Using a heat pump for the heating of houses and the supply of hot water is on the rise lately. The technique is very simple: you extract heat from the outside to heat your house on the inside. In Germany and in the Scandinavian countries, this technique is being used for much longer and is an integral part in the design of a home. But also here in Glasgow there is more and more interest in this alternative heat source.
A heat pump is basically an reverse refrigerator. Whith a refrigerator, the heat from within the refrigerator, is pulled out via a heat pump installation and released on the outside. Around the House, you can use heat from the air, the soil or from the (ground)water. In the ground for example, the temperature is more than 0°c from a depth of 1.5 metres throughout the year.
How does a heat pump work?
The current generation of heat pumps is usually based on an electrically powered compression technique. Fluid is being pumped in a closed circuit. This fluid is in liquid or gaseous state depending on the pressure and temperature. It is these changes of state that makes that the heat is being contained and then released. A heat pump installation consists of a fluid circuit, a pump, an expansion valve and two heat exchangers. The evaporator extracts the heat from outside and the capacitor releases the heat again.
A heat pump is pumping coolant around in a closed circuit. To do this, the pump uses gas or electricity. The efficiency of the heat pump is expressed in the coefficient of performance COP (Coefficient of Performance). This gives a ratio of energy output. A coefficient of performance of 3 means that to produce three heat-pump units, one unit of electrical energy is needed. The COP is always greater than 1, so therefore the returns are always higher than 100%. A heat pump is of interest as the power consumption of the pump is more than offset by the gained heat (high COP). This rate of return is determined by the difference and the stability of the temperature between the cold source and the heat source, the efficiency of the heat exchangers and the electricity consumption of the compressor.
Heat from the ground
When a heat pump gets its heat from the ground we speak of a ground source heat pump. There are two systems that are being used, the heat exchanger that is layed horizontally in the soil of the garden and the heat exchanger that is drilled vertically in the deeper layers of the soil.
Horizontal heat pump
The sun heats up the Earth and this energy can be recovered by a distribution system which is about 70 centimeters below the surface. If You have a well insulated House then the available land in the garden needs to be about 1.5 times as large as the heating surface od the floor. This when a system is utilised from Incognito Underfloor Heating Glasgow. A poorly insulated house needs a larger surface area to extract sufficient heat from the ground. Take into account the design and vegitation of the garden, roots can damage the pipes of the heat pump.
Vertical heat pump
It is also possible to dril the pipes vertically in the ground to a depth of about 50 to 150 meters. The temperature of the ground is higher at that depth. This heat comes from solar radiation, warmth from surface and by heating from the Earth’s core. A vertical pump is ideal for residential houses that have insufficient space for a horizontal placement of the pipe system.
Air source heat pump
An air source heat pump withdraws heat from the outside air. The evaporator consists of a series of tubes where the coolant flows through. These tubes are in contact with the ambient air. The air can flow naturally around (heat exchanger with static air) or is supported using a fan. The disadvantage of an air heat exchanger is that it is dependent on the temperature of the air, and as everyone knows this strongly fluctuates. The return (COP) of this air heat pumps varies strongly as well. As a result, it is usually necessary to combine this system with another heat source in order to be able to boost it if not enough heat is generated.
Heat from water
It is also possible to heat from the groundwater, a pond or even a river. This technique can be interesting because these sources generally a relatively stable temperature can deliver what benefits the return. However, it is not in every situation possible.
