I am interested in meeting people who are in constant search. Among them is my colleague Alexander, a fan of electric vehicles. You can find information about its development and the formation of an electric vehicle fleet in Ukraine here. But, oddly enough, in addition to the electric car, he is also interested in solar panels with high efficiency.
After asking him a question, I had to sweat a little, and that's what came of it.
Silicon crystal PV modules
The efficiency of the cells of silicon modules today is about 15 - 20% (polycrystals - single crystals). This figure may soon be increased by several percent. For example, SunTech Power, one of the world's largest manufacturers of crystalline silicon modules, announced its intention to launch PV modules with an efficiency of 22% within two years.
Existing laboratory samples of monocrystalline cells show a productivity of 25%, polycrystalline - 20.5%. The theoretical maximum efficiency of silicon single-junction (p-n) elements is 33.7%. Until it is achieved, and the main task of manufacturers, in addition to increasing the efficiency of cells, is to improve the production technology, to reduce the cost of PV modules.
Sanyo's PV modules manufactured using HIT technology (Heterojunction with Intrinsic Thin layer) using several silicon layers, similar to tandem multilayer cells, are positioned separately. The efficiency of such elements made of single-crystal C-Si and several layers of nano-crystalline nc-Si is 23%. This is the highest efficiency of the cells of serial crystalline modules to date.
Thin Film Solar Cells
Several different technologies have been developed under this name, the performance of which can be said as follows.
Today, there are three main types of inorganic film solar cells - silicon films based on amorphous silicon (a-Si), films based on cadmium telluride (CdTe), and copper-indium-gallium selenide (CuInGaSe2, or CIGS) films.
Efficiency of modern thin-film solar panels based on amorphous silicon about 10%, photomodules based on cadmium telluride - 10-11% (manufactured by First Solar), based on copper-indium-gallium selenide - 12-13% (Japanese solar modules SOLAR FRONTIER). Efficiency indicators of serial cells: CdTe have an efficiency of 15.7% (MiaSole modules), and CIGS cells produced in Switzerland - 18.7% (EMPA).
The efficiency of individual thin-film solar cells is much higher, for example, data on the performance of laboratory samples of amorphous silicon cells - 12.2% (United Solar), CdTe cells - 17.3% (First Solar), CIGS cells - 20.5% ( ZSW). So far, solar converters based on thin films of amorphous silicon lead in terms of production among other thin-film technologies - the volume of the world market for thin-film Si cells is about 80%, solar cells based on cadmium telluride - about 18% of the market, and copper-indium-gallium selenide - 2% market.
This is due, first of all, to the cost and availability of raw materials, as well as higher stability of characteristics than in multilayer structures. Note that silicon is one of the most abundant elements in the earth's crust, while indium (CIGS elements) and tellurium (CdTe elements) are scattered and mined in small quantities. In addition, cadmium (CdTe cells) is toxic, although most manufacturers of such solar panels guarantee complete recycling of their products.
The further development of photoelectric converters based on inorganic thin films is associated with the improvement of production technology and stabilization of their parameters.
And yet, based on the stability of characteristics and relatively inexpensive prices, preference is given to solar cells made on the basis of amorphous silicon. But the efficiency, as we can see, is no more than 12.2%.
Higher results have been achieved so far in laboratory conditions. An example is the development of engineers from the Swiss National Laboratory of Materials, Science and Technology EMPA, who managed to achieve a high efficiency factor (20.4%) working with a new generation of thin-film solar panels. The new panels are based on flexible polymers from the complex compound CIGS or copper indium gallium (di) selenid (copper indium gallium (di) selenide).
Posted date: 30.04.2015
In our time, renewable energy, especially where solar energy is used, is developing very intensively. In this regard, an active search for methods and devices continues, increasing productivity existing systemsallowing the most efficient conversion of solar energy into electricity. Two areas can be distinguished here - direct conversion of solar radiation into electricity, and multiple conversion of solar energy - into heat, then into mechanical workand then into electricity. So far, better results have been achieved in the second direction - industrial solar plants with concentrators, turbines or Stirling engines show excellent productivity of solar energy conversion. Thus, at a solar station operating in New Mexico with solar concentrators and Stirling engines, the output efficiency was obtained, taking into account the energy consumption for the orientation system, etc. - 31.25%.
