THERMAL ENERGY CONVERSION METHOD

• US 20110061387A1
• Filed: 12/04/2009
• Published: 03/17/2011
• Est. Priority Date: 09/17/2009
• Status: Active Grant

• Current Assignee: Echogen Power Systems, LLC
• Original Assignee: Echogen Power Systems, LLC
• Inventors: Miller, Jason D., Held, Timothy J., Hostler, Stephen, Hume, Brian F.
• Granted Patent: US 8,794,002 B2
• Time in Patent Office: Days
• US Class Current: 60/651
• CPC Class Codes: F01K 25/103 Carbon dioxide F01K25/065 takes precedence
• CPC Class Codes: F01K 3/185 using waste heat from outside the plant F02G5/00 takes precedence
• CPC Class Codes: F01K 3/186 using electric heat
• CPC Class Codes: F01K 7/165 Controlling means specially adapted therefor
• CPC Class Codes: F24H 2240/12 with thermodynamic cycle for converting thermal energy to mechanical power to produce electrical energy
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A waste heat recovery system, method and device executes a thermodynamic cycle using a working fluid in a working fluid circuit which has a high pressure side and a low pressure side. Components of the system in the working fluid circuit include a waste heat exchanger in thermal communication with a waste heat source also connected to the working fluid circuit, whereby thermal energy is transferred from the waste heat source to the working fluid in the working fluid circuit, an expander located between the high pressure side and the low pressure side of the working fluid circuit, the expander operative to convert a pressure/enthalpy drop in the working fluid to mechanical energy, a recuperator in the working fluid circuit operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit, a cooler in thermal communication with the low pressure side of the working fluid circuit operative to control temperature of the working fluid in the low side of the working fluid circuit, a pump in the working fluid circuit and connected to the low pressure side and to the high pressure side of the working fluid circuit and operative to move the working fluid through the working fluid circuit, and a mass management system connected to the working fluid circuit, the mass management system, method and device having a working fluid vessel connected to the low pressure side of the working fluid circuit and configured to passively control an amount of working fluid mass in the working fluid circuit.

Claims

1. A method of converting thermal energy into mechanical energy by use of a working fluid in a closed loop thermodynamic cycle contained in a working fluid circuit having components interconnected by conduit, the components including at least one heat exchanger operative to transfer thermal energy to the working fluid, at least one expansion device operative to convert thermal energy from the working fluid to mechanical energy, at least one pump operative to transfer working fluid through the working fluid circuit, the working fluid circuit having a high pressure side and a low pressure side, and a mass management system comprising a mass management vessel connected by conduit to the low pressure side of the working fluid circuit, the method comprising the steps of:

placing a thermal energy source in thermal communication with a heat exchanger component;

pumping the working fluid through the working fluid circuit by operation of the pump to supply working fluid in a supercritical or subcritical state to the expander;

directing the working fluid away from the expander in a sub-critical state through the working fluid circuit and to the pump;

controlling flow of the working fluid in a super-critical state from the high pressure side of the working fluid circuit to the mass management vessel;

controlling an amount of working fluid in a sub-critical or super-critical state from the mass management vessel to the low pressure side of the working fluid circuit and to the pump.

2. The method of claim 1 further comprising the step of providing carbon dioxide as the working fluid.

3. The method of claim 1 wherein the working fluid is carbon dioxide in a supercritical state in the high pressure side of the working fluid circuit.

4. The method of claim 1 wherein the mass management vessel of the mass management system is connected by conduit also to the high pressure side of the working fluid circuit.

5. The method of claim 1 further comprising the step of providing ammonia as the working fluid.

6. The method of claim 1 wherein the working fluid is ammonia in a supercritical state in the high pressure side of the working fluid circuit.

7. The method of claim 4 further comprising the step of providing an amount of working fluid mass in the working fluid circuit by controlling an amount of working fluid in a supercritical state from the high pressure side of the working fluid circuit to the mass management vessel, and providing an amount of working fluid in a sub-critical or super-critical state from the mass management vessel to the low pressure side of the working fluid circuit and to the pump.

8. The method of claim 7 further comprising the steps of detecting the temperature of the working fluid in the working fluid circuit, and controlling the temperature of the working fluid between the working fluid circuit and the working fluid vessel according to detected amounts of working fluid mass in the working fluid circuit.

