AIR COOLING AND / OR HEATING SYSTEM USING GEOTHERMAL ENERGY

Abstract

The present invention provides a vertical geothermal air heating / cooling system that supplies air to a room at a comfortable temperature. This is achieved by increasing the interaction area between the air and the heat dissipation surface through the heat exchanger pipe and the subsoil, thanks to the incorporation of a metallic porous medium. With this addition, the heat exchanger pipe eliminates the need for deep excavation to achieve efficient heat exchange.

Description

AIR COOLING AND / OR HEATING SYSTEM USING GEOTHERMAL ENERGY DESCRIPTION OBJECT OF THE INVENTION The present invention provides a system for cooling and / or heating outdoor air using geothermal energy to supply it to a room, where said system includes a U-shaped heat exchanger filled with a porous material. The present invention falls within the field of technologies for harnessing renewable energy, especially geothermal energy. BACKGROUND Geothermal energy is a renewable energy source obtained by harnessing the Earth's internal heat, which is transmitted through hot rock formations or through conduction and convection. The temperature of the subsurface near the surface is around 20°C and remains stable throughout the year, meaning it is cool in the summer months and warm in the winter months. This characteristic has been harnessed through geothermal energy systems. There are two types of geothermal energy systems: horizontal and vertical. Horizontal systems require a large area of ​​land but are shallow (up to 1.5 meters deep) and require the installation of a large network of pipes at that depth. Vertical systems, on the other hand, generally reach depths greater than 50 meters, require less land, and are more stable than horizontal systems because the ground temperature is more constant at that depth. (Aulí Mellado, E. (2010). Sustainability in healthcare facilities. Plataforma Editorial. Barcelona, ​​Spain). Within the prior art, several vertical geothermal systems have been found that include, as part of their components, heat exchangers with specific technical characteristics that allow for more efficient heat exchange. For example, patent application CN110118159A describes a geothermal system for generating electricity and desalinated water using an artificial porous system that functions as the heat exchanger. This system is designed for implementation on islands where freshwater is scarce.This system recovers seawater by means of a pump; subsequently, the saltwater is injected into a well or insulation pipe that has a depth of up to 3000 meters. Adjacent to this well or insulation pipe, in the section between 2000 and 3000 meters deep, there is an external artificial porous system obtained by injecting a metallic or ceramic proppant. Through internal channels, seawater can flow from the insulation pipe to the artificial porous system where heat transfer will occur to obtain hot water, which will subsequently be directed to a flash tank. In subsequent processes, fresh or desalinated water and electricity will be obtained from the steam. Furthermore, invention patent KR101368362B1 presents a geothermal heating / cooling system where system efficiency is improved by modifying the heat exchanger structure. This invention involves recirculating air from a room, where the heat exchanger pipe has slit-type grooves at regular intervals, either on its external or internal surface. These grooves facilitate heat exchange by providing a larger contact area and allow the heat exchanger pipe to be buried at a depth of 100 to 150 meters, which is less than the depth typically found in these heating / cooling systems. MA / a / ZUZU / UUÜI / 0 The system described in KR1020160054839A features a zigzag or coil-shaped heat exchanger. The pipe length in this case is greater, thus requiring a larger excavation area, which most buildings or homes do not have. Ambient air is drawn into the system by a fan located in the inlet duct, which also prevents the entry of foreign objects. This invention includes a second fan in the outlet duct and a second heat exchanger to ensure airflow at a comfortable temperature. One of the main drawbacks of vertical geothermal systems is that they require deep excavations (generally exceeding 50 meters) and therefore considerable lengths of piping to achieve effective heat exchange with the subsoil so that the fluid reaches a comfortable temperature (approximately 20°C). Vertical geothermal systems require at least 100 meters of excavation; while horizontal geothermal systems that rely on the use of fans for airflow, such as the one reported in KR1020160054839A, require a large area of ​​land for installation, making them unsuitable for urban sites. The technical problem that the invention solves is to provide a vertical geothermal air heating / cooling system that does not require deep excavations. This is achieved through a modification to the heat exchanger located underground, which allows it to perform a more effective temperature exchange than heat exchangers without these characteristics. BRIEF DESCRIPTION OF THE FIGURES Figure 1. Schematic view of the air cooling and / or heating