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 sends out free, clean energy? The Sun, a smoldering nucleus, has enough fuel to provide power to our Solar System for five billion more years. Solar panels can transform this energy into an inexhaustible power source.
Although solar power may seem unusual or out of the ordinary, it is already very common. A solar-powered watch or calculator for your pocket might be at your fingertips. A lot of gardeners use solar-powered lights. Solar panels are often seen on spacecrafts and satellites. NASA one of the American space agency, even designed a solar-powered plane. Global warming is threatening the environment and it is likely that solar energy will become an increasingly significant source of renewable energy. How do they work?
What is the maximum amount of solar power we can get from the Sun?
It’s amazing how solar power operates. Each square meter of Earth receives on average 163 watts solar energy. We’ll discuss this figure in greater detail later. This means that you could put an electric table lamp of 150 watts on every square inch of Earth and utilize the sun’s energy to illuminate the entire planet. Another way to put it this way, if we covered only 1percent of the Sahara desert in solar panel, then we would generate enough solar energy to power the entire planet. The best aspect of solar energy is that it has a large amount of it, more than we could ever need.
There’s a drawback. The Sun’s energy arrives as an amalgamation of light and heat. Both are vital. Light is what helps plants grow and provide us with food. Heating keeps us warm enough to live. However, we cannot utilize the sun’s heat or light directly to solar power a TV or car. It is important to convert solar energy into another form of energy is more readily available such as electricity. That’s precisely what solar cells do.
In Summary:
- The cell’s surface gets illuminated by sunlight
- Photons carry energy through the cells’ layers.
- Photons transfer their energy to electrons that reside in lower layers.
- The energy used by electrons to let electrons escape the circuit and jump back into the upper layers.
- The power of the device is generated by electrons that move through the circuit.
What are solar cells?
Solar cells are electronic devices which absorbs sunlight and converts it into electric energy. It’s roughly the same size as an adult’s hand and is octagonal in shape and colored in a bluish-black color. Many 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 individual solar cells per roof) or chopped into chips (to provide power to small devices like digital watches and pockets calculators).
The cells in solar panels work similar ways to a battery. But, unlike battery’s cells, which generate electricity using chemicals, solar panels’ cells are able to capture sunlight and produce electricity. Photovoltaic cells (PV) are able to make electricity from sunlight (photo comes in the Greek word that means 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 often thought of as tiny particles known as photons. The sun’s beam is similar to an enormous yellow firehose that shoots trillions of trillions. Solar cells can be placed within the path of these photons to capture them , and later convert them into an electric current. Every cell can produce a few volts, so the function of solar panels is to combine the energy of multiple cells to create a useful amount of electric current 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 and is found in sand). However, as we’ll soon learn, other materials might also be viable. The sun’s energy blasts electrons from the solar cells when it is exposed to sunlight. These electrons can later be used to power any electronic device that is powered by electricity.
How are solar cells made?
Silicon is the main material from which microchips’ transistors (tiny switches), are made. Solar cells also work similarly. The term semiconductor refers to a form of material. Conductors are substances that permit electricity to flow easily through them, including metals.
Other materials, such as plastics and wood, don’t permit electric current to pass through; they’re known as insulation. Semiconductors such as silicon are not conductors or insulators. However we can make them conduct electricity in certain conditions.
A solar cell is composed consisting of two different layers of silicon, each of which has been treated or doped so that electricity can move through it in a specific way. The lower layer contains slightly lower electrons since it’s doped. The layer is known as positively-type silicon, also known as p-type. It is awash with electrons, which is why it is negatively charged. To provide the layer with an excess of electrons, it is doped to the other direction. This is referred to as negative-type or n-type silicon. (Read more about semiconductors and doping in our articles about transistors and integrated circuits.
A barrier is created by the interplay between two layers of n-type as well as p-type silica. This barrier forms the essential border where both types of silicon come together. It is unaccessible to electrons so even if the silicon sandwich is connected to a flashlight, the current won’t flow and the lightbulb won’t switch on. If you shine light onto the sandwich, it will produce some amazing results. The light could be considered as{ a|| an evaporation} flow or “light particles” that are energetic, and are referred to as photons. Photons that pass through the sandwich release their energy to the silicon atoms when they move through. The energy incoming knocks electrons out of the lower, p type layer. They then cross barriers to get into the n-type above and then flow through the circuit. The greater the amount of light then the more electrons leap up and more electricity will flow.
