Heat pumps are undoubtedly the new stars in the heat generator market, mainly due to their high energy efficiency performance. They are an advanced solution not only for heating but also for cooling and producing domestic hot water. Let's explore together why and how they work.
What is a heat pump?
A heat pump is a generator that operates based on the refrigeration cycle, a specific thermodynamic cycle that allows it to extract heat from a cold source and transfer it to a warmer one.
How does a heat pump work and what are its main components?
The operation of a heat pump relies on the use of fluids with special thermodynamic properties, known as refrigerants.
The refrigerant is contained within a closed circuit called the refrigeration circuit, whose main components include the evaporator, compressor, condenser, and expansion valve. As the refrigerant moves through these components, it changes its state, enabling the heat pump to achieve the desired outcome.
- Evaporator. Inside the evaporator, the refrigerant in its liquid state evaporates, turning into a gas by absorbing heat from an external source (e.g., air or water).
- Compressor. After passing through the evaporator, the gaseous refrigerant reaches the compressor, where it is compressed and heated.
- Condenser. Next, the refrigerant condenses, changing from a gaseous to a liquid state by releasing the heat accumulated in the previous two stages, transferring heat to the external fluid (e.g., air or water).
- Expansion valve. Finally, after condensation, the refrigerant passes through the expansion valve, where its pressure is reduced, ensuring its cooling.
How does a heat pump work?
Based on the type of energy source, heat pumps are divided into four categories.
- Air-to-air heat pumps. These devices use air for direct heat exchange with the refrigerant in both the evaporator and the condenser.
- Air-to-water heat pumps. These pumps use air for direct heat exchange with the refrigerant in the evaporator, while water is used for heat exchange in the condenser.
- Water-to-water heat pumps. These generators use water for direct heat exchange with the refrigerant in both the evaporator and the condenser.
- Geothermal heat pumps. These pumps utilise the heat from the ground through geothermal probes for direct heat exchange with the refrigerant in the evaporator.
Their efficiency is measured using different coefficients, depending on whether their performance is being assessed for heating or cooling: for heating operations, the Coefficient of Performance (COP). The COP indicates the ratio between the thermal energy supplied and the electrical energy consumed for its operation.
In addition to the COP, a second specific coefficient is used to measure performance during cooling operations, called the Energy Efficiency Ratio (EER). The EER indicates the ratio between the thermal energy removed from the indoor environment and the electrical energy consumed for its operation.
Thanks to the advanced technology they are equipped with, energy consumption is reduced, making heat pumps an excellent choice from an environmental perspective.
What is a heat pump climate control system?
As mentioned earlier, a heat pump is not limited to heating; it also contributes to cooling and dehumidifying during the summer season.
Let's take an air-to-water heat pump as an example. During the heating phase:
- thermal energy is absorbed from the air through the evaporator, even at low temperatures;
- the heat is then transferred to the water in the system via the condenser, distributed throughout the house, and released indoors through terminal units (such as radiators, radiant heating, or fan convectors).
For cooling, the process is reversed.
- The thermal energy of the system's water is absorbed by the unit through the evaporator, cooling the water, which then cools the indoor environment through terminal units (in this case, fan coils or radiant cooling).
- The heat is then released to the outside through heat exchange between the condenser and the outdoor air.
Considering both functions, it is clear that heat pumps offer a complete climate control experience. The term "climate control" refers to the ideal thermal conditions for spaces used by people for their daily activities, at any time of the year and in any climate situation.
Heat pumps are particularly used in new buildings, where design considers their environmental impact. By harnessing renewable energy, they achieve optimal energy performance, positively affecting both sustainability and the energy expenses incurred by users.
On the other hand, we have seen how air-to-water heat pumps can be used to cool homes with underfloor systems and fan coils. An air-to-water pump draws from a renewable source (air) to produce heat that circulates as hot or cold water, depending on the need, in the pipes. Of course, in the case of a radiator system, the cooling function is not possible.
At the same time, they ensure a positive impact on older homes and represent the ideal alternative to traditional gas boilers. Despite a significant initial investment, they provide considerable economic advantages, including increasing the property's value due to improved energy efficiency.
To contain the energy costs of so-called active cooling, by combining heat pumps and photovoltaic systems, significant energy-saving benefits can be achieved, maximising the system's sustainability.
What is the difference between an air conditioner and a heat pump?
The operating scheme of a heat pump may resemble that of an air conditioner. It is not surprising, then, that users often wonder about the difference between an air conditioner and a heat pump and whether there is a clear distinction between the two devices.
Let's clarify this.
First, it is important to note that this comparison should be made with a specific category of heat pumps, namely air-to-air heat pumps. Both devices use a refrigerant fluid, operate via a refrigeration circuit, and consist of an outdoor unit that can be paired with one (monosplit system) or more (multi split system) indoor units.
The main difference lies in the fact that heat pumps can reverse the flow of the refrigeration cycle, ensuring not only cooling and dehumidification in the summer but also heating during the winter months.
