A heat pump is a device which uses mechanical energy to transfer heat from a low thermal source (“heat source”) at surrounding environment temperature and hence not immediately usable, towards a destination (“heat sink”) with higher thermal power, that is opposite to the direction of spontaneous heat flow.
Based on the type of heat source, there are several kinds of heat pumps:
1. Air-source heat pumps based on outside air
These pumps transfer heat from the outside air to an inside hot water installation, hence their usual name of “AIR-WATER” heat pumps.
While their main advantage lies in the accessibility of the air source, they are less efficient when outside temperature falls below 0 degrees Celsius, precisely when the need for heating is the highest.
2. Ground-source heat pumps (geothermal heat pumps)
Under 10m below ground level, temperature remains basically constant (10-14 degrees Celsius), not influenced by outside temperature.
In this case, the heat source is accessed either directly (by using groundwater at ground temperature) or indirectly (through geothermal drilling and ground heat exchangers).
The superior efficiency of geothermal heat pumps is obvious especially in temperate continental climates such as Romania’s, where the differences in temperature between seasons are relatively large (freezing cold winters and hot summers).