How solar panels work and work. Operating principle, design and types of solar panels

Effectively converting free rays of the sun into energy that can be used to power homes and other facilities is the cherished dream of many green energy apologists.

But the principle of operation of the solar battery and its efficiency are such that there is no need to talk about the high efficiency of such systems yet. It would be nice to have your own additional source of electricity. Isn't it? Moreover, even today in Russia, with the help of solar panels, a considerable number of private households are successfully supplied with “free” electricity. Still don't know where to start?

Below we will tell you about the design and operating principles of a solar panel; you will learn what the efficiency of a solar system depends on. And the videos posted in the article will help you assemble a solar panel from photocells with your own hands.

There are quite a lot of nuances and confusion in the topic of “solar energy”. It is often difficult for beginners to understand all the unfamiliar terms at first. But without this, it is unreasonable to engage in solar energy, purchasing equipment for generating “solar” current.

Unknowingly, you can not only choose the wrong panel, but also simply burn it when connecting it or extract too little energy from it.

The maximum return from a solar panel can only be obtained by knowing how it works, what components and assemblies it consists of, and how it is all connected correctly

First, you should understand the existing types of equipment for solar energy. Solar panels and solar collectors are two fundamentally different devices. Both of them convert the energy of the sun's rays.

However, in the first case, the consumer receives electrical energy at the output, and in the second, thermal energy in the form of a heated coolant.

The second nuance is the concept of the term “solar battery”. Typically, the word “battery” refers to some kind of electrical storage device. Or a banal heating radiator comes to mind. However, in the case of solar batteries the situation is radically different. They do not accumulate anything in themselves.

The solar panel generates a constant electric current. To convert it to variable (used in everyday life), an inverter must be present in the circuit

Solar panels are designed solely to generate electric current. It, in turn, is accumulated to supply the house with electricity at night, when the sun goes below the horizon, already in the batteries that are additionally present in the facility’s energy supply circuit.

The battery here is meant in the context of a certain set of similar components assembled into a single whole. In fact, it is just a panel of several identical photocells.

Internal structure of a solar battery

Gradually, solar panels are becoming cheaper and more efficient. They are now used to recharge batteries in street lamps, smartphones, electric cars, private homes and on satellites in space. They even began to build full-fledged solar power plants (SPPs) with large generation volumes.

A solar battery consists of many photocells (photoelectric converters) that convert the energy of photons from the sun into electricity

Each solar battery is designed as a block of a certain number of modules, which combine semiconductor photocells connected in series. To understand the principles of operation of such a battery, it is necessary to understand the operation of this final link in the solar panel device, created on the basis of semiconductors.

Types of photocell crystals

There are a huge number of FEP options made from different chemical elements. However, most of them are developments in the initial stages. So far, only panels made from silicon-based photovoltaic cells are currently produced on an industrial scale.

Silicon semiconductors are used in the manufacture of solar cells due to their low cost; they cannot boast of particularly high efficiency

A typical photocell in a solar panel is a thin wafer of two layers of silicon, each of which has its own physical properties. This is a classic semiconductor p-n junction with electron-hole pairs.

When photons hit the photovoltaic cell between these semiconductor layers, due to the inhomogeneity of the crystal, a gate photo-emf is formed, resulting in a potential difference and an electron current.

Silicon wafers of solar cells differ in manufacturing technology into:

1. Monocrystalline.
2. Polycrystalline.

The former have a higher efficiency, but the cost of their production is higher than that of the latter. Externally, one option can be distinguished from another on a solar panel by its shape.

Monocrystalline solar cells have a homogeneous structure; they are made in the form of squares with cut corners. In contrast, polycrystalline elements have a strictly square shape.

Polycrystals are obtained by gradual cooling of molten silicon. This method is extremely simple, which is why such photocells are inexpensive.

