Solar panels how they work. Solar heating of houses. Depending on the materials used, solar panels can be
Every second great amount Solar energy reaches the surface of our planet, giving life to all living things. A worthy challenge for inquiring minds is a solution that would make it serve the needs of people. And those who have invented the design of a solar battery capable of converting sunlight V electrical energy.
It is easier to understand how a solar battery works using the example of a design based on monocrystalline silicon.
Two layers of silicon with different physical properties form a thin wafer. The inner layer is monocrystalline pure silicon with p-type conductivity, which is coated on the outside with a layer of “contaminated” silicon. This could be, for example, an admixture of phosphorus. It has n-type conductivity. The back side of the plate is covered with a continuous metal layer.
The photocells are fixed in the frame in such a way that they can be replaced if they fail. The entire structure is covered tempered glass or plastic that protect it from negative impact external factors.
The principle of operation of a solar battery
As a result of the flow of charges at the boundary of the p- and n-layers, a zone of uncompensated positive charge is formed in the n-layer, and a zone of negative charge is formed in the p-layer, i.e. known to everyone from school course physics p-n junction. The potential difference that appears at the junction, the contact potential difference (potential barrier), prevents the passage of electrons from the p-layer, but freely allows minority carriers to pass in the opposite direction, which makes it possible to obtain a photo-emf when sunlight hits the photovoltaic cell.
When irradiated by sunlight, the absorbed photons begin to generate nonequilibrium electron-hole pairs. The electrons generated near the transition move from the p-layer to the n-region.
In a similar way, excess holes from the n layer enter the p-layer (Figure a). It turns out that a positive charge accumulates in the p-layer, and a negative one in the n-layer, causing voltage in external circuit(Figure b). The current source has two poles: positive - p-layer and negative - n-layer.
This is the basic operating principle of solar cells. The electrons thus seem to be running in circles, i.e. leave the p-layer and return to the n-layer, passing the load (battery).
The photoelectric outflow in a single-junction element is provided only by those electrons that have an energy higher than the width of a certain band gap. Those that have less energy do not participate in this process. This limitation can be removed by multilayer structures consisting of more than one solar cell, with different band gaps. They are called cascade, multi-junction or tandem. Their photovoltaic conversion is higher due to the fact that such solar cells operate with a wider solar spectrum. In them, photocells are located as the band gap decreases. The sun's rays hit the photocell with the widest area first, and the photons with the highest energy are absorbed.
Then, photons transmitted by the upper layer reach next element etc. In the field of cascade elements, the main direction of research is the use of gallium arsenide as one component or several. Such elements have a conversion efficiency of 35%. The elements are connected into a battery, since it is necessary to make a separate element big size(and therefore power) is not allowed by technical capabilities.
Solar cells can operate for a long time. They have proven themselves to be stable and reliable source energy, having been tested in space, where the main danger for them is meteor dust and radiation, which lead to the erosion of silicon elements. But, since on Earth these factors do not have such a negative effect on them, it can be assumed that the service life of the elements will be even longer.
Solar panels are already in the service of humans, serving as a power source for various devices, starting from mobile phones and ending with electric vehicles.
And this is already the second attempt by man to harness the limitless solar energy, forcing it to work for his own benefit. The first attempt was to create solar collectors, in which electricity was generated by heating water to boiling point with concentrated rays of the sun.
Advantage solar panels the fact that they directly produce electricity, losing energy much less than solar multi-stage collectors, in which the process of obtaining it is associated with the concentration of the sun's rays, heating water, releasing steam that rotates a steam turbine, and only after that the generation of electricity by a generator. The main parameters of solar panels are, first of all, power. Then it is important how much energy they have.
This parameter depends on the capacity of the batteries and their number. The third parameter is peak power consumption, meaning quantity at one time possible connections devices. One more important parameters is the rated voltage on which the choice depends additional equipment: inverter, solar panel, controller, battery.
