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Geography and features of the use of solar collectors in Russia. Types of solar collectors. Calculation of solar power plant output based on insolation values

The energy of the Sun is the source of life on our planet. The sun heats the atmosphere and the surface of the earth. Thanks to solar energy winds blow, the water cycle is carried out in nature, the seas and oceans heat up, plants develop, animals have food. It is thanks to solar radiation that fossil fuels exist on earth. Solar energy can be converted into heat or cold, driving force and electricity.

SOLAR RADIATION

Solar radiation is electromagnetic radiation, concentrated mainly in the wavelength range of 0.28 ... 3.0 microns. The solar spectrum consists of:

Ultraviolet waves with a length of 0.28 ... 0.38 microns, invisible to our eyes and constituting approximately 2% of the solar spectrum;

Light waves in the range of 0.38 ... 0.78 microns, constituting approximately 49% of the spectrum;

Infrared waves with a length of 0.78 ... 3.0 microns, which account for most of the remaining 49% of the solar spectrum.

The remaining parts of the spectrum play an insignificant role in the heat balance of the Earth.

HOW MUCH SOLAR ENERGY GET TO EARTH?

The sun radiates great amount energy - approximately 1.1x10 20 kWh per second. A kilowatt hour is the amount of energy required to run a 100 watt incandescent light bulb for 10 hours. The outer layers of the Earth's atmosphere intercept approximately one millionth of the energy emitted by the Sun, or approximately 1500 quadrillion (1.5 x 10 18) kWh annually. However, due to reflection, scattering and absorption by atmospheric gases and aerosols, only 47% of all energy, or approximately 700 quadrillion (7 x 10 17) kWh, reaches the Earth's surface.

Solar radiation in the Earth's atmosphere is divided into the so-called direct radiation and scattered by particles of air, dust, water, etc. contained in the atmosphere. Their sum forms the total solar radiation. The amount of energy falling per unit area per unit time depends on a number of factors:

latitude, local climate, season of the year, angle of inclination of the surface with respect to the Sun.

TIME AND PLACE

The amount of solar energy falling on the Earth's surface changes due to the movement of the Sun. These changes depend on the time of day and season. Usually more solar radiation hits the Earth at noon than early in the morning or late in the evening. At noon, the Sun is high above the horizon, and the length of the path of the Sun's rays through the Earth's atmosphere is reduced. Consequently, less solar radiation is scattered and absorbed, which means more reaches the earth's surface.

The amount of solar energy reaching the Earth's surface differs from the average annual value: in winter time- less than 0.8 kWh/m² per day in the North (50˚ latitude) and more than 4 kWh/m² per day in summer time in the same region. The difference decreases as you get closer to the equator.

The amount of solar energy also depends on the geographical location of the site: the closer to the equator, the greater it is. For example, the average annual total solar radiation incident on a horizontal surface is: in Central Europe, Central Asia and Canada - approximately 1000 kWh/m²; in the Mediterranean - approximately 1700 kWh / m²; in most desert regions of Africa, the Middle East and Australia, approximately 2200 kWh/m².

Thus, the amount of solar radiation varies significantly depending on the time of year and geographical location(see table 1). This factor must be taken into account when using solar energy.

Table 1

The amount of solar radiation in Europe and the Caribbean, kWh/m² per day.
Southern Europe Central Europe Northern Europe Caribbean region
January 2,6 1,7 0,8 5,1
February 3,9 3,2 1,5 5,6
March 4,6 3,6 2,6 6,0
April 5,9 4,7 3,4 6,2
May 6,3 5,3 4,2 6,1
June 6,9 5,9 5,0 5,9
July 7,5 6,0 4,4 6,4
August 6,6 5,3 4,0 6,1
September 5,5 4,4 3,3 5,7
October 4,5 3,3 2,1 5,3
November 3,0 2,1 1,2 5,1
December 2,7 1,7 0,8 4,8
YEAR 5,0 3,9 2,8 5,7

CLOUDS

The amount of solar radiation reaching the Earth's surface depends on various atmospheric phenomena and on the position of the Sun both during the day and throughout the year. Clouds are the main atmospheric phenomenon that determines the amount of solar radiation reaching the Earth's surface. At any point on the Earth, solar radiation reaching the Earth's surface decreases with increasing cloud cover. Consequently, countries with predominantly cloudy weather receive less solar radiation than deserts, where the weather is mostly cloudless. The formation of clouds is influenced by the presence of local features such as mountains, seas and oceans, as well as large lakes. Therefore, the amount of solar radiation received in these areas and the regions adjacent to them may differ. For example, mountains can get less solar radiation than the adjacent foothills and plains. Winds blowing towards the mountains cause part of the air to rise and, cooling the moisture in the air, form clouds. The amount of solar radiation in coastal areas may also differ from those recorded in areas located inland.

The amount of solar energy received during the day is largely dependent on local atmospheric phenomena. At noon, with clear skies, the total solar radiation falling on a horizontal surface can reach (for example, in Central Europe) a value of 1000 W / m² (in very favorable weather conditions this figure can be higher), while in very cloudy weather - below 100 W / m² even at noon.