But their productivity in terms of generating electricity from solar rays rarely exceeds 15%. This is due to the “impurity” of the resulting silicon wafers and their internal structure. Here, the purer the p-silicon layer, the higher the efficiency of the solar cell from it.

The purity of single crystals in this regard is much higher than that of polycrystalline analogues. They are made not from molten, but from artificially grown solid silicon crystal. The photoelectric conversion coefficient of such solar cells already reaches 20-22%.

Individual photocells are assembled into a common module on an aluminum frame, and to protect them they are covered on top with durable glass, which does not in any way interfere with the sun’s rays

The top layer of the photocell plate facing the sun is made from the same silicon, but with the addition of phosphorus. It is the latter that will be the source of excess electrons in the pn junction system.

Operating principle of solar panel

When sunlight falls on a photocell, nonequilibrium electron-hole pairs are generated in it. Excess electrons and holes are partially transferred through the pn junction from one layer of the semiconductor to another.

As a result, voltage appears in the external circuit. In this case, a positive pole of the current source is formed at the contact of the p-layer, and a negative pole at the n-layer.

The potential difference (voltage) between the contacts of the photocell appears due to a change in the number of “holes” and electrons on different sides of the p-n junction as a result of irradiation of the n-layer with solar rays

Photocells connected to an external load in the form of a battery form a vicious circle with it. As a result, the solar panel works like a kind of wheel along which electrons “run” together between proteins. And the battery gradually gains charge.

Standard silicon photovoltaic converters are single-junction cells. The flow of electrons into them occurs only through one p-n junction with a zone of this transition limited in photon energy.

That is, each such photocell is capable of generating electricity only from a narrow spectrum of solar radiation. All other energy is wasted. That is why the efficiency of FEP is so low.

To increase the efficiency of solar cells, silicon semiconductor elements for them have recently begun to be made multi-junction (cascade). There are already several transitions in the new solar cells. Moreover, each of them in this cascade is designed for its own spectrum of sunlight.

The total efficiency of converting photons into electric current for such photocells ultimately increases. But their price is much higher. Here, either ease of manufacture with low cost and low efficiency, or higher returns coupled with high cost.

The solar battery can work both in summer and winter (it needs light, not heat) - the less cloudy and the brighter the sun shines, the more electric current the solar panel will generate

During operation, the photocell and the entire battery gradually heat up. All the energy that was not used to generate electric current is transformed into heat. Often the temperature on the surface of the solar panel rises to 50–55 0 C. But the higher it is, the less efficient the photovoltaic cell operates.

As a result, the same model of solar battery generates less current in hot weather than in cold weather. Photocells show maximum efficiency on a clear winter day. There are two factors at play here - a lot of sun and natural cooling.

Moreover, if snow falls on the panel, it will still continue to generate electricity. Moreover, the snowflakes won’t even have time to lie on it much, having melted from the heat of the heated photocells.

Solar battery efficiency

One photocell, even at noon in clear weather, produces very little electricity, only sufficient to operate an LED flashlight.

To increase the output power, several PV cells are combined in a parallel circuit to increase the DC voltage and in a series circuit to increase the current.

The efficiency of solar panels depends on:

• temperature of the air and the battery itself;
• correct selection of load resistance;
• angle of incidence of sunlight;
• presence/absence of anti-reflective coating;
• luminous flux power.

The lower the temperature outside, the more efficient the photocells and the solar battery as a whole work. Everything is simple here. But with load calculation the situation is more complicated. It should be selected based on the current supplied by the panel. But its value varies depending on weather factors.

Solar panels are produced with an output voltage that is a multiple of 12 V - if the battery needs to be supplied with 24 V, then two panels will have to be connected in parallel to it

Constantly monitoring the parameters of a solar battery and manually adjusting its operation is problematic. To do this, it is better to use a control controller, which automatically adjusts the settings of the solar panel in order to achieve maximum performance and optimal operating modes from it.