Types of solar panels
All solar panels appear at first glance to be the same - dark glass-covered elements with metal strips that conduct current, placed in an aluminum frame.
But, solar panels are classified according to the power of electricity they generate, which depends on the design and area of the panel (they can be miniature plates with a power of up to ten watts and wide “sheets” with a power of two hundred or more watts).
In addition, they differ in the type of photocells that form them: photochemical, amorphous, organic, and also those created on the basis of silicon semiconductors, whose photoelectric conversion coefficient is several times higher. Consequently, the power is greater (especially during sunny weather). A competitor to the latter may be a solar battery based on gallium arsenide. That is, there are five types of solar panels on the market today.
They differ in the materials used for their manufacture:
1. Panels made of polycrystalline photovoltaic cells, with the characteristic blue color of a solar panel, crystalline structure and efficiency of 12-14%.
Polycrystalline panel
2. Panels made from monocrystalline elements are more expensive, but also more efficient (efficiency - up to 16%).
3. Solar panels made of amorphous silicon, which have the lowest efficiency - 6-8%, but they generate the cheapest energy.
4. Panels made of cadmium telluride, created using film technologies (efficiency - 11%).
Panel based on cadmium telluride
5. Finally, solar panels based on CIGS semiconductor, consisting of selenium, indium, copper, gallium. The technologies for their production are also film, but the efficiency reaches fifteen percent.
In addition, solar panels can be flexible and portable.
Very convenient are flexible panels that can be easily rolled up, like regular paper. Although their cost is higher than their solid-state counterparts, they have occupied their niche in the market. They are mainly in demand among tourists and travelers who, in the absence of electrification, need to charge mobile gadgets. The main manufacturer of flexible batteries powered by solar energy is Sun Charger, which, by the way, recently updated its the lineup models 34 W and 9 W.
The first model is suitable for powering tablets, cell phones, video cameras, digital cameras, GPS, gel batteries 6 and 12 volts, i.e. it can meet the needs of several people during a hike.
SunCharger SC-9/14 - folded battery
She is in an open form
Battery features: compact folding design, operating in a temperature range from -50 to +70 degrees, weighing only 420 grams, equipped with anti-reflective coating, built-in LED, eyelets for fastening. The output jack is round (5.5 mm / 2.1 mm).
Electrical characteristics: working output voltage 13.5 V (standard 12V), no load – 19V; operating output current – 0.65 A; dimensions when folded and unfolded - 20.5x15x3 cm and 50x41.5x0.4 cm; output power – 8.6 W.
The second model SunCharger SC-34/18 is by far the most powerful in the line of flexible solar panels. It was developed specifically for universal drives (laptops), which have a charging input of, as a rule, 17-19 volts. Maximum power – 18V. It connects directly to the drives, ensuring perfect matching. It is clear that it is also suitable for less “gluttonous” drives, including twelve-volt lead-acid batteries used in cars.
The solar array produces 18V at its maximum power point and is directly connected to these storage devices. Thus, she is “perfectly” aligned with them.
Naturally, this battery is also suitable for charging less voracious consumers. As you know, there is never enough power. And also quietly charges 12 V lead acid batteries, including automobile ones (after a few hours of charging, you can already start the car). Its thickness is 4 cm (i.e. it has become a little larger), but the battery turned out to be even a little more compact than conventional 12 V batteries.
This was achieved due to the thinner fabric used in its production and laminated photocells of a larger area.
The same battery opened
In addition to the features characteristic of previous model, here at the output, in addition to the round connector, there is also a “mother” and “father”.
Electrical characteristics: output power, as is clear from the markings, 34 W; operating output current – 1.9 A; dimensions 40x18x4 cm (folded) and 40x18x4 cm (opened). Output voltage – 18 V and 26 V (no load). The weight, of course, is much more - 1.7 kg.
