Solar Cell
Solar Cell
Why waste our time digging for oil or shoveling coal when there is a huge power plant high above us that is sending out free and clean energy? The Sun as a burning nucleus can provide enough energy to provide power to this 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, it is already very widespread. A solar-powered clock or calculator for your purse could be on your wrist. Many gardeners have solar-powered lights. Solar panels are typically seen on spacecrafts and satellites. NASA, one of the American NASA space agency even designed an aircraft powered by solar energy. Global warming is harming our planet and it is likely that solar energy will be an ever-growing source of renewable energy. What is the process?
What is the maximum amount of solar power we can get from the Sun?
It’s amazing how solar power operates. Each square meter on Earth receives an average 163 watts solar energy. This figure will be discussed in greater detail later. This means that you could put a 150 watt table lamp on every square inch of Earth and make use of the solar energy of the Sun to illuminate the entire planet. Another way to put it is that if we covered only one percent from the Sahara desert in solar cells, it would be possible to produce enough solar energy to provide power to the entire globe. The great thing about solar energy is that there’s plenty of it, more than we’ll ever need.
There is a downside. The Sun’s energy is a mixture of light and heat. Both are vital. Light is what helps plants grow and provide us with food. Heat keeps us sufficiently warm to survive. However, we cannot use the Sun’s light or heat directly to fuel a car or TV. It is important to convert solar energy into a different type of energy that we can use more easily like electricity. This is precisely what solar cells do.
In summary:
- The cell’s surface gets illuminated by sunlight
- Photons carry energy through the cell’s layers.
- Photons transmit energy to electrons that reside in lower layers
- This energy is utilized by electrons to let electrons escape the circuit and jump back to the top layers.
- The power for a device is provided through the flow of electrons around the circuit.
What are solar cells?
A solar cell is an electronic device that absorbs sunlight and converts it into electricity. It’s about similar to an adult’s hand and is octagonal in shape and colored in a bluish-black color. Numerous solar cells can be put together to create larger units called modules. These are then connected into larger units, referred to as solar panels. (The blue or black tiles you see on homes generally have hundreds of individual solar cells per roof) Or chopped into chips (to power small gadgets such as digital watches or small calculators in pockets).
The cells in a solar panel work in the same manner as batteries. However, unlike a battery’s cells which produce electricity through chemical reactions the cells of solar panels are able to capture sunlight and produce electricity. Photovoltaic cell (PV), as they produce electricity using sunlight (photo is derived in the Greek word meaning light). The word “voltaic” however, refers to Alessandro Volta (1745-1827), an Italian electrical engineer who was a pioneer in the field.
Light can be thought of as tiny particles known as photons. A beam of sunlight is like an enormous Yellow firehose which releases trillions of trillions. A solar cell can be placed within the path of these photons to capture them , and later convert them into an electric current. Every cell can produce some volts, and the purpose of a solar panel is to combine the energy of several cells to generate a useful amount of electric energy and voltage. Nowadays, solar cells are almost all made of slices of silicon (one the most common chemical elements{ found|| that are found} on Earth and is found in sand). But, as we’ll see, other materials may be a possibility. The sun’s radiation blasts electrons away from the solar cell when it’s exposed to sunlight. They can then be used to power any electrical device powered by electricity.
How are solar cells made?
Silicon is the material from which microchips’ transistors (tiny switches), are made. Solar cells work in a similar way. A semiconductor is a type of material. Conductors are substances that permit electricity to flow freely through them, such as metals.
Other materials, such as plastics and wood, aren’t able to allow electric current to pass through; they’re known as insulation. Semiconductors, like silicon, aren’t conductors or insulators. However, we can make them conduct electricity in certain conditions.
The solar cells are composed of two layers of silicon, each one having been modified or doped to permit electricity to flow through it in a certain manner. The lower layer contains slightly less electrons because it is doped. This layer is referred to as the p-type or positive-type silicon. It is awash with electrons and therefore is negatively charged. In order to give the layer an overabundance of electrons it is charged with a negative charge. This is known as n-type and negative-type silicon. (Read more about doping and semiconductors in our articles about transistors and integrated circuits.
