Geothermal Heating: Heating by geothermal energy, electricity generation … One of the renewable energies with more boom in recent years, has been geo thermal energy (heat from the earth).
Although geothermal energy has been used for centuries, it is a great unknown, but it does not lack great potential. In this article, we will explain what geo thermal energy consists of, how it works, what its applications are, and what energy savings we can achieve, using this technology. An Alternative Energy!!!. Green Energy!!
Unlike most renewable energies, geo thermal energy does not originate mainly from the sun’s radiation, but rather from the difference in temperatures that exists between the interior of the earth and its surface.
Therefore, we can define geothermal energy as energy stored in the form of heat below the surface of the earth. It encompasses the heat stored in soils, rocks, underground waters whatever their temperature, depth and origin.
In this way, we know that, to a greater or lesser extent, an energy that we can and must take advantage of is stored under our feet. An Alternative Energy!!!.
Depending on the enthalpy and the temperature in the subsoil, the following classification can be made:
As we can see, geo thermal energy can be used, depending on its enthalpy and temperatures, for two main applications: heat (air conditioning, sanitary hot water, geothermal heating) and electric power generation whith an alternative energy.
In the following graph, the different applicable technologies for each use are indicated. In this article we will focus on the Heat Pump
The application of geo thermal energy of very low enthalpy for heat production to geothermal heating and / or air conditioning for single family homes, residential buildings, office buildings, schools, is the most commonly used system in building.
How do we take advantage of the Geothermal Energy of Very Low Enthalpy?
If you look at the graph, for different times of the year, the ground temperature tends to be constant (10ºC – 50ºF) at 10 meters ( 32ft.)
The blue color corresponds to winter (0ºC -50ºF outside), and as we deepen the temperature increases, until reaching a value of 10ºC (50ºF).
The red colour corresponds to the summer time (20ºC – 68ºF outside), where the opposite occurs. As we go deeper, the temperature drops to a value of 10ºC-50ºF.
Therefore, at a depth of 15 to 20 meters (50 to 65 ft.), it is considered that the ground begins to be at a constant temperature all year round, regardless of the outside temperature, with a value slightly higher than the annual average of the surface (For example, in Spain they are considered 15ºC-59ºF).
Below 20 meters (68 ft.), the temperature increases at a rate of about 3ºC (37,4ºF) per 100 meters (328ft) of depth, due to the geothermal gradient. That is to say, as it deepens, greater importance acquires the energy coming from the interior of the earth and less the one coming from the sun. However, in the first few tens of meters, the sun is a real source of energy, which not only heats the earth’s crust, but also heats the entire atmosphere, and consequently the rainwater that becomes an extra supply of energy to the terrain.
This available energy, we can take advantage of by exchanging it with a heat transfer fluid. How do we capture Geo thermal Energy?.
In the following video, we explain visually everything that we have commented so far in summary.
We have seen so far, that we have an inexhaustible source of energy during all times of the year.
To take advantage of this energy, we need systems that allow us to capture or transfer it as a consequence of the thermal jump between the terrain and the heat transfer fluid.
Also, it is possible to extract the groundwater and take advantage of its temperature. Let’s see the systems for capturing geothermal energy:
Vertical Capture with Geo thermal Probes. Geothermal Heating
It consists of the installation of a series of polyethylene pipes, called horizontal collectors, through which water with glycol (antifreeze) circulates. It is necessary that the plot has a wide surface to be able to perform the laying of the circuit at a shallow depth
In this system, due to the low depth to which the pipes are buried (5 ft. ), the climate has a special influence. The ground serves as an accumulator of the sun’s energy, providing geothermal energy with a secondary role.
Vertical Capture with Geothermal Probes in Piles. Alternative Energy- Geothermal Heating
When for reasons of foundation and low resistance of the terrain, it is necessary to have piles, these elements are used for the capture of geothermal energy by integrating the probes in the reinforcements. They are called energy piles.
