A fridge in reverse: the air source heat pump
Posted by Anna Carlini on 11 January 2017 at 12:10 pm
What is an air source heat pump?
Air source heat pumps allow us to generate hot water or warm air, by making the most of the free heat in the air outside our house. But how exactly do they work? This informative video produced by YouGen member, Nu-Heat, explains the process the air source heat pump uses to generate hot water for use in the home.
The air source heat pump uses the same technology that cools our fridges, just on a somewhat larger scale. Whereas a fridge removes energy from a well-insulated box and dumps it on the outside, a heat pump takes the energy in the outside air and uses it for heating.
In both cases heat is being extracted from a potentially very cold environment - the outside air or the interior of our fridge. So the heat pump doesn’t need warm air to work. Outside temperatures can be as low as -15° C . The air is cold, but it still contains energy which can be converted into heat.
Heat can’t flow from a cold environment to a warmer one, at least not without putting more energy into the system. But by exploiting the behaviour of gases under pressure we can get around this annoying aspect of thermodynamics and concentrate the energy that is in the cold outside air.
How it works:
- Fans draw air from outside the building into a device called the heat exchanger where it flows over an antifreeze mix in a closed loop.
- The heat pump forces this heat exchange fluid through a compressor. Compressing a gas causes its temperature to increase, so the air gets hotter the more it is squashed into a confined space. More information on this process can be found on this page about the workings of a fridge .
- Electricity is needed to operate the fan and compressor but the cost will be low relative to the value of the warmth the heat pump produces.
- Heat always moves from a warmer medium to a cooler one, so once the air becomes warmer than its surroundings it will begin to lose heat through conduction. We can use this heat flow from the hot air to warm up other things, like air or cold water.
- A heat pump typically generates water of 50oC. This can then be stored in an internal cylinder from which it is fed to baths, showers and underfloor heating.
By Anna Carlini and Alex Barrett
More information about Heat Pumps on YouGen.
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