But such solar power plants are extremely complex and expensive, effective in conditions of very high solar insolation, and have not yet received sufficient development in the world. Therefore, direct converters of solar radiation - solar panels , occupy a leading position in the world of solar energy in terms of installations and range of applications. The productivity of serial industrial solar panels today, depending on the technology, ranges from 7 to 20%. Technologies do not stand still, they are developing and improving, new cells are already being developed and tested, at least twice as productive as existing ones. Let's try to briefly consider the main directions of development of photovoltaic panels, technologies and their productivity.
The overwhelming majority of cells of solar converters of modern serial photomodules are made of monocrystalline (C-Si), or polycrystalline (MS-Si) silicon. Today, such silicon photovoltaic modules occupy about 90% of the market for photovoltaic converters, of which about 2/3 falls on polycrystalline silicon and 1/3 on monocrystalline silicon. Next come solar modules, the photocells of which are made using thin-film technology - by the method of deposition, or sputtering of photosensitive substances on various substrates. A significant advantage of modules made from these elements is the lower cost of production, because they require about 100 times less material compared to silicon wafers. And so far, the least represented are multijunction solar cells from the so-called tandem, or multijunction cells.
Market shares of photovoltaic panels of various technologies:
Silicon crystal PV modules.
The efficiency of the cells of silicon modules today is about 15 - 20% (polycrystals - single crystals). This indicator as a whole may soon be increased by several percent. For example, SunTech Power, one of the world's largest manufacturers of crystalline silicon modules, has announced its intention to launch PV modules with an efficiency of 22% within the next couple of years. Existing laboratory samples of monocrystalline cells show a productivity of 25%, polycrystalline - 20.5%. The theoretical maximum efficiency of silicon single-junction (p-n) elements is 33.7%. Until it is achieved, and the main task of manufacturers, in addition to increasing the efficiency of cells, is to improve the production technology, to reduce the cost of PV modules.
Sanyo's PV modules manufactured using HIT technology (Heterojunction with Intrinsic Thin layer) using several silicon layers, similar to tandem multilayer cells, are positioned separately. The efficiency of such elements made of single-crystal C-Si and several layers of nano-crystalline nc-Si is 23%. This is the highest indicator of the efficiency of cells of serial crystalline modules for today, a kind of nano solar batteries.
Thin film solar cells efficiency.
This name means several different technologies, the performance of which will be briefly discussed. Currently, there are three main types of inorganic film solar cells - silicon films based on amorphous silicon (a-Si), films based on cadmium telluride (CdTe), and copper-indium-gallium selenide films (CuInGaSe2, or CIGS). The efficiency of modern thin-film solar cells based on amorphous silicon is about 10%, photomodules based on cadmium telluride - 10-11% (First Solar), based on copper-indium-gallium selenide - 12-13% (Japanese solar modules SOLAR FRONTIER). Efficiency indicators of pre-serial cells: CdTe have an efficiency of 15.7% (MiaSole modules), and CIGS cells have an efficiency of 18.7% (EMPA). The efficiency of individual thin-film solar cells is much higher, for example, data on the performance of laboratory samples of amorphous silicon cells - 12.2% (United Solar), CdTe cells - 17.3% (First Solar), CIGS cells - 20.5% ( ZSW). So far, solar converters based on thin films of amorphous silicon are leading in terms of production among other thin-film technologies - the volume of the world market for thin-film Si cells is about 80%, solar cells based on cadmium telluride - about 18% of the market, and copper-indium-gallium selenide - 2% market. This is due, first of all, to the cost and availability of raw materials, as well as higher stability of characteristics than in multilayer structures. After all, silicon is one of the most abundant elements in the earth's crust, while indium (CIGS elements) and tellurium (CdTe elements) are scattered and mined in small quantities. In addition, cadmium (CdTe cells) is toxic, although all manufacturers of such solar modules guarantee the complete disposal of their products. Also, the degradation process in the elements of thin-film modules proceeds faster than crystalline cells. The further development of photoelectric converters based on inorganic thin films is associated with the improvement of production technology and stabilization of their parameters.
