Solar Cell
Solar Cell
Why do we have to dig for oil or shoveling coal when there’s a massive power station high above us that provides free green energy? The Sun as a burning ball of nuclear energy is able to supply the energy needed to power this Solar System for five billion more years. Solar panels can transform this energy into an unending amount of electricity.
Although solar power may seem unusual or out of the ordinary but it’s actually quite popular. A solar-powered watch or calculator for your purse could be in your wrist. Many gardeners are equipped with solar-powered lighting. Solar panels are commonly located on spacecrafts and satellites. NASA the American NASA space agency has also created a solar-powered plane. Global warming is threatening our environment and it is likely that solar energy will become an increasingly important source of energy that is renewable. How do they work?
What is the maximum amount of solar power we can get from the Sun?
It is incredible how solar power operates. Each square meter of Earth receives on average 163 watts solar energy. This figure will be discussed in more detail in the next paragraph. It means you could put the power of a table lamp that is 150 watts on every square meters of Earth and utilize the sun’s energy to light up the entire planet. Another way of putting it this way, in the event that we only covered one percent of the Sahara desert with solar cells, it would be possible to produce enough electricity to solar provide power to the entire globe. The good aspect of solar energy is that it has a large amount of it, much more than we’ll ever require.
There’s a drawback. The Sun’s energy comes as an amalgamation of light and heat. Both are vital. The light helps plants grow and provide us with food. The heat keeps us warm enough to live. But, we can’t utilize the sun’s heat or light directly to solar power a car or TV. It is important to convert solar energy into a different form of energy that is more readily available such as electricity. That’s precisely the job solar cells perform.
In Summary:
- The cell’s surface is lit by sunlight
- Photons carry energy through the cells’ layers.
- Photons transmit energy to electrons located in the lower layers
- This energy is used by electrons to escape from the circuit and jump back to the top layers.
- The power for the device is generated by electrons that move through the circuit.
What are solar cells?
Solar cells are electronic devices which captures sunlight and converts it into electric energy. It is about similar to the hand of an adult with a shape that is octagonal and colored in a bluish-black color. Many solar cells can be put together to create bigger units, also known as modules. These are then connected into bigger units known by solar panels. (The black- or blue-tinted tiles you see on homes generally have hundreds of solar cells per roof) Or cut into chips (to power small gadgets such as digital watches and pockets calculators).
The cells in a solar panel work in the same way as batteries do. However, in contrast to battery’s cells that produce electricity from chemicals 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 in the Greek word meaning light). The term “voltaic” however, is a reference to Alessandro Volta (1745-1827), an Italian electrical engineer who was a pioneer in the field.
Light is considered as tiny particles called photons. The sun’s beam is similar to an enormous Yellow firehose which releases trillions upon trillions. A solar cell can be placed within the direction of these light beams to capture them and then transform them into an electrical current. Each cell can generate some volts, and the purpose of the solar panel is to combine the energy produced by multiple cells to create the required amount of electrical energy and voltage. Today’s solar cells are almost all composed of pieces of silicon (one the most well-known chemical elements{ found|| that are found} on Earth that is found in sand). But, as we’ll see, other materials may also be viable. The sun’s energy blasts electrons from the solar cells when it’s exposed to sunlight. Then, they can be used to power any electrical device that runs on electricity.
How are solar cells made?
Silicon is the main material that microchips’ transistors (tiny switches) are constructed. Solar cells function in a similar way. A semiconductor is a kind of material. Conductors are the materials that allow electricity to flow easily through them, including metals.
Others, like plastics and wood, aren’t able to allow electric current to pass through. they are called insulation. Semiconductors such as silicon are not conductors , nor insulators. However they can conduct electricity in certain conditions.
The solar cells are made up consisting of two different layers of silicon each of which has been treated or doped to permit electricity to move throughout it in a particular way. The lower layer contains slightly less electrons due to it being doped. This layer is referred to as p-type, or positive-type silicon. It is filled with too many electrons, which is why it is negatively charged. To provide the layer with an overabundance of electrons it is charged with a negative charge. This is called negative-type and n-type silicon. (Read more about semiconductors and doping in our articles about transistors and integrated circuits.
A barrier forms at the junction between two layers of n type and silica of the p-type. This barrier is the crucial border where both types of silicon come into contact. The barrier is inaccessible to electrons, so even if the silicon sandwich is connected to a flashlight, the current won’t flow and the lightbulb won’t be able to turn on. If you shine light onto the sandwich, it will produce some amazing results. The light could be thought of as{ a|| an evaporation} streaming stream, or “light particles” which are energetic, referred to as photons. Photons that pass through the sandwich transfer their energy to silicon atoms they pass through. The energy that is absorbed knocks electrons out of the lower layer, which is p type. They then cross the barrier to reach the n-type layer above and flow around the circuit. The greater the amount of light then the more electrons leap up and more electricity flows.
