Physicists from Russia have improved the efficiency of solar panels by 20%

Relationship between efficiency and materials and technologies

How do solar panels work? Based on the properties of semiconductors. The light that falls on them produces knocking out by its particles of electrons located in the outer orbit of atoms. A large number of electrons creates an electric current potential - under closed circuit conditions.

To provide a normal power indicator, one module will not be enough. The more panels, the more efficient the operation of the radiators, which give electricity to the batteries, where it will accumulate.It is for this reason that the efficiency of solar panels also depends on the number of installed modules. The more of them, the more solar energy they absorb, and their power index becomes an order of magnitude higher.

Can battery efficiency be improved? Such attempts were made by their creators, and more than once. The way out in the future may be the production of elements consisting of several materials and their layers. The materials are followed in such a way that the modules can absorb different types of energy.

For example, if one substance works with the UV spectrum, and the other with the infrared spectrum, the efficiency of solar cells increases significantly. If you think at the level of theory, then the highest efficiency can be an indicator of about 90%.

Also, the type of silicon has a great influence on the efficiency of any solar system. Its atoms can be obtained in several ways, and all panels, based on this, are divided into three varieties:

• single crystals;
• polycrystals;
• amorphous silicon elements.

Solar cells are produced from monocrystals, the efficiency of which is about 20%. They are expensive because they are the most efficient. Polycrystals are much lower in cost, since in this case the quality of their work directly depends on the purity of the silicon used in their manufacture.

Elements based on amorphous silicon have become the basis for the production of thin-film flexible solar panels. The technology of their manufacture is much simpler, the cost is lower, but the efficiency is less - no more than 6%. They wear out quickly. Therefore, to improve their service life, selenium, gallium, and indium are added to them.

Usage

Portable electronics

To provide electricity and / or recharge the batteries of various consumer electronics - calculators, players, flashlights, etc.

Energy supply of buildings

Solar battery on the roof of the house

Large-sized solar cells, like solar collectors, are widely used in tropical and subtropical regions with a large number of sunny days. Especially popular in the Mediterranean countries, where they are placed on the roofs of houses.

New homes in Spain have been equipped with solar water heaters since March 2007 to provide between 30% and 70% of their hot water needs, depending on the location of the home and expected water consumption. Non-residential buildings (shopping centers, hospitals, etc.) must have photovoltaic equipment.

Currently, the transition to solar panels is causing a lot of criticism among people. This is due to the increase in electricity prices, clutter of the natural landscape. Opponents of the transition solar panels are criticized for such transition, as the owners of houses and land on which solar panels installed and wind farms, receive subsidies from the state, while ordinary tenants do not. In this regard, the German Federal Ministry of Economics has developed a bill that will allow in the near future to introduce benefits for tenants living in houses that are provided with energy from photovoltaic installations or block thermal power plants. Along with the payment of subsidies to owners of houses that use alternative energy sources, it is planned to pay subsidies to tenants living in these houses.

Use in space

Solar panels are one of the main ways to generate electrical energy on spacecraft: they operate for a long time without consuming any materials, and at the same time they are environmentally friendly, unlike nuclear and radioisotope energy sources.

However, when flying at a great distance from the Sun (beyond the orbit of Mars), their use becomes problematic, since the flow of solar energy is inversely proportional to the square of the distance from the Sun. When flying to Venus and Mercury, on the contrary, the power of solar batteries increases significantly (in the region of Venus by 2 times, in the region of Mercury by 6 times).

Use in medicine

South Korean scientists have developed a subcutaneous solar cell. A miniature energy source can be implanted under the skin of a person in order to ensure the smooth operation of devices implanted in the body, such as a pacemaker. Such a battery is 15 times thinner than a hair and can be recharged even if sunscreen is applied to the skin.

What is efficiency

So, the efficiency of a battery is the amount of potential it actually generates, indicated as a percentage. To calculate it, it is necessary to divide the power of electrical energy by the power of solar energy falling on the surface of solar panels.