The ideal angle of incidence of the sun's rays on a solar battery is straight. However, if the deviation is within 30 degrees from the perpendicular, the efficiency of the panel drops by only about 5%. But with a further increase in this angle, an increasing proportion of solar radiation will be reflected, thereby reducing the efficiency of the solar cell.

If the battery is required to produce maximum energy in the summer, then it should be oriented perpendicular to the average position of the Sun, which it occupies on the equinoxes in spring and autumn.

For the Moscow region, this is approximately 40–45 degrees to the horizon. If the maximum is needed in winter, then the panel should be placed in a more vertical position.

And one more thing - dust and dirt greatly reduce the performance of photocells. Photons simply do not reach them through such a “dirty” barrier, which means there is nothing to convert into electricity. The panels must be washed regularly or placed so that the dust is washed off by rain on their own.

Some solar panels have built-in lenses to concentrate radiation onto the solar cell. In clear weather this leads to increased efficiency. However, in heavy clouds, these lenses only cause harm.

If a conventional panel in such a situation continues to generate current, albeit in smaller volumes, then the lens model will stop working almost completely.

The panels must be installed so that there are no trees, buildings or other obstacles in the path of the sun's rays.

House solar power supply diagram

The solar power supply system includes:

1. Solar panels.
2. Controller.
3. Batteries.

The controller in this circuit protects both solar panels and batteries. On the one hand, it prevents the flow of reverse currents at night and in cloudy weather, and on the other, it protects the batteries from excessive charge/discharge.

Rechargeable batteries for solar panels should be selected the same in age and capacity, otherwise charging/discharging will occur unevenly, which will lead to a sharp reduction in their service life

An inverter is needed to transform 12, 24 or 48 Volt DC into 220 Volt AC. Car batteries are not recommended for use in such a circuit due to their inability to withstand frequent recharging. It is best to spend money and purchase special helium AGM or flooded OPzS batteries.

Conclusions and useful video on the topic

The operating principles and connection diagrams of solar panels are not too difficult to understand. And with the video materials we have collected below, it will be even easier to understand all the intricacies of the functioning and installation of solar panels.

It is accessible and understandable how a photovoltaic solar battery works, in all details:

How solar panels work:

DIY solar panel assembly from photocells:

Each element in the solar power supply system of a cottage must be selected correctly. Inevitable power losses occur in the batteries, transformers and controller. And they must be reduced to a minimum, otherwise the already rather low efficiency of solar panels will be reduced to zero.

In recent years, so-called “alternative energy” has become increasingly popular. Particular attention is paid to the use of solar radiation. This is quite natural, because if you create an element that is capable of converting light rays into electricity, you can get a free inexhaustible energy source. And such an element was created. It was called a “solar photocell” or “solar battery”, and how a solar battery works is quite simple to understand.

Operating principle

The main thing is not to confuse photovoltaic batteries with solar collectors (both are often called “solar panels”). If the principle of operation of collectors is based on heating the coolant, then photocells directly produce electricity. Their work is based on the photoelectric effect, which consists in generating current under the influence of sunlight in semiconductor materials.

Semiconductors are substances whose atoms either contain an excess number of electrons (n-type), or, conversely, lack them (p-type). And those areas of the structure of p-elements where electrons could potentially be located are called “holes”. Accordingly, a photocell based on semiconductors consists of two layers with different types of conductivity.

How do solar cells with this structure work? As follows. The inner layer of the element is made of a p-semiconductor, the outer, much thinner one, is made of an n-semiconductor. At the boundary of the layers, the so-called “p-n transition zone” appears, formed due to the formation of positive volumetric charges in the n-layer and negative ones in the p-layer.

In this case, a certain energy barrier appears in the transition zone, caused by the difference in charge potentials. It prevents the penetration of major charge carriers, but freely allows minor ones to pass through, and in opposite directions. Under the influence of sunlight, some photons are absorbed by the surface of the element and generate additional “hole-electron” pairs. That is, electrons and holes move from one semiconductor to another, giving them an additional negative or positive charge. In this case, the initial potential difference between the n- and p-layers decreases, and an electric current is generated in the external circuit.

