The role of solar energy in the energy of the future

The problem of developing non-traditional and renewable energy sources is becoming more and more urgent. Unconventional renewable energy sources include solar, wind, geothermal, biomass, and ocean energy.

In the last decade, interest in these energy sources has been steadily increasing, as in many ways they are unlimited. As fuel supplies become less reliable and more expensive, these sources are becoming more attractive and more economical. The rise in oil and gas prices was the main reason that people turned their attention back to water, wind and sun.

Recently, interest in the use of solar energy has increased dramatically, and although this source also belongs to renewable sources, the attention it receives around the world makes it necessary to consider its possibilities separately. The potential possibilities of energy based on the use of direct solar radiation are extremely large. Using only 0.0005% of the Sun's energy could meet all the current needs of the world's energy sector, and 0.5% - fully cover the needs for the future.

Solar energy is the kinetic energy of radiation (mainly light) generated as a result of reactions in the interior of the Sun. Since its reserves are almost inexhaustible (astronomers have calculated that the Sun will "burn" for several million more years), it is classified as a renewable energy resource.

The role of solar energy in the energy of the future.

Solar energy resources are large and available to every country. The amount of solar energy­delivered to the territory of Russia in 1 week exceeds the energy of all Russian reserves of oil, gas, coal and uranium. The share of solar energy in the form of biomass and guide­of renergie is 6 % of the total energy production in developing countries, 80%, and the Share of renewable energy sources (RES) in energy consumption in the EU countries is expected to increase from 6 % in 2000 to 12% in 2010, while the installed capacity of solar energy systems (SES) increase from 32 to 3 000 MW of peak power in 2010. The share of renewable energy sources, including hydroelectric power, should make up­22.1 % of electricity consumption in­the UES countries by 2010. In 2003, energy consumption in the UES countries was 2,880. 8 TWh. In 2030, the­projected global installed capacity of solar power plants using the photovoltaic method­of solar energy conversion will be 300 GW at a price of 1,000 euros/kW and an electricity cost of 0.05 ... ... 0.12 euros/ (kWh). Renewable energy sources will replace coal, oil, gas, and uranium in the­production of electricity, heat, and liquid fuels.

In order for solar energy to compete with traditional energy, it must have­the following indicators::

1) The SES efficiency is not less than 20 %;

when combining a solar power plant into a power system, it should generate electricity 24 hours /day for 12 months a year;

the service life of the solar power plant is 50 years;

the cost of installed peak power is not higher than $ 1,000 / kW;

production of semiconductor material for solar power plants is more than 1 million tons / year at a price not exceeding $ 15 /kt;

production of semiconductor material for solar power plants is more than 1 million tons / year at a price not exceeding $ 15 /ct; materials and technologies for the production of solar cells and modules are environmentally friendly and safe. It is necessary to consider to what extent the current goals and directions of development of solar photovoltaic power meet these indicators.

New technologies and materials will make­it possible in the next 5 years to increase the efficiency of SES made on the basis of cascade heterostructuresin the laboratory to 40%, in­production — up to 26...30%, the efficiency of SES made of silicon -­up to 28% in the laboratory, and in industry-up to 22%.

In Russia and abroad, a new generation­of solar cells is being developed with a maximum efficiency of up to 93 %, using new physical principles, materials and structures. The­main efforts are aimed at making more complete use­of the entire spectrum of solar radiation and the total photon Energy according to the principle: each photon should be absorbed in a varizon or cascade semiconductor with a band gap whose width­corresponds to the energy of this photon, which will­reduce the losses in the SE by 47%. For this purpose, SE is developed:

cascaded semiconductors with a band gap­of various widths;

with a variable-width band gap;

with impurity energy levels in the forbidden­zone.

Other approaches to improving the efficiency of solar cells involve the use of concentrated solar­radiation, the creation of polymer solar cells, and nanostructures­тур based on silicon and fullerenes.

