theoretical maximum efficiency of a typical single-junction silicon solar panel is about 30 percent. This limit is known by The Shockley Queisser limitation. Since sunlight has a broad variety of wavelengths and energies that a single-junction silicon solar cell can only collect photons within a narrow frequency range. All other photons will be wasted. Some photons that strike the solar cells are too weak to produce enough electrons. Others have too much energy and end up being wasted. In the best conditions, lab cells equipped with modern technology are able to achieve just below 50 percent efficiency. They use multiple junctions to collect photons of different energies.
A real-world domestic panel might have an efficiency of approximately 15 percent. Single-junctionsolar cells of the first generation will not reach the 30 percent efficiency threshold that was set by Shockley-Queisser or the laboratory record that is 47.1 percent. There are many variables that affect the effectiveness of solar cells, like how they’re constructed, angled and positioned in relation to their location, whether they’re in shadow and how clean they are and how cool.
Different types of Photovoltaic Cell
The majority of solar cells you see on rooftops are silicon sandwiched. They’ve received the designation of “doped” to increase its electrical conductivity. These classic solar cells are called first-generation by scientists to distinguish them from two newer technology, second- and third generation. What is the difference?
First-generation Solar Cells
More than 90 percent of the solar cell production is made of silicon wafers that contain crystallized silicon (abbreviated “c-Si”), which are cut from huge ingots. This process could take up to one month and is carried out in extremely clean laboratories. Ingots may include single crystals (monocrystalline solar panels) or multi-crystalline (polycrystalline solar panels), depending on whether they have multiple crystals.
The first-generation solar cell functions the way we’ve shown them in the picture above. They make use of a simple connection between p-type and n-type layers of silicon. It is cut out of separate ingots. An n-type ingot is made by heating small pieces of silicon with small amounts (or antimony and phosphorus) as dopants. In a p-type ingot, you would use boron. The junction is formed by fusing slices of p type and n-type silicon. There are some additional bells and whistles that could add to the photovoltaic cell (like an antireflective layer that increases the absorption of light and gives them their blue color) and connections made of metal that allow them to be connected to circuits. But a simple P-N junction is the most common solar cells rely on. This is the way photovoltaic solar cells have been working since 1954 when Bell Labs scientists pioneered it: by shining sunlight onto silicon sand, they created electricity.
Second-generation Solar Cells
The traditional solar cells are thin solar cell wafers. They’re typically only a fraction of millimeter thick (around 200 micrometers, or 200 millimeters). They aren’t as thin than second generation solar cells (TPSC) or thin film solar cells, that are 100 times thinner (several millimeters or millionths of meters deep). Though the majority are still made of silicon (a form known as amorphous siliu or a-Si) where atoms are arranged in random crystal structures Some are composed of different materials like cadmium-telluride, Cd-Te, as well as copper-indium gallium diselenide, (CIGS).
Second generation cell are light and thin and can be laminated to skylights, windows and roof tiles. They are also compatible with all kinds of “substrates”, which are backers such as plastics and metals. Second-generation cells have less flexibility than those of the first generation, but they perform far better than them. First-generation cells of the highest quality can have an efficiency of 15 to 15 percent, however the amorphous silicon cells struggle to achieve above 7 percent) While the most efficient thin-film CdTe cells can only manage around 11 percent and CIGS cells can’t even reach 7-12%. This is among the reasons that the second-generation solar cells aren’t enjoyed much success on the marketplace despite their numerous advantages.
Third-generation Solar cells
The latest technologies combine the best characteristics of both first- and 2nd generation cells. They boast high efficiency (up to 30 percent) as do first-generation cells. They are more likely to be constructed from different materials that silicon (making second-generation photovoltaics OPVs) and perovskite crystals. Additionally, they may feature multiple junctions (made up of several layers of different semiconducting materials). They will be less expensive, more efficient, and practical than first- or second-generation cells. The{ current|| record-setting} worldwide record in efficiency of third-generation solar cell is 28.1. This record was set in December of 2018 with the perovskite-silicon tandem solar cell.
How are they made?
Like you see there are seven steps in the process of making solar cells.
Stage 1: Purify Silicon
It is then heated up in the electric oven. To release the oxygen carbon arcs, it is possible to be used. This results in carbon dioxide as well as molten silica, which is used to make solar cells. Even though this yields silicon with a 1% impurity, it’s not quite good enough. The floating zone method lets the silicon rods that are 99% pure to be passed through a hot zone many at a time, in the direction of. The process eliminates all impurities that are present on one side of the rod and allows it to be cleaned.
