Heat pumps are often described as fridges that operate in reverse, but this analogy doesn’t always help to fully understand how they work. In this article, we’ll break down the science behind heat pumps and explain how they can efficiently extract heat from the air to provide hot water.
A heat pump works by gathering a large volume of low-temperature heat and concentrating it into a small volume of high-temperature heat. For example, if the outside air temperature is 10°C, a heat pump can extract 8°C of heat from the air. The heat pump takes in over 150 litres per second of air, which equates to over 550,000 litres of air per hour. This large volume of air is then used to heat a small volume of water, typically around 300 litres.
The process of harvesting and concentrating heat from the air is the key to the heat pump‘s high efficiency. An electric hot water unit, for example, converts electricity directly into heat energy at around a 99% efficiency level. However, a heat pump gains 3/4 of its heat from harvesting and concentrating the heat from the air, and only 1/4 of the heat from converting electrical input into heat from the compressor. This results in an efficiency of 400%.
The efficiency of a heat pump, also known as the Coefficient of Production (COP), can vary depending on the brand and even the weather conditions. The temperature of the air that the heat pump is harvesting heat from and the temperature of the water being produced are two factors that determine the COP. Additionally, the heat pump‘s compressor and the overall design of the unit can also affect its efficiency.
In conclusion, heat pumps provide a highly efficient way to extract heat from the air and produce hot water. Understanding the science behind how they work can help you to make an informed decision on whether a heat pump is the right choice for your home.