A heat recovery system arranged to be used together with a first closed loop system (S1) configured as a first closed-loop thermodynamic Rankine cycle system, to convert heat from a heat generating unit (1) into electrical energy (E). Said heat recovery system comprising a second closed loop system (S2) comprising a second system working medium (W2) configured as a second closed-loop thermodynamic Rankine cycle system arranged to convert the heat in at least one heat stream (HS1) generated by the heat generating unit (1) into a first batch (E1) of electrical energy (E) and a third closed loop system (S3) comprising a circulating third system working medium (W3). In the second closed-loop thermodynamic Rankine cycle system the condensation heat enthalpy of a vaporised second working medium (W2) is transferred to said third system working medium (W3) and the heat from the third system working medium (W3) is used as an initial thermal input to the second closed loop system (S2), thus converting heat from the third system working medium (W3) into a second batch (E2) of electrical energy (E). The invention also relates to a method to use a heat recovery system together with a first closed loop system configured as a first closed-loop thermodynamic Rankine cycle system, to convert heat from a heat generating unit into electrical energy.