POLLUTION

Anthropogenic and natural phenomena can also limit the amount of solar radiation reaching the Earth's surface. Urban smog, smoke from forest fires and airborne volcanic ash reduce the use of solar energy by increasing the dispersion and absorption of solar radiation. That is, these factors have a greater influence on direct solar radiation than on the total. At heavy pollution air, for example, during smog, direct radiation is reduced by 40%, and the total - only by 15-25%. A strong volcanic eruption can reduce, and over a large area of ​​the Earth's surface, direct solar radiation by 20%, and total - by 10% for a period of 6 months to 2 years. With a decrease in the amount of volcanic ash in the atmosphere, the effect weakens, but the process full recovery may take several years.

POTENTIAL

The sun provides us with 10,000 times more free energy than is actually used worldwide. The global commercial market alone buys and sells just under 85 trillion (8.5 x 10 13) kWh of energy per year. Since it is impossible to follow the whole process, it is not possible to say with certainty how much non-commercial energy people consume (for example, how much wood and fertilizer is collected and burned, how much water is used to produce mechanical or electrical energy). Some experts estimate that such non-commercial energy accounts for one-fifth of all energy used. But even if this is so, then total energy, consumed by mankind during the year, is only approximately one seven thousandth of the solar energy falling on the Earth's surface in the same period.

In developed countries, such as the USA, energy consumption is approximately 25 trillion (2.5 x 10 13) kWh per year, which corresponds to more than 260 kWh per person per day. This indicator is the equivalent of running more than a hundred 100W incandescent bulbs daily for a whole day. The average US citizen consumes 33 times more energy than an Indian, 13 times more than a Chinese, two and a half times more than a Japanese and twice as much as a Swede.

The amount of solar energy reaching the Earth's surface is many times greater than its consumption, even in countries such as the United States, where energy consumption is huge. If only 1% of the country's territory was used for the installation of solar equipment (photovoltaic arrays or solar systems for hot water) operating at 10% efficiency, the US would be fully supplied with energy. The same can be said about all other developed countries. However, in a certain sense, this is unrealistic - firstly, due to the high cost of photovoltaic systems, and secondly, it is impossible to cover such large areas with solar equipment without harming the ecosystem. But the principle itself is correct. It is possible to cover the same area by dispersing installations on the roofs of buildings, on houses, along roadsides, on predetermined plots of land, etc. In addition, in many countries already more than 1% of the land is allocated for the extraction, conversion, production and transportation of energy. And, since most of this energy is non-renewable at the scale of human existence, this kind of energy production is much more harmful to the environment than solar systems.

USING SOLAR ENERGY

In most parts of the world, the amount of solar energy that hits the roofs and walls of buildings far exceeds the annual energy consumption of the inhabitants of these buildings. Using sunlight and heat is a clean, simple, and natural way to get all the forms of energy we need. With help solar collectors residential and commercial buildings can be heated and/or provided with hot water. Sunlight, concentrated parabolic mirrors (reflectors) are used to generate heat (with temperatures up to several thousand degrees Celsius). It can be used for heating or for generating electricity. In addition, there is another way to produce energy with the help of the Sun - photovoltaic technology. Photovoltaic cells are devices that convert solar radiation directly into electricity.

Solar radiation can be converted into useful energy using so-called active and passive solar systems. Active solar systems are solar collectors and photovoltaic cells. Passive systems are obtained through the design of buildings and the selection building materials in such a way as to maximize the use of solar energy.

Solar energy is also converted into useful energy indirectly by transforming into other forms of energy, such as biomass, wind or water energy. The energy of the Sun "controls" the weather on Earth. A large proportion of solar radiation is absorbed by the oceans and seas, the water in which heats up, evaporates and falls to the ground in the form of rain, "feeding" hydroelectric power plants. The wind required by wind turbines is formed due to non-uniform heating of the air. Another category of renewable energy sources arising from solar energy is biomass. Green plants absorb sunlight, as a result of photosynthesis, organic substances are formed in them, from which heat and electrical energy can subsequently be obtained. Thus, the energy of wind, water and biomass is a derivative of solar energy.

PASSIVE SOLAR ENERGY

Passive solar buildings are those designed to take into account local climatic conditions as much as possible, and where appropriate technologies and materials are used to heat, cool and light the building using solar energy. These include traditional building techniques and materials such as insulation, solid floors, and south-facing windows. Such living quarters can be built in some cases at no additional cost. In other cases, additional costs incurred during construction can be offset by lower energy costs. Passive solar buildings are environmentally friendly, they contribute to the creation of energy independence and an energy balanced future.

In a passive solar system, the building structure itself acts as a collector of solar radiation. This definition corresponds to most of the simplest systems where heat is stored in a building through its walls, ceilings or floors. There are also systems where special elements for heat accumulation are built into the structure of the building (for example, boxes with stones or tanks or bottles filled with water). Such systems are also classified as passive solar. Passive solar buildings are the perfect place to live. Here you feel the connection with nature more fully, in such a house there is a lot of natural light, it saves electricity.