Stage 2: Constructing Single Crystal Silicon
The Czochralski method is the most popular method to create single-crystalline silicon. It involves placing a crystal of seed made of silicon in the melted silicon. The result is a boule or cylindrical ingot by rotating the seed crystal when it is being removed from the silicon melt.
Third Stage Slice the Silicon Wafers
The second stage boule is used to cut silicon wafers using circular saws. This is the best job to do by using diamonds, which produce the silicon chips that are able to then be cut to make squares or hexagons. Although cut marks have been removed cut wafers, some producers leave them because they believe that more light may be absorption by a rougher solar cell efficiency.
Fourth Stage Doping
After cleansing the silicon at an earlier stage, it’s possible to introduce impurities to the silicon. Doping involves using particles accelerators to ignite phosphorus ions in the ingot. You can control the penetration depth by setting the speed of electrons. It is possible to skip this step by using the standard method of inserting boron while cutting the wafers.
Phase Five: Add electric contacts
Electrical contacts are utilized to connect the solar system to act as receivers for the generated current. The contacts, which are made of various metals, including palladium and copper are made of a thin layer enough to allow sunlight to enter the solar cell effectively. The metal is either deposited on the cells that are exposed or it is evaporated by vacuum using a photoresist. Tin-coated copper strips is typically placed between cells after the contacts are installed.
Stage Six Application of the Anti-Reflective Coating
Because it is shiny, it has the ability to be able to reflect as much as 35% sunlight. To decrease reflections, a coating of silicon can be applied. This is done by heating the surface until the molecules are boiling off. The molecules then move onto the silicon and condense. The high voltage could also be utilized to detach the molecules and then deposit them onto the silicon at the opposite electrode. This is called “sputtering”.
Stage Seven Step Seven: Encapsulate and Seal the Cell
They are then enclosed by silicon rubber or ethylene vinyl Acetate. Finally, they are placed in an aluminum frame that has an aluminum back sheet and a glass cover.
What amount of electrical energy can solar cells produce?
Theoretically speaking, it’s quite a bit. For the moment, let’s ignore solar cells and instead focus on pure sunlight. Every square meter of Earth can receive up to 1,000 watts in solar power. This is the theoretical power of direct sunlight during a clear day. The solar rays are directed perpendicularly to the Earth’s surface and provide the maximum illumination.
Once we have adjusted to Earth’s tilt and the time we will achieve between 100-250 watts for each square. meter in northern latitudes, even on days with no clouds. This translates to about 2-6 kWh/day. The entire year’s output produces 700- 2500 kWh per sq. meters (700-2500 units) of electricity. The potential of the sun’s energy in hotter regions is clearly more than Europe. For example, in the Middle East receives between 50 and 100 percent more solar energy per year than Europe.
However, solar cells are just 15 percent efficient so you can only harvest 4-10 watts per square foot. This is the reason panels that harness solar power have to be massive and the size of the area the area you can cover with cells directly impacts the power you generate. The typical solar panel consisting with 40 solar cells (each row of eight cells) will produce about 3-4.5 watts. A solar panel composed of 3-4 modules could produce many kilowatts, which would be enough to supply a house’s highest energy demands.
How about Solar Panel Farms?
However, what if we need to generate large amounts of solar energy? It will require between 500 to 1000 solar roofs to produce approximately the same quantity of power like a large wind turbine with an output peak of two or three megawatts. In order to compete with huge coal or nuclear power stations (rated as gigawatts), you would need around 1 000 solar rooftops. This would be equivalent to about 2000 wind turbines or perhaps a million of them. This assumes that both solar and wind power sources produce the maximum output. Even though solar cells can generate clean, efficient electricity however, they can’t claim to be efficient use of land. The vast solar farms that are popping up all over the country produce modest amounts of power, generally about 20 megawatts or 1 percentage less than the 2 gigawatt coal or nuclear plant. Shneyder Solar, a renewable energy company estimates that it will take approximately 22,000 panels to cover 12 ha (30-acres) space to produce 4.2 megawatts. This is roughly the same as two large wind turbines. The turbine also produces enough energy to power 1200 homes.
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