Considerations on the use of thermal energy at moderate temperature. Interest of the heat pump

The use of thermal energy at moderate temperatures (15 C to 80 C) is not a new problem as shown by applications as varied as domestic heating, greenhouse air conditioning for cultivation and breeding, food products sterilization, manufacture of many chemicals, desalination. However, the growing energy needs of the modern world necessitate an optimization of the use of available energy sources, an optimization that is not currently satisfied with the different energy sources that can be used for the moderate temperature range. The interest of using a thermal machine (heat pump) under certain conditions is highlighted, for the sake of economy and for its flexibility of use, its cleanliness, its reliability and the thermal depollution of certain geographical sites it may cause. The various thermal energy sources that could be used for moderate temperature production are first reviewed: production of thermal energy by combustion, by nuclear energy, by Joule effect, by recovery of geothermal energy, by recovery of solar energy. The possibility of an efficient use of heat pumps is then analyzed (operating principles and realization of a heat pump, different cold sources that can be used by heat pumps) followed by some considerations on the design of power-thermal plants with heat pumps