How do solar panels work? How many types of solar panels are there? What are the key parameters of solar panels? We would like to introduce all the key information about solar panels through this article to help you buy the best solar panels. We will also share our 10+ years of experience in the solar industry here.
- The power generation principle of solar cell modules
- characteristics of solar cell modules
- Classification of solar cells
- The composition of solar cell modules
- The Detailed explanation of key parameters of solar modules
The principle of solar cellsSolar cell modules are also called solar panels and photovoltaic modules. They are the core part of the solar power generation system and the most important part of the solar power generation system. Its function is to convert solar energy into electrical energy. The energy converter of solar photovoltaic power generation is a solar cell, also known as a photovoltaic cell. The principle of solar cell power generation is the photovoltaic effect. When sunlight shines on the solar cell, the cell absorbs light energy and generates photogenerated electron-hole pairs. Under the action of the built-in electric field of the battery, the photogenerated electrons and holes are separated, and the accumulation of opposite-signal charges occurs at both ends of the battery, that is, a “photogenerated voltage” is generated, which is the “photovoltaic effect”. If the electrodes are drawn on both sides of the built-in electric field and the load is connected, the load will have a “photo-generated current” flowing through, thereby obtaining power output. In this way, the light energy of the sun is directly converted into electricity that can be used. At the same temperature, the effect of light intensity on the solar panel: the greater the light intensity, the greater the open-circuit voltage and short-circuit current of the solar panel, and the greater the maximum output power. At the same time, it can be seen that the open-circuit voltage changes with the irradiation intensity. Not as obvious as the change of short-circuit current with irradiation intensity. Under the same light intensity, the effect of temperature on the panel: when the temperature of the solar cell increases, the output open-circuit voltage decreases significantly with the temperature, and the short-circuit current increases slightly, and the general trend is that the maximum output power decreases.
Features of solar cellsThe solar cell module has high photoelectric conversion efficiency and high reliability; advanced diffusion technology ensures the uniformity of conversion efficiency throughout the chip; ensures good electrical conductivity, reliable adhesion， and good electrode solderability; high precision The silk-screen printed graphics and high flatness make the battery easy for automatic welding and laser cutting.[/vc_column_text][vc_column_text]
Application of solar photovoltaic modules
Small Solar Power System1：The small solar panel power supply system ranges from 10 to 100W and is used for the daily electricity consumption of military and civilians in remote areas without electricity, such as plateaus, islands, pastoral areas, and border posts. 2：3-5KW home roof off-grid grid-connected power generation system. 3：Photovoltaic water pump: solve the drinking and irrigation of deep wells in areas without electricity.
TransportationBeacon lights, traffic/railway signal lights, traffic warning/signal lights, Yuxiang street lights, high-altitude obstruction lights, highway/railway wireless phone booths, unattended road class power supply, etc.
CommunicationSolar unattended microwave relay station, optical cable maintenance station, broadcasting/communication/paging power supply system, rural carrier telephone photovoltaic system, small communication machine, GPS power supply for soldiers, etc.
Oil, Ocean, WeatherOil pipeline and reservoir gate cathodic protection solar power system, life and emergency power supply of oil drilling platform, marine detection equipment, meteorological/hydrological observation equipment, etc.
Home Lighting Power SupplyGarden lights, street lights, portable lights, camping lights, mountaineering lights, fishing lights, black lights, tapping lights, energy-saving lamps, etc.
Photovoltaic power station10KW-50MW independent photovoltaic power station, wind-solar (diesel) complementary power station, various large parking plant charging stations, etc.
