What is solar energy? The principle of solar energy conversion, its application and prospects

Solar energy - receiving solar energy by accumulating it with the help of special installations. Today, solar energy is actively developing in Russia. Scientists of the country have been studying the possibilities of obtaining energy carriers for many years. But work since 2000 has been devoted to this issue with particular care.

At the moment, various systems and installations have been invented and are successfully used, which allow accumulating solar energy and converting it into energy carriers. Photovoltaic systems operate from scattered sunlight. Moreover, the power of the installation can be adjusted depending on the needs of the user. The simple addition of a photoconverter section can significantly increase the effective coefficient of action, thereby providing required amount energy.

Today's prospects for solar energy

Issues of improving the mechanism of using natural energy given a lot of attention modern man. That is why the prospects for solar energy for the future are very high. Already in the coming years, according to experts, the world will use the natural resource to the fullest extent, providing for itself an inexhaustible supply of energy resources.

For the world community, the development of this industrial sector is a priority. There are several reasons for this. Namely:

the possibility of using nature for energy;
ecological purity of the resulting product;
relative cheapness;
absolute security for environment;
minimal equipment costs (in comparison with the result obtained).

In other words, the energy obtained from the sun's rays has only positive aspects for humanity as a whole. The modern development of technical capabilities gives excellent prospects - the equipment being developed is capable of converting solar energy with minimal operating costs.

It is also important that solar installations are very easy to operate. They are easy to install, easy to repair and modify, adjusting to your own needs. Photoconverters take up little space, they are mounted on the roofs of buildings. In addition, they are able to accumulate energy even in bad weather.

Scientists have come to the conclusion that the amount of sunlight falling on the earth's surface in just one week is hundreds of times higher than the energy that can be obtained from all known terrestrial energy carriers (gas, coal, wood). This means that in just 7 days a person can get as much energy as, for example, several tons of coal can give.

The future belongs to solar energy

This statement is made by international experts. Considering the opportunities provided by diffused sunlight, there is no doubt about the correctness of this opinion. It is easy to verify this with a simple example.

To obtain one ton of coal requires enormous costs, consisting of time, human labor and the use of special equipment. It is easy to calculate how much each ton of solid fuel material costs the country.

What happens in the case of solar energy? It is required only once to install a storage device (battery, complex, system), and energy is constantly received, without direct human participation. That is, in order to heat a living space or get an uninterrupted power supply, the user does not have to constantly spend time, effort and financial resources.

In the world, the future of solar energy is seen as quite rosy. And there are reasons for that. In recent years, specialists have managed to significantly improve the quality of solar energy "receivers" and increase their conversion. As a result, super-powerful solar panels are available to humans, which are highly reliable and small in size.

An alternative source of energy will allow humanity to solve problems with the preservation of the environment. Do not forget about the exhausted deposits of other materials: coal, gas, wood. The sun's rays are a true friend of man.

Ministry of Education of the Republic of Belarus

educational institution

"Belarusian State Pedagogical University named after Maxim Tank"

Department of General and Theoretical Physics

Coursework in General Physics

Solar energy and prospects for its use

Students of 321 groups

Faculty of Physics

Leshkevich Svetlana Valerievna

Scientific adviser:

Fedorkov Cheslav Mikhailovich

Minsk, 2009

Introduction

1. General information oh sun

2. The sun is a source of energy

2.1 Solar energy research

2.2 The potential of solar energy

3. Use of solar energy

3.1 Passive use of solar energy

3.2 Active use of solar energy

3.2.1 Solar collectors and their types

3.2.2 Solar systems

3.2.3 Solar thermal power plants

3.3 Photovoltaic systems

4. Solar architecture

Conclusion

List of sources used

Introduction

The sun plays an exceptional role in the life of the Earth. The entire organic world of our planet owes its existence to the Sun. The sun is not only a source of light and heat, but also the original source of many other types of energy (energy of oil, coal, water, wind).

Since the appearance on earth, man began to use the energy of the sun. According to archaeological data, it is known that for housing, preference was given to quiet places, closed from cold winds and open to the sun's rays.

Perhaps the first known solar system can be considered the statue of Amenhotep III, dating back to the 15th century BC. Inside the statue there was a system of air and water chambers, which, under the sun's rays, set in motion a hidden musical instrument. IN Ancient Greece worshiped Helios. The name of this god today formed the basis of many terms related to solar energy.

The problem of providing electrical energy to many sectors of the world economy, the constantly growing needs of the world's population is now becoming more and more urgent.

1. General information about the Sun

The Sun is the central body of the Solar System, a hot plasma ball, a typical G2 dwarf star.

Characteristics of the Sun

1. Mass M S ~2*10 23 kg

2. R S ~629 thousand km

3. V \u003d 1.41 * 10 27 m 3, which is almost 1300 thousand times greater than the volume of the Earth,

4. average density 1.41 * 10 3 kg / m 3,

5. luminosity L S \u003d 3.86 * 10 23 kW,

6. effective temperature surface (photosphere) 5780 K,

7. rotation period (synodic) varies from 27 days at the equator to 32 days. at the poles

8. free fall acceleration 274 m/s 2 (with such a huge acceleration of gravity, a person weighing 60 kg would weigh more than 1.5 tons).

Structure of the Sun

In the central part of the Sun there is a source of its energy, or, figuratively speaking, that "stove" that heats it and does not allow it to cool down. This area is called the core (see Fig. 1). In the nucleus, where the temperature reaches 15 MK, energy is released. The core has a radius of no more than a quarter of the total radius of the Sun. However, half of the solar mass is concentrated in its volume and almost all the energy that supports the glow of the Sun is released.

