Geothermal power plant, device and principle of work

Geothermal power station, the device and principle of work.

 

 

Geothermal power plant (GeoPP or Geothermal) is one of the types of power plants that convert heat geothermal energy of underground springs (e.g. geysers) into electrical energy.

 

Geothermal power and geothermal energy

Types of geothermal energy

Types of geothermal water

Using geothermal power plant

The advantages of geothermal power plants

The difficulties and problems of operation of geothermal power plants

Electricity generation from geothermal power plants in Russia

 



Geothermal power and geothermal energy:

Geothermal power plant (GeoPP or Geothermal) is one of the types of power plants that convert heat – geothermal energy of underground springs (e.g. geysers) into electrical energy.

Geothermal energy is energy derived from the natural heat of the Earth. According to various estimates, the temperature in the center of the Earth is at least 6650 °C. Heat is formed due to the radioactive decay of uranium, thorium, potassium and other radioactive isotopes of chemical elements. The temperature in the center of the Earth is constant. Well of course, the Earth cools, but the cooling rate is equal to 300-350 °C in one billion years. Heat stream flowing from the Ground through its surface is 47±2 TW of heat or 400 thousand TWh per year, which is 17 times more than the development of the world’s energy and is equivalent to combustion of about 46 billion tons of coal. Thus, it appears that the Earth represents an inexhaustible source of heat geothermal energy.

Geothermal energy refers to alternative and renewable energy. This energy is in the form of heat can be used directly to heat homes and buildings, and for the production of electricity.

However, the thermal efficiency of geothermal power plants is low, around 7-10 %.

 


Types of geothermal energy:

Geothermal energy is subdivided into petrothermal energy and hydrothermal energy.

In the first case, the energy source is the temperature of the deep layers of the Earth.

So, when moving in depth to the center of the Earth increases the ambient temperature. For every 100 meters in depth the temperature increases by an average of 2.5 °C. Or geothermal gradient increases by 1 °C every 36 meters. At a depth of 5 km the temperature is about 125 °C and at 10 km to about 250 °C.

The highest geothermal gradient of 150 °C at 1 km, registered in Oregon (USA), the lowest in South Africa (6 °C per 1 km).

To retrieve the petrothermal energy drilled two wells, one of them pump water. When moving to the center of the Earth heats up, then flows into a connecting hole and extends in the form of steam to the surface.

In the second – hot underground water. In volcanic regions of the Earth, circulating in the depths of the planet’s water is overheated above the boiling point and the cracking rises to the surface. Hot water comes to the surface in the form of steam or hot water, sometimes manifesting itself in the form of geysers. Therefore, geothermal power plants are built directly in the water outlet on the surface in the form of geysers or in the areas around the edges of continental plates, because the crust in such areas is much thinner.

A promising and popular source is hydrothermal energy.

Hydrothermal regions are available in many parts of the world: Russia (Kamchatka, Kuril Islands, Krasnodar Krai, Stavropol Krai, Dagestan, Karachay-Cherkessia, Chechnya, North Ossetia, etc.), Iceland, New Zealand, Italy, France, Lithuania, Mexico, Nicaragua, Costa Rica, Indonesia, China, Japan, Kenya, Tajikistan, Philippines.

To extract hydrothermal energy also drilled wells.

 

Types of geothermal water:

temperature: slabitelnye up to +40 °C, thermal – from +40 to +60 °C, high – from +60 to +100 °C, overheated more than +100 °C;

– mineralization: fresh – up to 0.1 g dry residue on 1 l of fresh – 0,1-1,0 g/l, slightly saltish – 1,0-3,0 g/l, selenocyanate – 3,0-10,0 g/l, salt – 10,0-35,0 g/l, brine more than 35.0 g/l;

– total hardness: very soft, soft, medium, hard, very hard;

– acidity: strongly acidic – pH to 3.5, acid – 3,5-5,5 pH slightly acidic at 5.5 and 6.8, the neutral is 6.8 to 7.2 pH, slightly alkaline – 7,2-8,5 pH, alkaline – more than 8.5 pH;

– gas composition: hydrogen sulfide, hydrogen sulfide-carbon dioxide, carbon dioxide, nitrogen carbon dioxide, methane, nitrogen-methane and nitrogen;

– in saturation: weak – up to 100 mg/l, average – 100-1000 mg/l, high – over 1000 mg/L.

 

Using geothermal power plants:

For obtaining hydrothermal energy and convert it into electricity in geothermal power plants use several methods:

– direct method. Steam directly from the well is piped into a steam turbineconnected to an electric generator, and rotates its blades. Due to the rotational movement produced by an electric current;

– indirect method. Similar to the previous one with the only difference that before entering the vapor pipe is cleaned of gases that cause the destruction of pipes;

– mixed method. Similar to direct method with the only difference that pairs condenseries and out of the water and remove gases not diluted in it;

the binary method. As the working fluid is not used thermal water or steam and other fluid with low boiling point. Thermal water (or steam) from the well is passed through a heat exchanger which transfers heat to another fluid with a lower boiling point. This is another liquid to boil in the heat exchanger and its steam is fed to the steam turbine and spins its blades.

 

The advantages of geothermal power:

– geothermal power plant runs on renewable energy source

– the reserves of geothermal energy are inexhaustible,

– able to work autonomously, without human intervention,

– not dependent on seasonal, weather and other (day-night) factors

– geothermal energy is constant in time.

 


The difficulties and problems of operation of geothermal power plants:

the need revolving cycle of admission and re-injecting wastewater in the underground aquifer, which would require additional energy consumption. Pumping of wastewater is required to ensure that the pressure in the aquifer fell, leading to reduction in the production of geothermal station or its complete failure;

– in the thermal water contains large amounts of salts of various toxic metals (e.g. lead, zinc, cadmium), nonmetals (e.g. boron, arsenic) and chemical compounds (e.g., ammonia, phenols, sulfide, methane), which eliminates the discharge of such water into the natural water system located on the surface, on the one hand, and which adversely affect the operation of the equipment, on the other, and therefore subject to recovery and utilization.

 

Electricity generation from geothermal power plants in Russia:

In Russia there are several geothermal power plants:

– Verkhne-Mutnovskaya geothermal power plant (GeoPP), installed capacity of 12 MW (2011) and power generation of 69,5 million kWh/year (2010). Located on mutnovsko field in the Elizovsky district of the Kamchatka region, near the Mutnovsky hills;

– Mutnovskaya geothermal power plant (GeoPP), installed capacity of 50 MW (2011) and power generation of 360.5 million kWh/year (2010). Located on mutnovsko field in the Elizovsky district of the Kamchatka region, to the North-East of the Mutnovsky hills, at an altitude of about 800 meters above sea level;

– Pauzhetskaya geothermal power plant (GeoPP), the installed capacity of 14.5 MW (2011) and the production of 43,1 million kWh/year (2011). Located on Cambalkon field paramerters in the southwestern part of the Kamchatka Peninsula in the village of Pauzhetka volcanoes near the Kosheleva and kambalny river. This is the first time the construction of geothermal power plant, commissioned in 1966;

Ocean geothermal power plant (GeoPP), installed capacity of 2.5 MW (2009). Located at the foot of Baransky volcano on the Iturup island in the Sakhalin region near ocean;

– Mendeleevskaya geothermal power plant (GeoPP), installed capacity of 3.6 MW (2009). Located on the Kunashir island, near the Mendeleev volcano.

 

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