How efficient are Solar Panels?
The law of conservation energy is a basic principle of physics, stipulates that energy cannot be produced or made to disappear into thin air. It is only possible to transform it from one type of energy into another. A solar cell cannot produce more electricity than it receives in light every second. We will discover that the majority of solar cells convert 10 to 20 percent of the energy they receive to electricity. The theoretical maximum efficiency of a one-junction solar cell is approximately 30 percent. This is known by The Shockley Queisser Limit. Since sunlight has a broad variety of wavelengths and energies one-junction silicon solar cell can only capture photons within a narrow frequency range. The remainder of the photons are wasted. Some of the photons hitting a solar cell aren’t strong enough to create enough electrons. Others have too much energy and go to waste. In the most ideal conditions, lab cells equipped with modern technology are able to be able to achieve just below 50% efficiency. They use multiple junctions to capture photons with various energy levels.
A practical domestic panel may have an efficiency of approximately 15 percent. First-generation solar cells with a single junction aren’t able to reach the 30 percent efficiency limit that was set by Shockley-Queisser or the record set by the laboratory that is 47.1 percent. There are many factors that can affect the nominal effectiveness of solar cells, like how they’re built, angled and placed and whether or not they’re in shadow, how clean they are and how cool.
Different types of Photovoltaic Cell
A majority of the solar cells that are on roofs are simply silicon sandwiches. They have been “doped” to enhance the electrical efficiency of their cells. These classic solar cells are referred to as first-generation by researchers to differentiate them from two newer technology, second- and third-generation. What’s the difference?
First-generation Solar Cells
More than 90 percent of the world’s solar cells are made of wafers made up of the crystalline silicon (abbreviated “c-Si”), that are then cut out of large ingots. This process can take as long as one month and is carried out in super-clean laboratories. Ingots can be one crystal (monocrystalline solar panels) or multi-crystalline (polycrystalline solar panels) dependent on whether they contain multiple crystals.
First-generation solar cells function the way they are shown in the box above. They use one, simple junction between n and p-type layers of silicon. It is made from separate ingots. The n-type ingot is created by heating tiny pieces of silicon using tiny amounts (or antimony and phosphorus) as dopants. A p-type one would use boron. The junction is created by fusing slices of p-type and n-type silicon. There are some additional bells and whistles which can add to the photovoltaic cell (like an antireflective coating, which improves light absorption and creates their blue hue) as well as metal connections so they can be connected to circuits. A simple p-n junction is what most solar cells are relying 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 produced electricity.
Second-generation Solar Cells
The most common solar cells consist of thin of solar wafers. They’re usually only tiny fractions of millimeters in thickness (around 200 micrometers, or 200 millimeters). They aren’t as thin as second-generation solar cells (TPSC), or thin-film solar cells, which are 100 times smaller (several millimeters or millionths of a meter deep). Though the majority are made from silicon (a form known as amorphous siliu (a-Si)) that is where the atoms are placed in random crystal structures however, some are made of different materials like Cd-Te, cadmium-telluride as well as copper-indium gallium diselenide, (CIGS).
The second generation cells are thin and light and are able to be laminated with skylights, windows and roof tiles. They are also compatible with all types of “substrates” which are backers like plastics and metals. Second-generation cells are less flexible than the first generation ones, however they still perform better than the first generation. The top first-generation cells can achieve efficiency of 15-20 percent, however, amorphous silicon struggles to get over 7%) While the most efficient thin-film CdTe cells manage only about 11 percent efficiency, with CIGS cells are no better than 7-12%. This is among the reasons why second-generation solar cells have not enjoyed much success on the market , despite their numerous advantages.
Third-generation Solar cells
These new technologies combine the best qualities of the first and second generation cells. They promise high efficiency (up to 30 percent) similar to first-generation cells. They tend to be made of different materials than silicon (making second-generation photovoltaics, OPVs) or perovskite crystals. Furthermore, they could have multiple junctions (made by multiple layers from different semiconducting material). They would be more affordable as well as more efficient and 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 record was set in December of 2018 with an equidistant perovskite solar cell.
How are they made?
Like you see, there are seven steps in the process of creating solar cells.