Immediately around the nucleus, a zone of radiant energy transfer begins, where it propagates through the absorption and emission of portions of light by matter - quanta. It takes a very long time for a quantum to seep through the dense solar matter to the outside. So if the "stove" inside the Sun suddenly went out, then we would know about it only millions of years later.

Rice. 1 Structure of the Sun

On its way through the inner solar layers, the energy flow encounters a region where the opacity of the gas increases greatly. This is the convective zone of the Sun. Here, energy is no longer transferred by radiation, but by convection. The convective zone begins approximately at a distance of 0.7 radius from the center and extends almost to the most visible surface of the Sun (photosphere), where the transfer of the main energy flux again becomes radiant.

The photosphere is the radiating surface of the Sun, which has a granular structure called granulation. Each such "grain" is almost the size of Germany and is a stream of hot matter that has risen to the surface. Relatively small dark areas can often be seen on the photosphere - sunspots. They are 1500˚С colder than the photosphere surrounding them, the temperature of which reaches 5800˚С. Due to the difference in temperature with the photosphere, these spots appear completely black when viewed through a telescope. Above the photosphere is the next, more rarefied layer, called the chromosphere, that is, the "colored sphere". The chromosphere got its name because of its red color. And, finally, above it is a very hot, but also extremely rarefied part of the solar atmosphere - the corona.

2. The sun is a source of energy

Our Sun is a huge luminous ball of gas, within which complex processes take place and as a result, energy is continuously released. 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.

The sun evaporates water from the oceans, seas, from the earth's surface. It turns this moisture into water droplets, forming clouds and fogs, and then causes it to fall back to Earth in the form of rain, snow, dew or frost, thus creating a gigantic moisture cycle in the atmosphere.

Solar energy is the source of the general circulation of the atmosphere and the circulation of water in the oceans. It, as it were, creates a gigantic system of water and air heating of our planet, redistributing heat over the earth's surface.

Sunlight, falling on plants, causes the process of photosynthesis in it, determines the growth and development of plants; falling on the soil, it turns into heat, heats it, forms the soil climate, thereby giving vitality seeds of plants, microorganisms and living beings in the soil, which without this heat would be in a state of anabiosis (hibernation).

The sun radiates a huge amount of 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 Earth's outer atmosphere intercepts approximately one millionth of the energy emitted by the Sun, or approximately 1500 quadrillion (1.5 x 10 18) kWh annually. However, only 47% of all energy, or approximately 700 quadrillion (7 x 10 17) kWh, reaches the Earth's surface. The remaining 30% of solar energy is reflected back into space, about 23% evaporate water, 1% of the energy comes from waves and currents, and 0.01% from the formation of photosynthesis in nature.

2.1 Solar energy research

Why does the Sun shine and not cool down for billions of years? What "fuel" gives him energy? Scientists have been looking for answers to this question for centuries, and only at the beginning of the 20th century was it found correct solution. It is now known that, like other stars, it shines due to thermonuclear reactions occurring in its depths.

If the nuclei of atoms of light elements merge into the nucleus of an atom of a heavier element, then the mass of the new one will be less than the total mass of those from which it was formed. The rest of the mass is converted into energy, which is carried away by the particles released during the reaction. This energy is almost completely converted into heat. Such a reaction of the synthesis of atomic nuclei can occur only at very high pressure and temperatures above 10 million degrees. That is why it is called thermonuclear.

The main substance that makes up the Sun is hydrogen, it accounts for about 71% of the total mass of the star. Almost 27% belongs to helium and the remaining 2% to heavier elements such as carbon, nitrogen, oxygen and metals. The main "fuel" of the Sun is hydrogen. From four hydrogen atoms, as a result of a chain of transformations, one helium atom is formed. And from each gram of hydrogen involved in the reaction, 6x10 11 J of energy is released! On Earth, this amount of energy would be enough to heat 1000 m 3 of water from a temperature of 0º C to the boiling point.

2.2 The potential of solar energy

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 true, then the total energy consumed by mankind during the year is only approximately one seven thousandth of the solar energy that hits the surface of the Earth 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.

3. Use of solar energy

Solar radiation can be converted into useful energy using so-called active and passive solar systems. Passive systems are obtained through building design and selection building materials in such a way as to maximize the use of solar energy. Solar collectors are active solar systems. Photovoltaic systems are also currently being developed - these are systems that convert solar radiation directly into electricity.

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.

Energy is the driving force of any production. The fact that man had a large amount of relatively cheap energy at his disposal greatly contributed to industrialization and the development of society.

3.1 Passive use of solar energy

solar energy thermal power plant

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 fits most of the most simple systems where heat is retained in a building by 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.

3.2 Active use of solar energy

Active use of solar energy is carried out with the help of solar collectors and solar systems.

3.2.1 Solar collectors and their types

At the heart of many solar energy systems lies the use of 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.

The technology of manufacturing solar collectors reached almost the modern level in 1908, when William Bailey of the American "Carnegie Steel Company" invented a collector with a heat-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.

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. Currently, the market offers many different models of collectors.

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 desired temperature in traditional installations, for example, in geysers. 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, using no moving parts (pumps), requiring minimal maintenance, with zero operating costs.

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.

Flat-plate collectors are divided into liquid and air. Both types of collectors are glazed or unglazed.

Solar tubular vacuum collectors

Traditional simple flat plate solar collectors have been designed for use in regions with warm sunny climates. They drastically lose their effectiveness in bad 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 domestic water where higher temperature 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 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.

