A power generation system includes a heating fluid circuit thermally coupled to multiple heat sources from at least an integrated hydrocracking plant and diesel hydro-treating plant of a petrochemicalrefining system. A first subset of the heat sources includes diesel hydro-treating plant heat exchangers coupled to streams in the diesel hydro-treating plant. A second subset of the heat sources includes hydrocracking plant heat exchangers coupled to streams in the hydrocracking plant. The heat exchangers are connected to a power generation system that includes an organic Rankine cycle (ORC) including a working fluid that is thermally coupled to the heating fluid circuit to heat the working fluid, an expander configured to generate electrical power from the heated first working fluid, and acontrol system configured to activate a set of control valves to selectively thermally couple the heating fluid circuit to at least a portion of the heat sources.