Portable solar battery - especially for tourists
Everyone nowadays has electronic gadgets. It doesn’t matter that some have less and some have more. All of them need to be charged, and for this we need charging device. But this issue is especially acute for those who find themselves in places where there is no power supply. The only way out is solar panels. But their prices remain high, and the choice remains small. The best option, as is commonly believed, is a product of the Goal Zero company (although there are both Russian and Chinese products - as always raising doubts).
But it turned out that not everything that is made in China or Korea is bad. Particularly pleased with the solar battery was the YOLK company from Chicago, which began production of a compact solar Solar batteries Paper – the thinnest and lightest. Its weight is only 120 grams. But there are other advantages - a modular design that allows you to increase power. The solar battery looks like a plastic box, similar in size to an iPad, only twice as thin. There is a solar panel on its front side. There is an output for a laptop on the case and USB ports and for connecting other solar panels, as well as a flashlight. Inside this miracle box are batteries and a control board. You can charge the device from an outlet, and it can be a phone and two laptops at the same time. Of course, the device is also charged from the sun. As soon as light hits it, the indicator lights up. IN hiking conditions The solar panel is simply irreplaceable: it successfully charges everything necessary devices– phones are faster, laptops.
Portable solar panels are compact in size: They are even available in the form of keychains, which can be attached to anything. They were developed so that you could take them fishing, hiking, etc. They definitely have a flashlight so that at night you can illuminate the road, tent, etc., mounts that make it easy to place them on backpacks, kayaks, tents . It is very important that such a device has a built-in battery that allows you to charge devices at night.
Scientists are working to increase the coefficient useful action, but so far solar panels made from monocrystalline elements are leading in this indicator. Consisting of several layers, monocrystalline panels are designed so that one of the layers absorbs green energy, another - red, and the third - blue. But, the cost of such panels is very high.
A solar battery, as you know, consists of several required parts. Its basis, like the engine of a car or the heart of a person, is a solar panel - a transparent rectangular box with dark squares of thinly sliced silicon inside. Silicon used in production, or rather its oxide (compound with oxygen), is the main element in the production of solar cells.
The technologies underlying the production of solar panels are constantly being improved and consist of several stages.
- At the first stage, raw materials are prepared: quartz sand is cleaned by calcining it with coke. As a result, it is freed from oxygen, turning into pieces of pure silicon, somewhat reminiscent of coal. Then, crystals are grown from it - the basis of solar panels, ordering the structure of silicon. To do this, pure silicon is lowered into a crucible and heated to high temperature, adding a seed to the molten lava. You can compare it with a sample of a future crystal, around which silicon of an ordered structure grows, layer by layer. After several hours of growth, a monosilicon crystal is obtained (or polycrystalline silicon, the production process of which is more expensive, which affects the price of solar panels made from it), resembling a large icicle. Then the cylindrical workpiece is turned into a parallelepiped. After this, the workpiece is cut into plates with a thickness of 100-200 microns (the thickness of three human hairs), they are tested, sorted and sent to the next stage of processing.
- In the second stage the plate soldered into sections, from which blocks are formed on glass to eliminate the possibility of mechanical impact on the finished solar cells. Sections usually consist of 9-10 solar cells, blocks - from 4-6 sections.
- Third stage involves laminating plates soldered into blocks with ethylene vinyl acetate film, and then protective coating, which is carried out using a computer that monitors pressure, vacuum and temperature.
- The fourth stage is final. During this process, the connection box and aluminum frame are installed. Testing is carried out again, during which the indicators are measured: open circuit voltage, current short circuit, voltage and current point of maximum capacity.
The leaders among enterprises producing solar panels are the following countries: China (Trina Solar, Yingli, Suntech companies), Japan (Sharp Solar) and the USA (First Solar), which not only produces them, but also participates in the design of solar stations and their construction. The most powerful solar power plant in the world, Agua Caliente in Arizona, is the work of this company. The construction of the largest solar power plant "Perovo" in Ukraine was carried out by an Austrian company (Activ Solar).
