Additional information
As you know the split air-conditioners are also able to heat which means they are a sort of air-to-water heat pumps. But simple refrigerators or freezers can also be called heat pumps (since they 'pump out' the heat from inside). Nevertheless they are not used for heating simply because they are not designed for this.
A heat pump, as an apparatus, that is designed with all its technical data and operational parameters definitely for heating, is manufactured to work effectively in defined working ranges.
Heat pump systems based on water as the primary source, use the heat of surface (rivers, lakes, etc.) or underground waters (water wells) that 'contain' hugh amount of heat energy that comes from the soil or sunshine.
There are two main types of such systems:
- Open systems are characterized by direct pumping out of water and the used water is pumped back into the ground at a lower temperature.
- In case of closed systems plastic pipeles are put in the surface waters at different depths and the clear water pumped through these pipelines is warmed up by the water of the lake, sea, etc.
It is necessary to take into consideration that in open systems the water must go through filters since dirt can lead to serious failures of the heat pump.
Another important issue is the environmental protection: surface and underground waters are protected by law and its violation will be punished.
Sufficient water supply and of the open systems must be designed by qualified specialist.
Advantages:
- because of the very good thermal conductivity of water, open systems have the best efficiency (COP, SPF) among all systems,
- correctly designed water wells on one hand are able to supply the necessary flow rates for the heat pumps and on the other hand their water temperatures are generally suitable for heating and active or passive cooling,
- from about 10-12°C of water temperature even a low quality heat pump can gain heat energy with acceptable COPs
Disadvantages:
- costs of well-designed water wells are quite high. Because of the requirements of environmental protection the system design and the licences themselves are an expensive investment,
- the user must pay a special fee that depends on the quantity of pumped out water,
- in case of small houses the small lands can cause distance problems between pairs of water wells,
- filters and additional pumps must be installed in primary systems to prevent serious failures or blockages in the pipes and heat exchangers,
- the filters must be regularly cleaned for additional operational costs,
- in general, both installation and operational costs of the pumps of open systems are more expensive in comparison with closed systems that leads to reduction of efficiency. Waste-heat of used thermal water can be utilized with high efficiency but such systems must be carefully designed because of high content of mineral salts and other minerals. Do not forget that if you want to pump out thermal water for energetic purposes only, you must care of pumping back this water to the same depth of ground and this is a very expensive thing.