system using geothermal energy, showing an air inlet (1), a fan (2), a conventional pipe (3) consisting of pipe segment A (4) and pipe segment B (5), a geothermal heat exchanger (6), a conventional pipe with thermal insulation (7) consisting of pipe segment C (8) and pipe segment D (9), and an air outlet (10) that expels air into a room. The arrows indicate the airflow in the system. Figure 2. Comparison graph of three experiments carried out at high external temperatures (36°C, 38°C and 39°C) where it can be seen that the geothermal system that has the heat exchanger in the shape of an “LJ” filled with porous metallic material gives up more temperature from the subsoil than the same system where the heat exchanger in the shape of a “U” is not filled with any material. Figure 3. Comparison graph of three experiments carried out at low external temperatures (4°C, 5°C and 8°C) where it can be seen that the geothermal system that has the U-shaped heat exchanger filled with porous metallic material captures a higher temperature from the subsoil than the same system where the U-shaped heat exchanger is not filled with any material. DETAILED DESCRIPTION OF THE INVENTION The technical problem solved by this invention is to provide a vertical geothermal air heating / cooling system that does not require deep excavations. This is achieved by increasing heat dissipation through the heat exchanger pipe with the subsoil by incorporating a porous metallic medium inside the heat exchanger pipe. This medium increases the tortuosity and contact area of ​​the medium, forcing the ambient air to travel a greater length of pipe in a shorter distance, resulting in more effective heat exchange. This modification may cause an increase in differential pressure; however, this problem is mitigated by a fan located at the beginning of the system, which maintains the airflow. The air cooling and / or heating system using geothermal energy of the present invention allows the supply of outside ambient air to a room at a comfort temperature and is made up of an air inlet (1) located on the surface of the earth that allows the entry of outside ambient air which is propelled by means of a fan (2) into the interior of a conventional pipe (3) that directs the ambient air towards a U-shaped geothermal heat exchanger (6). The conventional pipe (3) is divided into a pipe segment A (4) located above the surface of the earth and a pipe segment B (5) that is buried in the subsoil. The U-shaped geothermal heat exchanger (6) is filled with a porous metallic material that allows the ambient air entering the system to decrease or increase its temperature to reach the temperature of the subsoil.Once the ambient air passes through the geothermal heat exchanger (6), it is conducted to the earth's surface via a conventional thermally insulated pipe (7) to prevent the ambient air from losing the subsurface temperature. The conventional thermally insulated pipe (7) comprises a pipe segment C (8) buried in the subsurface and a pipe segment D (9) above the earth's surface, directed to an air outlet (10) connected to a room for expelling the ambient air at the subsurface temperature. The porous metallic material used in the geothermal heat exchanger (4) is any material with a thermal conductivity κ between 15 and 386 W / (mK) and is selected from the group consisting of aluminum (thermal conductivity (κ) equal to 209 W / (mK)), stainless steel (κ = 15 W / (mK)), bronze (κ = 52 W / (mK)), brass (κ = 111 W / (mK)), and copper (κ = 386 W / (mK)). Furthermore, the conventional pipe (3) and the conventional pipe with thermal insulation (7) are selected from the group consisting of polyvinyl chloride (PVC) pipes, or other commercial plastics such as polyethylene terephthalate (PET), high-density polyethylene (HDPE), or low-density polyethylene (LDPE). and the thermal insulation of the conventional pipe with thermal insulation (7) is selected from the group consisting of expanded polystyrene, also known as Styrofoam or dry ice, fiberglass, polyurethane foam or volcanic material known as “rock wool”. MA / a / ZUZU / UUÜI / 0 EXAMPLE OF USE OF THE INVENTION The present example is provided in an illustrative and non-limiting manner and with the sole objective of showing the operation of the present invention. The following stages were carried out for the assembly of the air cooling and / or heating system using geothermal energy: 1. An aluminum fiber, as a porous metallic material, is inserted into the U-shaped aluminum pipe by hand along its entire length. To facilitate this, the pipe was heated to 70 °C, the porous material was inserted, and then it was allowed to cool to room temperature. This process creates the geothermal heat exchanger (6). 2. The pipe segment B (5) made of polyvinyl chloride (PVC) is assembled with the geothermal heat exchanger (6) by means of a straight coupling also made of polyvinyl chloride (PVC). 3. The pipe segment C (8) made of polyvinyl chloride (PVC) is coated with thermal insulation material (expanded polystyrene) and subsequently joined to the other end of the geothermal heat exchanger (6). The connection is also made with a polyvinyl chloride (PVC) coupling. 