Now this figure is in the range from 12 to 25%. Although in practice, given the weather and climatic conditions, it does not rise above 15. The reason for this is the materials from which solar batteries are made. Silicon, which is the main "raw material" for their manufacture, does not have the ability to absorb the UV spectrum and can only work with infrared radiation.Unfortunately, due to this deficiency, we waste the energy of the UV spectrum and do not put it to good use.

Impact on performance of various factors.

Increasing the efficiency of solar modules is a headache for all researchers working in this direction. To date, the efficiency of such devices is in the range from 15 to 25%. The percentage is very low. Solar batteries are an extremely whimsical device, the stable operation of which depends on many reasons.

The main factors that can affect performance in two ways include:

• Base material for solar cells. The weakest in this regard is polycrystalline solar panels with an efficiency of up to 15%. Modules based on indium-gallium or cadmium-tellurium, which have up to 20% of productivity, can be considered promising.
• Solar receiver orientation. Ideally, solar panels with their working surface should face the sun at a right angle. In this position, they should be as long as possible. To increase the duration of the correct positioning of the modules in the area of ​​the sun, more expensive counterparts have in their arsenal a sun tracking device that rotates the batteries following the movement of the star.
• Overheating of installations. Elevated temperatures have a negative effect on power generation, therefore, during installation, it is necessary to ensure sufficient ventilation and cooling of the panels. This is achieved by installing a ventilated gap between the panel and the installation surface.
• The shadow cast by any object can significantly spoil the efficiency of the entire system.

Having fulfilled all the requirements, and, if possible, installing the panels in the right position, you can get solar panels with high efficiency. It is high, not maximum. The fact is that the calculated, or theoretical efficiency, is a value derived in laboratory conditions, with average parameters of daylight hours and the number of cloudy days.

In practice, of course, the percentage of efficiency will be lower.

Picking up solar batteries for your home, it is better to focus on the lower performance limit, rather than the upper one. By selecting thus the solar modules and all the components appropriate for the operation, one can be sure of the sufficient capacity of the installation to be installed. By choosing a lower performance limit in the calculations, you can save on the purchase of additional panels that are bought for reinsurance in case of a lack of power.

Encouraging development prospects.

To date, the absolute record of efficiency in solar energy belongs to American developers and is 42.8%. This value is 2% higher than the previous record in 2010. A record amount of energy was achieved with the improvement of a solar cell made of crystalline silicon. The uniqueness of such a study is the fact that all measurements were carried out exclusively in working conditions, that is, not in laboratory and greenhouse premises, but in real places of the proposed installation.

On the sidelines of all the same technical laboratories, work to increase the last record does not stop. The next goal of the developers is the efficiency limit of solar modules at 50%.Every day humanity is getting closer to the moment when solar energy will completely replace the harmful and expensive currently used energy sources, and will become on a par with such giants as hydroelectric power plants.

Efficiency of different types of solar panels

All modern solar cells operate on the basis of the physical properties of semiconductors. Photons of sunlight, falling on photovoltaic panels, knock out electrons from the outer orbits of atoms. As a result, their movement begins, which leads to the appearance of an electric current.

Single panels cannot provide normal power, so they are connected in certain quantities to a common solar battery. The more photovoltaic cells are involved in the system, the higher the power output of electricity will be.

Knowing the principle of the panels, you can determine their efficiency. Theoretically, the definition of efficiency is the amount of electricity produced divided by the amount of energy from the sun's rays falling on a given panel. Theoretically, modern systems are capable of delivering up to 25%, but in reality this figure is no more than 15%. A lot depends on the material from which the panels are made. For example, widely used silicon is able to absorb only infrared rays, and the energy of ultraviolet rays is not perceived by it and is wasted.

Currently, work is underway on the creation of multilayer panels, which makes it possible to manufacture solar panels with high efficiency. Their design includes various materials located in several layers. They are selected in such a way that they are able to capture all the main energy quanta.That is, each layer of a certain material is capable of absorbing one of the types of energy.

Theoretically, for such devices, the efficiency can increase up to 87%, but in practice, the technology for manufacturing such panels is quite complicated. In addition, their cost is much higher compared to standard solar systems.