Thin-film solar cells also include organic / polymer thin-film photosensitive elements and sensitized dyes. In this direction, the commercial use of solar cells is still limited, everything is in the laboratory stage, as well as in the improvement of the technology of future serial production. A number of sources stated that the efficiency of elements based on organic converters was more than 10%: the German company Heliatek -10.7%, the University of California UCLA - 10.6%. A team of scientists from the laboratory at EPFL achieved an efficiency of 12.3% of the cells from sensitized dyes. In general, the direction of organic thin-film elements, as well as light-sensitive dyes, is considered one of the most promising. Statements are regularly made about achieving another record in efficiency, technology going beyond the walls of laboratories, and soon covering all available surfaces with highly efficient and cheap solar converters - Konarka, Dyesol, Solarmer Energy. The work is focused on improving the stability of characteristics, reducing the cost of technology.
Multi-junction (multilayer, tandem) solar panels characteristics.
The cells of such elements contain layers of different materials, forming several p-n transitions... An ideal solar cell, in theory, should have hundreds of different layers (pn junctions), each tuned to a small range of light wavelengths across the entire spectrum, from ultraviolet to infrared. Each transition absorbs solar radiation with a specific wavelength, thus covering the entire spectrum. The main material for such elements is gallium (Ga) compounds - indium gallium phosphide, gallium arsenide, etc.
One of the particular solutions for converting the entire solar spectrum is the use of prisms that decompose sunlight into spectra, concentrating on single-junction elements with different ranges of radiation conversion. Despite the fact that research in the field of multi-junction solar cells has been going on for two decades, and PV modules from such cells are successfully operating in space (solar batteries of the Mir station, Mars Exploration Rover rovers, etc.), their practical terrestrial use has begun relatively recently. The first commercial products with such elements entered the market several years ago and showed excellent result, and research in this direction constantly attracts attention. The fact is that the theoretical efficiency of two-layer cells can be 42% efficiency, three-layer cells 49%, and cells with an infinite number of layers - 68% of unfocused sunlight... The productivity limit of cells with an infinite number of layers is 86.8% using concentrated solar radiation. To date, practical efficiency results for multijunction cells are in the order of 30% in unfocused sunlight. This is not enough to compensate for the production costs of such cells - the cost of a multi-junction cell is about 100 times higher than a silicon one of the same area, therefore, in the design of modules from multi-junction cells, concentrators are used to focus light by a factor of 500 - 1000. A concentrator in the form of a Fresnel lens and a parabolic mirror collects sunlight from an area 1000 times the cell area. The total cost of photomodules from multijunction cells using concentrators (CPV) is significantly reduced in price due to inexpensive lenses and substrates, offsetting the high cost of manufacturing the cell itself. In this case, the productivity of the cells increases up to 40%.
Solar panels characteristics. For example, SolFocus 5.5mm x 5.5mm cells are 40% efficient when using concentrators; and the average dimensions of cells in CPV systems have dimensions in the range from 5.5 mm x 5.5 mm to 1 cm x 1 cm. What does 1 cm for the production of? cells require 1/1000 of raw materials in comparison with a cell of similar productivity from crystalline silicon. For multi-junction cells to work with maximum efficiency, a constant high intensity of solar radiation is required; for this, two-axis orientation systems of CPV systems are used. The deployment sites of solar farms based on modules of multi-junction cells with concentrators are regions with high solar insolation.
The maximum efficiency of multi-junction cells, obtained in laboratory conditions using concentrators, is 43.5% today (Solar Junction), and is predicted to increase to 50% in the next couple of years.
As you can see, today there are solar cells with high productivity, manufactured using various technologies, and the main task of manufacturers is to reduce the cost of the final product, adapt laboratory research for mass production. Despite the low consumption of raw materials in thin-film solar cells, the cost of some components in different types quite high, just as the production technologies themselves are energy-intensive. The long-term stability of the parameters remains questionable. Multi-junction solar cells are still very expensive, and for their maximum efficient operation, moreover, an increased concentration of solar radiation is required. Therefore, crystalline silicon cells in the near future will maintain a leading position in the market of photovoltaic converters, decreasing in price. They will be replaced only by efficient and cheap thin-film modules, possibly made of polymer semiconductors or light-sensitive dyes. But forecasts in the development of this or that technology are not rewarding. Wait and see.
