Hybrid thermal power and desalination apparatus and methods

A method for concentrative desalination of a geothermal brine from a supply well of a geothermal field while controlling the temperature and saturation of the brine feed so as to separately collect power, fresh water and a mineral concentrate, which comprises in combination,

• (a) exchanging heat from a geothermal brine input with a recirculating working fluid in an evaporator—superheater, and driving a Rankine Cycle engine with the vapor therefrom, wherein the Rankine Cycle engine loop is configured with a turbine generator for generating a power output;
• (b) thermally contacting the geothermal brine input with a liquid boost stream input, the liquid boost stream input having a heat content for driving increased power output from the Rankine Cycle engine, and discharging a geothermal brine discharge and a liquid boost stream discharge;
• (c) providing a thermal chimney as a heat sink, the thermal chimney having a base, a top, and a central airway with surrounding wall, wherein the base is defined by a bottom cool air inlet to the central airway, the top is defined by a heated air outlet from the central airway, and the central airway is configured for conducting an exergy driven air stream rising from the bottom cool air inlet to the top heated air outlet thereof, said rising air stream having a mass flow, a momentum, a dew point, and a relative humidity that is at or about saturation;
• (d) providing a stack of heat exchangers at the base of the thermal chimney in the central airway, one for receiving the geothermal brine discharge from the Rankine Cycle engine, one for receiving a liquid boost stream discharge, and one configured at the bottom of the stack as a condenser for receiving and condensing the working fluid from the Rankine Cycle engine when thermally contacted with the rising air stream;
• (e) admitting the geothermal brine discharge to the stack of heat exchangers;
• admitting the liquid boost stream discharge to the stack of heat exchangers;
• circulating the working fluid through the condenser at the bottom of the stack;
• (f) providing an evaporator zone above the stack of heat exchangers, therein fluidly contacting the geothermal brine discharge with the air stream rising in the central airway, and evaporatively cooling the geothermal brine to a temperature below the solubility product of at least one mineral salt dissolved therein, thereby precipitating the mineral as a solid mineral fraction and forming a supernatant discharge;
• (g) admitting the rising air stream into a condenser zone proximate to the top of the thermal chimney, the condenser zone having an axial cyclone with inlet guide vanes, and decompressing and cooling the water vapor below the dew point of the airstream therein, thereby forming a fresh water condensate;
• and,
• (h) collecting the power output from the Rankine Cycle engine;
• collecting the fresh water condensate;
• collecting the solid mineral concentrate;
• and pumping the supernatant discharge and geothermal brine discharge into a return well in the geothermal field.