Solar BuildingCombining solar power generation with building materials will enable large buildings in the future to achieve self-sufficiency in electricity, which is a major development direction in the future
OtherMatching with cars: solar cars/electric cars, battery charging equipment, car air conditioners, ventilation fans, cold drink boxes, etc; Renewable power generation system of solar hydrogen production and fuel cell; Power supply for desalination equipment; Satellites, spacecraft, space solar power plants, etc. [/vc_column_text][vc_column_text]
Classification of solar cells and the characteristics of various types of solar cells
According to the different materials used, solar cells can be divided into silicon solar cells, multi-compound thin-film solar cells, polymer multilayer modified electrode solar cells, nanocrystalline solar cells, organic solar cells, plastic solar cells, among which silicon solar cells are the most mature and dominate the application.[/vc_column_text][dt_media_gallery_carousel image_border_radius=”0px” project_icon_border_width=”0px” arrow_bg_width=”36x” arrow_border_width=”0px” r_arrow_icon_paddings=”0px 0px 0px 0px” r_arrow_v_offset=”0px” l_arrow_icon_paddings=”0px 0px 0px 0px” l_arrow_v_offset=”0px” include=”2297,2298,2299,2300,2301,2302″][vc_column_text]
Silicon solar cellsSilicon solar cells are divided into three types: monocrystalline silicon solar cells, polycrystalline silicon solar cells， and amorphous silicon thin-film solar cells. Monocrystalline silicon solar cells have the highest conversion efficiency and the most mature technology. The highest conversion efficiency in the laboratory is 26%, and the efficiency in large-scale production is 20% (22% by 2022). It still occupies a dominant position in large-scale applications and industrial production, but due to the high cost of monocrystalline silicon, it is difficult to greatly reduce its cost. In order to save silicon materials, polycrystalline silicon and amorphous silicon thin films have been developed as monocrystalline silicon solar cells. replacement product. Compared with monocrystalline silicon, polycrystalline silicon solar cells have lower costs and higher efficiency than amorphous silicon cells. The highest conversion efficiency in the laboratory is 20%, and the conversion efficiency in industrial-scale production is 15% (as of 2022, it is 18%). Therefore, polycrystalline silicon cells will soon dominate the solar cell market.
Multi-compound thin-film solar cellsPolycrystalline thin-film batteries cadmium sulfide and cadmium telluride polycrystalline thin-film batteries are more efficient than amorphous silicon thin-film solar cells, and their cost is lower than that of single-crystal silicon batteries, and they are also easy to mass-produce. The environment causes serious pollution, therefore, it is not the most ideal substitute for crystalline silicon solar cells.
Polymer multilayer modified electrode solar cellsNanocrystalline chemical energy solar cells are newly developed, and their advantages lie in their cheap cost, simple process, and stable performance. Its photoelectric efficiency is stable above 10%, and the production cost is only 1/5 to 1/10 of that of silicon solar cells. The lifespan can reach more than 20 years. The research and development of such batteries have just started, and will gradually enter the market in the near future.
Nanocrystalline solar cellsOrganic thin-film solar cells are solar cells whose core parts are composed of organic materials. It is reasonable that everyone is unfamiliar with organic solar cells. More than 95% of solar cells in mass production today are silicon-based, while less than 5% are also made of other inorganic materials.
Organic solar cellsIn dye-sensitized solar cells, a pigment is attached to TiO2 particles and then soaked in an electrolyte. When the pigment is irradiated with light, free electrons and holes are generated. The free electrons are absorbed by TiO2, flow out from the electrode into the external circuit, pass through the electrical appliance, flow into the electrolyte, and finally return to the pigment. The low manufacturing cost of dye-sensitized solar cells makes them highly competitive. Its energy conversion efficiency is around 12%.
Plastic solar cellsPlastic solar cells use recyclable plastic films as raw materials and can be mass-produced through “roll-to-roll printing” technology, which is low-cost and environmentally friendly. However, plastic solar cells are not yet mature. It is expected that in the next 5 to 10 years, solar cell manufacturing technology based on organic materials such as plastics will mature and be put into use on a large scale.[/vc_column_text][vc_column_text]
What is a silicon solar cell? Introduction to the classification of silicon solar cellsSilicon solar cells refer to solar cells with silicon as the base material. The earliest silicon solar cells arose out of interest in using silicon for point-contact rectifiers. The rectifying properties of sharp metal contacts for various crystals were discovered as early as 1874. In the early days of radio technology, such crystal rectifiers were widely used as detectors in radio reception equipment. However, with the development of thermionic tubes, this crystal rectifier has been replaced by thermionic tubes, except that it is still used in the ultra-high frequency field. The most typical example of such a rectifier is the point contact of tungsten on the silicon surface. This technique has led to improvements in silicon purity and has led to hopes for a better understanding of silicon’s properties. Silicon solar cells have special design and material requirements compared to most other silicon electronic devices. In order to obtain high energy conversion efficiency, silicon solar cells not only require almost ideal passivation of the silicon surface, but also the bulk material properties must be of uniformly high quality. This is because some wavelengths of light must travel hundreds of micrometers in silicon to be absorbed, and the resulting carriers must still be able to be collected by the cell. Classification of silicon solar cells Silicon solar cells are solar cells based on silicon. According to the thickness of the silicon wafer, it can be divided into crystalline silicon solar cells and thin-film silicon solar cells. According to the crystalline form of the material, crystalline silicon solar cells are divided into two types: monocrystalline silicon (c-Si) and polycrystalline silicon (p-Si) solar cells; thin-film silicon solar cells are divided into amorphous silicon (a-Si) thin-film solar cells, microcrystalline silicon solar cells There are three types of crystalline silicon (c-Si) solar cells and polycrystalline silicon (p-Si) thin-film solar cells.
