Why do we have to dig for coal or digging for oil when there’s a gigantic power station high above us that is sending out free green energy? The Sun is a glowing ball of nuclear energy can provide enough energy to supply power to this Solar System for five billion more years. Solar panels are able to convert the energy into an endless amount of electricity.
While solar power might seem futuristic or strange however, it’s already common. A solar-powered calculator or watch for your pocket might be in your wrist. A lot of gardeners use solar-powered lights. Solar panels are often seen on spacecrafts and satellites. NASA an American Space Agency, has also created an aircraft powered by solar energy. Global warming is threatening our environment and it seems certain that solar energy will become an increasingly significant source of energy that is renewable. How does it work?
What is the maximum amount of solar power we can get from the Sun?
It’s incredible how solar power works. Every square meter on Earth gets an average of 163 watts solar energy. We’ll go over this figure in greater detail later. This means that you could put an electric table lamp of 150 watts on every square meters of Earth and utilize the solar energy of the Sun to light up the entire globe. Another way to think about it is that in the event that we only covered 1percent of the Sahara desert with solar cells, it would be possible to create enough electricity to provide power to the entire globe. The great thing about solar energy is that there’s a lot of it, more than we’ll ever need.
There’s a drawback. The Sun’s energy is the result of light and heat. Both are essential. The light is what makes plants grow and provides food for us. The heat keeps us comfortable enough to live. But, we can’t use the Sun’s energy or light directly to fuel a car or TV. It is important to convert solar energy into a different form of energy is more readily available like electricity. This is exactly the job solar cells perform.
- The cell’s surface gets illuminated by sunlight
- Photons transport energy through cell’s layers.
- Photons transmit energy to electrons located in the lower layers
- This energy is used by electrons to get out of the circuit and jump back to the top layers.
- The power of a device is provided by the electrons that flow around the circuit.
What are solar cells?
The solar cell can be described as an electrical device that absorbs sunlight and converts it into electric energy. It’s about similar to a hand of an adult and is octagonal in shape and colored bluish-black. Many solar cells are able to be joined together to form larger modules. They are then joined to form larger units referred to as solar panels. (The blue or black tiles that you see on your homes typically have hundreds of solar cells on top of the roof) Or chopped into chips (to power small gadgets such as digital watches and small calculators in pockets).
The cells of solar panels work the same manner as batteries do. But, unlike battery’s cells, which generate electricity through chemical reactions solar panel’s cells are able to capture sunlight and produce electricity. Photovoltaic cells (PV) is a term used to describe solar cells that make electricity from sunlight (photo comes directly from Greek word meaning light). The term “voltaic” however, refers to Alessandro Volta (1745-1827), an Italian electrical engineer who was a pioneer in the field.
Light is often described as tiny particles called photons. The sun’s beam is similar to a huge yellow firehose that shoots trillions upon trillions. A solar panel can be placed in the path of these photons to collect them and convert them into an electric current. Each cell produces a few volts, so the function of solar panels is to combine energy from multiple cells to create an appropriate amount of electric electricity and voltage. Today’s solar cells are almost all composed of pieces of silicon (one the most well-known chemical elements that are found on Earth, found within sand). However, as we’ll see, other materials may be a possibility. The sun’s energy blasts electrons from the solar cells when it is exposed to sunlight. They can then be used to power any electronic device that is powered by electricity.
How are solar cells made?
Silicon is the material that microchips’ transistors (tiny switches), are made. Solar cells function in a similar manner. A semiconductor is a form of material. Conductors are substances that permit electricity to flow easily through them, such as metals.
Others, like plastics and wood, don’t permit the flow of electricity through them; they’re known as insulation. Semiconductors like silicon are not conductors or insulation. However, we can make them conduct electricity under certain conditions.
A solar cell is composed from two silicon layers each one having been treated or doped so that electricity can move throughout it in a particular way. The lower one has 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, and is therefore negatively charged. To provide the layer with an excess of electrons it is doped with a negative charge. This is referred to as negative-type and n-type silicon. (Read more about semiconductors and doping in our posts on integrated circuits and transistors.
