Solar Cell
Solar Cell
Why do we have to dig for oil or shoveling coal when there’s a gigantic power plant high above us that provides free and clean energy? The Sun is a glowing mass of nuclide energy, has enough fuel to supply power to our Solar System for five billion more years. Solar panels can transform the energy into an endless supply of electricity.
Although solar power might appear odd or futuristic however, it’s already common. A solar-powered clock or calculator for your purse could be in your wrist. A lot of gardeners use solar-powered lights. Solar panels are typically located on spacecrafts and satellites. NASA an American Space Agency, has also created the first solar-powered plane. Global warming is harming our planet and it’s likely that solar energy will become an increasingly significant source of renewable energy. 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. Each square meter on Earth gets an average of 163 watts solar energy. This figure will be discussed in greater detail later. It means you could place an electric table lamp of 150 watts on every square inch of Earth and make use of the sun’s energy to light the entire planet. Another way of putting it, in the event that we only covered 1percent or less of Sahara desert in solar cells, it would be possible to generate enough electricity to solar power the entire planet. The best thing about solar energy is that there’s plenty of it, more than we could ever need.
There’s a down side. The Sun’s energy comes as a mixture of heat and light. Both are vital. Light is what helps plants grow, and also provides food for us. Heat keeps us sufficiently warm to survive. However, we cannot use the Sun’s energy or light directly to power a TV or car. It is essential to transform solar energy into another form of energy we can use more easily such as electricity. This is exactly what solar cells do.
In summary:
- The cell’s surface is illuminated by sunlight
- Photons transport energy through cells’ layers.
- Photons transmit energy to electrons in lower layers.
- This energy is utilized by electrons to let electrons escape the circuit and jump back to the top layers.
- The power of the device is generated by electrons that move around the circuit.
What are solar cells?
Solar cells are electronic devices which is able to capture sunlight and transform it into electric energy. It is about similar to an adult’s hand, octagonal in form, 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 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 like digital watches and pocket calculators).
The cells of solar panels function in similar ways to a battery. But, unlike battery’s cells that produce electricity using chemicals the cells of solar panels absorb sunlight and generate electricity. Photovoltaic cell (PV) are able to make electricity from sunlight (photo is derived in the Greek word that means light). The word “voltaic”, however, is a reference to Alessandro Volta (1745-1827), an Italian electrical engineer who was a pioneer in the field.
Light is described as tiny particles known as photons. A beam of sunlight is like an enormous Yellow firehose which releases trillions of trillions. Solar cells can be placed within the direction of these light beams to capture them , and later transform them into an electrical current. Each cell can generate a few volts, so the function of solar panels is to combine the energy produced by many cells to produce the required amount of electrical current and voltage. The solar cells of today are nearly entirely made of silicon (one the most well-known chemical elements{ found|| that are found} on Earth and is found in sand). However, as we’ll learn, other materials might be a possibility. The sunlight’s energy blasts electrons out of the solar cells when it’s exposed to sunlight. They can then be utilized to power any electrical device that runs on electricity.
How are solar cells made?
Silicon is the material used to make microchip transistors (tiny switches), are made. Solar cells function in a similar manner. It is also a kind of material. Conductors are substances that permit electricity to flow freely through them, including metals.
Others, like plastics and wood, do not permit the flow of electricity through them; they’re referred to as insulation. Semiconductors, like silicon, aren’t conductors or insulators. However they can conduct electricity under certain conditions.
The solar cells are composed from two silicon layers each of which has been modified or doped to permit electricity to flow throughout it in a certain manner. The lower layer has slightly less electrons because it is doped. The layer is known as positively-type silicon, also known as p-type. It has too many electrons, and is therefore negatively charged. To give the layer an excess of electrons it is charged to the other direction. This is known as negative-type and n-type silicon. (Read more about doping and semiconductors in our posts on integrated circuits and transistors.
A barrier is created at the intersection of two layers of n type and p-type silica. This barrier forms the essential boundary where both kinds of silicon come together. It is unaccessible to electrons. Therefore, even if the sandwich is connected to a lightbulb but the current isn’t flowing and the lightbulb won’t be able to turn on. But, if you shine light on the sandwich, it will produce something amazing. The light can be considered as{ a|| an evaporation} flow of light or “light particles” which are energetic, referred to as photons. Photons entering the sandwich give up their energy to silicon atoms when they move through. The energy that is absorbed is able to knock electrons away from the lower, p type layer. They then jump across barriers to get into the higher n-type and flow around the circuit. The more light that is available the greater chance that electrons will rise and more current will flow.
