Only the smartest and most sustainable energy solutions endured the selection of the time

Only the smartest and most sustainable energy solutions endured the selection of the time

Heat pump

Naturally, heat taken from the air, soil or water

Heat pumps are being used to provide buildings and processing entities with the required heat. To this effect heat pumps extract heat from a heat source (air, water, soil, processing) and transmit that heat at a higher temperature to a heat delivery system. More specifically, it means that there is a coolant successively circulating, evaporating, being compressed, condensed and then released.


With the addition of a certain amount of energy,
a much larger amount of thermal energy can be
generated, and as a consequence the yield (COP)
is more than 100%."


Heat pumps have an outstanding yield factor when they are being used in combination with high input temperature at one side and low output temperature at the other side, such as floor or wall heating and fan convectors for the heating of buildings.

When a heat pump is being used for heating, it can also,after a couple of slight adjustments, be deployed for the sake of passive cooling. The heat pump is shorted, a process whereby heat is being extracted from the building indoors (via floor, ceiling or wall) and pumped back outdoors in the air, soil or groundwater.

Heat pump

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Advantages of the heat pump

  • Investment in lower energy costs
  • Typical payback between 8 and 10 years
  • Passive cooling
  • In the long run cheaper than a conventional central heating system
  • Very high comfort thanks to radiant heat
  • No need for a chimney, due to losses of flue gases

How does a heat pump work?

The law of physics naturally prescribes that any object that is warmer than its direct environment cools down and passes its heat on to that environment. A heat pump does exactly the opposite: it pumps the heat up from a lower to a higher temperature level.

The cycle of a heat pump runs through an evaporator, a compressor, a condenser and a release.

Warmtepomp werking

1. The evaporator absorbs the heat by evaporation
A heat conveying liquid circulates between the heat source and the heat pump. Inside the evaporator of the heat pump this liquid transfers heat to a coolant which consequently evaporates at low pressure.

2. The compressor sends off compressed steam to the condenser
Subsequently the compressor sucks the gases out of the evaporator and compresses them with the natural effect that both temperature and boiling point increase. You can compare this with the heat you feel at your thumb on the valve of the pump while inflating the tires of your bicycle. In this case the compressor is the only device that requires a certain level of energy itself.

3. The coolant emits heat to the condenser
These gases flow through the condenser due to the high pressure and the increasing temperature. In this condenser, they convey heat to the delivery system (floor heating, ...) whereby they cool down and turn again into liquid.

4. The expansion valve sends the liquid back to the evaporator
The release or the expansion valve will lower again the pressure of the coolant in such a way that the temperature is lower than the natural heat source and heat can be extracted again in the evaporator. And then the cycle can start all over again.

Coefficient of Performance

The compressor is the only part of the heat pump that consumes (a minimum amount of) energy. It goes without saying that the energy consumption of the compressor is one of the important factors determining the efficiency of the heat pump. The yield can be calculated by dividing the delivered useful energy of the heat pump by the assimilated electrical energy of the compressor. This is called the yield factor or COP (Coefficient of Performance).

The COP indicates the ratio between the amount of heat produced and the amount of energy consumed by the heat pump; this is the energy being used by the heat pump through the compressor. The lower the temperature of transmitted heat, and the higher the temperature of the source, the higher the COP. Duly engineered systems have a COP of 3.5 to 6.

Nature has endowed us with a couple of free sources for heating, such as soil, groundwater and air. Beside these there are some other (waste) heat sources at our disposal such as industrial processes, ventilation, sewage, ...  What is essential in the selection of the heat source is its availability, its average temperature as well as its minimum temperature. Furthermore, the exact needs for heating and cooling the targeted building or processing entity should be taken into account. The choice of the most appropriate source depends on the total picture of the overall project. Linea Trovata can install both a groundwater heat pump with vertical and horizontal heat exchangers or an air-water heat pump, depending on the need.

In a groundwater heat pump glycol water is used to extract heat from the soil. This process can take place both via a horizontal or a vertical heat exchanger. The absorbed heat is released through the evaporator to the coolant and then transferred through the compressor to the condenser. In the condenser the water of the heat delivery system absorbs both the heat assimilated in the evaporator and the energy delivered to the compressor.


Soil
heat exchanger

A soil heat exchanger is a network of pipes through which a mix of water and anti-freeze liquid (often glycol) circulates. This liquid transfers the heat from the source to the evaporator. It is of great importance that the soil heat exchanger is correctly sized. When the heat exchanger is too small, the temperature produced will be too low which will finally lead to a loss of efficiency. Depending on the choice, Linea Trovata can install both the vertical and horizontal soil heat exchanger.


Vertical
soil heat exchanger

A vertical soil heat exchanger consists of multiple U-shaped heat exchangers which are placed  in drill-holes up to 100 m deep by means of a drilling machine. A correct sizing is key, there is an important calculation for this in which various essential factors play their role such as:

  • number of operating hours
  • peak moments
  • capacity of the heat pump
  • available space
  • legislation
  • geology

The drilling is carried out by making use of either the flush drilling or the suction drilling method. The distance between the holes is 5 to 10 meters, the depth varies between 25 and 100 meters. The vertical soil heat exchanger is a closed system with a circulation pump.