Focusing Collectors

Focusing collectors (concentrators) use mirror surfaces to concentrate solar energy on an absorber, also called a "heat sink". They reach temperatures much higher than flat-plate collectors, but they can only concentrate direct solar radiation, resulting in 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 and in desert areas.

There are other inexpensive technologically simple solar collectors for a narrow purpose - solar ovens (for cooking) and solar distillers, which allow you to get distilled water cheaply from almost any source.

solar ovens

They are cheap and easy to make. They consist of a spacious, well-insulated box lined with reflective material (such as foil), covered with glass and equipped with an external reflector. The black pot serves as an absorbent, heating up faster than regular aluminum or of stainless steel. Solar ovens can be used to disinfect water by bringing it to a boil.

There are box and mirror (with a reflector) solar ovens.

solar distillers

Solar stills provide cheap distilled water, even salty or heavily polluted water can be used as a source. They are based on the principle of evaporation of water from an open container. The solar distiller uses the sun's energy to speed up this process. It consists of a dark-colored heat-insulated container with glazing, which is tilted so that the condensed fresh water flows into a special container. A small solar distiller - about the size of a kitchen stove - can produce up to ten liters of distilled water on a sunny day.

3.2.2 Solar systems

Solar hot water systems

Hot water is the most common type of direct application of solar energy. A typical installation consists of one or more collectors in which the liquid is heated by the sun, as well as a storage tank. hot water heated by a heat transfer fluid. Even in regions with relatively little solar radiation, such as Northern Europe, a solar system can provide 50-70% of the hot water demand. It is impossible to get more, except perhaps with the help of seasonal regulation. In Southern Europe, a solar collector can provide 70-90% of the hot water consumed. Heating water with the help of solar energy is a very practical and economical way. While photovoltaic systems achieve 10-15% efficiency, thermal solar systems show 50-90% efficiency. In combination with wood-burning stoves, the domestic need for hot water can be met by almost all year round without the use of fossil fuels.

Thermosiphon solar systems

Thermosiphon solar water heating systems with natural circulation (convection) of the coolant are called, which are used in warm winter conditions (in the absence of frost). In general, these are not the most efficient of solar energy systems, but they have many advantages in terms of housing construction. Thermosyphon circulation of the coolant occurs due to a change in the density of water with a change in its temperature. The thermosyphon system is divided into three main parts:

flat collector (absorber);

pipelines;

· Storage tank for hot water (boiler).

When the water in the collector (usually flat) is heated, it rises up the riser and enters the storage tank; in its place in the collector from the bottom of the storage tank enters cold water. Therefore, it is necessary to locate the collector below the storage tank and insulate the connecting pipes.

Such installations are popular in subtropical and tropical areas.

Solar water heating systems

Most often used for heating pools. Although the cost of such an installation varies depending on the size of the pool and other specific conditions, if solar systems are installed to reduce or eliminate fuel or electricity consumption, they will pay for themselves in two to four years in energy savings. Moreover, pool heating allows you to extend the swimming season for several weeks at no additional cost.

In most buildings, it is not difficult to arrange a solar heater for the pool. It can be reduced to a simple black hose through which water is supplied to the pool. For outdoor pools, you only need to install an absorber. Indoor pools require the installation of standard manifolds to ensure warm water and in winter.

Seasonal heat storage

There are also installations that allow using the heat accumulated in the summer by solar collectors and stored with the help of large storage tanks (seasonal storage) in winter. The problem here is that the amount of liquid needed to heat a house is comparable to the volume of the house itself. In addition, the heat storage must be very well insulated. In order for a conventional domestic storage tank to retain most of the heat for half a year, it would have to be wrapped in a layer of insulation 4 meters thick. Therefore, it is advantageous to make the storage capacity very large. As a result, the ratio of surface area to volume decreases.

Large solar district heating installations are used in Denmark, Sweden, Switzerland, France and the USA. Solar modules are installed directly on the ground. Without storage, such a solar heating installation can cover about 5% of the annual heat demand, since the installation must not generate more than the minimum amount of heat consumed, including losses in the district heating system (up to 20% during transmission). If there is daytime heat storage at night, then a solar heating installation can cover 10-12% of the heat demand, including transmission losses, and with seasonal heat storage, up to 100%. There is also the possibility of combining district heating with individual solar collectors. The district heating system can be switched off for the summer when the hot water supply is provided by the Sun and there is no demand for heating.

Solar energy combined with other renewable sources.

A good result is the combination of various renewable energy sources, for example, solar heat combined with seasonal heat storage in the form of biomass. Or, if the remaining energy demand is very low, liquid or gaseous biofuels can be used in combination with efficient boilers in addition to solar heating.

An interesting combination is solar heating and solid biomass boilers. This also solves the problem seasonal storage solar energy. The use of biomass in summer is not optimal solution, as the efficiency of boilers at partial load is low, in addition, the losses in the pipes are relatively high - and in small systems, burning wood in the summer can be inconvenient. In such cases, all 100% of the heat load in summer can be provided by solar heating. In winter, when the amount of solar energy is negligible, almost all heat is generated by burning biomass.

There is a lot of experience in Central Europe in combining solar heating and biomass combustion for heat production. Typically, about 20-30% of the total heat load is covered by the solar system, and the main load (70-80%) is provided by biomass. This combination can be used both in individual residential buildings and in central (district) heating systems. In the conditions of Central Europe, about 10 m 3 of biomass (eg firewood) is enough to heat a private house, and a solar installation helps to save up to 3 m 3 of firewood per year.