Features of the structure

Many modern photocells have only one p-n junction. In this case, freely transferring charge carriers are generated only by those photons whose energy is either greater than or equal to the width of the “gap” at the transition boundary. This means that photons with lower energy levels are simply not used, which in turn significantly reduces the efficiency of the cell. To overcome this limitation, multilayer (more often four-layer) photostructures were created.

They allow the use of a significantly larger part of the solar spectrum and have higher productivity. Moreover, the photocells are positioned in such a way that the rays hit the junction with the widest band gap first. In this case, more “energy-intensive” photons are absorbed, while photons with less energy travel deeper and stimulate other elements.

What types of solar panels are there?

Solar cells, the operating principle of which is based on the photoelectric effect, have been created for a long time. The main difficulty in their production is the selection of materials capable of generating a sufficiently powerful current. The first experiments were carried out with selenium cells, but their efficiency was extremely low (about 1%). Nowadays, photovoltaic cells mainly use silicon; the productivity of such devices is about 22%. In addition, new cell samples are constantly being developed (for example, using gallium or indium arsenide) with higher efficiency. The maximum efficiency of solar panels today is 44.7%.

But such elements are very expensive and are so far produced only in laboratory conditions. Cells based on monocrystalline or polycrystalline silicon, as well as thin-film elements, have become widespread. Photobatteries based on monocrystals are more expensive, but have greater performance, while polycrystals are cheaper, but due to their heterogeneous structure, they are less efficient. In the production of thin-film cells, it is not crystals that are used, but silicon layers deposited on a flexible substrate.

At all times, humanity has strived to make the most of the benefits provided by nature. Proof of this is the invention of solar panels. The principle of operation of solar panels is quite simple. It was thanks to them that our calculators previously worked at any time of the day, summer and winter, regardless of the type and frequent battery changes. The modern world is characterized by the use of solar energy in different areas and scales, from modern tablets to airplanes. This article will inform you about how a solar battery works, its types and operating principle.

• A little bit of history
• Classification

A little bit of history

As you know, the solar battery is not the first invention that uses the all-encompassing energy of the Sun as an alternative to electrical energy. The first attempts to use sunlight were terminal power plants, which have a more common name as “collectors”. The principle of their operation was to heat water to 100 ° C using sunlight, which resulted in the generation of electricity. The work of the collectors consisted of a multi-stage transformation of energy: accumulation of solar rays, boiling of liquid, formation of steam, movement of a steam engine and conversion of thermal energy into mechanical energy.

Unlike a collector, a solar battery directly transforms the sun's output into electrical energy. It is also worth noting such a feature of the solar battery as the use of light rather than heat, which allows the generation of electricity even in winter.

Today, the operating principle of these devices is based on converting the action of rays into electric current (photoelectric effect) using special semiconductors, which make up the entire battery.

The discoverers of the photoelectric effect are three distinguished physicists. The very phenomenon of such a process was described by a physicist of French origin - Alexandre Edmond Becquerel in 1839. Then, in 1873, the first semiconductor was discovered to implement the photoelectric effect by the English electrical engineer Willoughby Smith. And the principle of operation, the circuit of the solar battery were described in more detail and the laws of the previous discoverers were confirmed in 1905 by the world famous Nobel Prize laureate Albert Einstein.

Definition and Basics of Energy Transformation

The solar battery device consists of a plate equipped with a chain of connected semiconductors (photocells). Photocells perform the function of converting sunlight into electrical current. Therefore, in order to understand the principle of operation of this device, you should study its basics, namely photocells.

