NOVELTY - The method comprises heating a condensed working fluid in an evaporator to form a vapor, driving the vapor through a turbine, condensing the vapor in a condenser and pumping the condensed working fluid back into the evaporator, and air-cooling the condenser by a passive convective draft flow in a central channel of a thermal chimney. The thermal chimney develops a suction pressure that is passively driven by heat from the condenser rising in a central channel of the thermal chimney. A mass flow rate of the draft flow is passively driven by waste heat from the condenser.    USE - The method is useful for driving a Rankine cycle turbine that is useful in a power generation plant for concentrative desalination of a geothermal brine (all claimed) to provide fresh water for crops or future power generation.    ADVANTAGE - The method is capable of efficiently driving a Rankine cycle turbine with less energy consumption, and allows the desalination of the geothermal brine without any environmental impact.    DETAILED DESCRIPTION - The method comprises heating a condensed working fluid in an evaporator to form a vapor, driving the vapor through a turbine, condensing the vapor in a condenser and pumping the condensed working fluid back into the evaporator, and air-cooling the condenser by a passive convective draft flow in a central channel of a thermal chimney. The thermal chimney develops a suction pressure that is passively driven by heat from the condenser rising in a central channel of the thermal chimney. A mass flow rate of the draft flow is passively driven by waste heat from the condenser. The thermal chimney comprises a natural convective cooling tower. The method further comprising harnessing air updraft in a central channel of the thermal chimney to generate power in the thermal chimney. The power includes electric power, pneumatic power, and/or hydraulic power. The geothermal heat is supplemented by heating from a solar collector. An INDEPENDENT CLAIM is included for a Rankine cycle power generation plant.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a geothermal power generator.