The meaning of solar cells or PV.
Solar cells or PV have many names, such as solar cells or photovoltaic cells. Which have originated from the word Photovoltaic which is separated into photo Mean light and volt Means voltage, when the term is combined, refers to the process of generating electricity from the incident light on an object capable of converting light energy directly into electrical energy. This concept has been discovered since A.D. 1839, but solar cells were not built until in the year. Solar cells were invented in 1954 and were used as a source of energy for satellites in space 1959. So it can be concluded that solar cells are inventions made from semiconductors such as silicon, Gallium Arsenide, Indium Phosphide, Cadmium. Telluride) and Copper Indium Diselenide, etc. When exposed to direct sunlight, solar cells will transform into an electric carrier and will be separated into positive and negative electric charges in order to create voltage at both poles of solar cells when conducting polar Blue of photo-voltaic devices connected to a DC electric current will flow into those devices can run.
Types of solar cells
Divided according to the material used into 3 main types which are
- Solar cells made from single crystalline silicon (also known as Monocrystalline Silicon solar cells and collective crystals) (Polycrystalline Silicon Solar Cell) is a hard and very thin silicon sheet.
- Solar cells made from Amorphous Silicon solar cells, thin film only 0.5 microns (0.0005 mm), very light weight and 5-10% efficiency.
- Solar cells made from other semiconductors such as Gallium Arsenide, Cadmium Tellide and Copper Indium Diselenide etc. There are both Single Crystalline and Polycrystalline solar cells made from Gallium R. Zenide will provide up to 20-25% efficiency.
Structure of solar cells
The most popular structure is the PN joint of the semiconductor, the cheapest and most abundant semiconductor in the world, silicon, which is then used to make solar cells by smelting and going through the purification process until to be crystallized and then taken through the process of diffusion of contaminants to create the joints. When adding phosphorus, it is a semiconductor type N. (Because the electrically conductive electrons have a negative charge) and when added with boron doped, it is a P type semiconductor (Because conductive with Hole, which has a positive charge), therefore, when the P and N semiconductors are connected, the PN joints will be formed. The structure of silicon solar cells may have a circular or square thickness of 200. -400 microns (0.2-0.4 mm) The light-receiving surface will have a permeable layer with electrical conductivity. The front electrode that receives light looks like a herringbone to get the most light-receiving area. Electric fence behind a full metal surfaces.
General working principles of solar cells
When sunlight hits the solar cell, negative and positive electric carriers are created, such as electrons and holes. The PN joint structure acts to create an electric field inside the cell to separate the electron carrier to the negative pole. And the Hole carrying electricity to the anode (Usually at the base uses a P type semiconductor, the back electrode is an anode, while the light side uses an N type semiconductor, so the electrode is a negative pole) resulting in a DC voltage at both electrodes when connected to the end. The electrical circuit will cause current to flow.
Silicon solar cells with a diameter of 4 An inch will give about 2-3 electricity. Amperes and provide an open circuit voltage of about 0.6 Volts, because the current from the solar cell is not much, so in order to get enough power for use, many solar cells are connected together to be called Solar Modules. The connection of a solar panel depends on whether the current or voltage is needed.
- Parallel solar panel connection will increase the electric current.
- Connecting the serial solar panel will result in higher voltages.
Solar cell production process
- Solar cells made from single crystal or monocrystalline silicon. There are production procedures as follows
- Take the smelting silicon to melt into a liquid at a temperature of about 1400 ° C and then pull the crystal out of the liquid by slowly lowering the temperature until the silicon crystal is solid and then cut into glasses.
- The crystalline silicon crystals are infused with various additives to create the PN joints in the diffusion furnace with a temperature of about 900-1000 ° C and then to create an anti-reflective layer with an oxidation furnace that has high temperatures
- Make a two-side electrode by plastering the metal vapor under vacuum. When finished, it must be tested with artificial sunlight and measured for electrical properties.
