How heat pumps work

 

In this article we explain how heat pumps work, what types exist and what their advantages and disadvantages are.

Heat pumps are devices that take advantage of thermal energy from the environment to transfer it from one place to another, depending on the heating or cooling needs. 

How heat pumps work

What is a heat pump?

A heat pump is a system that uses a refrigerant fluid to absorb heat from a cold source and transfer it to a hot source, through a reversible thermodynamic cycle. The refrigerant fluid changes from liquid to gaseous state and vice versa, depending on the pressure and temperature to which it is subjected.

The basic operation of a heat pump can be summarized in four stages:

- Evaporation: the refrigerant fluid circulates through an evaporator, where it absorbs heat from the environment (air, water or earth) and evaporates.

- Compression: the refrigerant vapor passes through a compressor, where its pressure and temperature are increased.

- Condensation: the refrigerant vapor reaches a condenser, where it gives off heat to the medium to be heated (air or water) and condenses.

- Expansion: the refrigerant liquid passes through an expansion valve, where its pressure and temperature are reduced, and returns to the evaporator to start another cycle.

What types of heat pumps are there?

There are different types of heat pumps, depending on the medium from which they extract heat and the medium to which they transfer it. The most common are:

- Air-to-air heat pumps: they extract heat from the outside air and transfer it to the inside air, through a ventilation system. They are used to air condition closed spaces, such as homes, offices or commercial premises.

- Air-water heat pumps: they extract heat from the outside air and transfer it to the water of a hydraulic circuit, which can feed radiators, underfloor heating or domestic hot water. They are used for heating and hot water production in homes or buildings.

- Water-water heat pumps: they extract heat from the water of a well, a river or an underground source and transfer it to the water of a hydraulic circuit, which can feed radiators, underfloor heating or domestic hot water. They are used for heating and hot water production in homes or buildings with access to a water source.

- Ground-water heat pumps: they extract heat from the subsoil, through tubes buried at a certain depth, and transfer it to the water of a hydraulic circuit, which can feed radiators, underfloor heating or domestic hot water. They are used for heating and hot water production in homes or buildings with enough space to install the pipes.

What are the advantages and disadvantages of heat pumps?

Heat pumps have several advantages over other air conditioning systems:

- They are efficient: they take advantage of the thermal energy from the environment, which is free and renewable, and they only consume electricity to operate the compressor. The performance of a heat pump is measured by the coefficient of performance (COP), which indicates the relationship between the thermal energy it produces and the electrical energy it consumes. A high COP means the heat pump is more efficient. For example, a COP of 4 means that for every electrical kWh consumed, 4 thermal kWh are produced.

- They are versatile: they can operate in both heating and cooling modes, depending on whether the direction of the thermodynamic cycle is reversed. In addition, they can be adapted to different heat sources and uses, depending on the type of heat pump chosen.

- They are safe: they do not require combustion nor do they emit polluting gases or dangerous waste. They also do not need chimneys or fuel tanks.

However, heat pumps also have some drawbacks :

- They are climate dependent: their performance may vary depending on the outside temperature. The lower the outside temperature, the lower the capacity to extract heat and the higher the electrical consumption. Therefore, in very cold areas they may need an auxiliary heating system to guarantee thermal comfort.

- They are noisy: the compressor and the fan generate a noise level that can be annoying, especially in air-to-air heat pumps. Therefore, it is important to choose a suitable location to install the outdoor unit and acoustically insulate it if necessary.

- They are expensive: the initial investment to install a heat pump can be high, especially in types that require works or drilling, such as water-water or land-water heat pumps. However, the energy savings they represent can offset the cost in the long term.

We hope this article has helped you understand how heat pumps work and what benefits they can bring to your home or business.