1. Thermodynamics reminder

Before tackling the subject, it is interesting to know the theoretical power required to carry out the refrigeration operation at any temperature: what is the ideal value (i.e. minimum calculated by describing a Carnot cycle) of the power to be expended at room temperature (generally, power taken from the electrical network) to be able to absorb one unit of thermal power dissipated at a temperature lower than room temperature? There are two cases to consider, depending on whether operation is isothermal or non-isothermal.