Monocrystalline silicon solar cellsMonocrystalline silicon solar cells have the highest conversion efficiency and the most mature technology. The highest conversion efficiency in the laboratory is 26%, and the efficiency in large-scale production is 20% (22% by 2022). It still occupies a dominant position in large-scale applications and industrial production, but due to the high cost of monocrystalline silicon, it is difficult to greatly reduce its cost. In order to save silicon materials, polycrystalline silicon and amorphous silicon thin films have been developed as monocrystalline silicon solar cells. replacement product.
Polycrystalline silicon solar cellsCompared with monocrystalline silicon, polycrystalline silicon solar cells have lower costs and higher efficiency than amorphous silicon cells. The highest conversion efficiency in the laboratory is 20%, and the conversion efficiency in industrial-scale production is 15% (as of 2022, it is 18%). Therefore, polycrystalline silicon cells will soon dominate the solar cell market.
Amorphous silicon thin-film solar cellsAmorphous silicon thin-film solar cells are low-cost, light-weight, easy to mass-produce, and have great potential. Amorphous silicon, its atomic structure is not as regularly arranged as crystalline silicon, but a semiconductor with an amorphous crystal structure. Amorphous silicon belongs to the direct band system material, which has a high absorption coefficient of sunlight. Only a 1 μm thick film can absorb 80% of sunlight. Amorphous silicon thin-film solar cells came out in 1976, due to the shortage of silicon raw materials and rising prices, which promoted the technology of using silicon efficiently and the development of amorphous silicon thin-film solar cells. The low cost of amorphous silicon thin-film cells makes up for their lack of photoelectric conversion efficiency. However, due to a large number of defects in amorphous silicon, the efficiency of the prepared solar cell is relatively low, and due to the photoelectric efficiency decline effect caused by its material, the stability is not high, which directly affects its practical application. Microcrystalline silicon (μc-Si) thin-film solar cells are also unstable due to the photoelectric efficiency decay effect. Development is limited. Polycrystalline silicon thin-film solar cells are a hot spot in solar cell research in recent years. Although polysilicon is an indirect bandgap material and is not an ideal thin-film solar cell material, with the continuous development of light trapping technology, passivation technology, and carrier confinement technology, it is entirely possible to prepare high-efficiency and inexpensive polysilicon thin-film solar cells.[/vc_column_text][vc_column_text]
Detailed explanation of the composition and function of each part of monocrystalline silicon solar cellsMonocrystalline silicon solar cells are solar cells that use high-purity monocrystalline silicon rods as raw materials and are currently the fastest-developed solar cells. At present, the structure and production process of monocrystalline silicon solar cells have been finalized, and the products have been widely used in space and ground.
- Tempered glass: the function of tempered glass is to protect the main body of power generation (such as a battery), and the selection of tempered glass is required. First, the light transmittance must be high (generally more than 91%); second, ultra-white tempering treatment.
- EVA: EVA is used to bond and fix the tempered glass and the main body of power generation (such as solar cells). The quality of the transparent EVA material directly affects the life of the module. The EVA exposed to the air is easy to age and turn yellow, thus affecting the light transmittance of the module. In addition to the quality of EVA itself, the lamination process of module manufacturers is also very influential. For example, the adhesion of EVA is not up to standard, and the bonding strength of EVA to tempered glass and backplane is not enough, which will cause EVA to age prematurely. , affecting component life.
- Solar cell: The main function of solar cells is to generate electricity. The mainstream in the power generation market is crystalline silicon solar cells and thin-film solar cells, both of which have their own advantages and disadvantages. Crystalline silicon solar cells have relatively low equipment costs, high consumption, and cell costs, and high photoelectric conversion efficiency; thin-film solar cells are suitable for power generation in outdoor sunlight, with relatively high equipment costs, low consumption, battery costs, the photoelectric conversion efficiency is more than half that of crystalline silicon cells, but the low-light effect is very good, and it can also generate electricity under ordinary light, such as solar cells on calculators.
- Backboard: The function of the backplane is to seal, insulate, and waterproof (generally, TPT, TPE, and other materials must be resistant to aging). Component manufacturers have a 25-year warranty. Tempered glass and aluminum alloy are generally no problem, the key is whether the backplane and silicone can meet the requirements.