9. The method of claim 7 further comprising the steps of detecting the pressure of the working fluid in the working fluid circuit, and controlling the pressure of the working fluid between the working fluid circuit and the working fluid vessel according to detected amounts of working fluid mass in the working fluid circuit.

10. The method of claim 1 further comprising the step of controlling a rate of operation of the expander.

11. The method of claim 1 further comprising the step of controlling the thermodynamic cycle in the working fluid circuit to optimize conversion of thermal energy into mechanical energy under ambient conditions.

12. The method of claim 1 further comprising the step of using a portion of the working fluid from the high pressure side of the working fluid circuit as coolant for the expander.

13. The method of claim 12 further comprising the step of using a portion of the working fluid from the high pressure side of the working fluid circuit is used as coolant for a coupling which is coupled to the expander.

14. The method of claim 11 further comprising the step of using a portion of the working fluid from the high pressure side of the working fluid circuit directed through the working fluid circuit to the expander as coolant for the expander and a coupling between the expander and an alternator.

15. The method of claim 12 further comprising the step of substantially matching a pressure value of a portion of the working fluid from the high pressure side of the working fluid circuit for cooling the expander to a pressure value of the working fluid from the high pressure side of the working fluid circuit at an inlet to the expander.

16. The waste heat recovery system of claim 1 wherein the pump is a positive displacement pump operative to increase pressure of the working fluid in the high pressure side of the working fluid circuit.

17. The method of claim 1 further comprising the step of controlling a rate of operation of the pump to control a mass flow rate of working fluid in the high pressure side of the working fluid circuit.

18. The method of claim 1 further comprising the step of using a variable frequency drive operative to control a speed of operation of the pump.

19. The method of claim 1 further comprising the step of providing a second expansion device in the working fluid circuit and coupled to the pump, the second expansion device operated by expansion of the working fluid in the second expansion device.

20. The method of claim 1 further comprising the step of coupling an alternator to the expander, the alternator operatively connected to electrical power electronics, and a providing a cooling system operative to control a temperature of the alternator, and controlling the cooling system to control an operating temperature of the electrical power electronics.

21. The method of claim 1 further comprising the step of connecting the mass management system to the low pressure side of the working fluid circuit proximate to an inlet to the pump.

22. The method of claim 1 further comprising the step of providing working fluid to the working fluid circuit through a fill port to the working fluid vessel.

23. The method of claim 1 further comprising the step of controlling the temperature of the working fluid in the working fluid vessel by operation of a working fluid vessel thermal control system.

24. The method of claim 1 further comprising the step of controlling a pressure of the working fluid pressure in the mass management system to be substantially equal to a pressure of the working fluid in the low pressure side of the working fluid circuit.

25. The method of claim 1 further comprising the step of controlling the components and the mass management system so that the working fluid vessel contains working fluid in different phases.

26. The method of claim 1 further comprising the step of controlling flow of the working fluid into and out of the working fluid vessel by operation of valves in conduit between the working fluid vessel and the working fluid circuit.

27. The method of claim 1 further comprising the step of controlling flow of the working fluid in and out of the working fluid vessel by controlling a temperature of the working fluid vessel.

28. The method of claim 26 wherein the operation of the valves is automated.

29. The method of claim 1 further comprising the step of providing a working fluid to the working fluid circuit which is a blend of working fluids selected from the group of:

carbon dioxide, ammonia, nitrogen, argon, propane, natural gas.

30. The method of claim 1 further comprising the step of providing a skid on which is located the components and the working fluid circuit, and connections to the working fluid circuit and to the expander.

31. The method of claim 1 further comprising the step of controlling the thermodynamic cycle by controlled operation of the components to generate electrical power from an alternator coupled to the expander in a range of approximately 50 kW to 10,000 kW or greater.

32. The method of claim 1 further comprising the step of controlling thermodynamic cycle in the working fluid circuit by controlling a rate of operation of the pump.

33. The method of claim 1 further comprising the step of controlling an output of an alternator coupled to the expander by control of power electronics operatively connected to the alternator.

