What is the main disadvantage of hydroelectric power plants. Are hydroelectric power plants more environmentally friendly than other types of power plants? Advantages of nuclear power plants over thermal power plants
Recently, as an alternative to classic medium-high-pressure dam hydroelectric power stations, low-pressure hydroelectric power stations operating on natural flow, which are quite widespread in Western Europe. Let's try to figure out what these hydroelectric power plants are and what their pros and cons are.
An example of a low-pressure run-of-the-river hydroelectric power plant is the Iffezheim hydroelectric power station on the Rhine, commissioned in 1978. Photo from here
The concept of a low-pressure run-of-river hydroelectric complex involves the creation of a hydroelectric power station on a flat river with a head of several meters, whose reservoir is usually located in the natural flood zone of the floodplain during heavy floods. Such waterworks have the following advantages:
* A small flood area, which usually does not include (or almost does not include) built-up lands. Consequently, no one needs to be resettled, and the impact on ecosystems is much less significant.
* It is much easier to integrate fish passages into low-pressure dams, and fish pass down through the turbines with less injury.
The Saratov hydroelectric power station is the lowest pressure one in the Volga-Kama cascade.
Now let's move on to the disadvantages:
* Such hydroelectric power stations form small reservoirs, suitable at best for daily flow regulation, or even operating on a watercourse. As a result, the production of such hydroelectric power plants is highly dependent on the season and weather conditions - during low-water periods it drops sharply.
* The efficiency of using the runoff of such hydroelectric power plants is much less than that of classical ones - not being able to accumulate runoff during high waters and floods, they are forced to empty a lot of water.
* Without a capacious reservoir, such hydroelectric systems cannot combat floods.
* From the point of view of navigation, the construction of several low-pressure hydroelectric complexes instead of one large one leads to an increase in time for locking - instead of one lock, you need to go through several.
* Low-pressure hydroelectric power plants have a significantly higher unit cost (calculated per kW of power and kWh of generated electricity). The lower the pressure, the larger the dimensions and, accordingly, the metal consumption of the equipment; the inability to accumulate runoff in the reservoir leads to the need to create more powerful culvert structures; several sluices are more expensive than one, etc. For comparison, we can cite the low-pressure Polotsk hydroelectric power station in Belarus and the high-pressure Boguchanskaya hydroelectric power station. The first costs approximately $4500 per kW, the second - about $1000 per kW. The difference, as we see, is 4.5 times.
Hydroelectric power station Tucurui in Brazil. In the Amazonian jungle, as in the Siberian taiga, large hydroelectric power plants are more efficient.
Let's summarize. The advantages of low-pressure hydroelectric power plants are most significant in densely populated areas where land costs and a large number of Work to resettle people and remove structures and infrastructure make large hydroelectric power stations with large reservoirs unacceptable. That is why low-pressure hydroelectric power plants are most widespread in Europe, where the population density is high and there are few own energy resources, which forces the use of all available hydro potential, albeit in expensive ways.
At the same time, in relatively sparsely populated regions the advantages are obvious large hydroelectric power stations- in fact, they are basically being built there now all over the world (although the criteria for low population density in different countries vary significantly, for China, with its billion-strong population, the resettlement of several tens of thousands of people is quite acceptable).
Low-pressure run-of-river hydroelectric power plants do not compete with medium- and high-pressure hydroelectric power stations - each type of hydroelectric power station has its own “ecological niche” in which they are most effective. And references to run-of-the-river hydroelectric power stations in Western Europe when discussing hydropower projects in Eastern Siberia are a comparison of the incomparable.
Advantages of hydroelectric power stations:
Use of renewable energy.
Very cheap electricity.
The work is not accompanied by harmful emissions into the atmosphere.
Fast (relative to CHP/CHP) access to operating power output mode after turning on the station.
Disadvantages of hydroelectric power plants:
Flooding of arable land
Construction is carried out where there are large reserves of water energy
Mountain rivers are dangerous due to high seismicity of the areas
From an energy point of view, they have a number of advantages compared to all types of thermal power plants and nuclear power plants.
Firstly, they do not need fuel at all, due to which their energy is 5-6 times cheaper than the energy of thermal power plants and 8-10 times cheaper than the energy of nuclear power plants. The efficiency of hydroelectric power plants is very high, 80-90%.