The Fraunhofer Institute for Solar Energy Systems, Soitec, CEA-Leti and the Berlin Helmholtz Center announced that they have achieved a new world record for the efficiency of converting solar energy into electrical energy using a new solar cell structure with four layers. Like some other multilayer photocells, this microcircuit is designed to work with a concentrator that concentrates the flow sun rays 297.3 times, that is, the area of \u200b\u200bthe concentrator lenses is about 300 times the area of \u200b\u200bthe photocell. Efficiency 44.7% refers to a wide range of solar radiation: from ultraviolet to infrared. The energy of 200-1800 nm wavelengths is taken by four layers of the cell. This is an important step towards reducing the cost of using solar power and approaching the important milestone of 50% efficiency.
Solar cells made up of four layers of direct III-IV semiconductors have achieved an efficiency of 44.7%.
In May 2013, a German-French team from Fraunhofer ISE, Soitec, CEA-Leti and Helmholtz Center Berlin announced the creation of solar cells with an efficiency of 43.6%. Based on this result and through further intensive research and optimization steps, an efficiency of 44.7% was obtained.
These solar cells are used in the photovoltaic concentrator (PEC), a technology that is more than double that of conventional photovoltaic plants in sun-rich locations. The use of III-V semiconductors, which was originally used in space technology, has helped realize high efficiency in converting sunlight into electricity. In this connection of solar cells, cells made of III-V semiconductors are stacked on top of each other. Each layer absorbs different wavelengths from the solar spectrum.
External quantum efficiency of a four-cell solar cell (each of the four layers has its own color).
Current-voltage characteristic for record-breaking solar cells.
“We are incredibly proud of our team, which has been working on this solar cell for three years now,” says Frank Dimroth, Department Manager and Project Manager in charge of developing this area at the Fraunhofer Institute. “This type of solar cell connection has evolved over the years as a result of careful experimental work. In addition to improved materials and structural optimization, an important role is also played by new technology "plate ligament". With this technology, we are able to connect two semiconductor crystals that cannot be grown one on top of the other, while maintaining their high quality. In this way, we can create the optimal combination to achieve high solar cell efficiency. ”
"This world record, which increased efficiency levels by more than 1% in less than 4 months, demonstrates the extremely high potential of a new kind of solar cell coupling." Says André-Jacques Auberton-Herve, Chairman and CEO of Soitec. "The new achievement confirms the trend towards higher efficiency, which is key to the competitiveness of our own solar cell systems. We are very proud of this achievement and demonstrates the success of our collaboration."
"The new record reinforces confidence in the direct coupling of semiconductors. This method was developed in our collaboration with Soitec and the Fraunhofer Institute. We are very proud of this new result, which opens up broad prospects for solar technologies based on a new type of connection of elements. ", Said Leti CEO Laurent Malier.
The hub modules are manufactured by Soitec (the project started in 2005 under the name "Concentrix Solar" and was an offshoot of a similar project from the Fraunhofer Institute). This efficient technology is used in power plants located in areas with a high proportion of direct sunlight. Soitec currently has installations in 18 countries, including Italy, France, South Africa and the state of California.
The most efficient solar panels for the home today are not something extraordinary and new, but just a great alternative source of energy. But the more devices of this type appear on the market, the more often people ask themselves: which one should you choose? Which solar panel is the most efficient? But for everyone, this concept sounds as if it were different, since it is characterized by a number of individual needs, and we will talk about this further.
Let's start with the fact that the main question should not be “What are the most efficient solar panels?”, But “ Where is the optimal combination of price and quality?"For example, on the roof of your house or business there is free space on which you can place about a dozen solar panels, and you yourself have a choice: buy devices with the first class of energy efficiency, that is" A ", or give preference to cheaper, but less effective panels of class "B"? Perhaps the answer will surprise you, but the second option will be more appropriate in most cases. Simply put, our main task now is to determine which of the solar energy sources is most beneficial to use in a given situation.