Increasing the number of hours of use of installed solar power plant capacity

The average number of hours of installed­capacity use per year is 5,200 for thermal power plants and 1,000 for hydroelectric power plants...4,800, and 2,000 for wind farms . .3,000, for SES 1,000...2,500 hours

A stationary solar power plant with an efficiency of 20 % and a peak capacity of 1 kW generates 2,000 kW / h per year in central Russia and Germany, and up to 3,500 kW / h in the Sahara Desert. When tracking the Sun, electricity production under the same conditions can increase in Russia to 2,800, in the Sahara to 5,000 kWh / kW. The dependence­of the SES generated electricity on the time of day and weather conditions is the" Achilles 'heel" of SES in competition with power plants operating on fossil fuel­. Therefore, until now,­large-scale projects and forecasts for the development of solar energy have provided for the accumulation of solar­energy by electrolysis of water and accumulation of hydrogen.

Increasing the service life of a solar power plant

The service life of thermal power plants and nuclear power plants is 30-40 years, while that of semiconductor SES exceeds 50 years, since the­interaction of photons with atoms and electrons does not­lead to degradation of the crystal structure and­changes in the rate of surface and bulk recombination­of minor charge carriers. However, solar­modules (SM) have a service life of 20 years in tropical climates and 25 years in temperate climates due to the aging of polymer materials-ethylene vinyl acetate and tedlar, which are used to seal­the solar cells in the module. To increase the service life of­the module, it is necessary to exclude polymer materials from its design­. In the new design of the solar module, the solar cells are placed in a double-glazed unit made of two sheets of glass connected at the ends by soldering or welding. The end sealing technology guarantees­the module's hermeticity for 50 years. To reduce the­SE temperature and optical losses, the internal cavity of the module is filled with an organosilicon liquid (Fig. 3, 4) [9].

Reducing the cost of a solar power plant

The cost of installed 1 kW of power­is, USD: HPP-1 000 ... 2500, TPP-800... 1 400, WPP-800...3,000, AES-2,000...3 000.

The main component of modern solar­power plants that determines their cost is a solar module made of silicon-based solar cells. The cost of CM is 3,500...4,000 with a production capacity of 1 GW / year; SES — 6,000...$ 8,000 / kW. The cost of a solar power plant of $ 1,000 / kW is projected to reach in 2020.

The main ways to reduce the cost of solar power plants are to increase­the efficiency of solar power plants, increase the size of SM and the volume of­production, reduce the cost of solar silicon, reduce the consumption of solar silicon per unit of solar power plant capacity, and combine the production­of electricity and heat at solar power plants.

The maximum size of the solar module­is limited by the size of glass and is 2.5 x 3 m with an electrical­power of 1 kW. The volume of SM production is growing by 30% per year, and their cost­has decreased 10-fold since 1976.

Ensuring environmental characteristics of SES production

Humanity will not face an energy crisis associated with the depletion of oil, gas, and coal reserves if it masters solar energy technologies. The problems of combating environmental pollution from power plants and transport, providing high-quality food, and increasing the life expectancy and quality of life will also be largely solved. SES operation creates new jobs, increases the energy security and independence of SES owners due to fuel-free and distributed energy production.

Technological processes for the production of SES components are being developed, in which environmentally unacceptable chemical processes of etching and processing are replaced by vacuum, plasma-chemical, electron-beam and laser ones. Serious attention is paid to the disposal of industrial waste, as well as to the recycling of SES components after the end of their service life.

Figure 1 shows the change in the share of solar energy in global energy consumption. Until the 17th century, solar energy and wood burning energy, in which solar energy is accumulated through photosynthesis, were the only sources of energy for humans. And now 20 % of the world's energy production is obtained by burning wood, using the energy of rivers and wind, which are based on solar energy. New principles of solar energy conversion, new technologies for the production of polycrystalline silicon, the production of solar cells, the sealing of solar modules, the use of stationary solar concentrators and new methods of electricity transmission for the global solar power system will ensure the share of solar energy in world energy production by the end of the century (Figure 1), equal to 60...90%.

Figure 1The role of solar energy in global energy production

Development of solar energy in the Republic of Kazakhstan. State and prospects of using the solar potential.

