I. Classification of heat pumps by system structure
Monovalent heat pump heating system (without backup heating): Drilling of geothermal heat exchangers, installation of flat plate solar collectors, thermal and other waste heat, groundwater.
Bivalent heat pump heating system (with backup heating): Air, surface water
II. Classification of heat pumps by thermal media
The heat pumps transfer heat necessary for heating mainly from some sort of environment media such as air, groundwater or the soil itself.
Types of heat exchanger (primary) circle:
In case of horizontal ground loop system several hundred meters long copper tubes or PE tubes covered with special hard PVC shell are laid down in 1 to 2 meters deep for abstracting heat from the upper layers of the earth heated by the sun throughout the year. Its disadvantage is that a very large area (1.5 to 3-fold of the heated surface) should be moved and removed to lay down the tubes, therefore this system is suggested in case of newly built houses.
By using horizontal ground loops we can abstract 20 to 30 Watt energy per square meter. The quantity of energy depends on the heat conduction and the humidity of the soil, and the possible groundwater.
Horizontal ground loop system
In case of closed loop vertical bore hole system vertical bore holes around 150 mm wide and drilled at depth of up to 80-120 meters are made and U shaped loops are inserted in the boreholes where the refrigerant circulates in a closed system. At that depth the temperature is constant, 12 to 16 °C depending on territorial conditions, so the heat pump can operate with constant and high efficiency all over the year.
Closed loop vertical bore hole system
The groundwater, the natural deep groundwater can be used as an ideal heat source since its temperature is almost constantly around 10 to 14°C. Although the great advantage of systems built for abstracting under surface water sources is the stability of the temperature that may result in significant savings not only for heating but also for cooling, their use is, however, limited since the water quantity necessary for operating the system is not available at all places.
In case of heat pump system built on shallow groundwater well we operate the system mainly by developing (pairs of) producing and absorbing wells but if there is possibility (and the licensing authority will also agree) the water extracted from the water well will be absorbed to the surface water (streamlet, lake, river), or let it escape through drain tubes imbedded in the ground.
Following the principal extraction and utilization of water from the deep groundwater well the water will be absorbed to another well or to the surface water (streamlet, lake or river) or let it escape through drain tubes imbedded in the ground.
Water well system
A further special application is when a lake serves for heat source where the tubes as collectors are laid circularly here.
Tube system in lake
Utilization of outdoor or used air
The outdoor air is available all around us but it is still not the ideal solution. Its disadvantage is that the temperature of the air is not constant so the efficiency of the system is constantly changing. In addition to the changing efficiency another problem is that the extraction of energy is the most difficult when the demand of the building on heating is the largest, so to say in the winter season. This case the efficiency of the system is the lowest and even the operation costs increase as well as the ventilator noise might also mean problem.
The air of the cellar of the house can also be utilized. In case of a house provided with central ventilation system the used air to be discharged or the supplied air warmed or as supplement to heating system can also be used as heat source. (A rather simpler solution is the application of heat exchangers where the discharged hot and the supplied cold air transfers the heat in an equipment of large surface without mixing.)