STORY

Historically, building design has been influenced by local climatic conditions and availability of building materials. Later, humanity separated itself from nature, following the path of domination and control over it. This path led to the same type of buildings for almost any area. In 100 A.D. e. the historian Pliny the Younger built a summer house in Northern Italy, one of the rooms of which had windows made of thin mica. The room was warmer than the others and needed less wood to heat it. In the famous Roman baths in I-IV Art. n. e. specially installed big windows south facing for more solar heat entered the building. By VI Art. solar rooms in homes and public buildings became so commonplace that Justinian Code introduced a "right to the sun" to guarantee individual access to the sun. In the 19th century, greenhouses were very popular, in which it was fashionable to stroll under the canopy of lush plant foliage.

Due to power outages during World War II, by the end of 1947 in the United States, buildings passively using solar energy were in such great demand that the Libbey-Owens-Ford Glass Company published a book titled Your Sunshine Home, featuring 49 best projects solar buildings. In the mid-1950s, architect Frank Bridgers designed the world's first passive solar office building. The solar system for hot water installed in it has been operating smoothly since that time. The Bridgers-Paxton building itself is listed on the country's National Historic Register as the world's first solar-heated office building.

Low oil prices after World War II diverted public attention away from solar buildings and energy efficiency issues. Since the mid-1990s, the market has been changing its attitude towards ecology and the use of renewable energy, and trends appear in construction, which are characterized by a combination of the project of the future building with the surrounding nature.

PASSIVE SOLAR SYSTEMS

There are several main ways to passively use solar energy in architecture. Using them, you can create many different schemes, thereby obtaining a variety of building designs. Priorities in the construction of a building with passive use of solar energy are: good location of the house; a large number of south-facing windows (in the Northern Hemisphere) to let in more sunlight during the winter (and vice versa, a small number of windows facing east or west to limit unwanted sunlight in the summer); correct calculation of the heat load on the interior to avoid unwanted temperature fluctuations and keep warm at night, well-insulated building structure.

The location, insulation, orientation of windows and the thermal load on the premises must be a single system. To reduce internal temperature fluctuations, insulation should be placed on the outside of the building. However, in places with rapid internal heating, where little insulation is required, or where the heat capacity is low, the insulation should be on the inside. Then the design of the building will be optimal for any microclimate. It is worth noting the fact that the right balance between the thermal load on the premises and insulation leads not only to energy savings, but also to saving building materials.

ACTIVE SOLAR SYSTEMS

During the design of the building, the use of active solar systems, such as solar collectors and photovoltaic batteries. This equipment is installed on the south side of the building. To maximize the amount of heat in winter, solar collectors in Europe and North America must be installed with an inclination angle of more than 50° from the horizontal plane. Fixed photovoltaic arrays receive the greatest amount of solar radiation during the year when the angle of inclination relative to the horizon equals the geographic latitude at which the building is located. The angle of the roof of the building and its orientation to the south are important aspects when designing a building. Solar collectors for hot water supply and photovoltaic panels should be located in close proximity to the place of energy consumption. The main criterion for choosing equipment is its efficiency.

SOLAR COLLECTORS

Since ancient times, man has been using solar energy to heat water. At the heart of many solar energy systems lies the application solar collectors. The collector absorbs light energy from the sun and converts it into heat, which is transferred to a coolant (liquid or air) and then used to heat buildings, heat water, generate electricity, dry agricultural products or cook food. Solar collectors can be used in almost all processes that use heat.

For a typical residential building or apartment in Europe and North America, heating water is the second most energy intensive domestic process. For a number of houses, it is even the most energy-intensive. The use of solar energy can reduce the cost of domestic water heating by 70%. The collector preheats the water, which is then fed to a traditional column or boiler, where the water is heated to desired temperature. This results in significant cost savings. This system is easy to install and requires almost no maintenance.

Today, solar water heating systems are used in private homes, apartment buildings, schools, car washes, hospitals, restaurants, agriculture and industry. All of these establishments have something in common: they use hot water. Homeowners and business leaders have already seen that solar water heating systems are cost-effective and able to meet the need for hot water in any region of the world.

STORY

People have been heating water with the help of the Sun since ancient times, before fossil fuels took the lead in the world's energy. The principles of solar heating have been known for thousands of years. A black-painted surface heats up a lot in the sun, while light-colored surfaces heat up less, white ones less than all the others. This property is used in solar collectors - the most famous devices that directly use the energy of the sun. Collectors were developed about two hundred years ago. The most famous of these, the flat collector, was made in 1767 by a Swiss scientist named Horace de Saussure. It was later used for cooking by Sir John Herschel during his expedition to South Africa in the 1930s.

