Heat engine with cascaded cycles

Abstract

A method of converting thermal energy into another energy form using a thermodynamic cycle is disclosed, the method including the steps of: pressurizing a working fluid; supplying thermal energy to heat the working fluid from a liquid or substantially liquid state to a supercritical fluid state; in a first expander, substantially isentropically expanding the working fluid to yield energy in the other energy form; separating the expanded working fluid to form a first portion of the fluid diverted to a second expander and a second portion of the working fluid diverted to bypass the second expander; in the second expander, substantially isentropically expanding the first portion of the working fluid to yield energy in the other energy form; condensing the expanded first portion of the working fluid to a liquid or substantially liquid state; and recombining the first and second portions of the working fluid to be recirculated in the cycle.

1 . A method of converting thermal energy into another energy form using a thermodynamic cycle, the method comprising the steps of:
 pressurizing a working fluid;   supplying thermal energy to heat the working fluid from a liquid or substantially liquid state to a supercritical fluid state;   in a first expander, substantially isentropically expanding the working fluid to yield energy in the other energy form;   separating the expanded working fluid to form a first portion of the fluid diverted to a second expander and a second portion of the working fluid diverted to bypass the second expander;   in the second expander, substantially isentropically expanding the first portion of the working fluid to yield energy in the other energy form;   condensing the expanded first portion of the working fluid to a liquid or substantially liquid state; and   recombining the first and second portions of the working fluid to be recirculated in the cycle.   
     
     
         2 . The method of  claim 1 , wherein, in the first expander, the working fluid is progressively dried during at least a portion of the expansion. 
     
     
         3 . The method of  claim 2 , wherein, in the second expander, the first portion of the working fluid is progressively dried during at least a portion of the expansion. 
     
     
         4 . The method of  claim 1 , wherein the other form of energy comprises mechanical energy. 
     
     
         5 . The method of  claim 4 , wherein the first expander or the second expander comprises a turbine expander. 
     
     
         6 . The method of  claim 4 , wherein the first expander or the second expander comprises a piston expander. 
     
     
         7 . The method of  claim 1 , wherein the working fluid is an organic fluid. 
     
     
         8 . The method of  claim 7 , wherein the organic fluid comprises at least one fluid from the list consisting of: ammonia, benzene, butane, isobutane, carbon tetrachloride, HCFC-123, propane, R-245fa, R-245ca, and toluene. 
     
     
         9 . The method of  claim 7 , wherein the organic fluid has a critical temperature of about 200 degrees C. or less. 
     
     
         10 . The method of  claim 7 , wherein the organic fluid has a critical temperature of about 175 degrees C. or less. 
     
     
         11 . The method of  claim 7 , wherein the organic fluid has a critical temperature of about 150 degrees C. or less. 
     
     
         12 . The method of  claim 1 , wherein the step of condensing the expanded first portion of the working fluid to a liquid or substantially liquid state comprises rejecting heat from the cycle at a temperature of about 45 degrees C. or more. 
     
     
         13 . The method of  claim 12 , wherein the step of heating the working fluid comprise accepting heat from a heat sources at a temperature of about 200 degrees or less. 
     
     
         14 . The method of  claim 13 , wherein the cycle has a Carnot efficiency of about 30% or more. 
     
     
         15 . The method of  claim 13 , wherein the efficiency of the first expander and the second expander is about 80% or more. 
     
     
         16 . The method of  claim 13 , wherein the net cycle efficiency in about 15% or more. 
     
     
         17 . The method of  claim 13 , wherein the specific net work output of the cycle is about 20 kJ/Kg or more. 
     
     
         18 . The method of  claim 1 ., wherein the step of separating the working fluid comprises separating the working fluid with a bypass ratio of about 50%. 
     
     
         19 . The method of  claim 1 , wherein in the step of in a first expander, substantially isentropically expanding the working fluid, the expansion is characterized by an expansion ratio of in the range of 4:1 and 8:1. 
     
     
         20 . The method of  claim 1 , wherein in the step of; in a second expander, substantially isentropically expanding the first portion of the working fluid, the expansion is characterized by an expansion ratio in the range of 4:1 and 12:1. 
     
     
         21 . The method of  claim 1 , further comprising the step of:
 after condensing the expanded first portion of the working fluid and prior to recombining the first and second portions of the working fluid, substantially isentropically pressurizing the first portion of the working fluid.   
     
     
         22 . The method of  claim 1 , wherein the step of recombining the first and second portions of the working fluid, the first portion of the working fluid is at a lower temperature than the second portion of the working fluid. 
     