The efficiency of a solar battery largely depends on the type of silicon used in solar cells. All panels based on this material are divided into three types:

• Monocrystalline, with an efficiency of 10-15%. They are considered the most effective, and their price is noticeably higher than other devices.
• Polycrystalline have lower rates, but their cost per watt is much lower. When using high-quality materials, such panels are sometimes superior in efficiency to single crystals.
• Flexible thin-film panels based on amorphous silicon. They are easy to manufacture and low cost. However, the efficiency of these devices is very low, about 5-6%. Gradually, during operation, their performance decreases, productivity becomes lower.

pros

1. Due to the fact that there are no moving parts and elements in the panels, durability is increased. Manufacturers guarantee a service life of 25 years.
2. If you follow all routine maintenance and operating rules, the operation of such systems increases to 50 years. Maintenance is quite simple - timely clean the photocells from dust, snow and other natural contaminants.
3. It is the durability of the system that is the determining factor for the purchase and installation of panels. After all the costs have paid off, the electricity generated will be free.

The most important obstacle to the widespread use of such systems is their high cost. With the low efficiency of domestic solar panels, there are serious doubts about the economic need for this particular method of generating electricity.

But again, it is necessary to reasonably evaluate the capabilities of these systems and, based on this, calculate the expected return. It will not be possible to completely replace traditional electricity, but it is quite possible to save money by using solar systems.

In addition, it is difficult not to notice such benefits as:

• Getting electricity in the most remote areas from civilization;
• autonomy;
• Noiselessness.

Disadvantages of solar power

• The need to use large areas;
• The solar power plant does not work at night and does not work efficiently enough in the evening twilight, while the peak of power consumption occurs precisely in the evening hours;
• Despite the environmental cleanliness of the energy received, the solar cells themselves contain toxic substances, such as lead, cadmium, gallium, arsenic, etc.

Solar power plants are criticized due to high costs, as well as the low stability of complex lead halides and the toxicity of these compounds. Currently, active development of lead-free semiconductors for solar cells, for example, based on bismuth and antimony, is underway.

Due to their low efficiency, which reaches 20 percent at best, solar panels get very hot. The remaining 80 percent of solar energy The light heats the solar panels up to average temperature around 55°C. FROM an increase in the temperature of the photovoltaic cell by 1°, its efficiency drops by 0.5%.This dependence is non-linear and an increase in the element temperature by 10° leads to a decrease in efficiency by almost a factor of two. Active elements of cooling systems (fans or pumps) pumping refrigerant consume a significant amount of energy, require periodic maintenance and reduce the reliability of the entire system. Passive cooling systems have very low performance and cannot cope with the task of cooling solar panels.

Performance calculation

The use of solar energy and the economic rationality of such concepts determine the effectiveness of all types of solar panels systems. First of all, the costs of transformation are taken into account. solar energy into electricity.

How profitable and effective such systems are determined by factors such as:

• Type of solar panels and related equipment;
• The efficiency of photocells and their cost;
• Climatic conditions. Different regions have different solar activity. It also affects the payback period.

How to choose the right performance

Before buying panels, you need to know what the required efficiency of a solar battery can be.

If your household consumption level is, for example, 100 kW/month (according to the electricity meter), then it is advisable that the solar cells produce the same amount.

Decided on this. Let's go further.

It is clear that the solar station operates only during the daytime. Moreover, the nameplate power will be achieved in the presence of a clear sky. In addition, the peak power can be achieved under the condition that the rays of the sun fall on the surface. at a right angle.

As the position of the sun changes, so does the angle of the panel. Accordingly, at large angles, a noticeable decrease in power will be observed.This is only on a clear day. In cloudy weather, a power drop of 15–20 times can be guaranteed. Even a small cloud or haze causes a power drop of 2-3 times

This must also be taken into account

Now - how to calculate the operating time of the panels?

