French basements hide priceless treasures, but still unknown and too little exploited. Just under our feet is an "inexhaustible" source of heat and energy, contained in the water or air of the water tables. With heat pumps, it is now possible to take full advantage of these many resources, which will provide you with warmth or freshness throughout the year. Even if the ecological performances on an individual scale are debatable, HandymakerDuanche still chose to present the geothermal heat pump in the third part of the boiler file.
How does a heat pump work?
The heat pump captures the thermal energy of the outdoor environment (in the air or in the water) and restores it inside buildings to heat them. The operation of this system is based on the ability of the refrigerants to vaporize and condense at room temperature. The most used fluid so far was R22. Harmful to the ozone layer and powerful greenhouse gas, it is gradually being replaced by HFC replacement fluids, which are healthier for our environment.
Water or outside air enters the CAP circuit by external sensors under the ground. It then goes into the evaporator where it gives up its calories to the refrigerant, which then returns to boiling, then evaporates and eventually turns into gas. This gas, which is then at low temperature then undergoes a new cycle by being sucked into the compressor.
Its compression will then increase the temperature and the pressure of the gas. It then goes into an exchanger, the condenser or circulates the fluid (air or water from the domestic circuit) that it must heat up. For this, the gas must yield its energy to the fluid, which it does by condensing, that is to say by passing from the gaseous state to the liquid state (hence the name condenser).
While water or air is reintroduced by emitters into the buildings, the refrigerant, now in the liquid, hot, and with a lot of pressure is sent into the regulator. Its pressure will then drop causing a drop in temperature, the fluid then returns to the evaporator to restart the entire cycle and reheat the air or water.
In order to operate, the heat pump needs electricity, in particular to operate the compressor and the circulation pump which generates the displacement of the refrigerant in the circuit. The electricity consumed is three times lower than the energy produced by the CAP. The savings are therefore 70%, which also corresponds to the energy drawn from the ground.
Pumps can draw heat from different places, depending on the resources nature offers in the surrounding environment.
The heat is taken from the air and then transformed and transported in the house by the CAP. The pump can be installed inside or outside the building. This is called the air / air system.
The heat is taken from a lake, a water table or a watercourse. It then goes through the pump circuits and is redistributed in the house. Very effective, this system still requires special attention because the exploitation of water is subject to a specific regulation.
Soil: Geothermal heat pumps
The heat is taken in the ground thanks to a network of horizontal or vertical sensors, even a geothermal probe, more complicated and more expensive to the installation. In France the horizontal sensors are the least expensive and the most widespread, they claim however a large available surface.
There are three different systems of heat pumps whose operation varies at the level of the circuit.
In the direct expansion pumps, the flow circulates in closed circuit in the sensors and the heated floor. This system can only be used with horizontal sensors. The simplicity and the low cost of this type of pump are big advantages. It is a shame that this circuit can not be reversed to cool in summer.
The pumps with intermediate fluid have two additional hydraulic circuits. Add to the refrigerant, water and water coupled with antifreeze. This process works with both horizontal and vertical sensors.
The mixed technology pumps: the refrigerant circulates in the pump sensors and the water circulates in the heat emitters. This kind of operation is only possible with horizontal sensors and requires a big investment.
Installation and maintenance
Unless you are a handyman particularly confirmed, it is strongly recommended to have your heat pump system installed by a professional. Moreover, this will allow you to obtain a non-negligible tax credit, which you will not be entitled to if you set up your own CAP system. As for the maintenance, it does not require an annual contract as can be stated by some resellers or installers at exorbitant prices (150 to 200 € the contract). Just check the pressure, make sure there are no refrigerant leaks, and then regularly dust off your installation. The installation of a heat pump costs between 100 and 150 euros per m² of heated surface.