The use of solar energy as one­of the main types of renewable­energy sources (RES) is expanding all over the world. The sun emits 88·²⁴1024 cal, or 370·10 TJ of heat, every second. Of this amount, only 1.2·10 17 gets to the Earth in energy equivalent¹⁷W, i.e.^10-18 kWh / year, which is 10,000 times more than all the energy consumed in the world. In­comparison, all other sources produce negligible heat. If the total­potential of the Sun is determined by the input of solar energy falling only on­free untreated territories, then the average annual capacity of such a potential will be about 10,000 TWh, which is about 5,000 times more than the capacity­of all modern power plants in the world. ­We should also mention other advantages­of using solar energy: ecological cleanliness and practical inexhaustibility. However, there are some drawbacks: the low­density of solar radiation on the Earth­'s surface and the unregulated mode of entry (due to the Earth's rotation, cloud cover), which­creates significant technical difficulties (the need for large reflective surfaces­, orientation systems, batteries, etc.)

In Kazakhstan, the number of cloudy days is low during the year. The potential level­of solar energy flow is several­thousand billion kilowatt-hours with a continuous­sunshine intensity of 2200-3000 hours / year. The level of possible use of the energy flow under environmental conditions is about 1 thousand billion rubles. kW * h (with a conversion efficiency of 100%). The average component of solar radiation in the republic is 800W /^m2. Maximum sunshine occurs in July, only in the northern regions the longest duration is observed in June.

Solar energy can be intensively used in 2/3 of the republic's territory (south of 50⁰ N), but the most preferred­areas for solar­ций power plants are the Aral Sea region, Kyzylordaregion ., Almatyregion , Atyrau andШымкентскаяShymkent­ region. The potential generation based on photovoltaic consumers with a possible total capacity of гелиоэлектростанций25,000 MW of solar power plants­is 2.5 billion rubles. kWh/ year.

For the development of solar energy in the republicгелиоэнергетикики, two main areas should be developed­. The first is the construction­of a solar power plant with a central receiver and distributed parameters (modular­type). The second direction is­photoelectric transformation. ­Solar power plants can be widely used in the agricultural sector. Considering that Kazakhstan is an agricultural country (40% of the population is rural), solar energy should play an important role here. It is economically and technically expedient to use solar energy­for the following purposes::

heat and cold supply of­livestock farms;

desalination of water at watering points of semi-desert and desert pastures;

lifting of water from mine and tube wells for animal husbandry;

drying of agricultural products and materials.

Today, solar heat and cold supply is the most studied and mastered direction in technical terms. Solar water heating systems can be widely used (Fig. 2). Only about 200 such installations are used in the republic with a total гелиоприемнойsolar receiving surface area of 5-8 thousand m2 .² .

Solar installations for heating and hot water supply are most effective when used in a decentralized manner in rural areas. The annual use of solar energy with an efficiency of 50-60% can reach 2.5 million tons. Gcal for heating and 0.6 million cubic meters. Gcal — for hot water supply. The total annual savings of conventional fuel will amount to 700 thousand tons. Water heating devices are manufactured abroad, including in Russia, and their production is also possible in Kazakhstan.

Fig. 2 Diagram of a solar water heating system:

1-solar collector; 2-battery; 3-friction heater;

4-heat consumer

Currently, the most promising area of solar energy use is the creation of photovoltaic installations and power plants with direct conversion of solar radiation into electricity using solar photobatteries made of mono - or polycrystalline or amorphous silicon. Phototransformation allows you to generate electricity in scattered sunlight, create installations and power plants of various capacities, and change their capacity by adding or removing modules. Such installations are characterized by low energy consumption for their own needs, they are simply automated, safe in operation, reliable and maintainable. They can work either offline or with a network connection. Installation (Fig.3) consists of a solar panel, an inverter, a storage device (battery) and an automatic control system (ACS).

Modular installations such as solar-to-heat or electrical energy converters also deserve attention. Modular SES work as follows. The heat carrier (for example, water) is heated using concentrators (free-standing modules). The heated coolant is collected from all modules and piped to the turbo generator. Such solar power plants are mainly used in solar industrial heat supply and power generation systems.

Solar panels

Rectifiers and stabilizers

Fig. 3 Diagram of a solar photovoltaic installation

All solar installations of these types can be used on the territory of Kazakhstan and effectively operated in agriculture, the manufacturing sector, and everyday life. The cost of electricity generated by solar installations is constantly decreasing, and they may well become competitive with fossil fuel installations.

