Ground-Water Heat Pumps
Advantages
- stable heat output
- long service life
- up to 70% cost savings
- totally quiet operation
Disadvantages
- higher initial investment (bore hole)
- ground work required (flat collector)
How does a ground-water heat pump work?
You can find out more about what to watch for when buying a heat pump in the section Practical Tips.
An antifreeze coolant mix is circulating through a several hundred meter length of plastic pipe (ground collector). By passing through the ground, the temperature of the coolant increases by several degrees (below the frost line, the ground has a constant temperature of about 4 °C).
The coolant then travels to the heat pump's exchanger (evaporator) where it is chilled down (i.e. the collected heat is removed from the coolant and the chilled coolant once again travels through the collector to be reheated). This cycle continues repeating itself.
Such low potential energy can be collected from the ground using a horizontal (flat) collector or a vertical bore hole.
Capacity sizing of ground-water heat pumps:
If you're not sure about the heat loss of your building and don't know which particular type of heat pump is right for you, fill out this simple contact form.
In our climatic and economic conditions, the rule of thumb with respect to the capacity sizing of water-water and ground-water heat pumps, is to install a heat pump with an output, which is equivalent to approximately 70% of the heat loss of the building. The rest of the heat loss is compensated for when the temperatures are the lowest (and we are talking about only a few days out of any given heating season) by the secondary – divalent – heat source, most frequently an electric boiler.
Installing a heat pump with an output equivalent to 100% of the building's heat loss would increase the initial investment cost to a level at which the installation/operating cost savings ratio weakens considerably. The 70% mark is therefore an ideal compromise between the cost of the initial investment and the operating costs of the system.
Flat Collector System
The amount of land required for the installation of the heat source depends on the output of the heat pump and the characteristics of the local soil. The higher the moisture content of the soil, the greater the energy output. Generally, you will need approximately 30 m2 of land for every 1 kW of heat output. The following diagram will give you a better idea of how much land a flat collector requires.
Bore Hole System
The advantage of the vertical bore hole system is that it requires almost no land. The cost of drilling the bore hole however makes this the most expensive heat pump choice when it comes to the total installation cost. The system has a pair of ground-based, U-shaped heat exchangers, which are inserted into the bore hole. The maximum depth of a single bore hole is 100 m and multiple bore holes may be required if the heat pump needs more energy. Every 12 meters of the bore hole will supply the heat pump with enough energy to produce approximately 1 kW of output.
