REFRIGERANT POWERED VALVE FOR A GEOTHERMAL POWER PLANT
A vapor expansion system includes a normally closed pneumatic valve between the evaporator and the turbine inlet, with the valve being selectively actuated by the flow of refrigerant vapor from the evaporator so as to enable opening the valve only during periods in which sufficient pressure has built up in the evaporator to properly operate the turbine. A bypass line has a normally open pneumatic valve with an actuator that is similarly caused to operate by pressurized refrigerant vapor from the evaporator. Both actuators are vented to the condenser such that the refrigerant vapor vented from the actuator does not escape to ambient.
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This disclosure relates generally to geothermal power plants and, more particularly, to a method and apparatus for operating the turbine inlet and bypass valves thereof.
BACKGROUND OF THE DISCLOSUREIn order to effectively use geothermal energy such as that naturally occurring at various locations in the earth, a closed loop vapor expansion system, including an evaporator/boiler, a turbine, a condenser and a pump, are employed, with the heat from the geothermal source being applied to the evaporator/boiler to heat the working fluid prior to its flowing to the turbine for the purpose of generating electrical power. Most commonly, a refrigerant is used as the working fluid, and the system is known as an Organic Rankine Cycle System. One such system is shown and described in U.S. Pat. No. 7,174,716, assigned to the predecessor of the assignee of the present disclosure.
During periods in which the evaporator/boiler is either coming online or going off-line, such that the temperature of the working fluid is insufficient for driving the turbine, it is necessary to bypass the turbine and allow the working fluid to proceed directly from the evaporator to the condenser so that the closed loop circulation of the working fluid otherwise continues. Heretofore, a pneumatic power valve has been used for that purpose, with an outside pressurized gas source (normally either bottled nitrogen or compressed air) providing the power to operate the valves and with the gas then being vented to atmosphere. Adding a compressor or a bottled gas system to the site has caused problems in the past, primarily in connection with maintenance, reliability and cost. Further, with such a supplementary pressurized source, it was possible to operate the valves at times when the conditions were not favorable for proper turbine operation thereby possibly resulting in damage to the turbine rotor from entrained liquid. There are presently no electrical actuators available that are capable of meeting the requirements for such a function.
DISCLOSUREIn accordance with one aspect of the disclosure, provision is made to use the energy of the working fluid in the system to power the turbine inlet/bypass valves. This is accomplished by selectively connecting the valves to the evaporator/boiler by way of a regulator such that pressurized refrigerant is provided to operate the valves in a regulated manner.
In accordance with another aspect of the disclosure a normally open valve is used as a bypass valve and a normally closed valve is used as a turbine inlet valve. Thus the valves are not operable to direct working fluid to the turbine unless sufficient pressure exists in the evaporator to operate the valves.
By another aspect of the disclosure, the low pressure sides of the valve actuators are vented to the condenser such that the refrigerant remains in the closed loop system rather than entering the atmosphere.
While the present disclosure has been particularly shown and described with reference to a preferred mode as illustrated in the drawings, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the disclosure as defined by the claims.
Shown in
The heat source 18 for the evaporator 16 may be of any suitable type such as a naturally occurring geothermal heat source, or a generated heat source such as the exhaust of a gas turbine engine. Similarly, a cooling source 19, such as a cooling tower or a chiller is provided for the purpose of providing cooling water to the condenser 13.
A turbine inlet valve 21 is provided in a primary flow path line 15 between the evaporator 16 and turbine inlet 22. The turbine inlet valve 21 is a normally closed pneumatic valve with an actuator 23 that is shown in
Fluidly connected to the primary flow path line 15 is a bypass line 28, leading to a normally open pneumatic valve 29 and then to line 31 leading to the condenser 13. The pneumatic valve 29 has a rack-and-pinion actuator 32 similar to the actuator 23 described hereinabove. The actuator 32 is pressurized by refrigerant from the regulator 26 flowing along line 33 to the solenoid valve S2, which is controlled by the control C. Thus, the pneumatic valve 29 is normally open unless it is closed by way of the actuator 32 when receiving pressurized gas from the regulator 26 when the solenoid valve S2 is opened.