A barrier forms at the junction between two layers of n type and silica p-type. This barrier is the crucial boundary where both kinds of silicon meet. The barrier is not accessible to electrons, so even if the sandwich connects to a lamp but the current isn’t flowing and the light bulb won’t be able to turn on. But, if you shine light onto the sandwich, it’ll produce something amazing. The light could be described as an evaporation flow as well as “light particles”, which are energetic, and are referred to as photons. Photons that pass through the sandwich transfer their energy to the silicon atoms as they pass through. The energy incoming is able to knock electrons away from the lower layer, which is p type. They then jump across and over the wall to the n-type layer above and then flow through the circuit. The more light that is available, the more electrons will rise and more current flows.
How efficient are Solar Panels?
The law of conservation energy as a fundamental principle of physics, states that energy cannot be created or made to disappear into thin air. We can only change it from one form of energy into another. Solar cells cannot generate more electricity than it receives in light every second. As we’ll see, most solar cells can convert between 10 and 20 percent of energy that they get into electricity. The theoretical maximum effectiveness of a typical mono-junction silicon panel would be about 30 percent. This limit is known by the Shockley Queisser Limit. Since sunlight has a broad range of wavelengths and energy 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 not strong enough to generate enough electrons. Others are too energy-intensive and end up being wasted. Under the ideal conditions, lab cells that use advanced technology may attain just under 50 percent efficiency. They employ multiple junctions to capture photons of different energy levels.
A practical domestic panel may have an efficiency of approximately 15 percent. Single-junctionsolar cells of the first generation will not reach the 30 percent efficiency threshold set by Shockley-Queisser, or the record set by the laboratory that is 47.1 percent. There are a myriad of factors that could affect the efficiency of solar cells, including how they’re constructed, angled , and placed and whether or not they’re in shadow, how clean they are and how cool.
Different types of Photovoltaic Cell
The majority of solar cells that you will see today on roofs are simply silicon sandwiches. They have received the designation of “doped” to improve its electrical conductivity. 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
Over 90 percent of the solar cell production comes from wafers containing crystalline silicon (abbreviated “c-Si”), which are cut from huge ingots. This process could take for as long as one month, and it takes place in extremely clean laboratories. Ingots can include single crystals (monocrystalline solar panels) or multi-crystalline (polycrystalline solar panels) in the event that they contain multiple crystals.
First-generation solar cells function the way we have shown them in the picture above. They are based on a single, easy connection between p-type and n-type layers of silicon. It is cut from separate ingots. The n-type ingot is created by heating small silicon pieces using tiny amounts (or antimony or phosphorus) as dopants. A p-type one 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 coating, which increases light absorption and makes them blue) and connections made of metal that allow them to be connected to circuits. But a simple p-n junction is what most solar cells rely on. This is how photovoltaic solar cells have been working since 1954 when Bell Labs scientists pioneered it using sunlight to illuminate silicon sand they produced electricity.
Second-generation Solar Cells
The traditional solar cells consist of thin film of solar wafers. They’re usually only a fraction of millimeter thick (around 200 micrometers or 200mm). They’re not as thin as second-generation solar cells (TPSC) or thin film solar cells, which are 100 times smaller (several millimeters or millionths one meter deep). Though the majority are still made of silicon (a type of silicon known as amorphous silu (a-Si)), in which the atoms are placed in random crystal structures Some are composed of different materials like Cd-Te (cadmium-telluride) or copper indium gallium dielenide (CIGS).
Second generation cell are thin and light and can be laminated to windows, skylights as well as roof tiles. They can also be used with all kinds of “substrates”, which are the backers, such as metals and plastics. Second-generation cells are less flexible than those of the first generation, but they are still superior to them. First-generation cells of the highest quality can achieve efficiency of 15-20%, but the amorphous silicon cells struggle to achieve higher than 7 percent) While the most efficient thin-film CdTe cells manage only about 11 percent efficiency, with CIGS cells can’t even reach 7-12 percent. This is among the reasons that second-generation solar cells have not been able to make a mark in the marketplace despite their numerous advantages in practical use.
Third-generation Solar cells
These innovative technologies blend the best characteristics of both first- and 2nd generation cells. They are expected to have high efficiency (up to 30 %) as do first-generation cells. They tend to be composed of substances other that silicon (making second-generation photovoltaics, OPVs) as well as perovskite crystals. Additionally, they may feature multiple junctions (made from several layers of different semiconducting material). They will be less expensive and more efficient as well as practical than the first or second generation cells. The current global record of efficiency for third-generation solar cells stands at 28.9. This was achieved in December 2018 by an equidistant perovskite solar cell.
How are they made?