Secondly, hydroelectric power plants have exceptionally high maneuverability: a running hydraulic unit can increase power almost instantly, and starting a stopped hydraulic unit takes only 1-2 minutes. The unevenness of the load schedule has virtually no effect on the efficiency of hydroelectric power plant operation. These qualities make hydroelectric power plants indispensable for operating during the peak part of the schedule, while the load on thermal power plants is equalized and their fuel consumption is reduced.
The undeniable energy advantages of hydroelectric power plants do not, however, provide grounds for contrasting them with power plants of other types.
In a number of countries and economic regions, hydropower resources are either insufficient or remote from energy consumption centers.
Energy production at hydroelectric power stations fluctuates sharply depending on the water availability of the year.
The initial costs for the construction of hydroelectric power plants are often higher than for thermal power plants, and the construction time is longer. The costs associated with flooding when creating a reservoir are not always justified. At the same time, the operation of hydroelectric power plants is much cheaper than thermal and nuclear power plants. There are no fuel costs, no environmental fees for emissions, lower repair costs, and a small number of personnel.
These circumstances determined the place of hydroelectric power stations in the world energy sector. The share of participation of hydroelectric power plants in the energy sector of a number of countries is different, which is due to the different structure of the fuel and energy balance and different traditions in energy development. Hydroelectric power plants provide about 20% of Russian and global electricity generation. In many countries the share of hydropower is significantly higher. For example, in Canada, which is closest to Russia in terms of natural conditions, hydroelectric power plants produce 58% of electricity, in Brazil - 86%, in Norway, known for its strict environmental legislation, - 99%.
Hydropower is a component of another major industry National economy- water management.
Water, especially fresh water, which makes up only 2.5% of the world's water reserves, is an irreplaceable natural resource, one of the foundations of life on Earth. Available freshwater supplies are found mainly in rivers, whose average annual flow worldwide is about 39,000 km3.
If in past centuries in most parts of the planet water seemed to be a free and inexhaustible natural gift, then in the 20th century rapid growth industry and urban population
led to the fact that water began to be viewed as an expensive and, in some cases, scarce raw material.
The use of water resources is inextricably linked with measures for their protection, primarily to ensure the required water quality. When carrying out hydraulic engineering construction that makes significant changes to natural conditions, all factors of its impact on the environment must be carefully taken into account.
Traditionally, hydroelectric power plants (HPPs) are a source of cheap electrical energy. In them, the energy potential of huge masses of water is converted into electricity.
What are hydroelectric power plants and how do they work?
Most often, they are built for them on rivers. dams, thanks to which huge reservoirs of water resources are formed. At the same time, the river on which the power plant is supposed to be built must be full-flowing in order to ensure that the turbines of electric generators are supplied with water all year round. In addition, it should have the greatest possible slope. An ideal option for the construction of hydroelectric power stations are canyons formed by river beds.
The dam created to accommodate the station and others hydraulic structures provide the required pressure of the water flow that rotates the blades of hydraulic turbines and the rotors of electric generators. In addition to using water pressure, the natural current of water flow, called diversion, can be used to produce electricity. Sometimes both versions of water energy are used simultaneously. 
The equipment required by the power plant for generating electricity is installed directly in the premises of the hydroelectric power station. There, in separate rooms, units are installed that directly convert the force of the water flow into the mechanical energy of turbines, and then into electricity.
In addition, the hydroelectric power station must be equipped with various other equipment, with the help of which monitoring and management of the station’s operation is organized. Normal operation of the station is impossible without devices that distribute and transform electricity and many other systems. 
What are they like?
In accordance with the generated power, hydroelectric power stations are usually divided into categories. This is due to water flow and pressure, as well as the efficiency of the generators and water turbines installed at the station. Stations producing 25 MW or more are considered powerful. Medium-power ones include those that produce less than 25 MW. The productivity of low-power stations does not exceed 5 MW.
Hydroelectric power stations are high-pressure, when water comes from a height of over 60 m, medium-pressure, from 25 m, and low-pressure, where the water height can be from three to 25 meters. Their turbines are located in reinforced concrete or steel chambers. They may have different designs and technical parameters related to operating water pressure indicators.
At high-pressure stations, radial-axial and bucket turbines are used. They are installed in special spiral-shaped metal chambers. Radial-axial and rotary-blade turbines are used mainly at stations where the pressure is average. Low-pressure hydroelectric power plants are mainly equipped with turbines with rotating blades.