3.2.3 Solar thermal power plants

In addition to the direct use of solar heat, in regions with high level solar radiation, it can be used to produce steam, which rotates a turbine and generates electricity. The production of solar thermal electricity on a large scale is quite competitive. The industrial application of this technology dates back to the 1980s; since then, the industry has developed rapidly. More than 400 megawatts of solar thermal power plants have already been installed by US utilities, providing electricity to 350,000 people and displacing the equivalent of 2.3 million barrels of oil per year. Nine power plants located in the Mojave Desert (in the US state of California) have 354 MW of installed capacity and have accumulated 100 years of industrial operation experience. This technology is so advanced that, according to official information, it can compete with traditional power generation technologies in many parts of the United States. In other regions of the world, projects to use solar heat to generate electricity should also be launched soon. India, Egypt, Morocco and Mexico are developing corresponding programs, grants for their financing are provided by the Global Environment Facility (GEF). In Greece, Spain and the US, new projects are being developed by independent electricity producers.

According to the method of heat production, solar thermal power plants are divided into solar concentrators (mirrors) and solar ponds.

solar concentrators

Such power plants concentrate solar energy using lenses and reflectors. Since this heat can be stored, such stations can generate electricity as needed, day or night, in any weather.

Large mirrors - with a point or linear focus - concentrate the sun's rays to such an extent that the water turns into steam, while releasing enough energy to turn the turbine. Luz Corp. installed huge fields of such mirrors in the Californian desert. They produce 354 MW of electricity. These systems can convert solar energy into electricity with an efficiency of about 15%.

There are the following types of solar concentrators:

1. Solar parabolic concentrators

2. Dish type solar installation

3. Solar power towers with a central receiver.

solar ponds

Neither focusing mirrors nor solar cells can generate power at night. For this purpose, solar energy accumulated during the day must be stored in heat storage tanks. This process naturally occurs in the so-called solar ponds.

Solar ponds have a high salt concentration in the bottom water layers, a non-convective middle layer of water in which the salt concentration increases with depth, and a convective layer with a low salt concentration on the surface. Sunlight falls on the surface of the pond, and heat is retained in the lower layers of the water due to the high concentration of salt. High salinity water, heated by solar energy absorbed by the bottom of the pond, cannot rise due to its high density. It remains at the bottom of the pond, gradually heating up until it almost boils (while the upper layers of water remain relatively cold). The hot bottom "brine" is used day or night as a heat source, thanks to which a special organic coolant turbine can generate electricity. middle layer The solar pond acts as thermal insulation, preventing convection and heat loss from the bottom to the surface. The temperature difference between the bottom and the surface of the pond water is sufficient to drive the generator. The coolant, passed through the pipes through the lower layer of water, is fed further into the closed Rankin system, in which a turbine rotates to produce electricity.

3.3 Photovoltaic systems

Devices for the direct conversion of light or solar energy into electricity are called photocells (in English Photovoltaics, from the Greek photos - light and the name of the unit of electromotive force - volt). The conversion of sunlight into electricity takes place in solar cells made of a semiconductor material such as silicon, which, when exposed to sunlight, generate an electric current. By connecting photovoltaic cells into modules, and those, in turn, with each other, it is possible to build large photovoltaic stations. The largest such station to date is the 5-megawatt Carris Plain installation in the US state of California. The efficiency of photovoltaic installations is currently around 10%, however, individual photovoltaic cells can achieve an efficiency of 20% or more.

Solar photovoltaic systems are easy to handle and do not have moving mechanisms, but the photovoltaic cells themselves contain complex semiconductor devices similar to those used for the production of integrated circuits. The basis of the operation of photocells is the physical principle in which an electric current arises under the influence of light between two semiconductors with different electrical properties that are in contact with each other. The combination of such elements forms a photovoltaic panel or module. Photovoltaic modules, thanks to their electrical properties produce direct current, not alternating current. It is used in many simple battery powered devices. Alternating current, on the other hand, changes its direction at regular intervals. It is this type of electricity supplied by energy producers, it is used for most modern appliances and electronic devices. In the simplest systems, direct current from photovoltaic modules is used directly. In the same place where AC is needed, an inverter must be added to the system, which converts DC to AC.

In the coming decades, a significant part of the world's population will become familiar with photovoltaic systems. Thanks to them, the traditional need for the construction of large, expensive power plants and distribution systems will disappear. As the cost of solar cells declines and technology improves, several potentially huge markets for solar cells will open up. For example, solar cells built into building materials will provide ventilation and lighting for houses. Consumer products - from hand tools to automobiles - will benefit from the use of components containing photovoltaic components. Utilities will also be able to find new ways to use photovoltaic cells to meet the needs of the population.

The simplest photovoltaic systems include:

· solar pumps - photovoltaic pumping units are a welcome alternative to diesel generators and hand pumps. They pump water exactly when it is most needed - on a clear sunny day. Solar pumps are easy to install and operate. A small pump can be installed by one person in a couple of hours, and neither experience nor special equipment is needed for this.