Since the level of solar radiation decreases on cloudy days, SES systems should provide for power redundancy at the expense of other installations or high-quality storage of stored energy. Parallel operation of several power plants on different types of energy sources is most promising. There are the following types of combined systems:: SES – WPP, SES-HPP, SES-WPP-PSPP, SES-BPP, etc., and the SES can be a­photovoltaic station or энергокомп­a modular solar power complex.

It is advisable обьединение в один эергокомплексto combine solar, wind, hydraulic and biofuel installations operating for an autonomous consumer into one energy complex. In such a power complex , a biofuel plant is a guaranteed source of energy, i.e.­it ensures the constancy of energy production during a certain period of operation (­month, quarter, year). In addition, biofuel­ных plants use the residues of processed biomass to produce excellent fertilizers that are in high demand. Due to their sale, it is possible to reduce the payback period of the entire energy complex.

In conclusion, we can highlight the main measures necessary for the overall development of solar energy in the districts and regions­of the Republic of Kazakhstan:

conducting reconnaissance operations to find the most favorable locations for solar installations and identify­average annual levels of solar radiation;

economic justification for the construction of solar thermal and power plants:

selection of such locations of­energy installations, where it is possible­to use other types of energy resources based­on renewable energy sources:

selection схемof combined power plant schemes­лексовthat involve­several types of renewable energy installations at once;

ensuring that the received power capacity from such power complexes allows them to operate both for an autonomous consumer and for a local power system­ческой мощности от таких энергокомплексов возможности работы их как на автономного потребителя, так и на местную энергосисте­;

setting tariffs for heat and­electricity generated at such power­тахunits, which promote the mass use of non-traditional power installations by autonomous consumers.

Concept of solar energy development in Ukraine.

According to climatic conditions, Ukraine belongs to regions with an average intensity of solar radiation. The amount of solar energy received per unit area during the year is 1000-1350 kWh/^m2. According to the level of solar radiation intensity, the country can be divided into three or four regions - Western, Central, South-Eastern and Southern. The average intensity of solar radiation is about 1200 kWh/^m2.

    Pilot projects implemented in recent years have shown that the annual production of thermal energy in the conditions of Ukraine is 500-600 kWh/^m2. Taking into account the generally accepted Western potential of using solar collectors for developed countries, equal^{to 1 m2} per person, as well as the productivity of solar installations for the conditions of Ukraine, the annual resources of solar hot water supply and heating can reach 28 billion rubles. kWh of thermal energy. The implementation of this potential would save 3.4 million tons of fuel equivalent per year.

    Currently, the Ukrainian public utilities sector consumes about 74 million tons of fuel equivalent annually. Every year, the need for thermal energy increases by 1.5-2 %. There are estimates that with the resumption of economic growth, the level of consumption may increase significantly. On the other hand, according to various estimates, the potential for energy efficiency and energy saving in the public utilities sector of Ukraine is at least 50%. If this potential is used, economic growth should not lead to a significant increase in thermal energy consumption.

    Another way to curb the growth of thermal energy consumption is to fully develop the concept of solar buildings. In northern European countries, natural heating is used to provide 14% of the total heat needed by ordinary buildings. This estimate can be used as a lower limit for the conditions of Ukraine. In buildings built with the passive use of solar energy, the sun's contribution to heat consumption can be about 40 %. The share of passive heating is usually not taken into account by official statistics, but in reality it is the largest source of renewable energy use.

    A significant potential for using solar energy in Ukraine is the use of the sun for cooling and air conditioning, as well as in agricultural applications, for example, for drying various types of agricultural products and desalination of water in the southern regions.

    Several dozen pilot projects have been implemented in various sectors of the national economy in Ukraine. Among them are hot water supply systems for residential and public buildings, medical and health facilities; solar prefixes for fuel and electric boilers serving industrial, agricultural and municipal enterprises; small autonomous installations for individual residential buildings and consumer service enterprises. According to estimates made by Ukrainian experts, the payback period of implemented experimental solar water and heat supply installations is from five to ten years.