4. The heat exchanger assembly (6), consisting of pipe segment B (5) and pipe segment C (8), is placed in a hole in the ground where heat exchange between the air and the subsoil will take place. Once in place, the hole is backfilled with the same type of material that was originally in the subsoil to ensure optimal pipe-subsoil thermal contact. The geothermal heat exchanger assembly (6), with pipe segment B (5) and pipe segment C (8), must be long enough to reach from the subsoil, where the temperature is 20°C or lower, to the surface, allowing it to connect to the subsequent pipe segments located above ground. 5. Once the assembly described in step 4 is buried underground, a segment of chloride pipe A (4) is connected. MA / a / ZUZU / UUÜl / 0 polyvinyl (PVC) at the exposed end on the surface of pipe segment B (5). Pipe segments A (4) and B (5) make up the conventional pipe (3) that runs from the air inlet (1) where the fan (2) is also located to the heat exchanger (6). 6. Next, a polyvinyl chloride (PVC) pipe segment D (9) is connected to the exposed end of pipe segment C (8). Pipe segment D (9) runs from the exposed end to the air outlet (10), which connects to a room. Pipe segments C (8) and D (9) together form the conventional insulated pipe (7). It is important to note that the thermal insulation covers the entire length of the insulated pipe (7) from the heat exchanger (6) to the air outlet (10). The installation of the entire air cooling and / or heating system using geothermal energy must ensure that the geothermal heat exchanger (6) is located at a depth of 2 to 20 meters. The aluminum fiber used in stage 1 of the assembly process described above has the following characteristics: permeability 1.1 x 10-7m2; porosity 95% and thermal conductivity 209 W / (mk). It is important to emphasize that permeability is an intrinsic property of the geometry and arrangement of the material's pores, not of the material type itself. Therefore, the material can be replaced by any material with a thermal conductivity (κ) between 15 and 386 W / (mK), for example: aluminum fiber (thermal conductivity (κ) equal to 209 W / (mK)), stainless steel (κ = 15 W / (mK)), bronze (κ = 52 W / (mK)), brass (κ = 111 W / (mK)), copper (κ = 386 W / (mK)), provided that the permeability is high enough so that it does not represent a significant restriction to the airflow pushed by the fan, because otherwise a more powerful fan would be required, making the system economically unfeasible; but not so high that it allows the air to flow freely as if the pipe were empty, because in this second case the heat energy capture would be low. MA / a / ZUZU / UUÜI / 0 A geothermal air cooling and / or heating system was built following the steps mentioned above and a system in which the heat exchanger did not have a porous material incorporated inside and tests were carried out measuring the temperature given to the subsoil and heat capture by means of a type K thermocouple sensor, the conditions of the experiments shown in figures 2 and 3 were: air speed: 5 m / s and depth of the heat exchanger: 4 meters. According to the results shown in Figure 2, we can see how the vertical geothermal system that incorporates the heat exchanger (6) consisting of a U-shaped aluminum tube filled with aluminum fiber, in order to illustrate and not limit the invention, allows a higher temperature to be transferred to the subsoil (up to 7°C more) at a high external temperature (36°C to 39°C) compared to a vertical geothermal system in which the heat exchanger is a U-shaped tube without any filling. The results in Figure 3 show that the vertical geothermal system that incorporates a heat exchanger (6) consisting of a U-shaped aluminum tube filled with aluminum fiber is more efficient at capturing the subsurface temperature (up to 5°C more) when the ambient outside temperature is low (4°C to 8°C) compared to a vertical geothermal system in which the heat exchanger is an LJ-shaped tube without any filling. The geothermal system would offer significant advantages if the U-shaped pipe and the porous medium were made of any other metallic material with high thermal conductivity, such as stainless steel (15 W / (mK)), bronze (52 W / (mK)), brass (111 W / (mK)), or copper (386 W / (mK)). Furthermore, the conventional pipe (3) and the thermally insulated pipe (7) are made of polyvinyl chloride (PVC), but other commercially available plastics such as polyethylene terephthalate (PET), high-density polyethylene (HDPE), or low-density polyethylene (LDPE) could also be used. The insulation used for the thermally insulated pipe (7) was expanded polystyrene, also known as Styrofoam or expanded polystyrene foam. Other insulating materials that can be used successfully include fiberglass, polyurethane foam, or volcanic material known as rock wool. Evidence shows that the use of this vertical geothermal air heating / cooling system, which uses a porous metallic material fill in the heat exchanger, performs better in both capturing and releasing heat from the subsoil than a conventional vertical geothermal system. Furthermore, it requires less excavation depth for installation and is more economical because it requires less piping.