34. A method of converting thermal energy into mechanical energy comprising the steps of:

providing a working fluid in a working fluid circuit having components interconnected by conduit through which the working fluid flows, the components comprising;

a pump operative to transfer the working fluid through the working fluid circuit;

a heat exchanger for transferring thermal energy to the working fluid;

an expansion device operative to convert energy from the working fluid into mechanical energy;

a mass control tank connected by the conduit to a low pressure side of the working fluid circuit;

controlling flow of the working fluid through the working fluid circuit by operation of the pump;

controlling a rate of operation of the expansion device, and

controlling an amount of mass of the working fluid in the working fluid circuit by controlling the mass of the working fluid in the mass control tank.

35. The method of claim 34 further comprising the step of connecting the mass control tank to a high pressure side of the working fluid circuit.

36. The method of claim 34 further comprising the step of providing an amount of working fluid mass in the working fluid circuit by controlling flow of an amount of the working fluid in a supercritical state from a high pressure side of the working fluid circuit to the mass control tank, and controlling flow of an amount of the working fluid in a sub-critical state or supercritical state form the mass control tank to a low pressure side of the working fluid circuit.

37. The method of claim 34 further comprising the steps of detecting a temperature of the working fluid in the working fluid circuit, and controlling the temperature of the working fluid between the working fluid circuit and the mass control tank according to detected amounts of working fluid mass in the working fluid circuit.

38. The method of claim 34 further comprising the steps of detecting the pressure of the working fluid in the working fluid circuit, and controlling the pressure of the working fluid between the working fluid circuit and the mass control tank according to detected amounts of working fluid mass in the working fluid circuit.

39. The method of claim 34 further comprising the step of using a portion of the working fluid from working fluid circuit as coolant for the expansion device.

40. The method of claim 34 further comprising the step of substantially matching a pressure value of a portion of the working fluid from a high pressure side of the working fluid circuit for cooling the expansion device to a pressure value of the working fluid at an inlet to the expansion device.

41. The method of claim 34 further comprising the step of controlling a rate of operation of the pump to control a mass flow rate of working fluid in a high pressure side of the working fluid circuit.

42. The method of claim 34 further comprising the step of providing a second expansion device in the working fluid circuit and coupled to the pump, the second expansion device operated by expansion of the working fluid.

43. The method of claim 34 further comprising the step of coupling an alternator to the expander, the alternator operatively connected to electrical power electronics, and a providing a cooling system operative to control a temperature of the alternator, and controlling the cooling system to control an operating temperature of the electrical power electronics.

44. The method of claim 34 further comprising the step of connecting the mass control tank by conduit to a low pressure side of the working fluid circuit at a location in the working fluid circuit prior to an inlet of the pump.

45. The method of claim 34 further comprising the step of providing working fluid to the working fluid circuit through a fill port to the mass control tank.

46. The method of claim 34 further comprising the step of controlling a temperature of the working fluid in the mass control tank by operation of a mass control tank thermal control system.

47. The method of claim 34 further comprising the step of controlling a pressure of the working fluid pressure in the mass management system to be substantially equal to a pressure of the working fluid in a low pressure side of the working fluid circuit.

48. The method of claim 34 further comprising the step of controlling the components and the mass management system so that the working fluid vessel contains working fluid in different phases.

49. The method of claim 34 further comprising the step of controlling flow of the working fluid into and out of the mass control tank by operation of valves in conduit between the mass control tank and the working fluid circuit.

50. The method of claim 34 further comprising the step of controlling flow of the working fluid in and out of the mass control tank by controlling a temperature of the mass control tank.

51. The method of claim 34 further comprising the step of controlling flow of the working fluid in and out of the mass control tank by controlling a temperature of the working fluid in the mass control tank.

52. The method of claim 34 further comprising the step of controlling flow of the working fluid in and out of the mass control tank by controlling a pressure of the mass control tank.

53. The method of claim 34 further comprising the step of providing a working fluid to the working fluid circuit which is a blend of working fluids selected from the group of:

carbon dioxide, ammonia, nitrogen, argon, propane, natural gas.

54. The method of claim 34 further comprising the step of controlling the thermodynamic cycle by controlled operation of the components to generate electrical power from an alternator coupled to the expander in a range of approximately 50 kW to 10,000 kW or greater.

55. The method of claim 34 further comprising the steps of controlling the pressure and density of the working fluid in the working fluid circuit with reference to an ambient temperature.