· Battery photovoltaic systems - the battery is charged by a solar generator, stores energy and makes it available at any time. Even under the most adverse conditions and in remote locations, photovoltaic energy stored in batteries can power necessary equipment. Thanks to the accumulation of electricity, photovoltaic systems provide a reliable source of power day and night, in any weather. Battery-powered photovoltaic systems power lighting, sensors, sound recording equipment, household appliances, telephones, televisions and power tools around the world.

photovoltaic systems with generators - when electricity is needed continuously or there are periods when it is needed more than a photovoltaic array alone can produce, it can be effectively supplemented by a generator. IN daytime hours photovoltaic modules meet the daily energy requirement and charge the battery. When the battery is discharged, the motor-generator turns on and runs until the batteries are recharged. In some systems, the generator makes up for the lack of energy when the electricity demand exceeds the total capacity of the batteries. The engine-generator generates electricity at any time of the day. As such, it provides an excellent backup power source for duplicating photovoltaic modules at night or on a stormy day depending on the whims of the weather. On the other hand, the photovoltaic module operates silently, requires no maintenance and does not emit pollutants into the atmosphere. The combined use of photovoltaic cells and generators can reduce the initial cost of the system. If there is no backup installation, the PV modules and batteries must be large enough to provide power at night.

· Grid-attached photovoltaic systems - in a centralized power supply environment, a grid-connected photovoltaic system can provide part of the required load, while the other part comes from the grid. In this case, the battery is not used. Thousands of homeowners in different countries world use such systems. Photovoltaic energy is either used locally or fed into the grid. When the owner of the system needs more electricity than it generates - for example, in the evening, then the increased demand is automatically satisfied by the network. When the system generates more electricity than the household can consume, the surplus is sent (sold) to the grid. Thus, the utility network acts as a reserve for a photovoltaic system, like a battery for an off-grid installation.

· industrial photovoltaic installations - photovoltaic plants operate silently, do not consume fossil fuels and do not pollute the air and water. Unfortunately, photovoltaic stations are not yet very dynamically included in the arsenal of utility networks, which can be explained by their features. At modern method Calculating the cost of energy, solar electricity is still significantly more expensive than traditional power generation. In addition, photovoltaic systems generate energy only during daylight hours, and their performance depends on the weather.

4. Solar architecture

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 windows facing south (in the Northern Hemisphere) to let in more sunlight in winter time(and vice versa, a small number of windows facing east or west to limit the entry of unwanted sunlight into summer time); 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 fluctuations internal temperature insulation must be placed with outside building. However, in places with rapid internal heating, where little insulation is required, or where the heat capacity is low, the insulation should be 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. Passive Solar Buildings - perfect place for life. Here you feel the connection with nature more fully, in such a house there is a lot of natural light, it saves electricity.

Passive use of sunlight provides approximately 15% of the space heating demand in a typical building and is an important source of energy savings. When designing a building, it is necessary to take into account the principles of passive solar construction in order to maximize the use of solar energy. These principles can be applied everywhere and at virtually no additional cost.

During the design of a building, the use of active solar systems such as solar collectors and photovoltaic arrays should also be considered. 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 should be installed at an angle of more than 50° from the horizontal. Stationary photovoltaic arrays receive within a year the largest number solar radiation, when the angle of inclination relative to the horizon level is equal to the geographic latitude at which the building is located. The slope 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. It is important to remember that the proximity of the bathroom and kitchen allows you to save on the installation of active solar systems (in this case, you can use one solar collector for two rooms) and minimize energy losses for transportation. The main criterion for choosing equipment is its efficiency.

Conclusion

Currently, only a negligible part of solar energy is used due to the fact that existing solar panels have a relatively low coefficient useful action and very expensive to manufacture. However, one should not immediately abandon the practically inexhaustible source of clean energy: according to experts, solar energy alone could cover all conceivable energy needs of mankind for thousands of years to come. It is also possible to increase the efficiency of solar installations by several times, and by placing them on the roofs of houses and next to them, we will provide heating for housing, heating water and the operation of household electrical appliances even in temperate latitudes, not to mention the tropics. For the needs of industry that require large amounts of energy, you can use kilometer-long wastelands and deserts, completely lined with powerful solar installations. But solar energy faces many difficulties with the construction, placement and operation of solar power plants on thousands of square kilometers of the earth's surface. Therefore, the general specific gravity solar energy has been and will remain quite modest, at least for the foreseeable future.

At present, new space projects are being developed with the aim of studying the Sun, observations are being carried out, in which dozens of countries take part. Data on the processes occurring on the Sun are obtained using equipment installed on artificial Earth satellites and space rockets, on mountain peaks and in the depths of the oceans.

Much attention should also be paid to the fact that energy production, which is a necessary means for the existence and development of mankind, has an impact on nature and the human environment. On the one hand, heat and electricity have become so firmly established in the life and production activities of a person that a person cannot even imagine his existence without it and consumes inexhaustible resources for granted. On the other hand, people are increasingly focusing their attention on the economic aspect of energy and require environmentally friendly energy production. This indicates the need to address a set of issues, including the redistribution of funds to meet the needs of mankind, the practical use of achievements in the national economy, the search and development of new alternative technologies to generate heat and electricity, etc.

Now scientists are investigating the nature of the Sun, finding out its influence on the Earth, and working on the problem of using the almost inexhaustible solar energy.