Claims

Having sufficiently described my invention, I consider as a novelty and therefore claim as my exclusive property, the contents of the following clauses:

1. A vertical geothermal air heating / cooling system characterized in that it comprises an air inlet located above the earth's surface that allows the entry of outside ambient air, which is propelled by means of a fan into the interior of a conventional pipe that directs the ambient air towards a U-shaped geothermal heat exchanger; the conventional pipe is divided into a pipe segment A located above the earth's surface and a pipe segment B located underground; the U-shaped geothermal heat exchanger is filled with a porous metallic material that allows the ambient air entering the system to decrease or increase its temperature to reach the temperature of the subsoil.Once the ambient air passes through the geothermal heat exchanger, it is conducted to the earth's surface through a conventional, thermally insulated pipe to prevent the ambient air from losing its subsurface temperature. The conventional, thermally insulated pipe consists of a pipe segment C buried underground and a pipe segment D located above ground, leading to an air outlet connected to a room to expel the ambient air at the subsurface temperature.

2. The vertical geothermal air heating / cooling system according to claim 1, characterized in that the porous metallic material of the geothermal heat exchanger has a thermal conductivity of between 15 and 386 W / (mK).

3. The vertical geothermal air heating / cooling system according to claim 1 characterized in that the porous metallic material of the geothermal heat exchanger is selected from the group consisting of aluminum, stainless steel, copper, bronze and / or brass.

4. The vertical geothermal air heating / cooling system according to claim 1 characterized in that the material of the conventional pipe and the conventional pipe with thermal insulation is selected from the group consisting of polyvinyl chloride (PVC), polyethylene terephthalate (PET), high-density polyethylene (HDPE) and low-density polyethylene (LDPE).

5. The vertical geothermal air heating / cooling system according to claim 1 characterized in that the thermal insulation material covering the conventional pipe with thermal insulation is selected from the group consisting of expanded polystyrene, fiberglass, polyurethane foam and rock wool.

6. The vertical geothermal air heating / cooling system according to claim 1 characterized in that the geothermal heat exchanger is located underground at a depth of 2 to 20 meters.

7. The vertical geothermal air heating / cooling system described in claim 1 for use in supplying outside ambient air to a room at a comfort temperature.

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