Stage 1: Purify Silicon
The silicon dioxide is heated up in an electric furnace. To let oxygen out, a carbon arc can be applied. It results in carbon dioxide, and then molten silicon, which can be utilized to create solar cells. Even the silicon is produced with only 1% impurity it’s still not adequate enough. The floating zone technique is a method that permits the 99% pure silicon rods to pass through a zone that is heated several times in the same direction. The process eliminates all impurities from one end of the rod, allowing it to be cleaned.
2. Constructing Single Crystal Silicon
Czochralski Method is the most popular method for creating single-crystalline silicon. This involves placing a seed crystal composed of silicon inside melted silicon. The result is a boule or cylindrical ingot by turning the seed crystal when it is being removed from the silicon melt.
Third Stage: Make cuts in the Silicon Wafers
A second boule stage is utilized to slice silicon wafers with circular saws. This is the best job to do with diamond, which produces pieces of silicon that could be further cut into hexagons or squares. Although cutting marks of the saw are eliminated from cut wafers, some producers keep them in place because they believe that more light may be absorbed by rougher solar cell efficiency.
Stage 4: Doping
After cleaning the silicon at a earlier stage, it is possible to add impurities back into the material. Doping involves the use of particles accelerators to ignite the phosphorus ions within the ingot. You can regulate the penetration depth by altering the speed of electrons. You can avoid this step by employing the conventional technique of inserting boron into making the cut.
Step Five: Add the electrical contacts
Electrical contacts are used as a connection between the solar cells and act as receivers of the electricity generated. 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 exposed cells or it is evaporated by vacuum using a photoresist. The thin strips of copper lined with Tin is typically placed between cells after the contacts are installed.
Step Six Step Six: Apply the Anti-Reflective Coating
Because it is shiny, it can be able to reflect as much as 35% sunlight. To decrease reflections, a layer of silicon will be put on it. This is accomplished by heating the surface until the molecules begin to boil off. The molecules then move onto the silicon and begin to condense. A high voltage can also be used to eliminate 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
Solar cells sealed by silicon rubber or ethylene vinyl Acetate. Then, they are put inside an aluminum frame, with the back sheet as well as a glass cover.
What amount of electrical energy can solar cells produce?
Theoretically speaking, it’s a lot. At the moment, we should forget about solar cells and instead focus on the pure sun. Every square meter of Earth can absorb up to 1,000 watts in solar energy. That’s the estimated capacity of direct sunlight on a clear day. The sunlight’s rays are fired perpendicularly to Earth’s surface and provide the maximum luminosity.
When we adjust to how our earth tilts as well as the seasons we should receive between 100 and 250 watts per sq. meters in northern latitudes even on cloudless days. This translates to about 2-6 kWh per daily. Multiplying the entire year’s production results in 700-2500 kWh for every sq. meters (700-2500 units) of electricity. The potential of the sun’s energy in warmer regions is evidently higher than Europe. For instance the Middle East receives between 50 and 100 percent more solar energy per season than Europe.
Unfortunately, solar cells are only 15 percent efficient, so we only get 4-10 watts per square foot. This is why panels with solar power must be large: how big the area you can cover by cells will affect the power you generate. The typical solar panel comprised with 40 solar cells (each row of eight cells) can produce around 3-4.5 watts. But a solar panel comprised 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?
What if we need to generate huge amounts of solar energy? You will need between 500 to 1000 solar roofs to generate approximately the same quantity of electricity as a large wind turbine with the peak power of around 2.5 or 3.0 megawatts. In order to compete with huge coal or nuclear power stations (rated as gigawatts) the requirement is approximately 1 000 solar rooftops. This is equivalent to approximately 2000 wind turbines, and possibly one million. These comparisons assume that our solar and wind produce maximum output. Even though solar cells can produce clean, efficient energy, they cannot claim to be efficient in the use of land. Even the huge solar farms being built across the country produce modest amounts of power, typically around 20 megawatts , or one per cent less than a large 2 gigawatt nuclear or coal plant. Shneyder Solar, a renewable business, estimates that it takes approximately 22,000 panels to cover 12 ha (30-acres) surface to generate 4.2 megawatts. This is roughly the same that two wind turbines with large capacities. It also generates enough energy to power 1200 homes.
Top Residential Solar Companies
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