List of sources used

Literature

1. The search for life in the solar system: Translation from English. M.: Mir, 1988, p. 44-57

2. Zhukov G.F. General theory of energy.//M: 1995., p. 11-25

3. Dementiev B.A. Nuclear power reactors. M., 1984, p. 106-111

4. Thermal and nuclear power plants. Directory. Book. 3. M., 1985, p. 69-93

5. Encyclopedic dictionary of a young astronomer, M.: Pedagogy, 1980, p. 11-23

6. Vidyapin V.I., Zhuravleva G.P. Physics. General theory.//M: 2005, p. 166-174

7. Dagaev M. M. Astrophysics.// M: 1987, p. 55-61

8. Timoshkin S. E. Solar energy and solar batteries. M., 1966, p. 163-194

9. Illarionov A. G. The nature of energy.//M: 1975., p. 98-105

Websites

1. http://www.stroyca.ru

2. http://www.astro.alfaspace.net

3. http://www. solbat.narod.ru/1.htm

4.http://www. sunenergy.4hs.ru

5. http://solar-battery.narod.ru

Ministry of Education of the Republic of Belarus

educational institution

"Belarusian State Pedagogical University named after Maxim Tank"

Department of General and Theoretical Physics

Coursework in General Physics

Solar energy and prospects for its use

Students of 321 groups

Faculty of Physics

Leshkevich Svetlana Valerievna

Scientific adviser:

Fedorkov Cheslav Mikhailovich

Minsk, 2009

Introduction

1. General information about the sun

2. The sun is a source of energy

2.1 Solar energy research

2.2 The potential of solar energy

3. Use of solar energy

3.1 Passive use of solar energy

3.2 Active use of solar energy

3.2.1 Solar collectors and their types

3.2.2 Solar systems

3.2.3 Solar thermal power plants

3.3 Photovoltaic systems

4. Solar architecture

Conclusion

List of sources used

Introduction

Perhaps the first known solar system can be considered the statue of Amenhotep III, dating back to the 15th century BC. Inside the statue there was a system of air and water chambers, which under the sun's rays set in motion a hidden musical instrument. In ancient Greece they worshiped Helios. The name of this god today formed the basis of many terms related to solar energy.

The problem of providing electrical energy to many sectors of the world economy, the constantly growing needs of the world's population is now becoming more and more urgent.

1. General information about the Sun

The Sun is the central body of the Solar System, a hot plasma ball, a typical G2 dwarf star.

Characteristics of the Sun

1. Mass M S ~2*10 23 kg

2. R S ~629 thousand km

3. V \u003d 1.41 * 10 27 m 3, which is almost 1300 thousand times greater than the volume of the Earth,

4. average density 1.41 * 10 3 kg / m 3,

5. luminosity L S \u003d 3.86 * 10 23 kW,

6. effective surface temperature (photosphere) 5780 K,

7. rotation period (synodic) varies from 27 days at the equator to 32 days. at the poles

8. free fall acceleration 274 m/s 2 (with such a huge acceleration of gravity, a person weighing 60 kg would weigh more than 1.5 tons).

Structure of the Sun

Rice. 1 Structure of the Sun

The photosphere is the radiating surface of the Sun, which has a granular structure called granulation. Each such "grain" is almost the size of Germany and is a stream of hot matter that has risen to the surface. On the photosphere, one can often see relatively small dark areas - sunspots. They are 1500˚С colder than the photosphere surrounding them, the temperature of which reaches 5800˚С. Due to the difference in temperature with the photosphere, these spots appear completely black when viewed through a telescope. Above the photosphere is the next, more rarefied layer, called the chromosphere, that is, the "colored sphere". The chromosphere got its name because of its red color. And, finally, above it is a very hot, but also extremely rarefied part of the solar atmosphere - the corona.

2. The sun is a source of energy

Sunlight, falling on plants, causes the process of photosynthesis in it, determines the growth and development of plants; falling on the soil, it turns into heat, heats it, forms the soil climate, thereby giving vitality to the seeds of plants, microorganisms and living creatures in the soil, which without this heat would be in a state of anabiosis (hibernation).

2.1 Solar energy research

Why does the Sun shine and not cool down for billions of years? What "fuel" gives him energy? Scientists have been looking for answers to this question for centuries, and only at the beginning of the 20th century was the correct solution found. It is now known that, like other stars, it shines due to thermonuclear reactions occurring in its depths.

2.2 The potential of solar energy

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 is the equivalent of running more than 100 100W incandescent bulbs daily for a full 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.

Solar energy is used as a source of both electrical and thermal energy. It is environmentally friendly, and no harmful emissions are generated during its conversion. This relatively new way of generating electricity was rapidly developed in the mid-2000s, when the EU began to introduce a policy of reducing dependence on hydrocarbons in the field of electricity generation. Another goal was to reduce greenhouse gas emissions into the atmosphere. It was during these years that the cost of producing solar panels began to decline, and their efficiency began to increase.

Tropical and subtropical climatic zones are the most favorable, in terms of the length of daylight hours and the flow of sunlight throughout the year. Most favorable in temperate latitudes summer season, and as for the equatorial zone, then in it negative factor is cloudy in the middle of daylight hours.

It can be carried out through an intermediate thermal process or directly through. Photovoltaic stations supply electricity directly to the grid, or serve as a source of autonomous power supply to the consumer. Thermal solar stations are mainly used to generate thermal energy by heating various heat carriers, such as water and air.

As of 2011, all solar power plants in the world produced 61.2 billion kilowatt-hours of electricity, which corresponds to 0.28% of the total global electricity generation. This volume is comparable to half of the generation of electricity at hydroelectric power plants in Russia. Most of the world's photovoltaic capacity is concentrated in a small number of countries: in 2012, 7 leading countries had 80% of the total capacity. The most rapid development of the industry was in Europe, where 68% of the world's installed capacity was concentrated. In the first place is Germany, which accounts (2012) for about 33% of world capacities, followed by Italy, Spain and France.

In 2012, the installed capacity of solar photovoltaic plants worldwide was 100.1 GW, which is less than 2% of the total figure for the global electricity industry. Between 2007 and 2012, this volume increased 10 times.