    Currently, about ten enterprises in different regions of the country have mastered the production of solar collectors of various designs. The cost of SK is in the range of 60-150 US dollars per square meter. At the same time, the total output of collectors does not exceed several hundred square meters per year. The total area of ICS installed in Ukraine is approximately 10 thousand square meters, which corresponds to about a thousand individual installations.

Technical solutions for hot water supply

    For commercial use in the conditions of Ukraine, inexpensive hot water supply systems are suitable, combining the use of solar collectors (SC) and battery tanks (BA) with a capacity of 100-200 liters to meet the needs of the population with hot water (40-60^liters).C) during the summer period. The systems are easy to operate and can be installed by the consumer independently. They have a large market, which includes individual households in rural and urban areas, country cottages and summer cottages.

    The use of hot water supply systems with natural circulation is promising for systems of different scales. The BA capacity can be 100-500 liters or more at temperatures up to 50-60^о° C. The scope of such systems includes recreation centers, summer camps, preschool institutions, and farms. In conditions of unstable power supply, an important feature is independence from the availability of electricity.

    Also promising are higher-capacity systems using battery tanks with a capacity^{of 5-10 m3}. Such systems are suitable for hot water supply of recreation centers, sanatoriums and boarding houses. Most of these facilities are located in the southern part of Ukraine, on the coast of the Black and Azov Seas and are used mainly in summer, when the temporary population on the coast increases several times.

    The widespread use of solar energy in the recreational area would reduce the amount of coal, fuel oil and natural gas burned, thereby improving the region's ecology. However, all of these systems are attractive to potential consumers not only because they solve the problem of replacing fossil fuels and reducing the man-made burden on the environment. As a consumer product, solar systems improve living conditions and increase its comfort. This is especially important for rural areas.

    In district heating systems, solar installations can be used for preheating water using solar prefixes to boiler rooms. It is advisable to equip boiler rooms with solar prefixes during their reconstruction. If the standard depreciation period for boiler equipment is 20 years, the annual volume of reconstructed boiler houses should be 5 % of their total number.

With a well-developed system of state support, taking into account the existing Western experience in the pace of implementation of such systems, it can be assumed that 5 % of new construction will be equipped with modular installations. Forecast data on the volume of use of autonomous modular water heating installations in individual residential buildings in connection with the forecast of their construction volume (based on the area of 5^m2 solar collector installations per 140 m2 house²), as well as data on other types of installations, are presented in Table 1.

Type of solar installations (area in thousands^of m2)	2005	2010	1996-2010
Prefixes for boiler	rooms 371.0	695.0	4184.0
Recreation facilities	345.0	545.0	4000.0
Preschool institutions	25.0	35.0	245.1
Cottages	25.5	58.9	308.8
Total	766.5	1333.9	8737.9

 Table 1.

  European experience has shown the feasibility of combining the use of various types of renewable energy sources. The use of solar energy for heating can cover 20-30 % of the heat demand, while the remaining part can be obtained by burning biomass. In the conditions of Ukraine, the combined use of biomass and solar energy is possible for both cottages and small district heating systems. Suitable types of biomass are solid non-commercial wood and wood processing waste in the central and north-western regions of Ukraine, biogas, and landfill gas.

There is a large and underutilized potential for using solar energy in agriculture and industry. Let's list some of the possible applications:

         1) Solar water heating for hot water supply of livestock farms and other facilities;

         2) Drying of grain, fruits, vegetables, hay, tobacco and other agricultural products;

         3) Greenhouse crop production;

         4) Desalination of water in the southern drylands;

         5)alnechny heating of reinforced concrete structures in the production process at ZhBK.

The following factors can have a positive impact on the market:

        1) Promotion of consumer interests by the government, as well as the development of specific mechanisms for stimulating production in the form of subsidies, tax exemptions, and preferential tariff policies.

         2) Creation of national and regional structures to promote the development of solar technologies, including in construction.

       3) Development of modern and inexpensive solar engineering samples. Increased industry activity to increase the market. Organization of large-scale production of equipment, providing conditions for certification, installation and service.

        4) Creation of an information system on domestic and foreign developments in the field of solar technology, active and passive methods of using solar energy, advertising and marketing. Active work with the public, including in schools and higher educational institutions. Targeted work with a group of potential consumers of solar heat supply