Models of the most energy efficient solar panels
- Sharp... The efficiency indicator for the models of this company is 44.4%. Sharp is considered to be the absolute world leader in solar panels. These devices are quite complex, the solar modules are three-layer here, the manufacturers have spent several years on the development of the technology for their creation, during this period they have carried out many research and tests. own products... There are other simplified models as well. Some Sharp panel technology provides them with 37.9% efficiency, which is also a lot. The price of the devices is lower due to the fact that they do not use technical devices to concentrate sunlight on the module.
- Panels from the Spanish Research Institute (IES)... The efficiency of their work is 32.6%. Such modern solar panels with high efficiency are devices with two-layer modules, the cost of such an energy source is low compared to the previous manufacturer, but for ordinary residential buildings it is still too expensive and somehow pointless.
In fact, this list can be continued for a long time, taking into account the cheaper and cheaper models with a decreasing efficiency index. But everything remains standard: high efficiency - the corresponding price, low efficiency - is cheap. It happens that quite simple models are offered at a ridiculous cost, you will notice this when choosing, but back to our topic.
Famous companies for the production of solar modules
There is an opinion that today less and less time is devoted to the study of the operation of solar panels, and the study of certain solar cells, which are the main components of any alternative battery, has come to the fore. But this is the point that no one will be interested in panels with weak solar modules, this is what most buyers pay attention to in the first place. In the long-established market of these same modules, the leaders have already been determined, it is worth mentioning about them.
- We will be one of the first to recall devices with an efficiency of 36%, they are produced by a company Amonix, whose products are in almost every store with goods of this kind. For household purposes, such modules from Amonix are usually not used, since they are produced using special concentrating devices.
- You cannot pass by solar modules with an energy efficiency of 21.5%, their manufacturer is a well-known American brand Sun powerwhich has been on the market for quite some time. To some extent, this enterprise managed to set a kind of efficiency record. For example, the Sun Power SPR-327NE-WHT-D was voted best after field testing. Moreover, the next two positions in the ranking of the list of the best were also taken by the products of this company.
- Let us also recall the thin-film modules with an efficiency of 17.4% - a product from Q-Cells... The devices of this German company at some point ceased to be popular and in demand, Q-Cells went bankrupt, but then it was bought by the Korean company Hanwha and today the brand modules are gaining momentum in terms of sales again.
- Moving on, that is, towards solar modules with less efficiency. 16.1% give us devices from First solar, they are produced on the basis of a special cadmium-telluric transformation. Appliances of this type are not installed on residential buildings, however, this in no way affects the company's turnover, and they are very wide. First Solar is more popular in the American market: the company itself is from the United States. Modules of this brand are used in many industries, so the company has excellent momentum and has gained universal recognition, because it creates a really reliable product.
- As the last of the examples here will be solar modules with an efficiency of 15.5% from a company called MiaSole... Devices of this brand are recognized as the best among flexible modules. Yes, this type of personalized device is sometimes simply necessary for installation in certain structures.
When you are looking for high-power solar panels for your home or large production hall, focus not only on the price / quality ratio, but also on the brand. Manufacturers who have proven themselves to be the best should be trusted in such serious matters. If you are not an expert in assembling and installing solar panels, then no matter how carefully you approach the choice, it is impossible to examine each model for strength, durability, economy and other parameters, so it is better to trust the name.
To date, many experiments have also been carried out, their results can definitely help you. When looking for solar panels, be guided also by your own needs and ability to pay - there is no need to install a device on a residential building, which was developed for NASA.
With constantly rising electricity prices, you will inevitably start thinking about using natural sources for electricity supply. One of these possibilities is solar panels for home or summer cottages. If desired, they can fully meet all the needs of even a large house.
Solar Power System Design
Converting the energy of the sun into electricity - this idea did not let scientists sleep for a long time. With the discovery of the properties of semiconductors, this became possible. Solar cells use silicon crystals. When sunlight hits them, a directed movement of electrons is formed in them, which is called an electric current. When connecting a sufficient number of such crystals, we get quite decent currents in magnitude: one panel with an area of \u200b\u200bslightly more than a meter (1.3-1.4 m2 with a sufficient level of illumination can produce up to 270 W (voltage 24 V).