Depending on the pattern of water resource use, hydroelectric power stations are divided into:
- Channel rivers.
- Near the dam.
- Derivational.
- Pumped storage.
In the first option, the dam completely blocks the river. The water level in it rises to the design height. Water is discharged from it directly to the hydraulic turbines. Such a station is convenient where the river bed narrows and on rivers flowing through mountains.
The dam-side scheme also includes a dam, but the production building of the hydroelectric power station is located in its lower part. Here the water pressure is stronger than in the channel version. This requires the construction of special pressure tunnels to supply it to the turbines. 
In diversion-type stations, water flows directly through the hydroelectric power station building where the turbines are installed.
Pumped storage hydroelectric power plants allow you to accumulate hydropower for use during periods of peak loads. In a relaxed mode, for example, at night, its hydraulic turbines function as pumps, pumping water into the upper reservoir. When peak loads occur, water from it is directed into a pipeline that supplies it to the turbine blades.
Advantages of hydroelectric power plants
The construction and operation of hydroelectric power plants is accompanied by discussions regarding their pros and cons.
A positive factor for such electricity production is renewal of used natural resources. As a result, the cost of electrical energy obtained in this way is significantly lower than at other types of power plants. For example, at hydroelectric power stations in Russia it is half as much as at thermal power plants.
Hydraulic power plants are flexible in control. With the help of their turbines, it is possible to regulate the power of the station from minimum to maximum. At the same time, unlike thermal and some other stations, they are able to quickly gain operating power from minimum indicators.
The operation of hydroelectric power stations is not accompanied by harmful air pollution. TO positive factors It is also possible to attribute the influence of their reservoirs to the formation of more moderate climatic indicators in the corresponding region.
The construction of dams and education improve navigation, increase fish stocks in them, and promote fish farming.
Their disadvantages
Critics of hydroelectric power plants rightly point out problems, first of all environmental, which are caused by their appearance. First of all, this is the flooding of large tracts of agricultural land, including fertile lands. The remaining floodplain soil is losing moisture. Many types of vegetation are disappearing. As a result, less valuable nutrients enter the seas and oceans.
Limited or stopped water flows at dams force modifications to the unique ecological systems in river channels and floodplains. As a result, rivers become shallow and polluted, the number of fish decreases, and some species disappear. Dams sometimes prevent migratory fish from spawning, forcing local fisheries to adapt to new conditions. Some invertebrates and other aquatic animals disappear with the simultaneous appearance of an abundance of midges. Many migratory birds are deprived of their usual nesting sites.
When designing stations and their construction, priority is given only to areas with large water reserves. They are often located much further from consumers than thermal power plants. However, other factors are not always taken into account. Hydroelectric power plants on mountain rivers, which are sometimes built in areas with high seismic hazard, pose a potential danger.
Significantly higher capital costs are indicated compared to the construction of thermal stations. When constructing dams, huge costs are required for the construction of locks to transfer ships to the required water level.
All hydroelectric power plants use water flow energy as an energy source. Most often, hydroelectric power plants are built on rivers, creating dams and reservoirs.
All hydroelectric power stations can be divided into the following types:
Channel and dam. These types are the most common; water pressure is created by installing a dam that blocks the river or raises the water level to the desired level. These types of hydroelectric power stations are built on high-water plain rivers and mountain rivers.
- Near the dam. They are built in areas of maximum water pressure. To do this, the river is blocked by a dam, and the hydroelectric power station building is located in the lower part of this dam. Water enters the turbines through pressure tunnels.
- Derivational. Such power plants are built in places where there is a large slope of the river. And the concentration of water is created due to derivation. Diversion hydroelectric power plants can be with or without pressure diversion.
- Pumped storage. They accumulate electricity and use it only during peak loads. At the moment of maximum load, hydroelectric power station units operate like pumps from external sources and pump water into special pools, after which the water enters the pipeline and forces the turbines to operate.
Advantages of hydroelectric power stations:
- Application of renewable energy.
- Cheap electricity.
- No harmful emissions into the atmosphere.
- Very fast transition to operating power output mode after the first switching on of the station.
- It is advantageous to use as an emergency reserve, since station generators can be easily switched on/off depending on needs.
- Less negative impact on the air environment than other types of power plants.
