ABSTRACT
The low-temperature source in a heat pump system may be from air, soil, or water, which surrounds the evaporator. The main advantage of the heat pump is that it always provides more energy for heating than the energy used for driving it. If the actual coefficient of performance of the heat pump is above 2.8, it is economical to burn primary fuels at the power station to generate electricity to run the heat pump. If the temperature of air supplied to the evaporator is increased, the heat pump gives a corresponding increase in efficiency. This can be achieved by incorporating a solar collector in the system. For most buildings, no heating will be required when the outside temperature is 15.5 degrees C. Degree days may be used as a basis of comparison of the power used for district heating schemes in various parts of the country.