In China, the USA and Japan, solar energy capacities of 7-10 GW were located. Within a few recent years Solar energy is growing particularly fast in China, where the country's total photovoltaic capacity has grown 10 times in 2 years - from 0.8 GW in 2010 to 8.3 GW in 2012. Now Japan and China account for 50% of the global solar energy market. China's intention is to receive 35 GW of electricity from solar installations in 2015. This is due to the ever-increasing demand for energy, as well as the need to fight for the cleanliness of the environment, which suffers from the burning of fossil fuels.

According to forecasts of the Japan Photovoltaic Energy Association, by 2030 the total capacity of solar stations in Japan will reach 100 GW.

India plans to increase, in the medium term, the capacity of solar installations by 10 times, that is, from 2 GW to 20 GW. The cost of solar energy in India has already reached the level of 100 dollars per 1 megawatt, which is comparable to the energy received in the country from imported coal or gas.

Only 30 percent of sub-Saharan Africa has access to. Autonomous solar installations and micro-grids are being developed there. Africa, as a region with a strong mining industry, hopes to obtain an alternative to diesel power plants in this way, as well as a reliable backup source for unreliable electricity networks.

In Russia, the period of formation of solar energy is now underway. The first photovoltaic plant with a capacity of 100 kW, located in the Belgorod region, was launched in 2010. Solar polycrystalline panels for it were purchased at the Ryazan plant of metal-ceramic devices. Since 2014, the construction of a solar power plant with a capacity of 5 MW has begun in the Republic of Altai. Other possible projects in this area are also being considered, including in the Primorsky and Stavropol Territories, as well as in the Chelyabinsk Region.

As for solar thermal energy, according to the Renewable Energy Policy Network for the 21st Century, in 2012 its global installed capacity was 255 GW. Most of this thermal capacity is in China. In the structure of such capacities, the main role is played by stations aimed directly at heating water and air.

solar energy- this is light, heat and life on our planet, and also solar energy is the main alternative source, which exceeds the entire existing energy potential of the Earth by several orders of magnitude, and it is able to fully meet all its energy needs.

As the Sun is an endless source of heat and light (conditionally), so the energy of solar radiation has supported life on Earth for more than one million years. The Sun has the ability to provide all vital processes due to its composition. In percentage terms, it mainly consists of two elements: hydrogen (73%) and helium (25%). You can read more about the formation and life cycle of the Sun, for example, on Wikipedia.

The fusion reactions that take place in the Sun burn hydrogen, turning it into helium. The colossal energy of the sun's rays released during such processes is radiated into space. By the way, scientists are trying to repeat these reactions on earth (controlled thermonuclear fusion reaction, international TOKAMAK project).

All organisms that use the energy of sunlight provide their life processes with its help - sunlight is necessary for initial stage photosynthesis process. With its participation, the synthesis of substances such as oxygen and hydrocarbons occurs.

The amount of hydrogen in the Sun is gradually decreasing and sooner or later the time will come when its supply in the sun is exhausted. However, due to a large number hydrogen this will not happen, at least in the next 5 billion years.

Every second in the core of the Sun, about 4 million tons of matter is converted into radiant energy, resulting in the generation of solar radiation and a stream of solar neutrinos.

The main influx of solar energy that reaches the Earth's atmosphere is in the spectral range 0.1-4 µm. In the range of 0.3 1.5-2 microns, the Earth's atmosphere is almost transparent to solar radiation. Ultraviolet waves (wavelength shorter than 0.3 microns) are absorbed by the ozone layer, which is located at altitudes of 20-60 km. X-ray and gamma radiation almost do not reach the Earth's surface.

The concentration of solar energy is characterized by a value of 1367 W/m 2 , called the solar constant. It is this flow that passes through a perpendicular area 1 m 2 in size, if it is placed at the entrance to the upper layer of the Earth's atmosphere. When this stream reaches sea level, energy losses reduce it to 1000 W/m 2 at the equator. But the change of day and night reduces it by another 3 times. For temperate latitudes, taking into account the winter period, it is half of the quantitative indicator of the maximum flux at the equator.

Averaged over time and over the Earth's surface, this flux is 341 W/m 2 . Based on the full surface, or 1.74x10 17 W calculated on the full surface of the Earth. Thus, per day, the Earth on the surface will receive 4.176x10 15 kWh of energy, most of which returns to space in the form of radiation.

According to the IEA for 2015, global energy production was 19,099 Mtoe (equivalent to a megaton of oil). In terms of the usual kilowatt hours, this figure will be 6.07x10 11 kWh per day.

The sun gives the earth 8,000 times more energy than is necessary for all mankind. Obviously, the prospects for the use of this type of energy are very wide. With its participation, wind energy is being developed (wind occurs due to temperature differences), photoelectric converters are being used and pumped-storage stations are being built. There is a widespread use of solar panels.

The potential for using solar energy is very high.

Advantages and disadvantages of using solar energy

Benefits of using solar energy led to the fact that today we see its use in the most different types human activity.

The main advantages are:

The inexhaustibility of solar energy in the next 4 billion years;
The availability of this type of energy - it is with it that farmers, owners of private houses, and giant plants work safely and efficiently today;
Free and environmentally friendly generated energy;
The prospect of developing this source of energy, which is becoming increasingly relevant due to rising prices for other types of energy;
Because the number of annually put into operation equipment and its reliability is growing, the cost of generated kilowatt-hour of solar energy is decreasing.