For the installation of a vertical soil heat exchanger in Flanders one has the obligation –according to the official regulations of the Flemish government (Vlarem I)- of having a license (class 2) or of reporting (class 3).

When the depth of the vertical soil heat exchangers is limited to 50 meters, a simple reporting to the Board of Mayor and Aldermen of the community will suffice. At depths of more than 50 meters, a license is required from the same Board. The application for such a license may take 4 to 5 months.

Advantages Disadvantages
  • High and invariable COP
  • Takes little space
  • Passive cooling
  • Low consumption (only support)
  • High investment cost
  • Licence


Horizontal soil heat exchanger

Those who want to install a groundwater heat pump with a horizontal soil heat exchanger must have a piece of ground (e.g. garden) with sufficient area. The rule of thumb is that the available (outside) ground area is twice as large as the (inside) heated living area. A horizontal soil heat exchanger consists of a grid of tubes (a capture grid) that are buried about 1 meter under the surface of the ground. The capture grid is sized according to the soil type and the type of tubes that are being used. Linea Trovata offers two types of horizontal soil heat exchangers: one classic capture grid with PE tubes and another capillary grid of tubes. The horizontal soil heat exchanger is a closed system with a circulation pump.

Advantages Disadvantages
  • Average COP
  • Low investment
  • Simple
  • Low consumption
  • No licence
  • Large surface needed
  • Decreasing COP during the heating season
  • No passive cooling

The principle in short: the heat from ventilation (brought from the air outside) is transferred through an evaporator to the coolant and then through the compressor to the condenser.

Air-water heat pump based on the air outside

The air-water heat pump extracts heat from the outside air. Outside air is abundant, but can widely vary in temperature. It is this variation that the compressor of the heat pump will have to absorb. For a proper operation of the heat pump, it is important to work with large evaporators. A drawback of working with outside air is that, when outside temperatures drop below 5 ° C, the evaporator can freeze. The ice formed on the evaporator then acts as an insulator, making the heat transfer more difficult. In order to overcome this problem, the operation of the heat pump is reversed at regular intervals so that the evaporator can eventually defrost. This obviously causes additional energy consumption which cannot be applied in a useful way.

Advantages Disadvantages
  • Low investment
  • Simple
  • No licence
  • Noise
  • Lower COP
  • Lower efficiency (due to defrosting)
  • No passive cooling


Air-water heat pump based on ventilation

A ventilation system makes sure the house or residence enjoys a healthy indoor climate. Because of the high temperature of the ventilation air, a heat pump with ventilation as the source of heat still reaches a very acceptable COP, even at a higher output temperature. The flow rate is, however, limited, in such a way that in the end the application is only suitable for the heating of domestic hot water, possibly combined with partial heating of the house or residence.

Besides the classic heat pump with an electric compressor, Linea Trovata also offers gas absorption heat pumps to be deployed in large projects. In this case the electric compressor is replaced by a thermal compressor. The gas absorption heat pump extracts energy from an energy source (soil, water, ...) and will then, through an absorption cycle, bring this energy to a higher and more useful water temperature.An external energy source is needed for this absorption cycle, in this case a gas fired condensing boiler. Both the heat out of the heat pump and the residual heat out of the gas boiler are being utilized.

A heating system at low temperature is a prerequisite for the application of a heat pump.
The temperature of the water supplied should preferably not be higher than 50°C and the temperature of the returned water temperature should not exceed 35°C.

In order to heat a residence with a heating system at low temperature (between 20°C and 40°C) - with water as the in between medium - a heat release system with a large heat-emitting surface is required such as:

  • Floor heating
  • Wall heating
  • Ceiling heating
  • Ventilation convectors

The yield depends on the source and release temperature. The compressor is the only part of the heat pump which uses (electric) energy. A heat pump can generate heat between 2,5 and 6 KWh for every kilowatt hour of electricity it consumes. For each heat pump the principle goes: the smaller the difference in temperature between the source and the release system, the less energy the compressor needs to add. The highest source temperature and the lowest release temperature will yield the best profit.

New buildings can only be heated usinga heat  pump due to the required insulation level (K45) for new buildings. In this case we are talking about a unique-source system. In the other case where, due to circumstances (renovation with radiators, high temperature processes, ...), it is not possible to provide a building or processing entity with heat by the only use of a heat pump, the option for the combination with another heat source (e.g. central heating boiler,. ..) remains, which can eventually be an existing installation. In this case we are talking about a hybrid system.

A heat pump is ideal for:

  • Heating
  • Heating and cooling (passive cooling)
  • Preheating of domestic hot water
  • Hybrid systems (heat pump, central heating boiler, wood pellets, solar boiler combination)
  • Supplying heat from processing entities

Applicable anywhere

  • Private homes
  • Swimming pools
  • Office premises (cooling)
  • Sports infrastructure
  • Industry
  • Agriculture

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