Geothermal energy: pros and cons. Geothermal energy sources
Among the alternative sources, geothermal energy occupies a significant place - it is somehow used in about 80 countries around the world. In most cases this occurs at the level of the construction of greenhouses, pools, use as a therapeutic agent or heating.
In several countries - including the United States, Iceland, Italy, Japan and others - power plants have been built and are working.
Geothermal energy in general is divided into two types - petrothermal and hydrothermal. The first type uses as a source of hot rocks. The second is groundwater.
If you put all the data on the topic in one diagram, it turns out that in 99% of cases heat of rocks is used, and only in 1% geothermal energy is extracted from groundwater.
At present, the heat of the Earth’s interior is widely used in the world, and this is mainly the energy of shallow wells - up to 1 km.In order to provide electricity, heat or DHW, downhole heat exchangers are installed that operate on liquids with a low boiling point (for example, freon).
Now the use of a downhole heat exchanger is the most efficient way to extract heat. It looks like this: the coolant circulates in a closed circuit. The heated one rises along a concentrically lowered pipe, giving off its heat, after which, cooled, it is fed into the casing using a pump.
At the core of the use of the energy of the Earth’s subsoil is a natural phenomenon - as the Earth’s core approaches, the temperature of the Earth’s crust and mantle increases. At a level of 2-3 km from the surface of the planet, it reaches more than 100 ° C, increasing on average with each subsequent kilometer by 20 ° C. At a depth of 100 km, the temperature reaches already 1300–1500 ºС.
Water circulating at great depths, is heated to significant quantities. In seismically active areas, it rises to the surface through cracks in the earth's crust, but in calm regions it can be brought out with the help of wells.
The principle of operation is the same: heated water rises along the well up, gives off heat, and returns along the second pipe downwards.The cycle is almost endless and renewed as long as heat remains in the earth's interior.
In some seismically active regions, hot waters lie so close to the surface that one can observe firsthand how geothermal energy works. The photo of the surroundings of the Krafla volcano (Iceland) shows geysers that transmit steam for the geothermal power station operating there.
The main features of geothermal energy
Attention to alternative sources due to the fact that the reserves of oil and gas on the planet are not infinite, and gradually exhausted. In addition, they are not everywhere, and many countries depend on supplies from other regions. Among other important factors - the negative impact of nuclear and fuel energy on the human environment and wildlife.
The great advantage of the GoE is its renewability and universality: the ability to use it for water and heat supply, or for generating electricity, or for all three goals at once.
But the main thing is geothermal energy, the pros and cons of which depend not so much on the location as on the customer’s wallet.
Advantages and disadvantages of the GoE
Among the advantages of this type of energy are the following:
- it is renewable and almost inexhaustible;
- independent of the time of day, season, weather;
- universal - it can be used to provide water and heat supply, as well as electricity;
- geothermal energy sources do not pollute the environment;
- do not cause the greenhouse effect;
- stations do not take up much space.
However, there are disadvantages:
- geothermal energy is not considered completely harmless due to steam emissions, which may include hydrogen sulfide, radon and other harmful impurities;
- when using water from deep horizons, it is a question of its disposal after use - because of the chemical composition, such water must be drained either back into the deep layers or into the ocean;
- construction of the station is relatively expensive - it increases the cost and the cost of energy in the end.
Spheres of application
Today, geothermal resources are used in agriculture, horticulture, aqua and thermoculture, industry, housing and utilities. In several countries, built large complexes that provide the population with electricity. The development of new systems continues.
Agriculture and Horticulture
Most often, the use of geothermal energy in agriculture is reduced to heating and irrigation of greenhouses, greenhouses, aqua and hydro cultures. A similar approach is applied in several states - Kenya, Israel, Mexico, Greece, Guatemala and Ted.
Underground sources are used for watering fields, heating the soil, maintaining a constant temperature and humidity in the greenhouse or greenhouse.
Industry and Housing
In November 2014, the world's largest geothermal power station began operating in Kenya. The second largest is in Iceland - this is Helliesheidi, which takes heat from sources near the Hengidl volcano.
Other countries using geothermal energy on an industrial scale: USA, Philippines, Russia, Japan, Costa Rica, Turkey, New Zealand, etc.
There are four main schemes for obtaining energy at a geothermal power station:
- straight, when steam is directed through pipes to turbines connected to electric generators;
- indirect, similar to the previous one, except that the steam is cleared of gases before entering the pipes;
- binary — not water or steam, but another liquid having a low boiling point;
- mixed - is similar to a straight line, but after condensation, the undissolved gases are removed from the water.
In 2009, a group of researchers who were searching for usable geothermal resources reached molten magma at a depth of 2.1 km. Such a hit in magma is a rarity, it is just the second known case (the previous one occurred in Hawaii in 2007).
Although the pipe connected to magma has never connected to the Krafla Geothermal Power Plant located nearby, scientists have obtained very promising results. Until now, all operating stations took heat indirectly, from terrestrial rocks or from groundwater.
One of the most promising areas is the private sector, for which geothermal energy is the real alternative to autonomous gas heating. The most serious obstacle here is the relatively low initial cost of equipment, which is much higher than the cost of installing “traditional” heating.
MuoviTech, Geodynamics Ltd, Vaillant, Viessmann, Nibe offer their designs for the private sector.
Countries using the heat of the planet
The undisputed leader in the use of georesources is the United States - in 2012, energy production in this country reached 16.792 million megawatt-hours.In the same year, the total capacity of all geothermal stations in the United States reached 3,386 MW.
Geothermal power plants in the United States are located in California, Nevada, Utah, Hawaii, Oregon, Idaho, New Mexico, Alaska and Wyoming. The largest group of plants is called "Geysers" and is located near San Francisco.
In addition to the United States, the Philippines, Indonesia, Italy, New Zealand, Mexico, Iceland, Japan, Kenya and Turkey are also in the top ten leaders (as of 2013). At the same time, in Iceland, geothermal energy sources provide 30% of the country's total demand, in the Philippines - 27%, and in the USA - less than 1%.
Operating stations are just the beginning, the industry is just starting to develop. Research in this direction is ongoing: more than 70 countries are exploring potential deposits, 60 have mastered the industrial use of GE.
Seismically active areas look promising (as can be seen from the example of Iceland) - the state of California in the USA, New Zealand, Japan, the countries of Central America, the Philippines, Iceland, Costa Rica, Turkey, Kenya.These countries have potentially profitable non-explored deposits.
In Russia, these are the Stavropol Territory and Dagestan, Sakhalin Island and the Kuril Islands, Kamchatka. In Belarus, there is a certain potential in the south of the country, covering the cities of Svetlogorsk, Gomel, Rechitsa, Kalinkovichi and Oktyabrsky.
In Ukraine, the Transcarpathian, Nikolaev, Odessa and Kherson regions are promising.
The Crimea peninsula is quite promising, especially since most of the energy it consumes is imported from the outside.