Conditional disadvantages of solar energy include:

The main disadvantage of solar energy is the direct dependence of the amount of light and heat received on the influence of factors such as weather, time of year or day. The logical consequence in this case is the need to store energy, which increases the cost of the system;
For the production of equipment elements for this purpose, rare and, therefore, expensive elements are used.

Prospects for the development of solar energy

Today, technologies that use the energy of sunlight are increasingly being used. The most common are solar panels. Photovoltaic cells are successfully installed on various types of transport - from electric vehicles to airplanes. The Japanese practice installing them on trains.

Successfully functioning, one of the European solar power plants provides all the needs of the Vatican. The largest plant in California, the source of which is solar energy (photos give an idea of the scale), already now provides the state with its round-the-clock work.

The introduction of such technologies is faced with resistance from the leaders of the hydrocarbon industry - after all, alternative sources in the energy sector may soon displace their representatives from leading positions.

If speak about direct conversion, then the most widely used solar energy conversion devices are heat pipes (solar collectors) and solar photovoltaic cells.

The economics of a solar installation

When considering the possibility of installing a solar power plant, the focus is on environmental rather than economic aspects. They sound like this:

What is the cost of a solar installation?
What is its payback period?
Will the installation generate enough electricity?

It is advisable to consider small power plants with a capacity of up to 50 kW. Larger power plants are used mainly in industrial facilities.

Will a home solar power plant generate enough electricity?

To answer the third question, before starting the design of a solar installation, determines the energy consumption profile of the house. It can be recorded by installing an electricity meter at the facility with the function of saving the current parameters: mains voltage, current consumption, current power consumption, frequency. After a month, you can evaluate your consumption profile with average, maximum and minimum parameter values.

If such a device is not available, then the energy consumption profile can be estimated as follows: you need to record all the devices that can be used in the house and simulate possible options their daily use. After that, armed with a calculator, you can calculate the daily electricity consumption and peak power values.

The region where the building is located plays a significant role. The energy reaching the Earth's surface, depending on the region, can vary from more than 5 kWh/m 2 /day to 1.5 kWh/m 2 /day or less.

If the maximum consumption occurs during daylight hours, then to ensure the sufficiency of the generated electricity, it is necessary to divide the maximum power consumption by the power of one solar cell panel. The type and characteristics of panels are known from manufacturers' catalogs. It should be taken into account that the characteristics of solar panels are given at their maximum illumination - an amendment to the regional coefficient is required. winter period when batteries are covered with snow is not taken into account.

This calculation does not take into account next feature: During the day, the installation will always generate an excess amount of energy, and at night, for obvious reasons, the generation will be 0.

Rechargeable batteries on the one hand increase total cost systems, on the other hand, make it possible to reduce the number of solar panels by storing energy during periods of lower power consumption.

To calculate the battery bank, you need to answer the following questions:

Is the system supposed to be completely autonomous?
If the system is not autonomous, then what is the maximum possible term power outages.

The maximum consumption in kWh is multiplied by the number of hours without the main source (be aware that at the time of the shutdown the sun may not be). Based on these data, the capacity of the battery bank can be calculated. Discharging the battery to 0 shortens its service life, so the coefficient of the maximum discharge indicator is introduced in the calculation, for example, it can be 50, 40 or 30%. The lower the maximum discharge rate, the more batteries will be required.

The cost of installing solar generation

The main components of the system equipment are distributed by cost in the following percentage (conditionally):

Inverter and control system - 15-40%;
Solar panels and MPPT controllers - 20-40%;
Bank AKB - 30%.

The cost of solar panels and batteries will be identical for systems of all manufacturers, there are significant differences only in the cost of equipment for an inverter with a control system and an MPPT controller.

The difference in price reaches more than 200%, depending on the manufacturer. This is due not only to the “brand”, but also to the capabilities of the system, for example, ease of management, remote access, maximum load and resistance to 2x-3x overloads, the possibility of partial load shutdown, etc.

Each final technical solution will be slightly different from others due to the fact that all people use different household appliances at different times of the day. There is no ideal combination of equipment, even for a given power.

As an estimated cost of a functional solar installation in Vacation home taking into account the reservation of part of the power, you can roughly focus on the figures of 700-1800 USD / kW, depending on the equipment manufacturer.

Payback period for solar generation installation

If the owners conditionally go to the dacha only for the weekend, and at the same time there are no consumers in the house who work every day, then most likely the system will pay off at least 10-15 years, at current electricity tariffs.

With permanent residence, the payback period will be reduced to 6-10 years.

The positive side of the coin is that the owner of such a house receives a stable source of electricity and does not depend on power line breaks or power drops. Everyone is sitting without light, and you are with light, security systems are functioning, there is no need to manually open the garage, etc.

It can be assumed that the development of private electric transport will reduce the payback period for solar installations for households. The owner of such a car will “refuel” it for free from his own roof..

The payback period depends on the completeness of the use of electricity. If the building uses 100% of the generation and is connected to the central power supply network, then in general, there is no need to install a battery bank. The estimated full payback period for such an installation will be 3-5 years, and even less in hot regions.

An additional benefit is formed due to the fact that during the day the owner DO NOT PAY at the daily rate, and at night PAYING by night.

Such quickly payback facilities can be any energy-intensive industries with an empty flat roof, shopping and entertainment and sports centers and parking lots, refrigeration complexes, etc.

Surprisingly, such solutions, which can significantly reduce operating costs, are still not used by property owners.

In the foreseeable future, with the development of solar energy, an increasing number of building owners will use clean energy instead of hydrocarbon feedstock.