- Solar cells made from crystalline silicon (Polycrystalline) has the production process as follows
- Take the silicon that has been smelt and melt into a liquid and then pour it into the mold. When the silicon hardens, it becomes a silicon crystal bar and then cut into glasses.
- After that, it is dissolved with various impurities and bipolar electrode by the same method as the solar cell made from single crystal silicon.
- Solar cells made from amorphous silicon. There are production procedures as follows
- To decompose the silane gas into amorphous silicon using a device called Plasma CVD (Chemical Vapor Deposition), which is passing the silane gas into the glass cover with a high frequency electrode to make the gas separated to form a plasma and silicon atoms fall on the base or stainless steel placed in the glass cover, forming a thin film up to 1 micron (0.001 mm).
- While decomposing, the silane gas is mixed with phosphine and diboren gas into the impurities to create a PN joint for use as a solar cell structure.
- Electrode production is often done with translucent electrodes made from ITO (Indium Tin Oxide).
- Solar cells made from Gallium arsenide. There are production procedures as follows
- The process of growing crystalline layer using a tool is a liquid phase crystal growing furnace (LPE; Liquid Phase Epitaxy).
- The procedure for growing the crystalline layer that is connected to the PN using a molecular beam crystallizer (MBE; Molecular Beam Epitaxy).
Outstanding characteristics of solar cells
- Uses natural energy, sunlight, which is clean and pure, does not cause reactions that will poison the environment
- Is the use of energy from natural sources that are worthwhile and never run out of this world
- Can be used to produce electrical energy anywhere in the world and to use electrical energy directly
- There is no need to use any fuel other than solar energy, including combustion, therefore does not cause air and water pollution.
- No waste during use therefore there is no emissions to destroy the environment.
- No noise and no movement during use, so no noise pollution
- Is a stationary equipment and does not have any moving parts during operation, so it does not wear out
- Requires very little maintenance
- Long service life and stable performance
- Lightweight, easy to install, move easily and quickly
- Due to the modular nature, they can be assembled to the desired size.
- Help reduce the accumulation of various gases in the atmosphere such as carbon monoxide, sulfur dioxide, hydrocarbons and nitrogen oxides, etc., which is a result of combustion of fuels such as oil, coal and natural gas, all affecting the environment resulting in greenhouse effect. Global warming is caused by acid rain and toxic air etc.
Important equipment of the electricity generation system from solar cells.
Solar cells produce direct current, so electricity can only be used with DC power supplies. If you want to use it with electrical devices that use alternating current or store energy for further use, it must be combined with other devices as a whole. Into a system that produces electricity from solar cells. The important equipment are as follows
- Solar Module transforms solar energy into electrical energy which is direct current and has watts. Many solar cells are connected together in rows or in a solar array. In order to get the electrical energy to be used as needed, the serial connection will increase the voltage and the parallel connection will increase the electric power if the geographical location is different, it will affect the amount of the average peak sun hours per day, as well as temperature can affect the production of electricity at higher temperatures, power generation is reduced.
- Charge Controller charges the electricity produced by the solar panel into the battery and controls the charge to the right amount for the battery to extend the useful life of the battery including the supply current. Therefore, the operation of the charge controller is that when the electric charge is fully charged into the battery, it will stop or reduce the higher electricity (and it often has the ability to cut the electricity supply to the electrical equipment in case the battery voltage decreases). Solar power systems use charge controllers only when electrical energy is stored in the battery.
- Battery acts as a collector of electrical energy produced from solar panels to use when needed, such as when there is no sunlight, night time or other applications. There are many types and sizes of batteries to choose from appropriate
- Inverters convert electrical energy from direct current (DC) produced from solar panels into AC power so that it can be used with AC devices, divided into 2 types: Sine Wave Inverter. With all kinds of AC equipment and Modified Sine Wave Inverter can be used with AC motor without electronic ballast and fluorescent lamp
- Lightning protection systems protect against damage to electrical equipment when lightning strikes or induction leads to high voltages in general systems. Often this device is not used. It is used for large and important systems only. To have an effective grounding system as well