Photocells are semiconductors that transform the action of quanta of electromagnetic radiation, capable of moving only at the speed of light, into electrical energy. The process of this transformation is called the photoelectric effect, which appears under the influence of sunlight on the structure of the photocell. The peculiarity of the structure lies in its heterogeneity, which is created using alloys of various materials and impurities to change its properties from the point of view of physics and chemistry.

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These same impurities create negative and positive junctions (p-n), which are the basis for the operation of two semiconductors and conductivity between them. In addition to this method, which creates heterogeneity in the structure of photocells, the following are also used:

• combining semiconductors with different band gaps;
• changing the chemical composition of the photocell in order to form a graded-gap structure;
• a combination of the above methods.

Energy transformation directly depends on the physical and electrical properties of the structure and electrical conductivity of semiconductors (photoconductivity). A photocell consists of different types of electrons and layers of them. The electrode on which the charge arises is a negative type, and accordingly, the anode (receiver) of this charge is a positive type. The accumulation of solar energy occurs in this way: electrons emerging from the negative layer under the influence of sunlight are accepted by the anodes. Leaving the layer of positive electrons, they return to their original location. Then the steps are repeated. Therefore, the energy of the Sun remains inside the device.

Classification

Depending on the material and manufacturing method, the following types of solar cells are distinguished: silicon and film.

Silicon batteries are devices whose main active material is silicon. Silicon is characterized by high performance compared to other materials used to create these devices, and therefore is in great demand. According to their structure, silicon devices are divided into three subtypes:

Film devices are divided into the following types:

• based on cadmium telluride using film technology;
• based on an alloy of copper, indium and selenium, the efficiency of such devices is 16-20%;
• polymer film devices made from organic photocells, their efficiency is 5-6%.

The solar panel connection diagram involves calculating the load and setting up the charge controller. The simplest scheme can be considered using the example of a garden lantern. Such garden lights are gradually becoming widespread due to the bright illumination of paths, lawns and garden plots. In winter, the light from solar-powered garden lanterns is less bright than at other times. The circuit in this case consists of a photosensitive element, a storage battery, and a solar battery.

Today, developments are underway to produce large-scale fields of solar panels in Antarctica. Such power plants will accumulate energy during the six-month polar day, which occurs in the northern territories in the summer, and in the south in the winter. Solar energy is a worthy alternative to electric current, so its range of applications is wide. Batteries powered by sunlight are even used to manufacture spacecraft.

One of the energy sources is generating alternative solar energy. It appeared relatively recently, but has already gained popularity in the European Union due to its high efficiency and reasonable cost.

A solar battery is an almost inexhaustible source of energy, capable of storing and converting light rays into energy and electricity. In the CIS countries, a new source of energy is gradually gaining popularity. (By the way, you can read the article on how to choose a solar battery.)

Components

There are two types of their connection:

• sequential;
• parallel.

The only difference is that in a parallel connection the current increases, and in a series connection the voltage increases.

If there is a need for maximum operation of two parameters at once, then parallel-sequential is used.

But it is worth considering that high loads may cause some contacts to burn out. To prevent this, diodes are used.

One diode is capable of protecting one fourth of the photocell. If they are not in the device, then there is a high probability that the entire energy source will stop functioning after the first rain or hurricane.

Important point: Neither the accumulation nor the current strength completely correspond to the possible parameters of modern household appliances, so it is necessary to redistribute and accumulate electricity.

To do this, it is recommended to additionally connect at least two. One will be cumulative, and the second will be spare or reserve.

Let's give an example of how additional batteries work. When the weather is nice and sunny outside, the charge goes quickly and after a short amount of time, excess energy appears.

Therefore, this entire process is controlled by a special rheostat, which is capable of converting all unnecessary electricity into additional reserves at a certain moment.

You can read reviews from solar panel owners in this article:

Operating principle

What is the operating principle of an alternative energy source?

Firstly, solar cells are silicon wafers. In turn, silicon in its chemical composition is extremely similar to pure silicon. It was this nuance that made it possible to reduce the cost of a solar battery and put it on the assembly line.