- Aluminum Frame: The aluminum frame plays a certain role in sealing and supporting.
- Junction box: The junction box protects the entire power generation system and acts as a current transfer station. If the module is short-circuited, the junction box automatically disconnects the short-circuit battery string. What prevents the entire system from burning out is the selection of the most critical diode in the junction box. According to the cells in the module Different types of diodes correspond to different diodes.
- Silica gel: Silicone acts as a seal to seal the junction between the component and the aluminum alloy frame, the component， and the junction box. Some companies use double-sided tape and foam instead of silicone. Silica gel is widely used in China, the process is simple, convenient, easy to operate, and the cost is very low.
Solar module electrical parametersTaking a certain line of brand polycrystalline components as an example, the electrical parameters are as follows: Standard Test Conditions[STC]: irradiance 1,000 W/m2 ; AM 1,5; module temperature 25℃. Measuring uncertainty of power is within士3%. Tolerance of Pmpp: 0-+3%. Certified in accordance with IEC61215, IEC61730-1/2.
Maximum Power PmaxPm=Im*Vm, corresponding to the vertex of the power parabola in the figure below. The parabola is the power curve and the other is the UI curve. Component parameter nominal, generally based on “Standard Test Conditions STC”. With changes in environmental conditions such as temperature and irradiance, the corresponding parameters of the components will change. In addition, the power characteristic curve of the module is a “quasi-parabola”, which has the highest point, which is also the working point that the inverter MPPT “Maximum Power Point Tracking” needs to find.
Power tolerance“0~+5” means positive tolerance. Such as 265W solar modules, the power range between 265W to 270W is qualified.
Maximum power point operating voltage VMIt corresponds to the abscissa corresponding to the vertex of the power parabola in the above figure, which represents the working voltage of the component at the maximum power.
Maximum power point operating current IM
Open circuit voltage VocThe open-circuit voltage is the terminal voltage when the solar cell is not connected to the load, the intersection of the UI curve and the abscissa in the above figure. The value multiplied by the number of input components of the inverter should be less than the maximum DC voltage Vdcmax of the inverter.
Short circuit current IscThe short-circuit current is the output current when the cell is short-circuited, the focus of the UI curve and the ordinate in the above figure.
Solar Module EfficiencyIn theory, solar modules with the same size and maximum power must have the same efficiency. When the irradiance is 1000W/m2, the power received on a 1.627 square meter solar module is 1627W, and the efficiency is 16.3% when the output is 265W and 16.6% when the output is 270W.
Mechanical parameters of solar modules
Solar CellThe Solar cell is the smallest unit of photoelectric conversion, and the commonly used size is generally 125mm*125mm or 156mm*156mm. By 2022, the size of the largest solar cell is 210*210mm, and the maximum power solar panel can reach 600W. The working voltage of the solar cell is about 0.5V, and generally cannot be used alone. After the solar cells are packaged in series and parallel, they become photovoltaic modules.
Number of solar cellsFor example, a 300W monocrystalline solar panel is composed of 60 156*156mm solar cells.
Solar module sizeThe size of the 340W to 390W solar panel in the above picture can be 1956*992*40mm and 1980*1002*40mm. Usually, the size of the solar panels can also be customized if the quantity is sufficient.
Solar Module WeightThe weight per square meter of polycrystalline silicon modules commonly found on the market is about 12 kilograms (about 19 kilograms for a single solar module with 60 solar cells).
BackboardPerformance requirements for crystalline silicon cell module backboards typically include:
- Has good weather resistance
- No change in lamination temperature
- Bonds firmly to viscous materials
- Must have low thermal resistance and prevent the ingress of water or water vapor
FrameFlat-panel components must have a frame to protect the components and facilitate the connection and fixation of the components. The main materials of the frame are stainless steel, aluminum alloy, rubber, and reinforced plastic. Conventional photovoltaic frames are generally made of aluminum materials. The frame structure should have no protrusions to avoid the accumulation of water, dust, or other objects. The thickness of its surface oxide layer is greater than 10μm, which can ensure that it will not be corroded in the outdoor environment for more than 30 years, and it is firm and durable.
Junction BoxThe positive and negative poles of the components are connected with the designed cables in the junction box and connected with the external circuits. The junction box has the following main characteristics:
- The shell has strong anti-aging and UV resistance
- Meet the requirements of use in harsh outdoor environmental conditions