The technology of manufacturing solar collectors reached almost the modern level in 1908, when William Bailey invented a collector with a thermally insulated body and copper tubes. This collector was very similar to the modern thermosyphon system. By the end of World War I, Bailey had sold 4,000 of these collectors, and the Florida businessman who bought the patent from him sold almost 60,000 collectors by 1941. Copper rationing introduced in the US during World War II led to a sharp decline in the market for solar heaters.

Until the global oil crisis in 1973, these devices were neglected. However, the crisis has awakened new interest to alternative energy sources. As a result, there has been an increase in demand for solar energy. Many countries are keenly interested in the development of this area. The efficiency of solar heating systems has steadily increased since the 1970s, thanks to the use of tempered glass with reduced iron content (it transmits more solar energy than ordinary glass) to cover the collectors, improved thermal insulation and a durable selective coating.

TYPES OF SOLAR COLLECTORS

A typical solar collector stores solar energy in modules of tubes and metal plates mounted on the roof of a building, painted black for maximum radiation absorption. They are encased in glass or plastic and tilted to the south to capture maximum sunlight. Thus, the collector is a miniature greenhouse that accumulates heat under a glass panel. Since solar radiation is distributed over the surface, the collector must have a large area.

There are solar collectors of various sizes and designs depending on their application. They can provide households with hot water for laundry, bathing and cooking, or be used to pre-heat water for existing water heaters. The market currently offers many various models collectors. They can be divided into several categories. For example, there are several types of collectors in accordance with the temperature they give:

Low-temperature collectors produce low-grade heat, below 50 ˚C. They are used for heating water in swimming pools and in other cases when not too hot water is required.

Medium temperature collectors produce high and medium potential heat (above 50˚C, typically 60-80˚C). Usually these are glassed flat collectors, in which heat transfer is carried out by means of a liquid, or concentrator collectors, in which heat is concentrated. The representative of the latter is the collector evacuated tubular, which is often used to heat water in the residential sector.

High-temperature collectors are parabolic plates and are used primarily by power generating companies to produce electricity for the power grid.

Integrated manifold

The simplest type of solar collector is a "capacitive" or "thermosiphon collector", which received this name because the collector is also a heat storage tank in which a "one-time" portion of water is heated and stored. Such collectors are used to preheat water, which is then heated to the desired temperature in traditional installations, such as gas water heaters. In conditions household preheated water enters the storage tank. This reduces the energy consumption for its subsequent heating. Such a collector is an inexpensive alternative to an active solar water heating system that does not use moving parts (pumps), requires minimal maintenance, and has zero operating costs. Integrated storage collectors consist of one or more black tanks filled with water and placed in a heat-insulated box covered with a glass lid. Sometimes a reflector is also placed in the box, which amplifies solar radiation. The light passes through the glass and heats the water. These devices are quite inexpensive, but before the onset of cold weather, the water from them must be drained or protected from freezing.

Flat collectors

Flat-plate collectors are the most common type of solar collectors used in domestic water heating and heating systems. Typically, this collector is a heat-insulated metal box with a glass or plastic lid, in which a black-colored absorber (absorber) plate is placed. Glazing can be transparent or matte. Flat-plate collectors typically use frosted, light-only, low-iron glass (which lets through much of the sunlight that enters the collector). Sunlight hits the heat-receiving plate, and thanks to the glazing, heat loss is reduced. The bottom and side walls of the collector are covered with a heat-insulating material, which further reduces heat losses.

The absorber plate is usually painted black because dark surfaces absorb more solar energy than bright ones. Sunlight passes through the glazing and hits the absorbing plate, which heats up, converting solar radiation into thermal energy. This heat is transferred to the coolant - air or liquid circulating through the tubes. Since most black surfaces still reflect about 10% of incident radiation, some absorber plates are treated with a special selective coating that better retains absorbed sunlight and lasts longer than regular black paint. The selective coating used in solar panels consists of a very strong thin layer of amorphous semiconductor deposited on a metal substrate. Selective coatings are characterized by high absorption in the visible region of the spectrum and low emissivity in the far infrared region.

Absorbing plates are usually made of a metal that conducts heat well (most often copper or aluminum). Copper is more expensive, but conducts heat better and is less prone to corrosion than aluminum. The absorber plate must have a high thermal conductivity in order to transfer the accumulated energy to the water with minimal heat loss. Flat collectors divided into liquid and air. Both types of collectors are glazed or unglazed.

Liquid manifolds

In liquid collectors, solar energy heats the liquid flowing through tubes attached to an absorbing plate. The heat absorbed by the plate is immediately transferred to the liquid.

The tubes can be arranged parallel to each other, and each has an inlet and outlet, or in the form of a coil. The serpentine arrangement of the tubes eliminates the possibility of leakage through the connection holes and ensures a uniform flow of liquid. On the other hand, when draining the liquid to avoid freezing, it can be difficult, since water can remain in places in the curved tubes.

The simplest fluid systems use ordinary water, which is heated directly in the collector and enters the bathroom, kitchen, etc. This model is known as an "open" (or "direct") system. In regions with cold climates, fluid collectors need to be drained during the cold season when the temperature drops to the freezing point; or an antifreeze liquid is used as a heat carrier. In such systems, the heat transfer fluid absorbs the heat stored in the collector and passes through the heat exchanger. The heat exchanger is usually a water tank installed in the house, in which heat is transferred to the water. This model is called a "closed system".