Silicon must be crystallized, since it itself is a semiconductor. Single crystals are much simpler to manufacture, but do not have many edges, due to which electrons are able to move in a straight line.

Almost 100% of all the energy we use in everyday life is solar energy, converted in one way or another. Coal is dead plants that lived thanks to photosynthesis, oil is plants and animals that died out millions of years ago and grew due to the energy of the sun. Even when you burn wood, you release the solar energy that the wood has absorbed. In fact, any thermal power plant converts solar energy accumulated in the form of coal, oil, gas and other fossils into electricity.

The solar panel simply does this directly, without the participation of “middlemen”. Electricity is the most convenient form of using solar energy. The entire life of mankind is now built around electricity, and it is very difficult to imagine civilization without it. Despite the fact that the first solar cells appeared more than half a century ago, solar energy has not yet found proper distribution. Why? More on this at the end of the article, but for now let’s figure out how it all works.

It's all about the silicon

Solar cells are made up of smaller cells called photovoltaic cells, which are made of silicon.

A solar panel consists of several photocells.

Important. Silicon is the most abundant semiconductor on Earth (about 30% of the entire earth's crust)

Silicon is located between two conductive layers.

"Sandwich" of silicon and conductive layers

Each silicon atom is connected to its neighbors by four strong bonds that hold electrons in place, so current cannot flow that way.

Structure of silicon atoms

In order to obtain current, two different layers of silicon are used:

• N-type silicon has an excess of electrons
• P-type silicon – additional places for electrons (holes)

Silicon P and N type

Where two types of silicon are connected, electrons can move across the P-N junction, leaving a positive charge on one side and a negative charge on the other.

To make this easier to imagine, it's better to think of light as a stream of particles (photons) that hit our cell so hard that it knocks an electron out of its bond, leaving a hole. The negatively charged electron and the site of the positively charged hole can now move freely, but because we have an electric field at the P-N junction, they only move in one direction. The electron goes towards the N-conductor, the hole tends to the P side of the plate.

After being “released” the electron tends to the conductor

All electrons are collected by metal conductors at the top of the cell and go into the external network, powering current collectors, batteries for solar panels or an electric chair for a hamster :) . After the work done, the electrons return to the back side of the plate and take up places in those very “holes”.

Photocell operation

A standard plate, 150x150 mm, nominally produces only 0.5 volts, but if you combine them into one large panel, you can get more power and voltage. To charge a mobile phone, you need to combine 12 such plates. To power a home, you need to spend a lot more plates and panels.

Due to the fact that the only moving part in solar cells is electrons, solar panels do not require maintenance and can last 20-25 years without wearing out or breaking.

Why haven't people switched to solar energy completely?

You can talk a lot about politics, business and other conspiracy theories, but within the framework of this article I would like to talk about other problems.

1. Uneven distribution of solar energy over the surface of the planet. Some areas are sunnier than others and this is also variable. There is much less solar energy on cloudy days and none at all at night. And to fully rely on solar energy, efficient ways to generate electricity for all areas are needed.
2. Efficiency In laboratory conditions, a result of 46% was achieved. But commercial systems don't even achieve 25% efficiency.
3. Storage. The weakest link in solar energy is the lack of an efficient and cheap way to store the generated electricity. Existing batteries are heavy and significantly reduce the efficiency of an already weak solar system. In general, storing 10 tons of coal is easier and more convenient than 46 megawatts generated by the same coal or the sun.
4. Infrastructure. In order to power megacities, the roof areas of these cities will not be enough to satisfy all demands, therefore, to implement solar energy, it is necessary to transport energy, and for this it is necessary to build new energy facilities

Video about how solar panels are produced.

The video describes in detail the manufacturing process of polycrystalline solar cells, the principle of their operation in a solar power plant system, and the operating principle of the charge controller and inverter.