How much does a solar battery cost?
Selling solar panels is a profitable and promising business. Sales volume increases annually. First place in sales - Chinese manufacturers, whose products are characterized by low cost. This situation led to the bankruptcy of large German brands, which cost twice as much as Chinese solar panels.
The cost of solar panels depends on the manufacturer and power, and has a huge range - from 1800 UAH. up to 9000 UAH (for Ukraine), from 5 thousand rubles to 30 thousand (For Russia). The cost of these SunCharger SC-9/14 and SunCharger SC-34/18 batteries is also high (you have to pay for excellent characteristics). It amounts accordingly 6100 and 20700 rubles. But, in comparison with the AcmePower 32 W flexible battery, the price for which is 27 thousand rubles, this battery is much cheaper.
Those who want to save money can purchase solar crystalline folding batteries at a price that is 2.5 times less.
conclusions
Fantastic ideas are gradually becoming reality. Let’s remember, for example, a microcalculator based on photocells, which once seemed like a curiosity that allowed you not to change the battery for years. An invention of recent years is a mobile phone with a built-in solar panel, cars and planes, moving thanks to the same energy of the Sun. Solar panels in the future will certainly become the main source of energy, finally “curing” all gadgets from “outlet addiction” and giving humanity cheap energy.
Once upon a time, they used mirrors to heat water, but now they are creating entire power plants using solar panels. Let's look at the principle of operation of a solar battery and why they are so effective in generating energy.
Photovoltaic solar energy converters (PVCs) are the full name of solar panels. The principles of their operation have been known for more than 30 years, but they began to be actively implemented in everyday life only a few years ago. In order to select the right panels for the system alternative security energy, it is necessary to understand the principle of their operation.
The principle of operation of a solar battery
The converter panel consists of two thin wafers of pure silicon stacked together. Boron is applied to one plate and phosphorus to the second. In layers coated with phosphorus, free electrons appear, and in layers coated with boron, missing electrons appear. Under the influence of sunlight, electrons begin to move particles, and between them a electricity. To remove current from the plates, they are soldered with thin strips of specially treated copper. One silicon wafer is enough to charge a small flashlight. Accordingly, the larger the panel area, the more energy it generates.
The UV-transmitting plates, soldered together, are laminated with film and attached to the glass. The bonded layers are enclosed in an aluminum frame.
Efficiency of solar panels
The efficiency of converter panels depends on several factors and for traditional solar panels does not exceed 25%, although now, using a tracking system, it is possible to reach 40-50%. This system is designed so that the battery turns towards the sun. The area of the battery directly affects its power - the first solar panels we met were in calculators. To ensure water heating, a minimum of six panels installed on the roof will be required.
Efficiency also depends on the material of the modules. Wafers are made from monocrystalline, polycrystalline and amorphous silicon and films. The most common and popular today (due to their affordable cost) are thin-film panels. They are made from the same materials, but are a little lighter, although they are inferior in performance. The maximum efficiency is 25%.
Photovoltaic systems
To provide housing with solar energy, panels alone are not enough; for this you will need a photovoltaic system (PVS). There are three types of such systems:
- autonomous solar power plants– for detached private houses, in non-residential areas
- FES connected to the power grid– some of the devices are powered from the solar power plant, and some are powered from the centralized power grid
- backup solar power plants– used only in the event of a centralized power supply failure.
A solar power plant of any type necessarily consists of cables, a controller, an inverter and a battery.
The future of solar panels
According to research by ecologists and geologists, there are still 100 years of oil and gas reserves left. Sources of natural energy (water, wind and sun) are inexhaustible.
In the advanced European countries Providing new buildings with alternative energy has been the direct responsibility of developers since 2007. In our country, these projects are promoted thanks to environmental enthusiasts who manually assemble FES from scrap materials. But there are only a few of them, and it’s quite difficult to make them yourself.