Since the illumination changes depending on the weather, time of day, it is impossible to directly connect the devices to solar panels. You need a whole system. In addition to solar panels, you need:
- Battery. During the daylight hours, under the influence of sunlight, solar panels generate electric current for the house, summer cottage. It is not always used in full, its surplus accumulates in the battery. The stored energy is wasted in inclement weather.
- Controller. Not an obligatory part, but a desirable one (with sufficient funds). Monitors the battery charge level to prevent over-discharge or over-charge. Both of these conditions are detrimental to the battery, so having a controller extends the battery life. The controller also provides optimal mode solar panels work.
- DC to AC converter (inverter). Not all devices are designed for d.C.... Many operate on 220 volts AC. The converter makes it possible to obtain a voltage of 220-230 V.
Solar panels for home - only part of the system
By installing solar panels for your home or summer cottage, you can become completely independent from the official supplier. But for this you need to have a large number of batteries, a certain number of accumulators. A kit that generates 1.5 kW per day costs about $ 1000. This is enough to meet the needs of the summer cottage or part of the electrical equipment in the house. A set of solar panels for the production of 4 kW per day costs about $ 2200, for 9 kW per day - $ 6200. Since solar panels for a home are a modular system, you can buy an installation that will provide part of the needs, gradually increasing its performance.
Types of solar panels
With the rise in energy prices, the idea of \u200b\u200busing solar energy to generate electricity is becoming more popular. Moreover, with the development of technology, solar converters are becoming more efficient and, at the same time, cheaper. So, if you wish, you can provide your needs by installing solar panels. But they happen different types... Let's figure it out.
The solar battery itself is a number of photocells, which are located in a common housing, protected by a transparent front panel. For household use, solar cells are produced on the basis of silicon, since it is relatively inexpensive, and cells based on it have a good efficiency (about 20-24%). Monocrystalline, polycrystalline and thin-film (flexible) photocells are made on the basis of silicon crystals. A number of these photocells are electrically connected to each other (in series and / or in parallel) and brought out to terminals located on the body.
Photocells are installed in a closed housing. The solar cell body is made of anodized aluminum. It is lightweight and does not corrode. The front panel is made of durable glass, which must withstand snow and wind loads. In addition, it must have certain optical properties - have maximum transparency in order to transmit as many rays as possible. In general, a significant amount of energy is lost due to reflection, so the requirements for the quality of the glass are high and it is also coated with an anti-reflective compound.
Types of photovoltaic cells for solar panels
Solar panels for the home are made on the basis of three types of silicon cells;
If you have a pitched roof and the facade is turned to the south or east, it does not make sense to think too much about the occupied area. Polycrystalline modules can quite suit. With the same amount of energy produced, they are slightly cheaper.
How to choose the right solar panel system for your home
There are common misconceptions that lead you to spend extra money on equipment that is too expensive. Below are recommendations on how to properly build a solar power system and not spend extra money.
What to buy
Not all components of a solar power plant are vital for operation. Some parts are quite possible to do without. They serve to improve reliability, but without them the system is functional. The first thing to remember is to get solar panels in late winter, early spring. Firstly, the weather at this time is excellent, there are many sunny days, the snow reflects the sun, increasing the overall illumination. Secondly, discounts are traditionally announced at this time. Further tips are:
If you use only these tips, and connect only appliances that operate on constant voltage, a solar panel system for a home will cost a much more modest amount than the cheapest kit. But that's not all. You can also leave some of the equipment "for later" or do without it altogether.
What you can do without
The cost of a set of solar panels for 1 kW per day is more than a thousand dollars. Considerable investment. Involuntarily you will wonder whether it is worth it and what the payback period will be. With current tariffs, it will take more than one year to wait until your money is repaid. But costs can be reduced. Not at the expense of quality, but at the expense of a slight decrease in the comfort of using the system and due to a reasonable approach to the selection of its components.