Glazed liquid collectors are used for heating household water and also for space heating. Unglazed collectors usually heat water for swimming pools. Since such collectors do not need to withstand high temperatures, they use inexpensive materials: plastic, rubber. They do not need frost protection, as they are used in the warm season.

Air collectors

Air collectors have the advantage of avoiding the freezing and boiling problems that fluid systems sometimes suffer from. While a coolant leak in an air manifold is harder to spot and fix, it's less of a problem than a fluid leak. Air systems often use cheaper materials than liquid systems. For example, plastic glazing, because working temperature in them below.

Air collectors are simple flat-plate collectors and are mainly used for space heating and drying agricultural products. Absorbing plates in air collectors are metal panels, multilayer screens, including those made of non-metallic materials. Air passes through the absorber due to natural convection or under the influence of a fan. Since air is a poorer conductor of heat than liquid, it transfers less heat to the absorber than heat transfer fluid. Some solar air heaters have fans attached to the absorber plate to increase air turbulence and improve heat transfer. The disadvantage of this design is that it consumes energy to operate the fans, thus increasing the operating costs of the system. In cold climates, air is directed into the gap between the absorber plate and the insulated back wall collector: thus avoiding heat loss through the glazing. However, if the air is heated no more than 17°C above the outside temperature, the heat transfer medium can circulate on both sides of the absorber plate without much loss of efficiency.

The main advantages of air collectors are their simplicity and reliability. Such collectors have a simple device. With proper care, a quality collector can last 10-20 years and is very easy to manage. A heat exchanger is not required as the air does not freeze.

Solar tubular vacuum collectors

Traditional simple flat plate solar collectors have been designed for use in regions with warm sunny climates. They dramatically lose their effectiveness on adverse days - in cold, cloudy and windy weather. Moreover, weather-induced condensation and humidity will cause premature wear of internal materials, which in turn will lead to system degradation and failure. These shortcomings are eliminated by using evacuated collectors.

Vacuum collectors heat water for domestic use where hot water is needed. Solar radiation passes through the outer glass tube, hits the absorber tube, and is converted into heat. It is transmitted by the fluid flowing through the tube. The collector consists of several rows of parallel glass tubes, to each of which is attached a tubular absorber (instead of an absorber plate in flat-plate collectors) with a selective coating. The heated liquid circulates through the heat exchanger and gives off heat to the water contained in the storage tank.

Vacuum collectors are modular, i.e. tubes can be added or removed as needed, depending on the need for hot water. During the manufacture of collectors of this type, air is sucked out from the space between the tubes and a vacuum is formed. Due to this, heat losses associated with the thermal conductivity of air and convection caused by its circulation are eliminated. What remains is the radiative heat loss ( thermal energy moves from a warm to a cold surface, even in a vacuum). However, this loss is small and negligible compared to the amount of heat transferred to the liquid in the absorber tube. Vacuum in the glass tube - the best thermal insulation available for the collector - reduces heat loss and protects the absorber and heat pipe from adverse conditions. external influences. The result is excellent performance that surpasses any other type of solar collector.

There are many different types of vacuum collectors. In some, another, third glass tube passes inside the absorber tube; there are other designs of heat transfer fins and fluid tubes. There is a vacuum manifold that holds 19 liters of water in each tube, thus eliminating the need for a separate water storage tank. Reflectors can also be placed behind the vacuum tubes to further concentrate solar radiation on the collector.

In regions with high temperature differences, these collectors are much more efficient than flat collectors for a number of reasons. First, they work well under conditions of both direct and diffuse solar radiation. This feature, combined with the ability of vacuum to minimize heat loss to the outside, makes these collectors indispensable in cold, cloudy winters. Secondly, due to the round shape of the vacuum tube, sunlight falls perpendicular to the absorber for most of the day. For comparison, in a fixed flat collector, sunlight falls perpendicular to its surface only at noon. Vacuum collectors have a higher water temperature and efficiency than flat-plate collectors, but they are also more expensive.

Hubs

Focusing collectors (concentrators) use mirror surfaces to concentrate solar energy on an absorber, also called a "heat sink". The temperature they reach is much higher than flat-plate collectors, but they can only concentrate direct solar radiation, which leads to poor performance in foggy or cloudy weather. The mirror surface focuses sunlight reflected from a large surface onto a smaller surface of the absorber, thereby achieving a high temperature. In some models, solar radiation is concentrated at a focal point, while in others, the sun's rays are concentrated along a thin focal line. The receiver is located at the focal point or along the focal line. The heat transfer fluid passes through the receiver and absorbs heat. Such collectors-concentrators are most suitable for regions with high insolation - close to the equator, in a sharply continental climate and in desert areas.