A number of Ukrainian manufacturers (Avante, Atmosphere, ITnelcon of Ukraine, SINTEK, Techno-AS) are already producing such panels and installing solar power plants throughout the country. The cost of the products, unfortunately, is in the same range as foreign brands (Buderus, Wolf, Rehau, Vaillant, Viessmann, Chromagen, Ferroli, Rucelf, Solver).
Nowadays, almost everyone can assemble and have at their disposal their own independent source of electricity using solar batteries (in the scientific literature they are called photovoltaic panels).
Over time, expensive equipment is offset by the opportunity to receive free electricity. It is important that solar panels are an environmentally friendly source of energy. Behind last years prices for photovoltaic panels have fallen tens of times and they continue to decline, which indicates great prospects for their use.
IN classic look such a source of electricity will consist of the following parts: directly, a solar battery (DC generator), a battery with a charge control device and an inverter that converts D.C. into variable.
Solar panels consist of a set of solar cells (photovoltaic converters) that directly convert solar energy into electrical energy.
Most solar cells are made from silicon, which is quite expensive. This fact will determine the high cost of electrical energy, which is obtained by using solar panels.
There are two common types of photovoltaic converters: those made of monocrystalline and polycrystalline silicon. They differ in production technology. The former have an efficiency of up to 17.5%, and the latter - 15%.
The most important technical parameter The solar battery that has the main influence on the efficiency of the entire installation is its useful power. It is determined by voltage and output current. These parameters depend on the intensity of sunlight hitting the battery.
The electromotive force of individual solar cells does not depend on their area and decreases when the battery is heated by the sun, by approximately 0.4% per 1 g. C. The output current depends on the intensity of solar radiation and the size of the solar cells. The brighter the sunlight, the higher current generated by solar cells. Charging current and the output power in cloudy weather decreases sharply. This occurs by reducing the current supplied by the battery.
If a battery illuminated by the sun is connected to any load with resistance Rн, then an electric current I appears in the circuit, the magnitude of which is determined by the quality of the photoelectric converter, the intensity of illumination and the load resistance. The power Pн, which is released in the load, is determined by the product Pн = InUn, where Un is the voltage at the battery terminals.
The greatest power is released in the load at a certain optimal resistance Ropt, which corresponds to the highest efficiency of converting light energy into electrical energy. Each converter has its own value of Ropt, which depends on the quality, size of the working surface and degree of illumination.
A solar cell consists of individual solar cells that are connected in series and parallel to increase the output parameters (current, voltage and power). At serial connection elements, the output voltage increases, and in parallel, the output current increases.
In order to increase both current and voltage, these two connection methods are combined. In addition, with this connection method, the failure of one of the solar cells does not lead to the failure of the entire chain, i.e. increases the reliability of the entire battery.
Thus, a solar battery consists of parallel-series connected solar cells. The maximum possible current supplied by the battery is directly proportional to the number of parallel connected ones, and electromotive force- series-connected solar cells. So, by combining connection types, a battery with the required parameters is assembled.
The solar cells of the battery are shunted by diodes. Usually there are 4 of them - one for each ¼ of the battery. Diodes protect parts of the battery from failure that for some reason are darkened, that is, if at some point in time the light does not fall on them.
The battery temporarily generates 25% less output power than with normal sun illumination of the entire surface of the battery.
In the absence of diodes, these solar cells will overheat and fail, since during darkening they turn into current consumers (the batteries are discharged through the solar cells), and when diodes are used, they are shunted and no current flows through them.
The resulting electrical energy is stored in batteries and then transferred to the load. Batteries are chemical sources of current. The battery is charged when a potential is applied to it that is greater than the battery voltage.
The number of solar cells connected in series and parallel must be such that the operating voltage supplied to the batteries, taking into account the voltage drop in the charging circuit, slightly exceeds the battery voltage, and the load current of the battery provides the required amount of charging current.