How efficient are Solar Panels?
The conservation energy law as a fundamental principle of physics, stipulates that energy cannot be produced or transformed into thin air. We can only change it from one form of energy to another. A solar cell is unable to produce more electricity than it gets in light every second. We will discover that the majority of solar cells convert between 10 and 20 percent of energy that they get to electricity. The theoretical maximum efficiency of a mono-junction silicon panel would be around 30 percent. This is known as The Shockley Queisser limit. Because sunlight is a wide range of wavelengths and energy that a single-junction silicon solar cell can only be able to capture light in a very narrow frequency range. All other photons are wasted. Certain photons that hit the solar cells are not strong enough to generate enough electrons. Others are too energy-intensive and are wasted. In the most ideal conditions, laboratory cells with cutting-edge technology can be able to achieve just below 50% efficiency. They employ multiple junctions to capture photons with various energy levels.
A practical domestic panel may have an efficiency of around 15 percent. Single-junction, first-generation solar cells won’t achieve the 30 percent efficiency threshold that was set by Shockley-Queisser or the lab record for efficiency of 47.1 percent. There are a myriad of factors that could affect the efficiency of solar cells, like how they’re constructed, angled , and placed, whether they are ever in shadow and how clean they are and how cool they are.
Different types of Photovoltaic Cell
Most solar panels that you will see today on roofs are simply silicon sandwiches. They have had their silicon “doped” to increase its electrical conductivity. These classic solar cells are referred to as first-generation by researchers to differentiate them from two advanced technologies, second- and third-generation. What’s the difference?
First-generation Solar Cells
Over 90 percent of the solar cell production comes of silicon wafers that contain crystalline silicon (abbreviated “c-Si”), which are cut from huge ingots. This process could take up to a month and takes place in ultra-clean labs. Ingots may be one crystal (monocrystalline solar panels) or multi-crystalline (polycrystalline solar panels), depending on whether they contain multiple crystals.
The first-generation solar cell functions the way they are shown in the picture above. They are based on a single, easy junction between n and p-type layers of silicon. The latter is cut out of separate ingots. An n-type ingot is made by heating small silicon pieces using tiny amounts (or antimony or phosphorus) as the dopant. In a p-type ingot, you would use boron. The junction is created by combining slices of p-type and the n-type silicon. There are some additional bells and whistles which can add to the photovoltaic cell (like an antireflective coating, that increases the absorption of light and gives them their blue color), and metal connections so they can be wired into circuits. But a simple P-N junction is the most common solar cells rely on. This is how photovoltaic solar cells function since 1954 when Bell Labs scientists pioneered it using sunlight to illuminate silicon sand, they generated electricity.
Second-generation Solar Cells
The classic solar cells have thin solar cell wafers. They’re typically just one millimeter thickness (around 200 micrometers or 200mm). They’re not as thin than second generation solar cells (TPSC), or thin-film solar cells which are 100 times thinner (several millimeters, or millimeters of one meter deep). Though the majority are still composed of silicon (a type of silicon known as amorphous silu (a-Si)) where particles are distributed in random crystalline structures, some are made out of other materials , such as Cd-Te (cadmium-telluride) as well as copper-indium gallium diselenide (CIGS).
Second-generation cells are extremely thin and light and can be laminated to windows, skylights and roof tiles. They also work well with all kinds of “substrates” which are backers such as plastics and metals. Second-generation cells are less flexible than the first generation ones, however they still perform better than the first generation. A top-quality first-generation cell may achieve efficiency of 15-20 percent, however, the amorphous silicon cells struggle to achieve above 7 percent) and the top thin-film CdTe cells manage only about 11 percent, and CIGS cells no better than 7-12 percent. This is among the reasons that second-generation solar cells have not been able to make a mark in the market despite their many practical benefits.
Third-generation Solar cells
The latest technologies combine the best features of 2nd and first generation cells. They promise high efficiency (up 30 percent or more) just like the first generation cells. They are more likely to be constructed from substances other than silicon (making second-generation photovoltaics OPVs), or perovskite crystals. They may also have multiple junctions (made by multiple layers made of different semiconductor materials). They are more affordable, more efficient, and feasible than first or second generation cells. The{ current|| record-setting} world record for efficiency of third-generation solar cell is 28.1. This record was set in December 2018 by a tandem perovskite-silicon solar cell.
