Air source heat pump without underfloor heating: yes, it is possible

The source of aerothermal energy is the air

"Aerothermal" is a relatively new term but with ancient roots: aero-, from the Greek aéros, meaning air, and -thermal from the Greek thérmē, meaning heat. Aerothermal energy is that which is contained in the air, including cold winter air below 0°C.

Degrees Celsius, which take the freezing point of water as a reference point, are not suitable for measuring energy in the air because it can lead to errors. Cold winter air at −5°C, for example, is also at +268.15K or Kelvin, and although it may seem cold to us, it actually contains a considerable amount of thermal energy.

In physics, the concept of aerothermal energy refers to the exchange of energy between the air and another surface. It is precisely the mechanism that the heat pump uses to move thermal energy from one side to the other. Do you know how it works?

This is how the heat pump works, the machine behind aerothermal energy

A heat pump is a type of thermal machine that works by means of a closed gas circuit called a refrigerant (the name remains the same regardless of the season, whether it is summer or winter). In winter, the heat pump works like this:

• On the outside of the home, cold air transfers energy to the refrigerant. We should remember that even cold air has some thermal energy.
• This refrigerant is quickly compressed in a compressor similar to a bicycle pump, and that causes the temperature to rise quickly.
• When the refrigerant passes into the house, it is very hot because it has been compressed and this transfers heat to the inside.
• Once it has cooled down, a second element expands the refrigerant, an operation that causes its temperature to fall drastically.
• It cools down so much that when the refrigerant returns to the outside, the cold air transfers much more heat to it than the first time.
• And it is compressed again, transfers heat to the inside, expands, captures heat from outside, etc.

In summer, the heat pump does just the opposite: it heats the refrigerant with the air inside the house (say 30°C) and cools it with the outside air (35°C) after it has been compressed to reach 45°C.

There are a number of forms of aerothermal energy

Air-to-air aerothermal energy

Air conditioning with a "split" is probably the most well-known heat pump machine and aerothermal mechanism on the market. It uses an outdoor and an indoor unit, as well as a refrigerant gas line between them.

A little larger than this, but with exactly the same mechanism and a little more efficiency, is ducted air conditioning. The only thing that changes is the size of the indoor and outdoor unit, with the latter being installed in a false ceiling. It also requires a series of ducts through the false ceiling to move the air.

Air-to-water aerothermal energy

Air-to-water aerothermal energy uses the same heat transfer mechanism seen above, but adds one more step: Instead of heating the air in the home with the refrigerant, or the refrigerant with the air in the home, an intermediate water circuit is used. Although this adds an extra step, it is somewhat more efficient than air-to-air and some people find it more pleasant.

One of the advantages of air-to-water aerothermal energy is that it enables you to have an integrated hot water supply, so you will not need a separate electric water heater. It is also perfectly compatible with the radiator system of homes, as long as they are operational. You can actually use the water circuit that you used for the boiler for your radiator system.

You can also install underfloor heating with air-to-water aerothermal energy, which is usually more comfortable and distributes the heat better, but it is much more expensive when you need a new installation. An advantage of this type of system is that it can be installed even if there are already radiators there and underfloor heating can be added room by room years later.

Aerothermal energy, made possible by the invention of the heat pump and the refrigeration circuit, is one of the most efficient ways to control temperature in your home, together with other energy sources such as geothermal energy. Because of this you will find that there are subsidies available for many of these variations on the respective websites of the autonomous communities.