For example, to charge a 12 V lead battery, you need to have a solar battery consisting of 36 cells.
In weak sunlight, the battery charge decreases and the battery transfers electrical energy to the electrical receiver, i.e. Rechargeable batteries constantly operate in discharge and recharge mode.
This process is controlled by a special controller. For cyclic charging it is required constant pressure or constant charge current.
When there is good lighting, the battery is quickly charged to 90% of its rated capacity, and then at a slower charge rate to full capacity. Switching to a lower charging rate is performed by the charger controller.
The most effective use of special batteries is gel batteries (the battery uses sulfuric acid as an electrolyte) and lead batteries, which are made using AGM technology. These batteries are not needed special conditions installation and no maintenance required. The certified service life of such batteries is 10 - 12 years with a discharge depth of no more than 20%. Batteries should never be discharged below this value, otherwise their service life will be drastically reduced!
The battery is connected to the solar panel through a controller that controls its charge. When the battery is charged to full capacity, a resistor is connected to the solar panel, which absorbs excess power.
In order to convert direct voltage from the battery into alternating voltage, which can be used to power most electrical receivers, you can use solar batteries together special devices- inverters.
Without using an inverter, a solar battery can be used to power electrical receivers operating at constant voltage, incl. various portable equipment, energy-saving light sources, for example, the same LED lamps.
Author of the text: Andrey Povny. The text was first published on the website Electrik.info. Reprinted with the consent of the editors.
Is it expensive to heat your house with gas? Or do you constantly turn off the lights at your dacha? Or maybe you're tired of overpaying for electricity? Installing a solar panel will help you, which will provide you not only with electricity, but also with heating. In this article we will look at the operating principle of a solar battery and its differences from a solar collector.
What is the essence of how a solar battery works?
A solar battery, also known as a photobattery, is a photographic plate that changes the conductivity in its individual sections under the influence of sunlight.
This allows the energy of these transitions to be converted into electrical energy, which is either used immediately or accumulated.
In order to understand the principle of operation of a solar battery, you need to know a few points:
So how does a solar panel work?
Sunlight falls on a negatively charged panel. It causes the active formation of additional negative charges and “holes”. Under the influence of the electric field that is present in p-n junction, the separation of positively and negatively charged particles occurs. The former are sent to the upper layer, and the latter to the lower. Thus, a potential difference appears, in other words, a constant voltage (U). Based on this, it can be seen that one photoconverter operates on the principle of a battery. And when a load is connected to it, a current arises in the circuit. The current strength will depend on parameters such as:
There are several types of solar cells: poly- and monocrystalline, as well as amorphous.
Monocrystalline ones are the least productive, but at the same time the most inexpensive. In this regard, their use is justified as additional source energy in case of a centralized power supply failure.
Polycrystals occupy intermediate positions in these two parameters, and therefore can be used in remote areas without a centralized power supply.
Amorphous solar cells are highly efficient, but also very expensive. They are based on amorphous silicon.
These developments have not yet reached the industrial level and are at the experimental stage.
Why do you need a controller in a solar battery?
Solar batteries, the principle of operation of which was described above, could not effectively replace central power supply systems if they were not equipped with controllers capable of monitoring the degree of charge of the solar battery.
Controllers allow you to redistribute the energy received from solar panels, directing it, if necessary, directly to the source of consumption, or storing it in a battery.
There are several types of solar panel controllers, differing in the degree to which they increase the overall efficiency of the solar panel system.
To get started using alternative sources energy, it is not at all necessary to purchase an expensive solar battery. There are more accessible examples of using solar energy to generate electricity. It's about about currently popular garden lanterns on solar batteries.
Such flashlights allow you to illuminate your garden plot at night without spending additional electricity.
The principle of operation of such lanterns is that by means of a phytoplate mounted in top part flashlight, solar energy is captured and converted, which is accumulated in a small battery located at the base of the flashlight. The consumption of accumulated energy occurs in the dark.