How are they made?
You can observe 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 let oxygen out carbon arcs, it is possible to be applied. The result is carbon dioxide and molten silica which can be used to construct solar cells. But, even though this yields silicon with a 1% impurity, it is still not sufficient. The floating zone method lets the silicon rods that are 99% pure to be passed through a hot zone many time in the exact direction. This method removes any impurities that are present on one side of the rod, allowing it to be cleaned.
2. Making Single Crystal Silicon
Czochralski Method has become the well-known method to create single-crystalline silicon. This involves placing a seed crystal composed of silicon inside melted silicon. The result is a ball or cylindrical ingot by rotating the seed crystal when it is being removed from the silicon melt.
Third Stage Slice the Silicon Wafers
A second boule stage is utilized to slice silicon wafers with a circular saw. This task is best accomplished by using diamonds, which produce pieces of silicon that could then be cut into hexagons or squares. Although the cut marks have been removed the slices, some companies keep them in place because they believe that more light could be absorption by a rougher solar cells.
Stage 4: Doping
After purifying the silicon at a earlier stage, it is possible to add impurities back to the silicon. Doping involves using a particle accelerator to ignite the phosphorus ions inside the ingot. You can control the penetration depth by setting the speed of electrons. You can skip this step using the standard method of inserting boron during cutting the wafers.
Step Five: Add the electrical contacts
Electrical contacts are used as a connection between the solar cells to serve as receivers for the electricity generated. These contacts, composed from metals such as palladium or copper are made of a thin layer enough to allow sunlight to penetrate the solar cell efficiently. The metal is either deposited on the exposed cells , or it is evaporated by vacuum using a photoresist. The thin strips of copper lined with Tin are typically placed between cells after the contacts are installed.
Step Six Application of the Anti-Reflective Coating
Because silicon has a shiny appearance, it can absorb up to 35% of sunlight. To decrease reflections, a coating of silicon is applied to it. The process involves heating the surface until the molecules are boiling off. The molecules move on to the silicon and begin to condense. A high voltage can also be used to eliminate the molecules and deposit them on the silicon at an opposite end of the electrode. This is known as “sputtering”.
Stage Seven: Encapsulate and Seal the Cell
The solar cells are encapsulated by silicon rubber or ethylene vinyl Acetate. Then, they are put inside an aluminum frame, with a back sheet and glass cover.
What amount of electrical energy can solar cells produce?
Theoretically speaking, it’s an enormous amount. At the moment, we should put aside solar cells and instead focus on pure sunlight. Every square meter of Earth could receive as much as 1000 watts of solar power. This is the theoretical capacity of direct sunlight during a clear day. The sunlight’s rays are fired perpendicularly to Earth’s surface, giving maximum luminosity.
After we adjust to the tilt of our planet and the time, we can expect to get 100-250 watts per sq. meters in northern latitudes even on cloudless days. This is equivalent to 2-6 kWh per daily. When you multiply the whole year’s production, it produces 700- 2500 kWh per sq. meters (700-2500 units) of electricity. The solar energy potential in hotter regions is clearly more than Europe. For example the Middle East receives between 50 to 100 percent more solar energy each calendar year than Europe.
However, solar cells are just 15 percent efficient, so you can only harvest 4-10 Watts per square foot. This is why panels with solar power have to be massive: how big the area you can cover by cells will affect the power you can generate. A typical solar panel made up of 40 cells (each row of eight cells) can produce around 3-4.5 watts. A solar panel made up of 3-4 modules could generate many kilowatts, which would be enough to meet a home’s peak energy needs.
How about Solar Panel Farms?
What do we do if we have to produce massive amounts of solar power? You’ll need between 500 to 1000 solar roofs to generate approximately the same quantity of power like a large wind turbine with the peak power of around 2 or 3 megawatts. In order to compete with huge nuclear or coal power plants (rated as gigawatts), you would need around 1,000 solar roofing systems. This is roughly 2000 wind turbines or perhaps a million of them. These comparisons assume that our solar and wind power sources produce the maximum output. While solar cells do produce clean, efficient energy however, they can’t claim to be effective in the use of land. The vast solar farms that are appearing all over the country produce modest amounts of power, usually around 20 megawatts , or one per cent less than a 2 gigawatt nuclear or coal plant. Shneyder Solar, a renewable company estimates that it will take approximately 22,000 solar panels for a 12-hectare (30-acres) area to generate 4.2 megawatts. This is roughly the same as two wind turbines of a similar size. The turbine also produces enough energy to power 1200 homes.
Top Residential Solar Companies
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