Geothermal energy is a form of energy that uses the heat from inside the Earth. Imagine that the planet is like a large hot ball and in its core there is a large amount of heat. This heat spreads towards the Earth's surface due to pressure and temperature differences.
When we talk about geothermal, we mean using that heat to do useful things, like generating electricity or heating water. But how is that achieved?
Geothermal energy is used in two main ways:
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Geothermal plants to generate electricity: In some places on Earth, hot water exists beneath the surface. Drilling is done to reach that water and, when it comes to the surface, it turns into steam. This steam is used to drive turbines that generate electricity. In this way, the energy from the Earth's heat is converted into electricity that we can use in our homes.
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Heating and hot water: In addition to generating electricity, geothermal energy is also used to heat water. In some places, Earth's warm water is found near the surface. Wells are dug to reach that water and it is used directly to heat our homes or for hot water in the shower.
Geothermal energy is considered one of the cleanest and most renewable forms of energy. It does not pollute the air or emit greenhouse gases like fossil fuels, such as oil or coal. Additionally, the Earth's heat is constant, always present, so it will never run out.
Some places in the world are especially suitable for taking advantage of geothermal energy, such as Iceland, where there are many volcanoes, or countries with hot springs, such as Japan.
In Chile, in particular, we are surrounded by volcanoes, even under the sea. These volcanoes keep the earth at temperatures higher than those found on the surface, and according to thermodynamic laws, we can deduce that heat moves from the hottest points to the coldest areas.
The southern part of our country has low temperatures for most of the year, so heating is a fundamental need to live comfortably in these cold conditions.
In most cases, we look for simple solutions in our daily lives, opting for more common heating options, such as gas stoves, wood stoves or biomass-fueled boilers. However, these options generate pollution through the combustion of materials, releasing particles into the environment. At first, these emissions may not represent a major problem, but when we talk about areas where the need for heating is constant and the burning of materials takes place every day for months, the emissions from these systems skyrocket.
Geothermal systems require more specific studies of the areas in which they will be implemented and, in many cases, the initial investment is greater compared to other systems. However, these factors are offset by the energy efficiency of the system. Geothermal energy does not generate waste that harms the environment and is capable of providing heating and hot water to a home without major complications.
But how does the geothermal heating system work?
The fundamental system process takes place in a heat pump, which is the main component of a geothermal heating system. Its operation can be described in the following steps:
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Heat capture: The geothermal heat pump uses pipes buried in the ground or geothermal wells to capture heat from underground. These pipes contain a refrigerant liquid that circulates through them.
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Heat Transfer: The coolant absorbs heat from the ground as it circulates through the pipes. The soil acts as a constant source of heat, maintaining a higher temperature than the outside air throughout the year.
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Refrigerant compression: After absorbing heat from the ground, the liquid refrigerant is directed to the heat pump. In the heat pump, through an evaporator, it exchanges its temperature with that of a primary refrigerant. In turn, the primary refrigerant evaporates due to the heat obtained in the exchange and is directed to a compressor that compresses the refrigerant, increasing its pressure and temperature.
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Refrigerant condensation: The hot, compressed refrigerant passes through a condenser, where it transfers heat to the home's heating system. The heat is released in the form of hot air or water, depending on the type of heating system used.
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Refrigerant Expansion and Evaporation: Once the refrigerant has given up its heat to the heating system, it is in a high-pressure liquid state. It then passes through an expansion valve, which reduces its pressure and temperature, allowing the refrigerant to evaporate.
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Absorption of heat from the environment: The refrigerant in a gaseous state and at low temperature is directed to an evaporator, where it absorbs heat from the environment that needs to be cooled. This heat is extracted from the environment and transferred to the refrigerant in the form of a gas.
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Compression and repetition of the cycle: The refrigerant in a gaseous state is directed again to the compressor, where it is compressed again, increasing its temperature and restarting the cycle.
The process of heat transfer through the circulation of a refrigerant allows the geothermal heat pump to extract heat from the ground and use it to heat the home. It is important to note that this system can also operate in cooling mode, extracting heat from inside the home and releasing it into the ground.
However, not everything is as simple as it seems. Calculating a geothermal heating system involves considering several factors to determine the proper size and features of the system. Below are some general steps to calculate a geothermal heating system:
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Determine heat load: Heat load is the amount of heat required to heat a given space. It is calculated considering factors such as the size of the home, geographic location, insulation, the type of windows and doors, and the desired temperature inside. It is important to obtain accurate data to make this calculation, as it will affect the size of the geothermal system needed.
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Analyze the thermal conductivity of the soil: The thermal conductivity of the soil is a measure of its ability to transfer heat. A study of the ground must be carried out to determine its thermal conductivity, as this will affect the performance of the geothermal system. In some cases, thermal conductivity tests are performed in the field to obtain accurate data.
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Calculate system capacity: Once the thermal load and conductivity of the soil is known, the capacity of the necessary geothermal system can be determined. This includes the size and number of geothermal wells, the length of pipes buried in the ground, and the type of heat pump suitable.
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Perform an economic analysis: Along with the technical calculation, it is important to perform an economic analysis. This involves evaluating the installation costs of the geothermal system, the expected energy savings over time, and the payback period. Possible incentives or subsidies available for geothermal systems may also be considered.
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Consult a professional: The calculation and design of a geothermal heating system can be complex. It is recommended to seek the help of a professional in geothermal engineering or heating systems to carry out an accurate calculation and a design appropriate to the specific needs of your home.
Remember that each case is unique and may require additional considerations depending on location, terrain characteristics and other specific factors. A detailed analysis by a geothermal expert is essential to obtain an efficient and suitable geothermal heating system.
And you, did you know about the geothermal heating system?