The operating period in which the batteries can effectively operate at almost full capacity is approximately 7 hours. From 9:00 a.m. to 4:00 p.m. In summer, there is more daylight hours, but the generation of electricity in the morning and evening is very small - within 20–30%. The rest, this is 70%, will be generated, again, during the daytime, from 9 am to 4 pm.

So, it turns out that if the panels have a nameplate power of 1 kW, then in the summer, the sunniest a day will generate 7 kW / h electricity. Provided that they will work from 9 to 16 hours of the day. That is, it will amount to 210 kWh of electricity per month!

This is a panel kit. And one socket with a power of only 100 watts? For a day it will give 700 watts / hour. 21 kW per month.

How to make your solar panel work as efficiently as possible

The performance of any solar system depends on:

• temperature indicators;
• the angle of incidence of the sun's rays;
• surface condition (it must always be clean);
• weather conditions;
• the presence or absence of a shadow.

The optimal angle of incidence of the sun's rays on the panel is 90 °, that is, a straight line. There are already solar systems equipped with unique devices. They allow you to monitor the position of the star in space. When the position of the Sun in relation to the Earth changes, the angle of inclination of the solar system also changes.

The constant heating of the elements also does not have the best effect on their performance. When energy is converted, its serious losses occur.Therefore, a small space must always be left between the solar system and the surface on which it is mounted. The air currents passing in it will serve as a natural way of cooling.

The purity of solar panels is also an important factor affecting their efficiency. If they are heavily polluted, they collect less light, which means that their efficiency is reduced.

Also, the correct installation plays a big role. When mounting the system, it is impossible to allow a shadow to fall on it. The best side on which they are recommended to be installed is the south.

Turning to weather conditions, we can at the same time answer the popular question of whether solar panels work in cloudy weather. Of course, their work continues, because the electromagnetic radiation emanating from the Sun hits the Earth at all times of the year. Of course, the performance of the panels (COP) will be significantly lower, especially in regions with an abundance of rainy and cloudy days a year. In other words, they will generate electricity, but in much smaller quantities than in regions with a sunny and hot climate.

Factors affecting the efficiency of solar cells

Features of the structure of photocells cause a decrease in the performance of the panels with increasing temperature.

Partial dimming of the panel causes a drop in output voltage due to losses in the unlit element, which begins to act as a parasitic load. This drawback can be eliminated by installing a bypass on each photocell of the panel. In cloudy weather, in the absence of direct sunlight, panels that use lenses to concentrate radiation become extremely inefficient, since the effect of the lens disappears.

It can be seen from the operating characteristic of the photovoltaic panel that in order to achieve the greatest efficiency, the correct selection of the load resistance is required. To do this, the photovoltaic panels are not connected directly to the load, but use a photovoltaic system management controller that ensures the optimal operation of the panels.

How does a solar battery work?

All modern solar cells work thanks to the discovery made by the physicist Alexandre Becquerel in 1839 - the very principle of operation of semiconductors.

If the silicon photocells on the top plate are heated, then the atoms of the silicon semiconductor are released. They are trying to capture the atoms of the lower plate. In full accordance with the laws of physics, the electrons of the bottom plate must return to their original state. These electrons open one way - through the wires. The stored energy is transferred to the batteries and returned back to the top silicon wafer.

Story

In 1842, Alexandre Edmond Becquerel discovered the effect of converting light into electricity. Charles Fritts began using selenium to turn light into electricity. The first prototypes of solar cells were created by the Italian photochemist Giacomo Luigi Chamichan.

On March 25, 1948, Bell Laboratories announced the creation of the first silicon-based solar cells to generate electric current. This discovery was made by three company employees - Calvin Souther Fuller, Daryl Chapin and Gerald Pearson.Already 4 years later, on March 17, 1958, a satellite using solar panels, Avangard-1, was launched in the USA. On May 15, 1958, a satellite using solar panels, Sputnik-3, was also launched in the USSR.

This is interesting: In Germany, built the highest wind farm in the world

How quickly will solar panels pay off?