How efficient are Solar Panels?
The law of conservation energy, a fundamental rule of physics, stipulates that energy can’t be made or transformed in the air. It is only possible to transform it from one type of energy to another. Solar cells cannot generate more energy than it absorbs in light every second. As we will see, most solar cells can convert 10 to 20 percent of energy that they get to electricity. The theoretical maximum efficiency of a typical single-junction silicon solar panel is approximately 30%. This limit is known by the Shockley Queisser limitation. Because sunlight is a wide spectrum of wavelengths and energies that a single-junction silicon solar cell can only be able to capture light within a limited frequency range. All other photons will be wasted. Some photons that strike the solar cell are not strong enough to generate enough electrons. Some have too much energy and are wasted. Under the ideal conditions, lab cells that use modern technology are able to be able to achieve just below 50% efficiency. They employ multiple junctions to capture photons of various energies.
A practical domestic panel may have an efficiency of approximately 15 percent. Single-junction, first-generation solar cells aren’t able to reach the 30 percent efficiency threshold established by Shockley-Queisser, or the laboratory record that is 47.1 percent. There are many factors that could affect the efficiency of solar cells, like how they’re constructed, angled and positioned and whether or not they’re in shadow or not, their cleanliness, and how cool they look.
Different types of Photovoltaic Cell
The majority of solar cells you will see today on roofs are simply silicon sandwiched. They have been “doped” to improve its electrical conductivity. These solar cells of the past are called first-generation by scientists to distinguish them from the two advanced technologies, the second and third generation. What’s the difference?
First-generation Solar Cells
The majority of the solar cell production comes of silicon wafers that contain the crystalline silicon (abbreviated “c-Si”), which are cut from huge ingots. This process can take as long as one month and is carried out in super-clean laboratories. Ingots may be one crystal (monocrystalline solar panels) or multi-crystalline (polycrystalline solar panels), depending on whether they have multiple crystals.
First-generation solar cells function as we’ve shown them in the picture above. They use one, simple connection between p-type and n-type layers of silicon, which is made from separate ingots. An n-type ingot is made by heating small pieces of silicon with very little (or antimony and phosphorus) as the dopant. In a p-type ingot, you would use boron. The junction is formed by fusing slices of p-type and the n-type silicon. There are additional bells and whistles that could incorporate into photovoltaic devices (like an antireflective layer, which increases light absorption and makes them blue), and metal connections that allow them to be wired into circuits. A simple p-n junction is what most solar cells depend on. This is the way photovoltaic solar cells function 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 have thin films solar cell wafers. They’re typically only one millimeter thick (around 200 micrometers, or 200 millimeters). They aren’t as thin than second generation solar cells (TPSC) which are thin-film solar cells which are 100 times thinner (several millimeters, or millimeters of meters deep). While most of them are made from silicon (a type of silicon known as amorphous silu or a-Si) that is where particles are distributed in random crystalline structures 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 can be laminated to windows, skylights as well as roof tiles. They also work well with all types of “substrates” which are the backers, such as metals and plastics. Second-generation cells are less flexible than first-generation ones, but they are still superior to them. A top-quality first-generation cell may achieve efficiency of 15-20 percent, however, Amorphous silicon is struggling to reach above 7%) and the top thin-film CdTe cells manage only about 11 percent efficiency, with CIGS cells are no better than 7-12%. This is one of the reasons why second-generation solar cells haven’t enjoyed much success on the marketplace despite their numerous advantages in practical use.
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 percent) as do first-generation cells. They are more likely to be made of substances other that silicon (making second-generation photovoltaics (also known as OPVs), or perovskite crystals. Additionally, they may feature multiple junctions (made by several layers of different semiconducting material). They will be less expensive and more efficient as well as feasible than first or second generation cells. The{ current|| record-setting} worldwide record in efficiency of the third generation solar cells is currently 28 percent. This was achieved in December of 2018 with a tandem perovskite-silicon solar cell.
How are they made?