     
         23 . The method of  claim 22 , wherein the step of recombining the first and second portions of the working fluid comprises transferring heat from the second portion to the first portion by direct contact of the first and second portions of the working fluid. 
     
     
         24 . The method of  claim 1 , further comprising the step of:
 after the step of separating the expanded working and prior to the step of recombining the first and second portions of the working fluid, extracting heat from the second portion of the working fluid.   
     
     
         25 . The method of  claim 24 , further comprising:
 using the heat extracted from the second portion of the working fluid to drive a secondary thermodynamic cycle to convert the heat to another form of energy.   
     
     
         26 . The method of  claim 25 , wherein the secondary cycle converts the heat extracted from the second portion of the working fluid to mechanical work. 
     
     
         27 . The method of  claim 26 , wherein the secondary thermodynamic cycle comprises a trilateral flash cycle. 
     
     
         28 . The method of  claim 26 , wherein the secondary thermodynamic cycle comprises a Rankine cycle. 
     
     
         29 . The method of  claim 25 , wherein the secondary thermodynamic cycle operates on an organic working fluid. 
     
     
         30 . The method of  claim 25 , wherein the secondary thermodynamic cycle operates on an inorganic working fluid. 
     
     
         31 . The method of  claim 1 , wherein the step of supplying thermal energy to heat the working fluid from a liquid or substantially liquid state to a supercritical fluid state comprises:
 injecting a quantity of the working fluid in the liquid or substantially liquid state into a chamber without substantially expanding the fluid; and   holding the chamber at fixed volume while introducing energy to the quantity of the working fluid to vaporize the quantity of the working fluid.   
     
     
         32 . The method of  claim 29 , wherein the introducing energy to the quantity of the working fluid comprises introducing optical energy to the quantity of the working fluid through at least one light transmissive region of the chamber. 
     
     
         33 . The method of  claim 31 , wherein the quantity of working fluid is explosively vaporized without a chemical reaction. 
     
     
         34 . The method of  claim 1 , further comprising
 prior to condensing the expanded first portion of the working fluid, transferring heat from the expanded first portion of the working fluid to the recombined the first and second portions of the working fluid to be recirculated in the cycle.   
     
     
         35 . The method of  claim 34 , comprising using a heat exchanger to transfer the heat from the expanded first portion of the working fluid to the recombined the first and second portions of the working fluid to be recirculated in the cycle. 
     
     
         36 . The method of  claim 35 , wherein the heat exchanger does not mix the expanded first portion of the working fluid with thee combined the first and second portions of the working fluid. 
     
     
         37 . The method of  claim 1 , further comprising separating the first portion of expanded working fluid from the second expander to form a third portion of the fluid diverted to a third expander and a forth portion of the working fluid diverted to bypass the third expander. 
     
     
         38 . The method of  claim 37 , further comprising in the second expander, substantially isentropically expanding the first portion of the working fluid to yield energy in the other energy form. 
     
     
         39 . An apparatus for converting thermal energy into another energy form comprising:
 a closed cycled heat engine comprising:
 a first pump configured to pressurize a working fluid; 
 a first heat exchanger configured to supply thermal energy for a heat source to heat the working fluid from a liquid or substantially liquid state to a supercritical fluid state; 
 a first expander configured to receive the heated working fluid in the supercritical state and substantially isentropically expand the working fluid to yield energy in the other energy form; 
 a bypass mechanism configured to separate the expanded working fluid to form a first portion of the fluid diverted to a second expander and a second portion of the working fluid diverted to bypass the second expander; 
 the second expander configured to substantially isentropically expand the first portion of the working fluid to yield energy in the other energy form; 
 a condenser configured to reject heat from the expanded first portion of the working fluid to condense the expanded first portion of the working fluid to a liquid or substantially liquid state; and 
 a combining mechanism configured to recombine the first and second portions of the working fluid and directed the combined working fluid to the first pump to be recirculated in the cycle. 
   
     
     
         40 . The apparatus of  claim 1 , wherein the closed cycle heat engine further comprises
 a recuperating heat exchanger configured to transfer heat from the expanded first portion of the working fluid to the condensed working fluid which has exited the condenser.   
     
     
         41 . The apparatus of  claim 1 , wherein the closed cycle heat engine further comprises
 a second bypass mechanism configured to separate the first portion of expanded working fluid from the second expander to form a third portion of the fluid diverted to a third expander and a forth portion of the working fluid diverted to bypass the third expander;   the third expander configured to substantially isentropically expand the first portion of the working fluid to yield energy in a form other than heat.   
     
     
         42 . The apparatus of claim, further comprising a second combining mechanism configured to combine the third and fourth portions of the expanded first portion of the working fluid