Types of solar power plants: tower, disc, parabolic-cylindrical concentrator, solar-vacuum, combined

To convert solar radiation energy or in other words — solar heat and light, into electrical energy, for many years many countries around the world have been using solar power plants. These are engineering structures with a different design, working on different principles, depending on the type of power plant.

If someone, hearing the combination "solar power plant", imagines a huge area covered with solar panels, this is not surprising, because this type of power plants, called photovoltaic, is very popular today in many households. But this is not the only type of solar power plant.

All solar power plants known today that produce electricity on an industrial scale are divided into six types: tower, plate, photovoltaic, parabolic-cylindrical concentrators, solar-vacuum and combined.Let's take a detailed look at each type of solar power plant and pay attention to specific structures in different countries around the world.

Tower power plants

Solar Power Plant — A solar power plant in which radiation from an optical concentrating system formed by a field of heliostats is directed to a tower-mounted solar receiver.

Tower power plants were originally based on the principle of water evaporation under the influence of solar radiation. Here water vapor is used as the working fluid. Located at the center of such a station, the tower has a water tank on top that is painted black to best absorb both visible radiation and heat. In addition, the tower has a pump group whose function is to supply water to the reservoir. Steam, the temperature of which exceeds 500 ° C, turns a turbine generator located on the territory of the station.

In order to concentrate the maximum possible amount of solar radiation at the top of the tower, hundreds of heliostats are installed around it, whose function is to direct the reflected solar radiation directly to the water container. Heliostats are mirrors, the area of ​​each of which can reach tens of square meters.

Heliostat [heliostat] — A flat or focusing mirror element of an optical concentrating system having an individual orientation device for directing reflected direct solar radiation to a solar radiation receiver.

Mounted on supports equipped with an automatic focusing system, all heliostats direct the reflected solar radiation directly to the top of the tower, to the tank, as the positioning works according to the movement of the sun during the day.

On the hottest day, the temperature of the produced steam can rise to 700 °C, which is more than enough for the normal operation of the turbine.

For example, in Israel, on the territory of the Negev desert, by the end of 2017, the construction of a power plant with a tower with a capacity of more than 121 MW will be completed. The height of the tower will be 240 meters (the tallest solar tower in the world at the time of construction). , and around it will be a floor of hundreds of thousands of heliostats that will be positioned via Wi-Fi control. The steam temperature in the tank will reach 540 ° C. The $773 million project will cover 1% of Israel's electricity needs.

Water is not the only thing that can be heated by solar radiation in the tower. For example, in Spain, in 2011, the Gemasolar tower solar power plant was put into operation, in which a salt coolant is heated. This solution made it possible to heat even at night.

The salt, heated to 565 ° C, enters a special tank, after which it transmits heat to the steam generator, which turns the turbine. The entire system has a rated capacity of 19.9 MW and is capable of supplying 110 GWh of electricity (annual average) to power a network of 27,500 households operating at full capacity 24 hours a day for 9 months.

Lot power plants

In principle, power plants of this type are similar to tower plants, but are structurally different. It uses separate modules, each of which generates electricity. The module includes both a reflector and a receiver. A parabolic assembly of mirrors forming a reflector is mounted on the support.

Mirror Amplifier — A solar radiation concentrator with a mirror coating.Specular faceted concentrator — A specular concentrator of solar radiation consisting of individual mirrors of flat or curved shape forming a common reflecting surface.

The receiver is located at the focus of the paraboloid. The reflector consists of dozens of mirrors, each individually customized. The receiver may be a Stirling engine combined with a generator, or a tank of water which is converted into steam, and the steam turns the turbine.

For example, in 2015, Ripasso, Sweden, tested a parabolic helothermal unit with a Stirling engine in South Africa. The reflector of the installation is a parabolic mirror consisting of 96 parts and a total area of ​​104 square meters.

The focus was on a Stirling hydrogen engine equipped with a flywheel and connected to a generator. The plate turned slowly to follow the sun during the day. As a result, the efficiency factor was 34%, and each such "plate" was able to provide the user with 85 MWh of electricity per year.