Hubs work best when they are facing directly towards the Sun. To do this, tracking devices are used, which during the day turn the collector "face" to the Sun. Single-axis trackers rotate from east to west; biaxial - from east to west and an angle above the horizon (to follow the movement of the Sun across the sky during the year). Hubs are mainly used in industrial installations because they are expensive and trackers need permanent care. Some residential solar power systems use parabolic concentrators. These units are used for hot water supply, heating and water purification. In domestic systems, single-axis tracking devices are mainly used - they are cheaper and simpler than biaxial ones.

Rising energy prices in Russia are forcing interest in cheap energy sources. The most affordable is solar energy. The energy of solar radiation falling on the Earth is 10,000 times greater than the amount of energy produced by mankind. Problems arise in the technology of energy collection and in connection with the uneven supply of energy to solar plants. Therefore, solar collectors and solar batteries are used either in conjunction with energy storage or as a means of additional feeding for the main power plant.

Our country is vast and the picture of the distribution of solar energy over its territory is very diverse.

Average data for solar energy input

Intensity of solar energy input

Zones of maximum intensity of solar radiation. More than 5 kW is supplied per 1 square meter. hour. solar energy per day.

Along the southern border of Russia from Baikal to Vladivostok, in the Yakutsk region, in the south of the Republic of Tuva and the Republic of Buryatia, oddly enough, beyond the Arctic Circle in the eastern part of Severnaya Zemlya.

Solar energy input from 4 to 4.5 kW. hour per sq. meter per day

Krasnodar region, North Caucasus, Rostov region, southern part of the Volga region, southern regions of Novosibirsk, Irkutsk regions, Buryatia, Tyva, Khakassia, Primorsky and Khabarovsk region, Amur Region, Sakhalin Island, vast territories from the Krasnoyarsk Territory to Magadan, Severnaya Zemlya, northeast of the Yamalo-Nenets Autonomous Okrug.

From 2.5 to 3 kW. hour per sq. meter per day

Along the western arc - Nizhny Novgorod, Moscow, St. Petersburg, Salekhard, the eastern part of Chukotka and Kamchatka.

From 3 to 4 kW. hour per sq. meter per day

the rest of the country.

Sunshine duration per year

The energy flow has the highest intensity in May, June and July. During this period, in central Russia, per 1 sq. meter of surface accounts for 5 kW. hour a day. The lowest intensity is in December-January, when 1 sq. meter of surface accounts for 0.7 kW. hour a day.

Installation Features

If you install a solar collector at an angle of 30 degrees to the surface, then you can ensure the removal of energy in the maximum and minimum modes, respectively, 4.5 and 1.5 kWh per 1 sq. meter. in a day.

Distribution of the intensity of solar radiation in central Russia by months

Based on the above data, it is possible to calculate the area of ​​flat solar collectors required to provide hot water for a family of 4 in an individual house. Heating of 300 liters of water from 5 degrees to 55 degrees in June can be provided by collectors with an area of ​​5.4 square meters, in December 18 square meters. meters. If more efficient vacuum collectors are used, the required collector area is reduced by about half.

Solar DHW coverage

In practice, it is desirable to use solar collectors not as the main source of hot water, but as a device for heating water entering the heating installation. In this case, fuel consumption is sharply reduced. This ensures uninterrupted supply of hot water and saves money on hot water supply and heating the house, if it is a house for permanent residence. In dachas, in the summer, to get hot water, they use different kinds solar collectors. From factory-made collectors to home-made devices made from improvised materials. They differ primarily in terms of efficiency. The factory one is more efficient, but more expensive. Almost free of charge, you can make a collector with a heat exchanger from an old refrigerator.

In Russia, the installation of solar collectors is regulated by RD 34.20.115-89 " Guidelines on calculation and design of solar heating systems", VSN 52-86 (in RTF format, 11 Mb) "Installations of hot solar water supply. Design standards". There are recommendations on the use of non-traditional energy sources in animal husbandry, fodder production, peasant farms and the rural housing sector, developed at the request of the Ministry of Agriculture in 2002. GOST R 51595 "Solar collectors. Technical requirements", GOST R 51594 " solar energy. Terms and Definitions",

These documents describe in detail the schemes of solar collectors used and the most effective ways of their application in various climatic conditions.

Solar collectors in Germany

In Germany, the state subsidizes the cost of installing solar collectors, so their use is steadily growing. In 2006, 1 million 300 thousand square meters of collectors were installed. Of this amount, about 10% are more expensive and efficient vacuum collectors. The total area of ​​solar collectors installed to date is approximately 12 million square meters.

Materials and graphics courtesy of Viessmann

The intensity of sunlight that reaches the earth varies with time of day, year, location, and weather conditions. The total amount of energy calculated per day or per year is called irradiation (or in another way "the arrival of solar radiation") and shows how powerful the solar radiation was. Irradiation is measured in W*h/m² per day or other period.

