Mirror booster – A concentrator of solar radiation with a mirror coating. Mirror faceted concentrator – Mirror concentrator of solar radiation, consisting of individual mirrors of a 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 can be a Stirling engine combined with a generator, or a reservoir with water, which turns into steam, and the steam rotates the turbine.

In the focus of the “plate” of a solar power plant of this type, there can also be a container with oil, the heat from which can be transferred to the steam generator, which, in turn, rotates the turbine of the electric generator.

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The tower power plants were originally based on the principle of water evaporation under the influence of solar radiation. Water vapor is used here as a working fluid. Located in the center of such a station, the tower has a water reservoir on top, which is painted black for the best absorption of both visible radiation and heat. In addition, the tower has a pumping group, the function of which is to deliver water to the reservoir. Steam, whose temperature exceeds 500 ° C, rotates a turbine generator located on the site 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, the function of which is to direct the reflected solar radiation exactly to the container with water. Heliostats are mirrors, the area of ​​each of which can reach tens of square meters.

Heliostat – A flat or focusing mirror element of an optical concentrating system, having an individual orientation device for directing reflected direct solar radiation energy to a solar radiation receiver.

Mounted on supports equipped with an automatic focusing system, all heliostats direct the reflected solar radiation exactly to the top of the tower, to the reservoir, 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 go up 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 tower power plant with a capacity of more than 121 MW will be completed. The height of the tower will be 240 meters (the world’s tallest solar tower at the time of construction), and around it there will be a floor of hundreds of thousands of heliostats, which 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 commissioned, in which a salt-based heat transfer fluid is heated. This solution made it possible to keep warm even at night.

The salt heated to 565 ° C enters a special reservoir, then transfers heat to the steam generator, which rotates the turbine. The entire system has a nominal capacity of 19.9 MW and is capable of supplying 110 GWh of electricity (on average per year) to power a network of 27,500 households, operating at full capacity 24 hours a day for 9 months.

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A hydroelectric power plant (HPP) is a power plant that converts the energy of moving water into electrical energy. Hydroelectric power plants are being installed on rivers. With the help of the dam, a water height difference is created (before and after the dam). The resulting water pressure drives the turbine blades. The turbine drives generators that generate electricity.

Depending on the capacity of the generated electricity, hydroelectric power plants are divided into: small (up to 5 MW), medium (5-25 MW) and powerful (over 25 MW). According to the maximum used pressure, they are divided into: low-pressure (maximum pressure – from 3 to 25 m), medium-pressure (25-60 m) and high-pressure (over 60 m). Hydroelectric power plants are also classified according to the principle of using natural resources: dam, near dam, diversion and pumped storage.

Pros and Cons of Hydroelectric Power Plants

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If there is a settlement near the power plant, then the heat of the spent coolant is used to heat the water of the heating system of houses or hot water supply, and if not, then the excess heat of the spent coolant is simply discharged into the atmosphere in cooling towers or into a reservoir (pond, lake, river) cooler.

TPPs generate electrical energy as a result of the conversion of thermal energy released during the combustion of fossil fuel. Basically, most TPPs use thermal steam turbine units (STP), in which thermal energy is used in a steam generator to produce high pressure steam, which drives a steam turbine rotor, connected to the rotor of an electric generator (usually a synchronous generator). Coal (mainly), fuel oil, natural gas, lignite, peat, shale are used as fuel at such TPPs.

TPPs with steam turbines that have condensing turbines as a drive for electric generators and do not use the heat of the exhaust steam to supply heat energy to external consumers are called condensing power plants (IES or GRES). TPPs with steam turbines, equipped with cogeneration turbines and giving off heat from the waste steam to industrial or municipal consumers, are called combined heat and power plants (CHP).

TPPs driven by an electric generator from a gas turbine are called TPPs with gas turbine units (GTU). Gas or liquid fuel is burned in the combustion chamber of the GTU; combustion products with a temperature of 750 … 900 ° C are fed to a gas turbine that rotates an electric generator. The efficiency of such TPPs is usually 26 … 28%, the capacity is up to several hundred MW. Thermal power plants with gas turbines are usually used to cover peaks of electrical load.

TPPs come with a steam-gas turbine unit (CCGT), consisting of a steam turbine and a gas turbine unit. The efficiency of such a station can reach 42 … 43%. GTU and CCGT units can also supply heat to external consumers, i.e. operate as a CHP. Thermal power plants use widespread fuel resources, are relatively freely located and are able to generate electricity without seasonal fluctuations. Their construction is carried out quickly and is associated with less labor and material resources. But TPPs have significant drawbacks. They use non-renewable resources, have low efficiency (30 … 35%), have an extremely negative impact on the environmental situation.

TPPs all over the world annually emit 200 … 250 million tons of ash and about 60 million tons of sulfur dioxide into the atmosphere, and also absorb a huge amount of oxygen. It has been established that coal in micro doses almost always contains U238, Th232 and a radioactive isotope of carbon. Most TPPs in Russia are not equipped with efficient systems for cleaning exhaust gases from sulfur and nitrogen oxides. Although installations operating on natural gas are environmentally much cleaner than coal, shale and fuel oil, the laying of gas pipelines is harmful to nature.

Condensing power plants (CES) play a primary role among thermal installations. They gravitate towards both fuel sources and consumers and are therefore very widespread. The larger the IES, the further it can transmit electricity, i.e., as the capacity increases, the influence of the fuel and energy factor increases. CHP (combined heat and power plants) are installations for the combined production of electricity and heat. Their efficiency reaches 70% versus 32 … 38% at IES. CHPPs are tied to consumers, since the radius of heat transfer (steam, hot water) is 15 … 20 km. The maximum capacity of the CHPP is less than that of the IES. Recently, fundamentally new installations have appeared:

• gas turbine (GTU) installations, in which gas turbines are used instead of steam, which eliminates the problem of water supply;
• steam and gas turbine (CCGT), where the heat of the exhaust gases is used to heat water and obtain low pressure steam;
• magnetohydrodynamic generators (MHD generators), which convert heat directly into electrical energy.

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