Heat Pump Technology
What’s the magic behind heat pumps?
It all starts with the sun. The sun warms up our atmosphere and the outer layer of the earth’s crust. In one year the energy sent to the earth by the sun is 50 times higher than the total consumption of energy on our planet. This makes the sun a vast and inexhaustible source of energy.
On sunny days you can feel the thermal energy from the sun on your skin. But actually, there is always lots of thermal energy in the air, even on cold winter days or even at night. And not only in Florida or the south of Spain, but also in countries like Sweden or Norway where thousands of houses have already heat pumps.
Why do he at pumps contribute to low CO2 emissions?
Heat pumps emissions are considerably lower than those of conventional heating systems. Because heat pumps consume little energy, CO2 emissions are reduced too since these are restricted to the electricity the pumps need.
Where does it all start?
A heat pump only needs a heat source (the outside air), two heat exchangers (one to absorb and another one to release heat) and a relatively small amount of drive energy to keep the system going. A heat pump extracts thermal energy from the environment. In the case of Altherma the source is the outside air. The pump extracts the energy at a certain temperature, increases that temperature and then releases it into a medium which in Altherma system is the water running to your low temperature radiators, under floor heating system or fan coil units. Between those two media the heat is moved by means of a refrigerant.
What is a refrigerant and what is its role?
This refrigerant is a special liquid that evaporates at a lower temperature than the temperature of the outside air. Copper coils bring the outside air into contact with the refrigerant, which absorbs thermal energy from the air. This is the first heat exchange.
The refrigerant then evaporates and as you know, extracts heat. If you lick your finger and blow on the wet spot, the saliva dries up and your skin turns cold. What you feel is heat being extracted from the underlying tissues of your finger.
Compressor – the essence of heat pumps
As the refrigerant passes through the evaporator and extracts heat from the air, it turns into a gas. This is where the compressor comes up. When you compress a gas, the heat energy in the gas is concentrated together with the molecules and as a result, the temperature rises. If you inflate the tyre of your bicycle, you can feel the air inside warming up through the rubber.
In a heat pump compressor, the temperature rises far above the original temperature of the source (outside air in the case of Altherma). Inside your house the second heat exchange takes place when the compressed gas enters the condenser, a surface which is colder than the gas itself. Finally, the gas condenses and releases heat – the heat that warms up your house. Condensing means that the gas turns into a fluid again. It passes through an expansion valve, resumes its original pressure and the whole process can start all over.