A barrier forms at the junction between two layers of n type and p-type silica. This barrier forms the essential boundary where the two types of silicon meet. The barrier is inaccessible to electrons, so even if the silicon sandwich has been connected with a flashlight, the current won’t flow and the lightbulb won’t be able to turn on. But, if you shine light onto the sandwich, it will produce something amazing. The light could be thought of as{ a|| an evaporation} stream or “light particles”, which are energetic, and are referred to as photons. Photons that pass through the sandwich give up their energy to the silicon atoms as they pass through. The energy incoming knocks electrons out of the lower, p-type layer. They then jump across the barrier to reach the n-type above and then flow through the circuit. The more light that is available then the more electrons rise and more current will flow.
How efficient are Solar Panels?
The conservation energy law as a fundamental principle of physics, stipulates that energy can’t be made or transformed into thin air. We can only convert it from one form of energy into another. Solar cells cannot generate more energy than it absorbs in light every second. We will discover that most solar cells can convert between 10 and 20 percent of the energy they receive to electricity. The theoretical maximum efficiency of a mono-junction silicon panel would be around 30%. This is known by The Shockley Queisser limitation. Because sunlight can be found in a vast spectrum of wavelengths and energies that a single-junction silicon solar cell can only collect photons within a narrow frequency range. The rest of the photons will go to waste. Some of the photons hitting the solar cells are too weak to produce enough electrons. Some have too much energy and are wasted. In the best conditions, laboratory cells with advanced technology may be able to achieve just below 50% efficiency. They use multiple junctions to collect photons of various energy levels.
A practical domestic panel may be able to achieve an efficiency of about 15 percent. Single-junction, first-generation solar cells won’t achieve the efficiency of 30 percent set by Shockley-Queisser, or the laboratory record of 47.1 percent. There are many factors that could affect the effectiveness of solar cells, like how they’re constructed, angled and positioned in relation to their location, whether they’re in shadow or not, their cleanliness, and how cool they look.
Different types of Photovoltaic Cell
Most solar panels you see on roofs are simply silicon sandwiches. They’ve been “doped” to increase the electrical efficiency of their cells. These classic solar cells are called first-generation by scientists to distinguish them from the two newer technology, second- and third-generation. What’s the difference?
First-generation Solar Cells
The majority of the solar cell production comes from wafers containing crystallized silicon (abbreviated “c-Si”), that are then cut out of large ingots. This process could take as long as a month and takes place in extremely clean laboratories. Ingots may include one crystal (monocrystalline solar panels) or multi-crystalline (polycrystalline solar panels), depending on whether they have multiple crystals.
The first-generation solar cell functions the way they are shown in the box above. They make use of a simple connection between p-type and n-type layers of silicon, which is cut from separate ingots. Ingots of the n type are made by heating small pieces of silicon with very little (or antimony or phosphorus) as dopants. In a p-type ingot, you would use boron. The junction is made by fusing slices of p-type and n-type silicon. There are additional bells and whistles that can incorporate into photovoltaic devices (like an antireflective layer, which improves light absorption and creates their blue hue) and connections made of metal so they can be wired into circuits. But a simple p-n junction is the one that most solar cells rely on. 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 consist of thin films silicon wafers for solar cells. They’re usually only one millimeter in thickness (around 200 micrometers, or 200 millimeters). They’re not as thin than second generation solar cells (TPSC) or thin-film solar cells which are 100 times smaller (several millimeters, or millimeters of meters deep). While most of them are made from silicon (a form called amorphous siliu or a-Si) that is where particles are distributed in random crystalline forms Some are composed of other materials , such as Cd-Te, cadmium-telluride as well as copper-indium gallium diselenide (CIGS).
The second generation cells are light and thin and are able to be laminated with windows, skylights or roof tiles. They are also compatible with all kinds of “substrates” that are backers like metals and plastics. Second-generation cells are less flexible than the first generation ones, however they perform far better than them. First-generation cells of the highest quality can attain efficiency of around 15%, but Amorphous silicon is struggling to reach higher than 7 percent) While the most efficient thin-film CdTe cells achieve just 11 percent and CIGS cells can’t even reach 7-12%. This is one of the reasons that second-generation solar cells have not enjoyed much success on the market , despite their numerous advantages.
Third-generation Solar cells
These innovative technologies blend the best features of 2nd and first generation cells. They are expected to have high efficiency (up to 30 %) similar to the first generation cells. They are more likely to be composed of different materials that silicon (making second-generation photovoltaics (also known as OPVs), and perovskite crystals. Additionally, they may feature multiple junctions (made by multiple layers from different semiconducting material). They will be less expensive, more efficient, and feasible than first or second generation cells. The{ current|| record-setting} worldwide record in efficiency of third-generation solar cells stands at 28.9. It was reached in December 2018 by an equidistant perovskite solar cell.
