Supercritical carbon dioxide power cycle for waste heat recovery

• US 9,341,084 B2
• Filed: 10/10/2013
• Issued: 05/17/2016
• Est. Priority Date: 10/12/2012
• Status: Active Grant

• Current Assignee: Echogen Power Systems, LLC
• Original Assignee: Echogen Power Systems, LLC
• Inventors: Xie, Tao, Vermeersch, Michael, Held, Timothy
• Primary Examiner(s): Bogue, Jesse
• Assistant Examiner(s): STANEK, KELSEY L
• Application Number:
  US14/051,433
• Publication Number:
  US 20140102101A1
• Time in Patent Office: 950 Days
• Field of Search: 606/47, 606/71, 606/76, 606/77
• US Class Current: 1/1
• CPC Class Codes: F01K 25/103 Carbon dioxide F01K25/065 takes precedence
• CPC Class Codes: F01K 7/32 the engines using steam of critical or overcritical pressure

Abstract

Aspects of the invention disclosed herein generally provide heat engine systems and methods for recovering energy, such as by generating electricity from thermal energy. In one configuration, a heat engine system contains a working fluid (e.g., sc-CO₂) within a working fluid circuit, two heat exchangers configured to be thermally coupled to a heat source (e.g., waste heat), two expanders, two recuperators, two pumps, a condenser, and a plurality of valves configured to switch the system between single/dual-cycle modes. In another aspect, a method for recovering energy may include monitoring a temperature of the heat source, operating the heat engine system in the dual-cycle mode when the temperature is equal to or greater than a threshold value, and subsequently, operating the heat engine system in the single-cycle mode when the temperature is less than the threshold value.

Claims

1. A heat engine system, comprising:

a working fluid circuit comprising a working fluid, wherein the working fluid comprises carbon dioxide and at least a portion of the working fluid circuit contains the working fluid in a supercritical state;

a first heat exchanger fluidly coupled to and in thermal communication with the working fluid circuit, configured to be fluidly coupled to and in thermal communication with a heat source stream, and configured to transfer thermal energy from the heat source stream to the working fluid within the working fluid circuit;

a second heat exchanger fluidly coupled to and in thermal communication with the working fluid circuit, configured to be fluidly coupled to and in thermal communication with the heat source stream, and configured to transfer thermal energy from the heat source stream to the working fluid within the working fluid circuit;

a first expander fluidly coupled to the working fluid circuit and the first heat exchanger and disposed downstream of the first heat exchanger;

a second expander fluidly coupled to the working fluid circuit and the second heat exchanger and disposed downstream of the second heat exchanger;

a first recuperator fluidly coupled to the working fluid circuit, the first expander, and the first heat exchanger, the first recuperator disposed downstream of the first expander and upstream of the first heat exchanger;

a second recuperator fluidly coupled to the working fluid circuit, the second expander, and the second heat exchanger, the second recuperator disposed downstream of the second expander and upstream of the second heat exchanger;

a condenser fluidly coupled to the working fluid circuit and the first and second recuperators and disposed downstream of the first and second recuperators;

a first pump fluidly coupled to the working fluid circuit, the condenser, and the first and second recuperators, the first pump disposed downstream of the condenser and upstream of the first and second recuperators;

a second pump fluidly coupled to the working fluid circuit, the condenser, and the first recuperator, the second pump disposed downstream of the condenser and upstream of the first recuperator; and

a plurality of valves operatively coupled to the working fluid circuit and configured to switch the heat engine system between a dual-cycle mode, in which the first and second heat exchangers and the first and second pumps are active, and a single-cycle mode, in which the first heat exchanger and the first expander are active and at least the second heat exchanger and the second pump are inactive,

wherein the second pump is a turbopump, the second expander is a drive turbine, and the drive turbine is coupled to the turbopump and operable to drive the turbopump when the heat engine system is in the dual-cycle mode.