As you can see, there are seven steps to creating solar cells.
Stage 1: Purify Silicon
It is then heated up in an electrical furnace. In order to release oxygen carbon arcs, it is possible to be applied. This results in carbon dioxide as well as molten silica which can be utilized to create solar panels. Even the silicon is produced with only 1% impurity it is still not adequate enough. The floating zone method permits the 100% pure silicon rods to pass through a zone that is heated several times in the same direction. The process eliminates all impurities that are present on one side of the rod and permits it to be cleaned.
Second Stage: Constructing Single Crystal Silicon
Czochralski Method has become the sought-after method of creating single-crystalline silicon. This involves placing a crystal of seed made of silicon inside melted silicon. The result is a boule or cylindrical ingot, by spinning the seed crystal when it is removed from the silicon melting.
The second stage boule is used to cut silicon wafers by using the circular saw. This task is best accomplished with diamond, which produces pieces of silicon that could later be cut to make hexagons or squares. While the cut marks have been removed the sliced wafers, some manufacturers leave them on the grounds that more light could be captured by the rougher solar cell efficiency.
Fourth Stage Doping
Step Five: Add the electrical connections
Electrical contacts are utilized as a connection between the solar cells to serve as receivers for the generated current. The contacts, which are made of various metals, including palladium and copper, have a thin structure to allow sunlight to penetrate the solar cell effectively. The metal can be deposited on the exposed cells , or vacuum evaporated using a photoresist. The thin strips of copper lined with Tin are typically placed between the cells after the contacts have been inserted.
Step Six: Apply the Anti-Reflective Coating
Because it is shiny, it is able to be able to reflect as much as 35% sunlight. To reduce reflections, a silicon coating will be put on it. This is accomplished by heating the surface until the molecules boil off. The molecules move on to the silicon and begin to condense. A high voltage may also be utilized to detach the molecules and then deposit them onto the silicon at another electrode. This is referred to as “sputtering”.
Stage Seven Step Seven: Encapsulate and Seal the Cell
They are then encapsulated with silicon rubber or ethylene vinyl Acetate. They are then placed inside an aluminum frame, with a back sheet and glass cover.
What amount of electrical energy can solar cells produce?
Theoretically, it is an enormous amount. For the moment, let’s ignore solar cells and focus on pure sunlight. Each square meter of Earth can receive up to 1,000 watts in solar energy. It is the expected energy of direct sunlight on a clear day. The solar rays are directed perpendicularly to Earth’s surface and provide the maximum light.
When we adjust to how our earth tilts as well as the seasons, we can expect to get 100-250 watts per sq. Meter in northern latitudes, even on days with no clouds. This is roughly 2-6 kWh per daily. Multiplying the entire year’s production yields 700 to 2500 kWh per sq. m (700-2500 units) of electricity. The potential of the sun’s energy in the hotter regions is definitely higher than Europe. For instance in the Middle East receives between 50 to 100 percent greater solar power each calendar year than Europe.
Unfortunately, solar cells are only around 15 percent efficient, so you can only harvest 4-10 watts per square foot. This is the reason panels that harness solar power should be huge in size. The amount of area you are able to cover with cells will directly affect the power that you can produce. The typical solar panel consisting from 40 cell (each row of 8 cells) will produce about 3-4.5 watts. A solar panel comprised of 3-4 modules could generate several kilowatts. This is enough to supply a house’s highest energy demands.
How about Solar Panel Farms?
But, what happens do we do if we have to produce large amounts of solar energy? It will require between 500 to 1000 solar roofs to produce approximately the same quantity of electricity as a large wind turbine with an output peak of 2.5 or 3.0 megawatts. To compete with nuclear or coal power plants (rated as gigawatts), you would need about 1,000 solar roofing systems. This is equivalent to approximately 2000 wind turbines or perhaps a million of them. The calculations assume that solar and wind power sources produce the maximum output. While solar cells do produce clean, efficient power, they cannot claim to be effective in the use of land. Even the huge solar farms that are appearing all over the country produce modest amounts of power, generally around 20 megawatts or 1 percentage less than the 2 gigawatt nuclear or coal plant. LA Solar Group, a renewable company, estimates that it takes approximately 22,000 panels to cover 12 hectares (30-acres) area to produce 4.2 megawatts. It’s about the same amount as two wind turbines of a similar size. It also generates enough power to power 1,200 homes.
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