How are they made?
You can observe there are seven steps involved in making solar cells.
Stage 1: Purify Silicon
It is then heated up in an electrical furnace. 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 systems. Even the silicon is produced with only 1% impurity it’s still not adequate enough. The floating zone method permits the silicon rods that are 99% pure to be passed through a zone that is heated several at a time, in the direction of. The process eliminates all impurities that are present on one side of the rod, allowing it to be removed.
2. The Making of Single Crystal Silicon
Czochralski Method has become the popular method for creating single-crystalline silicon. It involves placing a crystal of seed made of silicon inside melted silicon. The result is a boule or cylindrical ingot by turning the seed crystal when it is removed from the melted silicon.
Stage Three Make cuts in the Silicon Wafers
Second stage boules are used for cutting silicon wafers using circular saws. This task is best accomplished with diamond, which produces the silicon chips that are able to later be cut to make squares or hexagons. Although the cutting marks of the saw are eliminated from slices, some companies leave them on the grounds that more light may be captured by the rougher solar cells.
4. Stage: Doping
After purifying the silicon at a earlier stage, it’s possible to introduce impurities to the silicon. Doping involves using an accelerator that ignites the phosphorus ions within the ingot. You can control the depth of penetration through setting the speed of electrons. It is possible to skip this step by employing the conventional technique of inserting boron into processing the wafers.
Step Five: Add the electrical contacts
Electrical contacts are utilized as a connection between the solar cells to act as receivers of the electricity generated. These contacts, composed from metals such as palladium or copper, are thin to allow sunlight to penetrate the solar cell in a way that is efficient. The metal can be deposited on the cells that are exposed or vacuum evaporated using a photoresist. Thin strips of copper coated with tin are usually placed between cells after the contacts have been installed.
Step Six: Apply the Anti-Reflective Coating
Because silicon has a shiny appearance, it can reflect up to 35% sunlight. To minimize reflections, a coating of silicon will be put on it. The process involves heating the substance until the molecules are boiling off. The molecules then move onto the silicon and begin to condense. The high voltage could also be utilized to detach the molecules and deposit them onto 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 then sealed using silicon rubber or vinyl Acetate. They are then placed in an aluminum frame with an aluminum back sheet and a glass cover.
What amount of electrical energy can solar cells produce?
Theoretically, it is an enormous amount. For the moment, let’s forget about solar cells and instead focus on pure sunlight. Every square meter of Earth could receive as much as 1,000 watts in solar energy. This is the theoretical capacity of direct sunlight on a clear day. The sunlight’s rays are fired perpendicularly towards the Earth’s surface, resulting in the greatest illumination.
Once we have adjusted for the tilt of our planet and the seasons we should achieve between 100-250 watts for each sq. Meter in northern latitudes, even on clear days. This is roughly 2-6 kWh daily. The entire year’s output yields 700 to 2500 kWh for every sq. meters (700-2500 units) of electricity. The solar energy potential in warmer regions is evidently higher than Europe. For instance, the Middle East receives between 50 and 100 percent more solar energy per calendar year than Europe.
However, solar cells are only 15 percent efficient. This means that we only get 4-10 watts per square meter. This is why panels with solar power have to be massive: how big you are able to cover with cells will directly affect the power you can generate. An average solar panel comprised with 40 solar cells (each row of eight cells) will produce about 3-4.5 watts. However, a solar panel comprised of 3-4 modules could produce many kilowatts, which would be enough to meet a home’s highest energy demands.
How about Solar Panel Farms?
However, what do we do if we have to produce large amounts of solar energy? You will need between 500 to 1000 solar roofs in order to generate similar amounts of electricity as a large wind turbine, with the peak power of around 2.5 or 3.0 megawatts. To compete with large coal or nuclear power plants (rated in the gigawatts), you would need about 1000 solar roofs. This is roughly 2000 wind turbines, and possibly a million of them. The calculations assume that solar and wind power sources produce the maximum output. Although solar cells are able to produce clean, efficient power however, they can’t claim to be efficient use of land. Even the huge solar farms appearing all over the country generate only a small amount of power, generally about 20 megawatts or 1 percent less than a large 2 gigawatt nuclear or coal plant. Shneyder Solar, a renewable company estimates that it requires approximately 22,000 solar panels for a 12-hectare (30-acres) surface to produce 4.2 megawatts. This is about the same amount as two large wind turbines. Additionally, it generates enough energy to power 1200 homes.
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