2. The heat engine system of claim 1, wherein the plurality of valves includes a valve disposed between the condenser and the second pump, wherein the valve is closed during the single-cycle mode of the heat engine system and the valve is open when the heat engine system is in the dual-cycle mode.

3. The heat engine system of claim 1, wherein the plurality of valves includes a valve disposed between the first pump and the first recuperator, the valve configured to prohibit flow of the working fluid from the first pump to the first recuperator during the dual-cycle mode of the heat engine system and to allow flow of the working fluid therebetween during the single-cycle mode of the heat engine system.

4. The heat engine system of claim 1, wherein the plurality of valves further comprises:

a first valve operatively coupled to the working fluid circuit, disposed downstream of the first pump, and disposed upstream of the second recuperator;

a second valve operatively coupled to the working fluid circuit, disposed downstream of the second recuperator, and disposed upstream of the condenser;

a third valve operatively coupled to the working fluid circuit, disposed downstream of the first pump, and disposed upstream of the first recuperator;

a fourth valve operatively coupled to the working fluid circuit, disposed downstream of the second pump, and disposed upstream of the first recuperator; and

a fifth valve operatively coupled to the working fluid circuit, disposed downstream of the condenser, and disposed upstream of the second pump.

5. The heat engine system of claim 4, wherein each of the first, second, fourth, and fifth valves is in an opened-position during the dual-cycle mode of the heat engine system and a closed-position during the single-cycle mode of the heat engine system, and the third valve is in an opened-position during the single-cycle mode of the heat engine system and a closed-position during the dual-cycle mode of the heat engine system.

6. The heat engine system of claim 4, further comprising a point on the working fluid circuit disposed downstream of the first and second recuperators and disposed upstream of the condenser, wherein the second valve is disposed upstream of the point and downstream of the second recuperator.

7. A heat engine system, comprising:

a working fluid circuit comprising a working fluid, wherein the working fluid comprises carbon dioxide and at least a portion of the working fluid circuit contains the working fluid in a supercritical state;

a first heat exchanger fluidly coupled to and in thermal communication with the working fluid circuit, configured to be fluidly coupled to and in thermal communication with a heat source stream, and configured to transfer thermal energy from the heat source stream to the working fluid within the working fluid circuit;

a second heat exchanger fluidly coupled to and in thermal communication with the working fluid circuit, configured to be fluidly coupled to and in thermal communication with the heat source stream, and configured to transfer thermal energy from the heat source stream to the working fluid within the working fluid circuit;

a first expander fluidly coupled to the working fluid circuit and the first heat exchanger and disposed downstream of the first heat exchanger;

a second expander fluidly coupled to the working fluid circuit and the second heat exchanger and disposed downstream of the second heat exchanger;

a first recuperator fluidly coupled to the working fluid circuit, the first expander, and the first heat exchanger, the first recuperator disposed downstream of the first expander and upstream of the first heat exchanger;

a second recuperator fluidly coupled to the working fluid circuit, the second expander, and the second heat exchanger, the second recuperator disposed downstream of the second expander and upstream of the second heat exchanger;

a condenser fluidly coupled to the working fluid circuit and the first and second recuperators and disposed downstream of the first and second recuperators;

a first pump fluidly coupled to the working fluid circuit, the condenser, and the first and second recuperators, the first pump disposed downstream of the condenser and upstream of the first and second recuperators;

a second pump fluidly coupled to the working fluid circuit, the condenser, and the first recuperator, the second pump disposed downstream of the condenser and upstream of the first recuperator; and

a plurality of valves operatively coupled to the working fluid circuit and configured to switch the heat engine system between a single-cycle mode and a dual-cycle mode, wherein the plurality of valves further comprises;

a first valve operatively coupled to the working fluid circuit, disposed downstream of the first pump, and disposed upstream of the second recuperator;

a second valve operatively coupled to the working fluid circuit, disposed downstream of the second recuperator, and disposed upstream of the condenser;

