Air-to-Water Heat Pump

Air-source heat pumps extract energy from the ambient air and thus cool it down. A distinction is made between the following types:

• Compact system with indoor installation: The heat pump and the evaporator are installed in the building (e.g. in the basement). Air is sucked in and blown out again through two outside air grilles. This variant is very compact and has relatively low investment costs, but requires that the airflow grilles do not pose any visual or acoustic impairment at the installation site.
• Compact system with outdoor installation: The heat pump including the evaporator is installed outside as a compact system. This type of construction is mainly used when there is a lack of space in the house, but is more expensive than the interior installation type.
• Split system: Here the heat pump is located in the building and the evaporator is set up outside, e.g. in the garden, both devices are connected to each other via a cooling pipe. This allows the location of air absorption to be determined or led away from the house. The space required in the building is reduced. This type of design is particularly suitable for retrofitting, as no air ducts and no intake/exhaust openings are required.

In the case of air-source heat pumps, particular attention must be paid to the noise emitted by the work of the rotor on the evaporator. This is necessary to suck in the ambient air. The rotor causes considerable flow noise, so the installation location must be chosen in such a way that users and neighbors are not disturbed. However, differences in the makes, the construction method and the care taken in the execution are also decisive factors for the noise emissions generated.

As with all heat pumps, the following principle applies: the higher the temperature of the medium, the higher the efficiency of the system. In the case of the air source heat pump, this correlation is particularly crucial, as the machine must deliver high performance especially when the temperature of the air is particularly low, i.e. in winter. In this range, the proportion of propulsion energy (electricity) is higher than at high air temperatures. Despite this divergence, the systems have now achieved such a high level of effectiveness that an acceptable coefficient of performance is achieved even at sub-zero temperatures. On an annual average, this so-called COP number is between 2.3 and 4.4, depending on the type and location. On the other hand, the acquisition costs of the air-source heat pump are particularly favourable compared to systems for geothermal energy or groundwater use.

1: Heat pump indoor unit

2: Buffer tank

3: Return

flow 4: Flow

5: Outdoor unit with fan and compressor

Source: bauwion