Geothermal energy is a type of renewable energy that is obtained from the heat of the Earth's interior. This thermal energy can be obtained without the combustion of fossil fuels or any other material. It is a form of clean energy with no carbon dioxide emissions.
The temperature in the inner layers of the Earth remains constant during the different seasons of the year. The inner layers of the Earth's crust are hotter than the surface in winter and cooler in summer.
Sometimes this energy is linked to other geological phenomena such as the presence of geysers, volcanoes or hot springs. These phenomena greatly facilitate the possibility of extracting thermal energy in installations near these areas.
To take advantage of the earth's heat, a fluid is passed through the hot zone. In this way, thermal energy can be transported to the surface. Later you can take advantage of the heat directly or convert it into electrical energy.
Geothermal Energy Production
The geothermal energy production system is based on the difference in temperatures between the subsoil and the surface. The energy is exchanged in the form of heat through two closed geothermal fluids loops that connect them.
In a Home or Building
One benefit is that it can be used for heating and cooling in winter and summer with high energy efficiency.
To obtain heat in winter, geothermal fluids inside the geothermal collector circuit runs through the subsoil until heated. The geothermal collector heats the water in the radiant emitting circuit. The emitter circuit is a closed loop that transfers heat to the building.
In summer the heat moves in the opposite direction. The efficiency of geothermal energy is greater the deeper the underground circuit is.
Another option for a home is to obtain sanitary hot water or heating systems.
In a Power Plant
Hot water can also be used to generate high pressure steam and power a dry steam turbine. In this way, geothermal energy is transformed into mechanical energy (kinetic energy).
Mechanical energy can be used to move machines, or to transform it into electrical energy: electricity.
An enhanced geothermal system (EGS) generates geothermal electricity without the need for natural convective hydrothermal resources.
Types of Geothermal Sources
These renewable energy sources are obtained through the extraction of the Earth's internal heat through geothermal wells. There are several areas with hot springs.
These hot springs can be those used in spas or other centers. Thermal waters are heated by the temperature of the Earth's interior.
Hot water with high internal energy can flow naturally by the impulses of the water and steam flows or by pumping. You have to select the method to use based on the method that is most economically profitable.
There is no single method of harnessing this type of energy. There have been projects that in some countries have had to be dismissed due to their economic infeasibility.
Magma is a great source of geothermal energy, since rocks are only found in a liquid state at high temperatures. Despite this, with the current geothermal technologies it is economically unfeasible.
The farms to extract hot water usually have an even number of geothermal wells. By one the hot water is extracted. The other is used to inject geothermal fluid again into the aquifer, when it is already cooled.
Types of Geothermal Resources
The different types of geothermal energy deposits are classified according to the temperature of their thermodynamic source. In this way we have high temperature, medium temperature geothermal energy and low and very low temperature geothermal energy.
1. High Temperature
This type of clean energy is found in areas where the layer of the Earth's surface is still active. Here, the temperature ranges from 150 ° C to 400 degrees Celsius. In these cases the steam rises to the surface through a dry steam turbine that generates electricity.
To find a geothermal area, you have to find an upper layer composed of:
Waterproof rock cover.
Aquifer or reservoir with high permeability.
Magmatic heat source.
It is needed doing drillings in order to extract hot water. Those drillings are similar as the one that is made to extract oil from wells.
2. Medium Temperature
In medium temperature geothermal energy installations temperatures range from 70 ° C to 150 degrees Celsius. The energy efficiency of steam-electricity conversion is much lower, in this case a volatile component must be added.
This type of geothermal energy can be transformed into small power plants.
For electricity production, the fluid needs to be between 120 ° C and 180 ° C.
3. Low Temperature
It is used in wide areas, in larger areas than the one that works at high or medium temperatures. It can be found in sedimentary basins. The fluid in these basins is at a temperature between 50 ° C and 70 ° C.
4. Very Low Temperature
It is used to serve domestic, urban, and agricultural needs. The fluids that can be found are at temperatures between 20 ° C and 50 ° C.
Geothermal Energy Uses
Air conditioned in summer. In a home with underfloor heating, the heating fluid can be circulated underground. A geothermal heat pump is used.
Winter heating. Geothermal heating.
Sanitary hot water. Used in the daily life of a house.
Electricity. Electricity is obtained from power plants. This type of plant reduces the energy dependence on fossil fuels and nuclear energy.
Heat production. This heat can be applied to industrial processes. For example, heating, drying, evaporation, distillation, sterilization, thawing, washing and salt extraction processes.
Geothermal Power Plants
Flash plants have the function of generating electricity from the thermal energy of the Earth's interior. Those binary plants have heat exchangers with the aim of generating water vapor.
Flash steam plants are the most common type of geothermal power used in United States and in the world today.
Fluid at temperatures are greater than 360°F (182°C). It is pumped under high pressure into a tank at the surface held at a much lower pressure. It causes some of the fluid to rapidly vaporize. Also called "flash."
With binary cycle geothermal power plants, pumps are used to pump hot water from a geothermal well. It is done through a heat exchanger. Then, the cooled water is returned to the underground reservoir.
With the pressure of the steam a dry steam turbine is activated, thus obtaining mechanical energy. The dry steam turbine is connected to an electric generator that produces electricity.