Advanced Tandem Organic Rankine Cycle (AT ORC) is described for recovering power from source of heat energy into two separated independent cycles with organic fluid of propane or mix of light hydrocarbons with similar thermal stability, namely the high temperature cycle realized in the high temperature closed loop thermally connected to the high temperature zone, and the low temperature cycle realized in the low temperature closed loop thermally connected to the low temperature zone of the source of heat energy. In the process of each cycle, organic fluid changes phases from pressurized liquid to pressurized superheated organic vapor using residual heat energy from depressurized superheated organic vapor, and heat energy from corresponding temperature zone. Separation of the source of heat energy on the high temperature zone and low temperature zone is implemented to maximize thermal and overall efficiency of recovering power in each cycle and of the overall AT ORC.