A method of re-using heat energy generated by an operational petrochemical refining system, the method comprising: identifying a geographic layout that comprises an arrangement of a plurality of sub-units of an operational petrochemical refining system, the geographic layout including a plurality of sub-units, each positioned at a respective sub-unit location; identifying a first subset of the plurality of sub-units of the petrochemical refining system, the first subset including a plurality of hydrocracking plant heat exchangers (102d-h) coupled to streams in the hydrocracking plant and a plurality of aromatics plant heat exchangers (103a-c) coupled to streams in the aromatics plant, wherein heat energy is recoverable from the first subset to generate electrical power; identifying, in the geographic layout, a second subset of the plurality of sub-unit locations, the second subset including sub-unit locations at which the respective sub-units in the first subset have been positioned; identifying a power generation system to recover heat energy from the sub-units in the first subset, the power generation system comprising: a first heating fluid circuit and a second heating fluid circuit, each heating fluid circuit fluidly connected to the sub-units in the first subset; a power generation system that comprises an organic Rankine cycle, the organic Rankine cycle comprising i) a working fluid that is thermally coupled to the first heating fluid circuit and the second heating fluid circuit to heat the working fluid, and ii) an expander configured to generate electrical power from the heated first working fluid; and a control system configured to activate a set of control valves to selectively thermally couple each of the first heating fluid circuit and the second heating fluid circuit to at least a portion of the plurality of heat sources; and identifying a power generation system location in the operational petrochemical refining system to position the power generation system, wherein a heat energy recovery efficiency at the power generation system location is greater than a heat energy recovery efficiency at other locations in the operational petrochemical refining system. identifying a geographic layout that comprises an arrangement of a plurality of sub-units of an operational petrochemical refining system, the geographic layout including a plurality of sub-units, each positioned at a respective sub-unit location; identifying a first subset of the plurality of sub-units of the petrochemical refining system, the first subset including a plurality of hydrocracking plant heat exchangers (102d-h) coupled to streams in the hydrocracking plant and a plurality of aromatics plant heat exchangers (103a-c) coupled to streams in the aromatics plant, wherein heat energy is recoverable from the first subset to generate electrical power; identifying, in the geographic layout, a second subset of the plurality of sub-unit locations, the second subset including sub-unit locations at which the respective sub-units in the first subset have been positioned; identifying a power generation system to recover heat energy from the sub-units in the first subset, the power generation system comprising: a first heating fluid circuit and a second heating fluid circuit, each heating fluid circuit fluidly connected to the sub-units in the first subset; a power generation system that comprises an organic Rankine cycle, the organic Rankine cycle comprising i) a working fluid that is thermally coupled to the first heating fluid circuit and the second heating fluid circuit to heat the working fluid, and ii) an expander configured to generate electrical power from the heated first working fluid; and a control system configured to activate a set of control valves to selectively thermally couple each of the first heating fluid circuit and the second heating fluid circuit to at least a portion of the plurality of heat sources; and a first heating fluid circuit and a second heating fluid circuit, each heating fluid circuit fluidly connected to the sub-units in the first subset; a power generation system that comprises an organic Rankine cycle, the organic Rankine cycle comprising i) a working fluid that is thermally coupled to the first heating fluid circuit and the second heating fluid circuit to heat the working fluid, and ii) an expander configured to generate electrical power from the heated first working fluid; and a control system configured to activate a set of control valves to selectively thermally couple each of the first heating fluid circuit and the second heating fluid circuit to at least a portion of the plurality of heat sources; and identifying a power generation system location in the operational petrochemical refining system to position the power generation system, wherein a heat energy recovery efficiency at the power generation system location is greater than a heat energy recovery efficiency at other locations in the operational petrochemical refining system.