a third valve operatively coupled to the working fluid circuit, disposed downstream of the first pump, and disposed upstream of the first recuperator;

a fourth valve operatively coupled to the working fluid circuit, disposed downstream of the second pump, and disposed upstream of the first recuperator; and

a fifth valve operatively coupled to the working fluid circuit, disposed downstream of the condenser, and disposed upstream of the second pump,

wherein each of the first, second, fourth, and fifth valves is in an opened-position during the dual-cycle mode of the heat engine system and a closed-position during the single-cycle mode of the heat engine system, and the third valve is in an opened-position during the single-cycle mode of the heat engine system and a closed-position during the dual-cycle mode of the heat engine system.

8. The heat engine system of claim 7, further comprising a point on the working fluid circuit disposed downstream of the first and second recuperators and disposed upstream of the condenser, wherein the second valve is disposed upstream of the point and downstream of the second recuperator.

9. The heat engine system of claim 7, wherein the second pump is a turbopump, the second expander is a drive turbine, and the drive turbine is coupled to the turbopump and operable to drive the turbopump during the dual-cycle mode of the heat engine system.

10. A method for recovering energy from a heat source, comprising:

operating a heat engine system in a dual-cycle mode, comprising;

heating a first mass flow of a working fluid in a first heat exchanger fluidly coupled to and in thermal communication with a working fluid circuit and a heat source stream, wherein the first heat exchanger is configured to transfer thermal energy from the heat source stream to the first mass flow of the working fluid within the working fluid circuit, the working fluid comprises carbon dioxide, and at least a portion of the working fluid circuit contains the working fluid in a supercritical state;

expanding the first mass flow in a first expander fluidly coupled to the first heat exchanger via the working fluid circuit;

heating a second mass flow of the working fluid in a second heat exchanger fluidly coupled to and in thermal communication with the working fluid circuit and the heat source stream, wherein the second heat exchanger is configured to transfer thermal energy from the heat source stream to the second mass flow of the working fluid within the working fluid circuit;

expanding the second mass flow in a second expander fluidly coupled to the second heat exchanger via the working fluid circuit;

at least partially condensing the first and second mass flows in one or more condensers fluidly coupled to the working fluid circuit;

pressurizing the first mass flow in a first pump fluidly coupled to the condenser via the working fluid circuit;

pressurizing the second mass flow in a second pump fluidly coupled to the condenser via the working fluid circuit;

transferring heat via a first recuperator from the first mass flow downstream of the first expander and upstream of the condenser to the first mass flow downstream of the second pump and upstream of the first heat exchanger; and

transferring heat via a second recuperator from the second mass flow downstream of the second expander and upstream of the condenser to the second mass flow downstream of the first pump and upstream of the second heat exchanger; and

switching the heat engine system from the dual-cycle mode to a single-cycle mode, comprising;

de-activating the second heat exchanger, the second expander, and the second pump;

directing the working fluid from the condenser to the first pump;

directing the working fluid from the first pump to the first heat exchanger; and

de-activating the second recuperator and directing the working fluid from the second pump to the first recuperator.

11. The method of claim 10, further comprising:

monitoring a temperature of the heat source stream;

operating the heat engine system in the dual-cycle mode when the temperature is equal to or greater than a threshold value; and

operating the heat engine system in the single-cycle mode when the temperature is less than the threshold value.

12. The method of claim 11, further comprising automatically switching from operating the heat engine system in the dual-cycle mode to operating the heat engine system in the single-cycle mode with a programmable controller once the temperature is less than the threshold value, wherein the threshold value of the temperature is within a range from 300°

C. to 400°

C.

13. The method of claim 11, further comprising manually switching from operating the heat engine system in the dual-cycle mode to operating the heat engine system in the single-cycle mode once the temperature is less than the threshold value, wherein the threshold value of the temperature is within a range from 300°

C. to 400°

C.