In previous articles we have talked about geothermal heating. In it, we mention that one of the components necessary to use this type of heating is the geothermal heat pump, which works in a similar way to a conventional heat pump. However, the key difference is that it uses heat energy extracted from the ground to operate.
Would you like to know in detail how a geothermal heat pump works and what its characteristics are? This information will be very useful if you are considering installing this type of system in your home.
Geothermal heat pump
To understand in detail what a geothermal heat pump is, it is essential to first remember what geothermal heating is. This technology uses heat extracted from the subsoil, either from rocks or groundwater, to heat a building. The heat is transported by hot water circulating through a system of specially installed underground pipes.
The geothermal heat pump is a key element within this system. In fact, its use has spread to the point that The heat pump market has grown by 20% annually in recent years. If you've ever noticed the heat coming out of the back tubes of a refrigerator, you already have a general idea of how it works: the refrigerator expels heat from the interior to the outside. The geothermal heat pump does something similar, but in the opposite direction; that is, it takes heat from outside (underground) and transfers it to the interior of the house.
How does a geothermal heat pump work?
The operating principle of the geothermal heat pump is similar to that of any refrigeration system, such as a refrigerator or air conditioner. The key to both systems is the use of a refrigerant fluid that circulates through a system of tubes. This fluid has the property of heating up when it is compressed and cooling down when it expands.
During the winter, the refrigerant fluid, which has been compressed and heated, circulates through a heat exchanger that transfers that energy to the home's heating system. The fluid then cools and expands, a process in which it again comes into contact with the geothermal source (the heat from the subsoil) to recharge its thermal energy. This cycle is repeated continuously to keep the home at a comfortable temperature.
Although the heat pump uses electricity to move the fluid through the system, its efficiency is remarkably high. Modern geothermal heat pump systems can generate up to 4 kW of heat for every kW of electricity consumed. This efficiency is possible because there is no need to generate heat, but simply extract it from the earth, where temperatures are always more stable than on the surface.
There are also reversible pumps, which can also cool the house during the summer. These pumps work in reverse, expelling heat from inside the house to the subsoil. This is achieved through a valve that controls the direction of the heat flow.
Ways to extract geothermal energy
There are several ways to harness geothermal energy with heat pumps. Users are usually familiar with using outside air for heating, but in the case of geothermal pumps, the energy source is the heat stored underground. This type of energy is considered renewable y practically infinite, providing efficient and sustainable heating all year round.
This type of system has a clear advantage over other heating methods that depend on the outside climate, such as aerothermal heating. While a conventional heat pump decreases its effectiveness when the outside temperature is too cold, the geothermal pump never loses efficiency, as the subsoil maintains a stable temperature, regardless of the weather conditions on the surface.
Types of geothermal heat pumps: vertical and horizontal
There are two main types of geothermal heat pumps, which differ in the way the pipes that extract heat from underground are installed:
- Vertical geothermal heat pumps: These are the most popular and are installed at depths between 150 and 200 feet below the surface. In this configuration, pipes are inserted into vertical holes in the ground, through which an antifreeze fluid circulates, raising the heat to the system's cooling fluid.
- Horizontal geothermal heat pumps: In this case, the pipes are placed closer to the surface, about 6 feet deep, and are laid out horizontally. This type of installation requires more space, making it ideal for large plots of land. Although it is less expensive than the vertical pump, it can also be less efficient in terms of heat transfer.
In both systems, the exchange probes can be installed on land close to bodies of water, such as rivers, lakes or lagoons, without affecting the efficiency of the system.
Geothermal capture in water
An interesting variant of geothermal systems is geothermal water capture, where pipes are introduced directly into a body of water, such as lakes or rivers. This system is simpler and cheaper in terms of installation and provides great efficiency as long as the water resource is available.
Initial investment and economic return
One of the main barriers faced by those considering installing a geothermal heat pump is the initial cost. Geothermal systems require a significant investment up front, as it requires prior soil surveys, drilling and the purchase of specialized equipment.
In a single-family home, for example, installing a geothermal system can cost between 6.000 and 13.000 eurosHowever, it is important to note that although the initial investment is high, geothermal heat pump systems allow for significant savings in the long term. It is estimated that users can reduce energy consumption for heating by between 30% and 70%, and for cooling by between 20% and 50%. Depending on the use, these savings allow the initial investment to be amortized within a period of between 5 and 10 years.
The use of this technology not only benefits the system owner, but also the environment, since the consumption of non-renewable energy sources is drastically reduced, and with it greenhouse gas emissions.
Geothermal heat pumps are an ideal option for those looking to minimise their long-term environmental impact while ensuring an efficient and economical heating and cooling system.