Moscow, 17 Feb – IA OilGasPlant.net. What is geothermal energy?
The hot force of the earth, obtained due to the course of natural processes (the heat of the planet, preserved from the time of formation, the thermal power generated by it due to radioactive elements, friction) is called geothermal energy. In fig. 1 shows the temperature distribution from the center of the Earth to its surface.
Geothermal energy is a direction of energy based on the use of thermal energy of the Earth’s interior for the production of electrical energy at geothermal power plants, or directly for heating or hot water supply. Usually refers to alternative energy sources using renewable energy resources (Wikipedia)
The Earth’s heat reserves are practically inexhaustible. When the core cools down by 1 ° C, 2 * 10twenty kWh of energy, which is 10,000 times more than all proven fossil fuels contain, and millions of times more than the annual energy consumption of mankind. At the same time, the core temperature exceeds 6000 ° C, and the cooling rate is estimated at 300-500 ° C per billion years.
The heat flux flowing from the bowels of the Earth through its surface is 47 ± 2 TWh of heat (400 thousand TWh per year, which is 17 times more than the entire world production, and is equivalent to burning 46 billion tons of coal), and the thermal power generated Earth due to the radioactive decay of uranium, thorium and potassium-40 is estimated at 33 ± 2028
TW, i.e. up to 70% of the Earth’s heat loss is replenished. Using even 1% of this capacity is equivalent to several hundred powerful power plants. However, the heat flux density is less than 0.1 W / m2 (thousands and tens of thousands of times less than the density of solar radiation), which makes it difficult to use.
Access to underground energy
In volcanic regions, the circulating water overheats above the boiling point at relatively shallow depths and rises along cracks to the surface, sometimes manifesting itself in the form of geysers. Access to underground warm waters is possible through deep drilling of wells.
To generate electricity, it is advisable to use geothermal water with a temperature of 150 ° C and above. Even for heating and hot water supply, a temperature of at least 50 ° C is required. The Earth’s temperature rises rather slowly with depth, usually the geothermal gradient is only 30 ° C per 1 km, i.e. even for hot water supply, a well more than a kilometer deep will be required, and for generating electricity – several kilometers. Therefore, almost all large GeoPPs are located in areas of increased volcanism, i.e. where geothermal waters are close to the surface.
At the moment, the development of geothermal energy is actively engaged in: the USA, Iceland, New Zealand, the Philippines, Italy, El Salvador, Hungary, Japan, Russia, Mexico, Kenya and other countries, where heat from the bowels of the planet rises to the surface in the form of steam and hot water, bursting out at temperatures reaching 300 ° C.
The thermal energy of the Earth in the form of hot water or steam is delivered to the surface, where it is used either directly, for example, for heating houses, or for generating electrical energy. As mentioned above, the thermal energy of the Earth, as a rule, is obtained by drilling wells, and the lifting of hot liquid is carried out by means of submersible pumps.
How geothermal power plants work
Currently, there are three schemes for generating electricity using hydrothermal resources:
- direct using dry steam,
- indirect using water vapor,
- mixed production scheme (binary cycle).
The type of conversion depends on the state of the medium (steam or water) and its temperature. Dry steam power plants were the first to be mastered. To generate electricity for them, the steam coming from the well is passed directly through a turbine / generator.
Power plants with an indirect type of electricity generation are by far the most common. They use hot underground water (up to 182 ° C), which is pumped at high pressure into generating sets on the surface.
Mixed geothermal power plants differ from the previous two types in that steam and water never come into direct contact with the turbine / generator.
Dry steam geothermal power plants
Steam power plants operate primarily on hydrothermal steam (Fig. 2). The steam goes directly to a turbine, which feeds a generator that produces electricity. The use of steam eliminates the need for fossil fuel combustion (it also eliminates the need for its transportation and storage). These are the oldest geothermal power plants, the first of which was built in Larderello (Italy) in 1904, and it is still operating today. Steam technology is used at the Geysers Power Plant in Northern California, the largest geothermal power plant in the world.
Geothermal power plants on steam hydrothermal vents
Superheated hydrothermal fluids (temperatures above 180 ° C) are used to generate electricity in such plants. The hydrothermal solution is pumped into the evaporator to reduce the pressure, which causes some of the solution to evaporate very quickly (Fig. 3). The resulting steam drives a turbine. If liquid remains in the tank, it can be evaporated in the next evaporator to obtain even more power.
Geothermal power plants with a binary cycle of electricity generation
Most geothermal areas contain water of moderate temperatures (below 1800
FROM). In power plants with a binary production cycle, this water is used to generate energy. Hot geothermal water and a second, additional liquid with a lower boiling point than water are passed through a heat exchanger (Fig. 4). The heat of the geothermal water evaporates the second liquid, the vapor of which drives the turbines. Since it is a closed system, there are practically no emissions into the atmosphere. Moderate water is the most abundant geothermal resource, so most geothermal power plants of the future will operate on this principle. What such a power plant looks like in reality is shown in Figure 5.
Novomet in geothermal projects
High-performance heat-resistant pumping systems “Novomet” (Fig. 6-7) are successfully used in geothermal projects today, saving energy costs in this case is 28%.
In 2018-2019, Novomet’s specialists applied all the accumulated experience in the production of oil submersible equipment for difficult conditions to solve the problem of profitable exploitation of a geothermal field. Turkey has become a pilot site for the development of this project of the company. A number of installations of installations in a special corrosion-resistant and heat-resistant version with a drive from a valve electric motors, which are characterized by a reduced heat release, have been carried out.
After receiving positive results from the first tests, it was decided to use the experience gained to develop a new line of high-performance pumps. In addition, in the implementation of geothermal projects, the volume of water lifted is important: the development of even more high-performance pumps and high-power electric motors was required. The new installations were named Geyser.
At the end of November 2019, three energy efficient Geyser units with a capacity of 10,000 m were shipped3/ day (NV75500), equipped with 660 kW brushless electric motors. Currently, these installations are in operation. A total of 21 Geyser units from Novomet are currently in the wells. The maximum operating time has exceeded 380 days. The temperature of the produced fluid is in the range of 155-1950FROM.
Application of ESP Geyser manufactured by JSC Novomet-Perm reduced the amount of electricity required to pump a cubic meter of water. For example: the closest competing pump in the region uses 1.25 kWh per cubic meter of water produced, while Novomet’s system uses only 0.9 kWh to lift the same volume of water. The difference is 28%.
Today, the use of alternative energy sources is especially important and will only grow in the future. Most countries at the national level are forced to implement costly programs that reduce energy consumption and reduce greenhouse gas emissions. In 2019, Russia joined the Paris Climate Agreement, the parties to which agreed to systematically reduce CO2 emissions into the atmosphere, and to establish an international exchange of green technologies in the field of energy efficiency, industry, construction and others, in order to curb the rise in the global average annual temperature on the planet.
It should be noted that by actively developing energy efficient technologies and Geyser technology, Novomet contributes to the development of alternative, “green” energy and contributes to the fulfillment of the conditions of the Paris Agreement.