The intensity of solar radiation in free space at a distance equal to the average distance between the Earth and the Sun is called the solar constant. Its value is 1353 W / m². When passing through the atmosphere, sunlight is attenuated mainly due to absorption of infrared radiation by water vapor, ultraviolet radiation by ozone, and scattering of radiation by atmospheric dust particles and aerosols. The indicator of atmospheric influence on the intensity of solar radiation reaching the earth's surface is called "air mass" (AM). AM is defined as the secant of the angle between the Sun and the zenith.

Figure 1 shows the spectral distribution of solar radiation intensity in various conditions. The upper curve (AM0) corresponds to the solar spectrum outside the Earth's atmosphere (for example, on board spaceship), i.e. at zero air mass. It is approximated by the intensity distribution of black body radiation at a temperature of 5800 K. Curves AM1 and AM2 illustrate the spectral distribution of solar radiation on the Earth's surface when the Sun is at the zenith and at an angle between the Sun and the zenith of 60°, respectively. In this case, the total radiation power is about 925 and 691 W / m², respectively. The average intensity of radiation on Earth approximately coincides with the intensity of radiation at AM=1.5 (the Sun is at an angle of 45° to the horizon).

Near the surface of the earth, one can take average value solar radiation intensity 635 W/m². On a very clear sunny day, this value ranges from 950 W/m² to 1220 W/m². The average value is approximately 1000 W / m². Example: Total radiation intensity in Zurich (47°30′ N, 400 m above sea level) on a surface perpendicular to the radiation: 1 May 12:00 1080 W/m²; 21 December 12:00 930 W/m² .

To simplify the calculation of solar energy, it is usually expressed in hours of sunshine with an intensity of 1000 W/m². Those. 1 hour corresponds to the arrival of solar radiation of 1000 W*h/m². This roughly corresponds to the period when the sun shines in summer in the middle of a sunny cloudless day on a surface perpendicular to the sun's rays.

Example
The bright sun shines with an intensity of 1000 W / m² on a surface perpendicular to the sun's rays. For 1 hour, 1 kWh of energy falls on 1 m² (energy is equal to the product of power and time). Similarly, an average solar input of 5 kWh/m² per day corresponds to 5 peak hours of sunshine per day. Do not confuse peak hours with actual duration daylight hours. During daylight hours, the sun shines with different intensity, but in total it gives the same amount of energy as if it shone for 5 hours at maximum intensity. It is the peak hours of sunshine that are used in the calculations of solar power plants.

The arrival of solar radiation varies during the day and from place to place, especially in mountainous areas. Irradiation varies on average from 1000 kWh/m² per year for northern European countries, to 2000-2500 kWh/m² per year for deserts. Weather conditions and the declination of the sun (which depends on the latitude of the area) also leads to differences in the arrival of solar radiation.

In Russia, contrary to popular belief, there are a lot of places where it is profitable to convert solar energy into electricity using. Below is a map of solar energy resources in Russia. As you can see, in most of Russia it can be successfully used in seasonal mode, and in areas with more than 2000 hours of sunshine per year - all year round. Naturally, in winter period Solar energy production is significantly reduced, but still the cost of electricity from solar power plant remains significantly lower than from a diesel or gasoline generator.

It is especially beneficial to use where there are no centralized electrical networks and energy supply is provided by diesel generators. And there are a lot of such regions in Russia.

Moreover, even where there are grids, the use of solar panels operating in parallel with the grid can significantly reduce energy costs. With the current trend of increasing tariffs from Russia's natural energy monopolies, installing solar panels is becoming a smart investment.

"Standard Sun"(peak radiation power that reaches the Earth's surface at sea level near the equator on a cloudless afternoon): 1000 W / m 2, or 1 kW / m 2.

This value is commonly used in the characteristics of photovoltaic systems. Here and below, all figures are given for surfaces that are optimally located relative to the sun (perpendicular to the rays) in accordance with latitude. For horizontal surfaces, you will get less sunlight: the farther from the equator, the lower the solar energy density.

Insolation(average number of hours of "standard sun" per day): from 4-5 hours of sunshine in the northeast of the United States to 5-7 hours in the southwest. Insolation is often reported in kWh, numerically derived from a "standard sun" value of 1 kW.

The total amount of radiated solar energy per day per m 2 at sea level: (energy per day) \u003d 1 kWh × (insolation in hours). Given an average US insolation of 5 solar hours, this value is typically 5 kWh/m 2 .

solar power, averaged over the whole day: Watts averag = (energy per day) / 24. For insolation of 5 kWh, the power averaged over the entire day is 5000 W / 24 = 208 W / m 2. Please note that only a small part of this energy can be converted into electricity due to not very high efficiency photovoltaic systems.

Typical characteristics of photovoltaic systems

Average efficiency common commercial solar panels: crystalline silicon (CSI) - 12-17%; thin-film (from amorphous silicon and other materials) - 8-12%.

Power generated by a panel of one square meter: PVwatts = (solar power) × (average efficiency), where the efficiency is converted to a decimal number.

Peak power on a cloudless afternoon: PVwatts-peak = 1000 W × efficiency. Typically peak power is 120170 W/m 2 for CSi and 80-120 W/m 2 for thin films (TF).

