Utilising a heat pump for the heating of homes and hot water supply is on the rise lately. The technique is very simple you will extract heat from outside to heat your house. In Germany and in the Scandinavian countries, this technique is used for much longer and is an integral part in the design of a home. But also in Scotland, there is a growing interest for this alternative source of heating.
A heat pump is basically a refrigerator that works the other way around. A refrigerator takes the heat from the refrigerator, a heat pump installation extracts the natural warmth from the outside to the inside. Around the house it can use heat from the air, the ground or the water. In the ground the temperature from a depth of 1.5 metres is for example throughout the year more than 0°c.
How does a heat pump work?
The current generation of heat pumps are usually based on an electrically powered compression technique. In a closed circuit fluid is being pumped. This fluid will depending on the pressure and temperature be in liquid or gaseous state. It is these changes of state that makes sure that the heat is 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 condensor releases the heat again. In steps the following happens:
Heat pump efficiency
A heat pump is pumping coolant around in a closed circuit. To do this, the pump uses gas or electricity. The efficiency of the pump is expressed in the coefficient of performance COP (Coefficient of Performance). This gives the 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. You therefore read always about returns higher than 100%. 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 geothermal heat pump. There are two systems being used. The heat exchanger that is laid horizontally in the soil in loops in the garden and a heat exchanger that is drilled vertically in the deeper layers of the ground.
Horizontal ground source 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 ground. If you have a well insulated house then the available land in the garden needs to be about 1.5 times larges as the heating surface. A poorly insulated house needs has a larger surface area to provide sufficient heat from the ground. Take into account the design and construction of the garden, roots may damage the pipes of the heat pump.
Vertical heat pump
It is also possible to drill pipes vertically in the ground to a depth of 50 to 150 meters. The temperature of the earth is at that depth higher. This heat comes from solar radiation, soil and water from surface water and by heating from the earth’s core. A vertical pump is ideal for residential houses that have insufficient space for the horizontal placement of the pipe loop system.
Air source heat pump
An Aerothermal heat pump draws heat from the outside air. The evaporator consists of a series of tubes where the coolant flowss through it. These tubes are in contact with the ambient air. The air can flow around naturally (heat exchanger with static air) or supported using a fan.
(image by Photographer Zwolle)
The disadvantage of an air heat exchanger is that it is dependent on the temperature of the air, and as everyone knows these strongly fluctuate. The return (COP) of this air heat pumps varies strongly. As a result, it is usually necessary to combine this system with another heat source in order to be able to jump if not enough heat.
Water source heat pump
It is also possible to extract heat from the groundwater, a pond or even a river. This technique can be of interest because of the number of lochs and rivers in Scotland. These sources generally have a relatively stable temperature what benefits the return. However, it is not in every situation possible. If you’re in Scotland or tthe Nortth of England, please cal Incognito Heat Pumps Scotland to discuss your ideas
Benefit from the heat with underfloor heating
You can use the heat won with a heat pump in different ways. The theory is that the lower the temperature used, the more efficient the installation works. In other words, the smaller the difference between the home and the heat source the higher the return. Low temperature heating is widely utilised applied through underfloor heating as weel as wall heating. Underfloor heating works by means of the large surface area with an even temperature distribution whereby the system can run on a much lower temperature whilst maintaining comfort.
Central heating powered by a heat pump is most suitable for new homes. From the start of the design and build, you can take into account the situation and choose the most efficient system. In most cases, this means excellent insulation in combination with low temperature underfloor heating. For existing builds, a heat pump installation will only work with rigorous alterations.