How does a Heat Pump work?
A heat pump works like an air conditioning unit in reverse. It extracts heat from the ambient air surrounding it, enabling it to heat the refrigerant which is then compressed causing it to get even hotter. This is then run through a heat exchanger in which the water is heated. The refrigerant is then allowed to expand again, thus cooling it down and enabling it to again absorb heat from the surrounding air. So only a little electricity is used to run a fan and compressor while the heat energy is provided indirectly by the sun.
The modern domestic heat pump is a very efficient water heating device which uses a small amount of electricity to drive a compressor which forms the heart of the heat pump. The heat energy produced is as much as four times the electrical energy used to drive the compressor. This means that your electricity consumption for water heating can be divided by up to four.
The heat pump is not reliant on sunshine or direct radiation but extracts heat energy from the air at any time of the day or night and so is effectively a solar heater in a different form. Even in extremely cold conditions (-5C and lower) the heat pump can still provide a saving of more than 50%. In most cases in South Africa, where our daytime temperatures are relatively high, the efficiency is going to be at least 3 x that of an element heated water system. Even in the colder climates of Europe heat pumps are extensively used in domestic applications. A heat pump looks similar to an air conditioner and can be installed either on the ground or on brackets on a wall. It is quiet and unobtrusive with a user friendly controller, has no greenhouse gas emissions and requires almost no maintenance.
Heat pump cycle