In fairness, we note that at the focus of the "plate" of a solar power plant of this type, a container of oil can be located, the heat of which can be transferred to the steam generator, which, in turn, rotates the turbine of the electric generator.

Parabolic tube solar power plants

Here again the heating medium is heated by concentrated reflected radiation. The mirror is in the form of a parabolic cylinder up to 50 meters long, located in the north-south direction and rotates following the movement of the sun. At the focus of the mirror is a fixed tube along which the liquid cooling agent moves.Once the coolant is warm enough, the heat is transferred to the water in the heat exchanger, where the steam turns the generator again.

Parabolic corridor concentrator — A mirror concentrator of solar radiation, the shape of which is formed by a parabola moving parallel to itself.

In the 1980s in California, Luz International built 9 such power plants, with a total capacity of 354 MW. However, after several years of practice, experts have come to the conclusion that today parabolic power plants are inferior both in terms of profitability and efficiency to tower and plate solar power plants.

However, in 2016, a power plant was discovered in the Sahara desert near Casablanca. solar concentrators, with a capacity of 500 MW. Half a million 12-meter mirrors heat the coolant to 393 ° C to turn water into steam for spinning generator turbines. At night, the thermal energy continues to work by being stored in molten salt. In this way, the state of Morocco plans to gradually solve the problem of an environmentally friendly source of energy.

Photovoltaic power plants

Stations based on photovoltaic modules, solar panels. They are very popular and widespread in the modern world. Modules based on silicon cells are widely used to power small sites, such as sanatoriums, private villas and other buildings, where a station with the required power is assembled from separate parts and installed on the roof or on a plot of a suitable area. Industrial photovoltaic power plants are able to supply electricity to small towns.

Solar Power Plant (SES) [solar power plant] — A power plant designed to convert the energy of solar radiation into electricity.

For example, in Russia, the largest photovoltaic power plant in the country was launched in 2015. The "Alexander Vlazhnev" solar power plant, consisting of 100,000 solar panels, with a total capacity of 25 MW, is located on an area of ​​80 hectares between the cities of Orsk and Gai. The capacity of the station is enough to supply electricity to half of the city of Orsk, including business and residential buildings.

The principle of operation of such stations is simple. The energy of light photons is converted into current in a silicon wafer; the intrinsic photoelectric effect in this semiconductor has long been studied and accepted by solar cell manufacturers. But crystalline silicon, which gives an efficiency of 24%, is not the only option. Technology is constantly improving. So in 2013, Sharp engineers achieved 44.4% efficiency from an indium-gallium-arsenide element, and the use of focusing lenses makes it possible to achieve all 46%.

Solar vacuum power plants

Absolutely ecological type of solar stations. In principle, the natural air flow is used, which occurs due to the temperature difference (the air on the surface of the earth is heated and rushes upwards). Back in 1929, this idea was patented in France.

A greenhouse is being built, which is a piece of land covered with glass. A tower protrudes from the center of the greenhouse, a tall pipe in which a generator turbine is mounted. The sun heats the greenhouse, and the air rushing up through the pipe turns the turbine.The draft remains constant as long as the sun heats the air in a closed glass volume and even at night as long as the surface of the earth retains heat.

An experimental station of this type was built in 1982, 150 kilometers south of Madrid, in Spain. The greenhouse was 244 meters in diameter and the pipe was 195 meters high. The maximum developed power is only 50 kW. However, the turbine ran for 8 years until it failed due to rust and high winds. In 2010, China completed the construction of a solar vacuum station that was able to provide 200 kW. It covers an area of ​​277 hectares.

Combined solar power plants

These are the stations where hot water and heating communications are connected to heat exchangers, in general they heat water for various needs. Combined stations also include combined solutions when the concentrators work in parallel with the solar panels. Combined solar power plants are often the only solution for alternative power supply and heating of private houses.