The invention discloses a novel energy conversion system. The novel energy conversion system includes a heat aggregation mechanism, an energy conversion mechanism, a cooling and liquefying mechanism, and a working medium circulation mechanism which are connected in a pairwise manner. The whole system accords with the operating principle of the Rankine heat engine cycle system and the second law of thermodynamics. In the heat aggregation mechanism, a gas-liquid phase combined heat exchange component is used for technological aggregation and transfer of heat from a natural environmental heat source or an artificial environmental heat source to a working medium; in the cooling and liquefying mechanism, a forced type condenser technology is used to achieve effective heat dissipation and liquefaction of a working medium tail gas; in the working medium circulation mechanism, a working medium pump and a liquid storage tank are used to achieve the possibility of circulatory movements of the working medium in a closed system; in the energy conversion mechanism, an energy conversion assembly is used to convert the heat energy of working medium gas flows entering the mechanism into mechanical energy, or further convert the mechanical energy into electric energy. The energy conversion system provided by the invention is an improved and innovative energy conversion system, which can utilize energies, including but not limited to various low-grade heat energies, and convert the low-grade heat energies into mechanical power for work. The novel energy conversion system is a novel power generation system when connected with a power generator.