So, if the budget is limited, you can get by with a few solar panels and rechargeable batteries, the capacity of which is 20-25% higher than the maximum charge of solar panels. For health monitoring, buy a car clock that still measures voltage. This saves you the need to measure the battery charge several times a day. Instead, you will need to look at the clock from time to time. That's all for the start. In the future, you can buy solar panels for your home, increase the number of batteries. If desired, you can buy an inverter.
Determine the size and number of photocells
A good 12 volt solar cell should have 36 cells, and a 24 volt battery should have 72 solar cells. This amount is optimal. With fewer photocells, you will never get the stated current. And this is the best option.
Don't buy dual solar panels - 72 and 144 cells, respectively. Firstly, they are very large, which is inconvenient for transportation. Secondly, at abnormally low temperatures, which we have periodically, they are the first to fail. The fact is that the laminating film greatly decreases in size during frost. On large panels, due to the high tension, it flakes off or even tears. Transparency is lost, performance drops dramatically. The panel is being repaired.
Second factor. Large panels should have more thickness of the case and glass. After all, windage and snow loads increase. But this is not always done, since the price increases significantly. If you see a double panel, and the price for it is lower than the two "regular" ones, you better look for something else.
Once again: the best choice is a 12 volt solar panel for your home, consisting of 36 solar cells. This is the best option, proven by practice.
Specifications: what to look for
Certified solar panels always indicate the operating current and voltage, as well as the open circuit voltage and short circuit current. It should be borne in mind that all parameters are usually indicated for a temperature of + 25 ° C. On a sunny day on the roof, the battery heats up to temperatures well above this figure. This explains the higher operating voltage.
Also pay attention to the open circuit voltage. In normal batteries, it is about 22 V. And all would be fine, but if you work on the equipment without disconnecting the solar panels, the open circuit voltage will damage the inverter or other connected equipment that is not designed for such a voltage. Therefore, for any work - switching wires, connecting / disconnecting batteries, etc. and so on - the first thing you should do is turn off the solar panels (remove the terminals). After going through the circuit, connect them last. This procedure will save you a lot of nerves (and money).
Body and glass
Solar panels for home have an aluminum casing. This metal does not corrode, with sufficient strength it has a small mass. A normal body should be assembled from a profile in which at least two stiffeners are present. In addition, the glass must be inserted into a special groove, and not fixed from above. These are all signs of normal quality.
Even when choosing a solar panel, pay attention to glass. In normal batteries, it is textured rather than smooth. To the touch - rough, if you hold your nails, you can hear a rustle. In addition, it must have a high-quality coating that minimizes glare. This means that nothing should be reflected in it. If the reflections of the surrounding objects are visible at least from any angle, it is better to find another panel.
Selection of cable cross-section and subtleties of electrical connection
It is necessary to connect solar panels for the home with a single-core copper cable. The cross-section of the cable core depends on the distance between the module and the battery:
- distance less than 10 meters:
- 1.5 mm2 per 100 W solar panel;
- for two batteries - 2.5 mm2;
- three batteries - 4.0 mm2;
- distance more than 10 meters:
- to connect one panel, we take 2.5 mm2;
- two - 4.0 mm2;
- three - 6.0 mm2.
You can take a larger section, but not less (there will be big losses, but we don't need it). When buying wires, pay attention to the actual cross-section, since today the declared dimensions very often do not correspond to the actual ones. To check, you will have to measure the diameter and read the section (you can read how to do this).
When assembling the system, you can carry out the advantages of solar panels using a multicore cable of a suitable cross-section, and for a minus use one thick one. Before connecting to the batteries, we pass all the "pluses" through diodes or diode assemblies with a common cathode. This prevents the battery from shorting out (could cause a fire) if the wires between the batteries and the battery are shorted or broken.
Diodes use SBL2040CT, PBYR040CT types. If they are not found, they can be removed from the old power supplies of personal computers. There are usually SBL3040 or similar. It is desirable to pass through diodes. Do not forget that they get very hot, so you need to mount them on a radiator (you can use a single one).
The system also requires a fuse box. One for each consumer. We connect the entire load through this block. First, the system is safer this way. Secondly, if a problem occurs, it is easier to determine its source (by a blown fuse).