The manner in which the valves 21 and 29 are operated by way of their respective actuators will now be described. During periods of start up and shut-down, when the pressure in the evaporator 16 is insufficient to drive the turbine 12, the pressure at the regulator 26 is at a reduced pressure, the solenoid valves S1 and S2 are closed, and the actuators 23 and 32 are non-operable. Thus, the normally closed pneumatic valve 21 is closed, and the normally open pneumatic valve 29 is open such that any vapor from the evaporator then flows along line 28, through the normally open pneumatic valve 29, through the line 31 to the condenser 13. When the pressure in the evaporator 16 is sufficient to operate the turbine, the pressure at the regulator 26 will be sufficient to operate the actuators 23 and 32, and the solenoid valves S1 and S2 are opened by the control C. The actuator 32 will then be caused to operate to close the pneumatic valve 29, and the actuator 23 will be caused to operate to open the pneumatic valve 21 such that the vapor from the evaporator 16 then flows through the pneumatic valve 21 and to the turbine inlet 22.
Referring now to
Shown in
Although the present disclosure has been particularly shown and described with reference to a preferred embodiment as illustrated by the drawings, it will be understood by one skilled in the art that various changes in detail made be made thereto without departing from the scope of the disclosure as defined by the claims.
Claims
1. A vapor expansion system of the type having in serial flow relationship a turbine, a condenser, a pump and an evaporator, comprising:
- a pneumatically actuated valve with an actuator moveable to a position for fluidly connecting the evaporator to a turbine inlet by way of said valve;
- a conduit which fluidly interconnects said evaporator to said actuator such that pressurized refrigerant from said evaporator is selectively caused to move said actuator to open said pneumatically actuated valve.
2. A vapor expansion system as set forth in claim 1 wherein said pneumatically actuated valve is a normally closed valve.
3. A vapor expansion system as set forth in claim 1 wherein said actuator includes a vented section and said vented section is fluidly connected to said condenser.
4. A vapor expansion system as set forth in claim 1 and including a pressure regulator between said evaporator and said actuator so as to provide pressurized refrigerant to said actuator at a predetermined pressure level.
5. A vapor expansion system as set forth in claim 1 and including a solenoid valve fluidly connected between said evaporator and said actuator.
6. A vapor expansion system as set forth in claim 5 wherein solenoid valve is a three way valve with a vent port being fluidly connected to the condenser.
7. A vapor expansion system as set forth in claim 1 wherein said actuator includes a spring for biasing a sliding piston in position.
8. A vapor expansion system as set forth in claim 1 wherein said actuator is of the rack-and-pinion type.
9. A vapor expansion system as set forth in claim 1 and including a bypass line for conducting the flow of refrigerant vapor around said turbine and to said condenser said bypass line having a pneumatic valve disposed therein.
10. A vapor expansion system as set forth in claim 9 wherein said pneumatic valve is a normally open valve with an actuator fluidly connected to said evaporator.
11. A method of controlling a vapor expansion system of the type having in serial flow relationship a turbine, a condenser, a pump and an evaporator, comprising the steps of:
- providing a pneumatically actuated valve with an actuator moveable to a position for fluidly connecting the evaporator to a turbine inlet by way of said valve;
- fluidly interconnecting said evaporator to said actuator such that pressurized refrigerant from said evaporator is selectively caused to move said actuator to open said pneumatically actuated valve.
12. A method as set forth in claim 11 wherein said pneumatically actuated valve is a normally closed valve.
13. A method as set forth in claim 11 wherein said actuator includes a vented section and including the step of connecting said vented section to said condenser.
14. A method as set forth in claim 11 and including the steps of providing a pressure regulator between said evaporator and said actuator and providing pressurized refrigerant to said actuator at a predetermined pressure level.
15. A method as set forth in claim 11 and including the step of connecting a solenoid valve fluidly between said evaporator and said actuator.
16. A method as set forth in claim 15 wherein solenoid valve is a three way valve with a vent port and including the step of fluidly connecting said vent to the condenser.
17. A method as set forth in claim 11 wherein said actuator includes a spring for biasing a sliding piston in position.
18. A vapor expansion system as set forth in claim 11 wherein said actuator is of the rack-and-pinion type.
19. A method as set forth in claim 1 and including the step of providing a bypass line for conducting the flow of refrigerant vapor around said turbine and to said condenser by way of a pneumatic valve.
20. A method as set forth in claim 19 wherein said pneumatic valve is a normally open valve and including the step of fluidly connecting said actuator to said evaporator.
Type: Application
Filed: Sep 10, 2008
Publication Date: Jul 7, 2011
Applicant:
Inventors: Peter S. Matteson (South Windsor, CT), Michael D. Arner (Manchester, CT)
Application Number: 13/063,024
International Classification: F25B 1/00 (20060101); F25B 41/04 (20060101);