Along with the four vital components of the heat pump its another equally important part is the refrigerant. The refrigerant used in the heat pump cycle is same as the refrigerant used in the refrigerator or the air conditioner. Some of the most commonly used refrigerants are the chlorofluorohydrocarbons though a number of other alternative refrigerants have also been discovered.
The refrigerant continuously flows through compressor, condenser, expansion valve and the evaporator in a closed cycle. It is the refrigerant that carries the heat from atmosphere which is at low temperature and delivers it to the room, which is to be maintained at high temperature.
All the problems and the environmental concerns caused by the chlorofluorohydrocarbons used in the refrigerators and air conditioners are also caused by the chlorofluorohydrocarbons used in the heat pumps. The chlorofluorohydrocarbons have the tendency to destroy the ozone layer in the atmosphere and cause greenhouse effect.
However, the total number of heat pumps being used in the entire world is much lesser compared to air conditioners, refrigerators, and freezers, hence they have not yet received much attention as regards to their potential to release ozone layer depleting gases in the atmosphere. However, just like the other chlorofluorohydrocarbons, whose production has to be totally stopped in phased manner, the production of the refrigerants used for the heat pumps is also slated to be stopped in the similar manner.