Like you see the seven steps to creating solar cells.
1. Purify Silicon
Silicon dioxide gets heated by the electric oven. To let oxygen out carbon arcs can be applied. It results in carbon dioxide, and then molten silicon, which is used to make solar panels. Even when this produces silicon with only 1% impurity it’s not quite good enough. The floating zone technique lets the 100% pure silicon rods to pass through a hot zone many times in the same direction. This process removes all impurities from one end of the rod and permits it to be sucked out.
Second Stage: Making Single Crystal Silicon
Czochralski Method is the most well-known method for creating single-crystalline silicon. This involves placing a seed crystal composed of silicon in the melted silicon. This creates a boule or cylindrical ingot by turning the seed crystal while it is removed from the silicon melting.
Third Stage: Make cuts in the Silicon Wafers
Second stage boules are used for cutting silicon wafers by using circular saws. This is the best job to do with diamonds, which create pieces of silicon that could later be cut into squares or hexagons. Although saw marks are removed from slices, some companies leave them because they believe that more light could be absorption by a rougher solar cells.
Fourth Stage Doping
After cleaning the silicon at a earlier point, it’s possible to incorporate impurities to the silicon. Doping involves using a particle accelerator to ignite the phosphorus ions within the ingot. You can control the penetration depth by setting the speed of electrons. You can skip this step by employing the conventional method of inserting boron while making the cut.
Stage Five: Add electrical contacts
The electrical contacts are used to connect the solar system and act as receivers for the generated current. The contacts, which are made of metals like palladium and copper, have a thin structure enough to allow sunlight to penetrate the solar cell efficiently. The metal is either deposited on the cells that are exposed or by using a photoresistor to evaporate the metal. Thin strips of copper coated with tin is typically placed between the cells after the contacts are installed.
Stage Six Step Six: Apply the Anti-Reflective Coating
Since silicon has a shiny appearance, it is able to absorb up to 35% of sunlight. To decrease reflections, a coating of silicon can be applied. The process involves heating the substance until the molecules begin to boil off. The molecules then move onto the silicon and condense. A high voltage may also be used to eliminate the molecules and deposit them onto the silicon on the opposite electrode. This is referred to as “sputtering”.
Stage Seven Stage Seven: Seal and Encapsulate the Cell
They are sealed using silicon rubber or vinyl Acetate. Then, they are put in an aluminum frame with an aluminum back sheet and a glass cover.
What amount of electrical energy can solar cells produce?
Theoretically speaking, it’s quite a bit. In the meantime, let’s put aside solar cells and focus on the pure sun. Each square meter of Earth can receive up to 1,000 watts in solar power. That’s the estimated capacity of direct sunlight during a clear day. The solar rays are directed perpendicularly to Earth’s surface, resulting in the greatest luminosity.
Once we have adjusted for how our earth tilts and the seasons we will get 100-250 watts per square. 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. m (700-2500 units) of electricity. The potential of the sun’s energy in hotter regions is clearly higher than Europe. For instance, the Middle East receives between 50 and 100 percent more solar energy each season than Europe.
The problem is that 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: how big the area you can cover with cells will directly affect the power that you can produce. A typical solar panel comprised of 40 cells (each row of 8 cells) produces around 3-4.5 watts. However, a solar panel made up of 3-4 modules can generate several kilowatts. This is enough to meet a home’s peak energy needs.
How about Solar Panel Farms?
What is the best option if we require massive amounts of solar power? You will need between 500 and 1000 solar roofs in order to generate the same amount of electricity as a wind turbine that has a peak output of about 2 or 3 megawatts. To compete with nuclear or coal power plants (rated in the gigawatts), you would need around 1 000 solar rooftops. This is roughly 2000 wind turbines or perhaps one million. The calculations assume that solar and wind produce maximum output. While solar cells do produce clean, efficient energy, they cannot claim to be efficient use of land. The vast solar farms popping up all over the country only produce small amounts of power, usually about 20 megawatts or 1 per cent less than a large 2 gigawatt nuclear or coal plant. Shneyder Solar, a renewable company estimates that it will take approximately 22,000 panels to cover 12 hectares (30-acres) space to generate 4.2 megawatts. This is about the same amount that two wind turbines with large capacities. It also generates enough power to power 1,200 homes.
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