The cost of solar panels today is quite high. And taking into account the low value of the efficiency of the panels, the issue of their payback is very relevant. The service life of batteries powered by solar energy is about 25 years or more. We will talk about what caused such a long service life a little later, but for now we will find out the question voiced above.

The payback period is affected by:

• Selected equipment type. Single-layer solar cells have a lower efficiency compared to multi-layer ones, but also a much lower price.
• Geographical location, that is, the more sunlight in your area, the faster the installed module will pay off.
• Cost of equipment. The more money you spent on the purchase and installation of elements that make up the solar energy saving system, the longer the payback period.
• The cost of energy resources in your region.

The average payback period for the countries of Southern Europe is 1.5-2 years, for the countries of Central Europe - 2.5-3.5 years, and in Russia the payback period is approximately 2-5 years. In the near future, the efficiency of solar panels will increase significantly, this is due to the development of more advanced technologies that increase efficiency and reduce the cost of panels. And as a result, the period during which the energy saving system on solar energy will pay for itself will also decrease.

Latest developments that increase efficiency

Almost every day, scientists around the world announce the development of a new method to increase the efficiency of solar modules. Let's get acquainted with the most interesting of them. Last year, Sharp introduced a solar cell to the public with an efficiency of 43.5%. They were able to achieve this figure by installing a lens to focus energy directly in the element.

German physicists do not lag behind Sharp. In June 2013, they introduced their solar cell with an area of ​​​​only 5.2 square meters. mm, consisting of 4 layers of semiconductor elements. This technology allowed to achieve an efficiency of 44.7%. Maximum efficiency in this case is also achieved by placing the concave mirror in focus.

In October 2013, the results of the work of scientists from Stanford were published. They have developed a new heat-resistant composite capable of increasing the performance of photovoltaic cells. The theoretical value of efficiency is about 80%. As we wrote above, semiconductors, which include silicon, are capable of absorbing only IR radiation. So the action of the new composite material is aimed at converting high-frequency radiation into infrared.

English scientists were next. They developed a technology capable of increasing cell efficiency by 22%. They proposed to place aluminum nanostuds on the smooth surface of thin-film panels. This metal was chosen due to the fact that it does not absorb sunlight, but, on the contrary, scatters it. Consequently, the amount of absorbed solar energy increases. Hence the increase in solar battery performance.

Only the main developments are given here, but the matter is not limited to them. Scientists are fighting for every tenth of a percent, and so far they are succeeding. Let's hope that in the near future the efficiency of solar panels will be at the proper level. After all, then the benefit from using the panels will be maximum.

The article was prepared by Abdullina Regina

Moscow is already using new technologies for lighting streets and parks, I think the economic efficiency has been calculated there:

Types of solar photocells and their efficiency

The operation of solar panels is based on the properties of semiconductor elements. Sunlight falling on photovoltaic panels knocks out electrons from the outer orbit of atoms by photons. The resulting large number of electrons provides an electric current in a closed circuit. One or two panels for normal power is not enough. Therefore, several pieces are combined into solar panels. To obtain the required voltage and power, they are connected in parallel and in series. A larger number of solar cells give a larger area for absorbing solar energy and produce more power.

Photocells

One of the ways to increase efficiency is the creation of multilayer panels. Such structures consist of a set of materials arranged in layers. The selection of materials is carried out in such a way that quanta of different energies are captured. A layer with one material absorbs one type of energy, with a second one another, and so on. As a result, it is possible to create solar panels with high efficiency. Theoretically, such sandwich panels can provide Efficiency up to 87 percent. But this is in theory, but in practice, the manufacture of such modules is problematic. Plus, they get very expensive.

The efficiency of solar systems is also affected by the type of silicon used in solar cells. Depending on the production of the silicon atom, they can be divided into 3 types:

• Monocrystalline;
• Polycrystalline;
• Amorphous silicon panels.

Solar cells made of single-crystal silicon have an efficiency of 10-15 percent. They are the most efficient and cost the most. Polycrystalline silicon models have the cheapest watt of electricity. Much depends on the purity of the materials, and in some cases, polycrystalline elements can be more effective than single crystals.

Amorphous silicon panel