Total average amount of energy produced by a panel of one m2 per day: PVday = PVwatts-peak × (Insolation in hours). For insolation at 5 o'clock this value will be 0.6-0.85 kW/m2 for CSi and 0.4-0.6 kW/m2 for TF.

Generated energy panels averaged over the whole day: PVwatts-average = PVday/24. This is approximately 25-35 W/m2 for CSi and 17-25 W/m2 for TF.

Total energy generated by the photovoltaic module per m2 per year: PVyear = ( total energy per day) × 365, which will be approximately 219-310 kWh for CSi and 146-219 kWh for TF. Please note that inverters are 95-97% efficient, so there will be 5% less actual electricity.

Expected cost of electricity from one m 2 saved per year: Saving = PVyear × 0.95 × (kWh cost), where 0.95 is the efficiency of the converter and losses in the wires.

On average in the US, the cost of one kWh of electricity is $0.12, which gives $24-35 per year for CSi and $17-24 for thin films. Thus, in the best case, it will be possible to save $35 per year per 1 m2 of panel. This figure refers to a high efficiency system with a nominal power of 170 W/m 2 . Given the fact that a typical photovoltaic system currently costs $8,000 per 1,000 W, such installations would cost 170/1,000 × $8,000 = $1,360 per m2. This means that in our example, the hypothetical payback period would be 1360/35 = 39 years. No piece of equipment can last that long. Discounts and credits can cut this time by more than half, but still, for the average household, installing a solar panel is unlikely to pay off. Of course, this is just an example. In areas with different insolation and other installation costs, the payback period may be longer or shorter.

Brief information about the Sun

  • Diameter: 1,392,000 km;
  • Mass: 1,989.100 × 1024 kg;
  • Surface temperature: ~5,700 °С;
  • Average distance from the Earth to the Sun: 150 million km;
  • Composition by mass: 74% hydrogen, 25% helium, 1% other elements;
  • Brightness (total amount of energy radiated in all directions): 3.85 × 10 26 W (~385 billion MW);
  • Radiation power density on the surface of the Sun: 63,300 kW per square meter.

A solar battery is a series of solar modules that convert solar energy into electricity and, using electrodes, transmit it further to other converter devices. The latter are needed in order to make an alternating current out of direct current, which they are able to perceive household electrical appliances. Direct current is obtained when solar energy is perceived by photocells and the photon energy is converted into electric current.

How many photons hit the photocell determines how much energy the solar battery provides. For this reason, battery performance is affected not only by the material of the photocell, but also by the amount of sunny days per year, angle of incidence sun rays on the battery and other factors beyond human control.

Aspects affecting how much power a solar panel produces

First of all, the performance of solar panels depends on the material of manufacture and production technology. Of those that are on the market, you can find batteries with a performance of 5 to 22%. All solar cells are divided into silicon and film.

Silicon module performance:

  • Monocrystalline silicon panels - up to 22%.
  • Polycrystalline panels - up to 18%.
  • Amorphous (flexible) - up to 5%.

Film module performance:

  • Based on cadmium telluride - up to 12%.
  • Based on meli-indium-gallium selenide - up to 20%.
  • On a polymer basis - up to 5%.

There are also mixed types panels, which, with the advantages of one type, make it possible to cover the disadvantages of another, thereby increasing the efficiency of the module.

The number of clear days in a year also affects how much energy a solar battery gives. It is known that if the sun in your area appears for a full day on less than 200 days a year, then installing and using solar panels is unlikely to be profitable.

In addition, the efficiency of the panels is also affected by the heating temperature of the battery. So, when heated by 1̊С, the performance drops by 0.5%, respectively, when heated by 10̊С, we have a half reduced efficiency. To prevent such troubles, cooling systems are installed, which also require energy consumption.

To maintain high performance throughout the day, solar tracking systems are installed to help keep the rays on the solar panels at a right angle. But these systems are quite expensive, not to mention the batteries themselves, so not everyone can afford to install them to power their home.

How much energy a solar battery generates also depends on the total area of ​​​​the installed modules, because each photocell can accept a limited amount.

How to calculate how much energy a solar panel provides for your home?

Based on the above points that should be considered when buying solar panels, we can derive a simple formula by which we can calculate how much energy one module will produce.

Let's say you have chosen one of the most productive modules with an area of ​​2 m2. The amount of solar energy on a typical sunny day is approximately 1000 watts per m2. As a result, we get the following formula: solar energy (1000 W / m2) × productivity (20%) × module area (2 m2) = power (400 W).

If you want to calculate how much solar energy is received by the battery in the evening and on a cloudy day, you can use the following formula: the amount of solar energy on a clear day × the sine of the angle of the sun's rays and the surface of the panel × the percentage of energy converted on a cloudy day = how much solar energy eventually converts the battery. For example, let's say that in the evening the angle of incidence of the rays is 30̊. We get the following calculation: 1000 W / m2 × sin30̊ × 60% = 300 W / m2, and the last number is used as the basis for calculating the power.