A method for generating power with improving thermal and overall efficiencies of Organic Rankine Cycle using a source of heat energy, said method comprising:
- a. separating said Organic Rankine Cycle into two cycles:
- a high temperature cycle realized in a high temperature closed loop and a low temperature cycle realized in a low temperature closed loop;
- b. dividing said source of heat energy into a high temperature zone connected thermally to said high temperature closed loop and a low temperature zone connected thermally to said low temperature closed loop;
- c. determining a maximum of the top temperature (Th1−ΔT′sh) of said high temperature cycle to maximize the thermal efficiency in generation of a first portion of power;
- d. determining a maximum of the temperature range (Th1-Th2(min)) of said high temperature zone to maximize the overall efficiency in generation of the first portion of power, where Th2(min) is:
- Th2(min)=[(Th1−ΔT′sh)×(P′2/P′1)^(γ′−1)/γ′×C′p2−(Ta+ΔT′c+ΔT′r)×C′p3+(Ta+ΔT′c)×C′p4]×1/C′p5+ΔT′sh
- Where:
- Th1—maximum temperature of the source of heat energy in said high temperature zone,
- Th2(min)—maximum temperature in said low temperature zone,
- ΔT′sh=Th1−Ths—temperature approach of first flow of pressurized superheated organic vapor with temperature Ths from an outlet of a high temperature superheater,
- ΔT′c—difference of temperature of condensed organic fluid flowing from an outlet of a first condenser and temperature of a coolant medium,
- ΔT′r—difference of temperature of depressurized organic vapor at the cold outlet of a high temperature recuperator and temperature of pressurized organic liquid at the cold inlet of said high temperature recuperator,
- Ta—ambient air temperature,
- P′2—pressure of depressurized superheated organic vapor in said high temperature closed loop,
- P′1—pressure of pressurized superheated organic vapor directed to a first expansion turbine,
- γ′=C′p1/C′v1—ratio of specific heats of pressurized superheated organic vapor directed to said first expansion turbine,
- C′p2, C′p3, C′p4, C′p5—specific heats of organic fluid directed to said first expansion turbine, the inlet of said first condenser, from the outlet of said first condenser, and the inlet of said high-temperature superheater respectively in said high temperature closed loop;
- e. determining a maximum of the top temperature (Th2−ΔT″sh) of said low temperature cycle to maximize thermal efficiency in generation of a second portion of power;
- f. determining a maximum temperature range (Th2(min)−Th3(min)) of said low temperature zone to maximize overall efficiency in generation of said second portion of power, where Th3(min) is minimum temperature of said low temperature zone according to the equation:
- Th3(min)=[(Th2(min)−ΔT″sh)×(P″2/P″1)^(γ″−1)/γ″×C″p2−(Ta+ΔT″c+ΔT″r)××C″p3+(Ta+ΔT″c)×C″p4]×1/C″p5+ΔT″sh>Tdp
- Where:
- ΔT″sh=Th2(min)—Tls—temperature approach of the second flow of pressurized superheated organic vapor with temperature Tls from an outlet of a low temperature superheater,
- ΔT″c—difference of temperature of condensed organic fluid flowing from an outlet of a second condenser and temperature of a coolant medium,
- ΔT″r—difference of temperature of depressurized organic vapor at the cold outlet of a low temperature recuperator and temperature of pressurized organic liquid at cold inlet of said low temperature recuperator,
- Ta—ambient air temperature,
- Tdp—dew point temperature,
- P″2—pressure of depressurized superheated organic vapor in said low temperature closed loop,
- P″1—pressure of pressurized superheated organic vapor directed to a second expansion turbine,
- γ″=C″p1/C″v1—ratio of specific heats of superheated organic vapor directed to said second expansion turbine,
- C″p2, C″p3, C″p4, C″p5—specific heats of organic fluid directed to said second expansion turbine, to the inlet of said second condenser, from the outlet of said second condenser, and to the inlet of said low temperature superheater respectively in said low temperature closed loop;
- g. providing the first flow of pressurized organic fluid in said high-temperature closed loop;
- h. providing the second flow of pressurized organic fluid in said low-temperature closed loop;
- i. providing thermal independency between said first flow of pressurized organic fluid and said second flow of pressurized organic fluid;
- j. providing preheating, vaporizing and preliminary superheating of said first flow of pressurized organic liquid in the process of recuperation in said high temperature closed loop;
- k. adapting heat energy from said high temperature zone and increasing the temperature of pressurized and preliminary superheated organic vapor up to allowable temperature considering the thermal stability of the chosen organic fluid;
- l. providing said first flow of pressurized and superheated organic vapor to said first expansion turbine in said high temperature closed loop;
- m. generating the first portion of power on said first expansion turbine in a process of expanding said first flow of pressurized superheated organic vapor flowing through said first expansion turbine;
- n. providing said first flow of depressurized superheated organic vapor from downstream of said first expansion turbine to said high temperature recuperator under pressure correlated to pressure of organic fluid at ambient air temperature;
- o. providing the process of recuperation of residual high temperature heat energy from said first flow of superheated and depressurized organic vapor inside said high temperature closed loop for preheating, vaporizing, and preliminary superheating pressurized organic liquid pumped with mass flow operated in said high temperature closed loop;
- p. producing condensate from depressurized organic vapor under pressure correlated to critical pressure of organic vapor at an ambient air temperature and returning condensate in the liquid phase under pressure of a first pump to said high temperature cycle of said high temperature closed loop;
- q. providing preheating, vaporizing and preliminary superheating of a second flow of pressurized organic liquid in the process of recuperation in said low temperature closed loop;
- r. adapting heat energy from said low temperature zone and increasing a temperature of pressurized and preliminary superheated organic vapor up to allowable temperature considering the thermal stability of chosen organic fluid;
- s. providing said second flow of pressurized and superheated organic vapor with increased temperature to a second expansion turbine;
- t. generating the second portion of power on said second turbine in the process of expanding second flow of pressurized and superheated organic vapor flowing through said second expansion turbine;
- u. providing said second flow of expanded depressurized superheated organic vapor from downstream of said second expansion turbine to said low temperature recuperator under pressure correlated to critical pressure of organic fluid at an ambient air temperature;
- v. providing the process of recuperation of residual heat of expanded superheated and depressurized organic vapor inside said low temperature closed loop for preheating, vaporizing, and preliminary superheating pressurized organic fluid pumped with a mass flow operated in said low temperature closed loop;
- w. producing condensate from depressurized organic vapor under pressure correlated to critical pressure of organic vapor at an ambient air temperature and returning said condensate in the liquid phase under pressure of a second pump to said low temperature cycle of said low temperature closed loop;
- x. providing minimum and equal condensing temperatures of said first and second flows of organic fluids in said high temperature cycle and low temperature cycle respectively to minimize heat losses in first and second condensers determined by the ambient air temperature.