- The frequency is well regulated and increasing peak loads are covered.
Disadvantages of hydroelectric power plants:
- Flooding of large areas of land.
- Construction is possible only in places with large reserves of water energy.
- On mountain rivers such stations are very dangerous due to the high seismicity of the areas.
- Unregulated water releases from reservoirs lead to the restructuring of unique ecosystems along river beds, so rivers become polluted, fish numbers decrease, and nesting sites for migratory birds disappear.
- The flow of nutrients into the oceans is reduced.
- Building a large dam requires a lot of material and is expensive.
- The construction of hydroelectric power plants, in comparison with other energy sources, is longer and more expensive.
- A very large area of reservoirs.
- The dam causes great harm to fisheries, as the route to spawning grounds is closed.
- Large hydraulic structures and dams cause rivers to dry up.
- Prospects for the development of the use of hydropower resources are minimal, since the territories of developed countries have practically exhausted the potential for the development of this area.
For example, Europe has only 25 percent of the unexploited areas suitable for hydropower projects, and the northern part of the United States has only 30 percent. But developing countries have better prospects; for example, South America and Africa have large areas suitable for the development of water resources. In Africa, only 7 percent of the water resource is currently developed, and in South America 33 percent.
A power plant is a complex of buildings, structures and equipment designed to generate electrical energy. That is, power plants transform different kinds energy into electricity. The most common types of power plants are:
— hydroelectric power stations;
— thermal;
- atomic.
A hydroelectric power plant (HPP) is a power plant that converts the energy of moving water into electrical energy. Hydroelectric power stations are being installed on rivers. With the help of a dam, a difference in water heights is created (before and after the dam). The resulting water pressure sets the turbine blades in motion. The turbine drives generators that produce electricity.
Depending on the power, 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 stations are also classified according to the principle of use of natural resources: dam, near-dam, diversion and pumped storage.
Advantages of hydroelectric power plants are: generation of cheap electricity, use of renewable energy, ease of management, quick exit to operating mode. In addition, hydroelectric power plants do not pollute the atmosphere. Disadvantages: attachment to water bodies, possible flooding of arable land, detrimental effect on river ecosystems. Hydroelectric power stations can only be built on lowland rivers (due to the seismic danger of mountains).
Thermal power plant(TPP) generates electricity by converting thermal energy obtained as a result of fuel combustion. The fuel for thermal power plants is: natural gas, coal, fuel oil, peat or hot shale.
As a result of fuel combustion in the furnaces of steam boilers, feed water is converted into superheated steam. This steam at a certain temperature and pressure is supplied through a steam line to a turbogenerator, where electrical energy is generated.
Thermal power plants are divided into:
— gas turbine;
— boiler-turbine;
- combined cycle;
— based on combined cycle gas plants;
- based on piston engines.
Boiler-turbine thermal power plants, in turn, are divided into condensing (CPS or GRES) and combined heat and power plants (CHP).
Advantages of thermal power plants
— low financial costs;
— high speed construction;
— possibility of stable work regardless of the season.
Disadvantages of thermal power plants
— work on non-renewable resources;
— slow return to operating mode;
- receiving waste.
Nuclear power plant (NPP)- a station in which electricity (or thermal energy) is generated through the operation of a nuclear reactor. For 2015, almost 11% of electricity.
During operation, a nuclear reactor transfers energy to the primary coolant. This coolant enters the steam generator, where it heats the secondary circuit water. In the steam generator, water is converted into steam, which enters the turbine and drives electric generators. The steam after the turbine enters the condenser, where it is cooled with water from the reservoir. Mainly water is used as the primary coolant. However, lead, sodium and other liquid metal coolants can also be used for this purpose. The number of circuits may vary.
Nuclear power plants are classified according to the type of reactor used. Nuclear power plants use two types of reactors: thermal and fast neutrons. Reactors of the first type are divided into: boiling water, water-water, heavy water, gas-cooled, graphite-water.
Depending on the type of energy received, nuclear power plants are of two types:
Stations designed to generate electricity.
Stations designed to generate electrical and thermal energy (CHP).
Advantages of nuclear power plants:
— independence from fuel sources;
— environmental cleanliness;
The main disadvantage of stations of this type- severe consequences in case of emergency situations.
In addition to the listed power plants, there are also: diesel, solar, tidal, wind, geothermal.