It has the advantage that we take advantage of necessary elements in the construction of the building, with which, it is not necessary to carry out exclusive surveys for its installation.
Capture of Lakes or Rivers. Alternative Energy. Geothermal Heating
It is the most economical system, since no wells or excavations are needed. It consists of taking advantage of rivers or lakes that have hot springs at an adequate temperature, introducing directly the collectors, making the thermal exchange with the water and not with the land.
The above systems correspond to closed circuits, in which the heat transfer fluid circulating in the pipes is not in contact with the ground, nor with the water, making a thermal exchange between them. There must be a hydraulic pump on the surface that has to overcome the pressure drop in the circuit.
There is an open system, which consists of the capture of groundwater. To do this, water is extracted to the heat pump and returned to another point of the subsoil in a different perforation. The hydraulic pump must have a high power, having to ensure a sufficient flow for the correct operation of the installation, so that the efficiency of the system can be lower than the systems described above, due to the high electrical consumption of the pump.
And as a picture is worth a thousand words, here is an explanatory video of the different systems that have been detailed.
How do we take advantage of Geothermal Energy? Geothermal Heating.
In the previous sections, we have explained what geothermal energy consists of and how we capture it. But we still need to develop the part that most interests us when it comes to operating a low temperature geothermal installation and its applications. How do we take advantage of this alternative energy?
For this, we need a device that allows us to absorb the energy captured from the hot bulb and transfer it to the cold bulb for use in heating, domestic hot water and / or air conditioning. That equipment is called a geothermal heat pump.
In our article on the inverter heat pump, we explain at length how a heat pump works. Remembering briefly, it is a thermal equipment that uses the refrigerant cycle of a refrigerant to, through a closed circuit, absorb heat from a hot bulb (either air or water) and transfer it to a cold bulb.
In an air-air heat pump, energy is absorbed from the outside air, transferring it to the indoor environment. It is the case of operation of VRV systems or inverter heat pumps in winter operation. These equipments have very good performances, and are widely used, but they reduce their performance (COP and EER) depending on the external environmental conditions.
Similarly happens with aerothermal heat pumps (air-water), which although they also have high yields, depend on outdoor weather conditions to be more or less efficient.
So, what is the advantage of Geothermal Heat Pumps compared to the previous ones? Well, if you have understood everything discussed so far, we will realize that by having a constant temperature throughout the year (the terrain), the performance of the geothermal heat pump does not depend on the external conditions, since it is always absorbing or releasing energy at the same temperature.
Therefore, the conclusion is that the water-water geothermal heat pump is one of the most efficient thermal transfer equipment on the market. Only, we will have the consumption of the circulator pump of the heat transfer fluid (water with antifreeze) and the compressor. These teams have experienced, in recent years, a great evolution, obtaining COP (Coefficient of Performance – hot) of up to 5 and EER (Coefficeint of Prefomance -cold) of up to 6 – 7, getting excellent seasonal yields very good.
We would be talking, therefore, of highly efficient equipment.
What Applications does Geo thermal Energy have?
Geothermal energy with wells The applications of geothermal energy are the following:
- Small and medium power geothermal heating
- Sanitary hot water by geothermal
- Swimming pools
- Refreshing soil: in summer, the cycle can be reversed, absorbing heat from the interior of the building and transferring it to the subsoil or to a swimming pool. With this, the radiant floor system will act as a cooling system for the house or premises.
The best option in any heat pump system with geothermal heating systems co water, is the installation of low temperature heating (underfloor heating), to obtain maximum efficiency. Even in combination with solar thermal installations, we will obtain significant energy savings and significant reductions in CO2 emissions, which would give us a good energy rating.
What are the advantages of Geothermal Energy?
- Clean energy
- Alternative energy
- Renewable energy
- Efficient energy
- Energy for everyone, under our feet
- Continuous energy, unlike solar and wind
- Current heat pumps with high efficiency. Very efficient geothermal heating systems.
- CO2 emissions much lower than other fuels
- Reduced operating costs.