Control System For A Heat Engine System Utilizing Supercritical Working Fluid

Abstract

A heat engine system and a method for generating electrical energy from the heat engine system are provided. The method includes circulating via a turbo pump a working fluid within a working fluid circuit of the heat engine system. The method also includes transferring thermal energy from a heat source stream to the working fluid by at least a primary heat exchanger, feeding the working fluid into a power turbine and converting the thermal energy from the working fluid to mechanical energy, and converting the mechanical energy into electrical energy by a generator coupled to the power turbine. At least one valve operatively coupled to a control system is modulated in order to synchronize the generator with an electrical grid. A generator breaker is closed such that the generator and electrical grid are electrically coupled and the electrical energy is supplied to the electrical grid.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. Prov. Appl. No. 61/779,275, filed on Mar. 13, 2013, the contents of which are hereby incorporated by reference to the extent not inconsistent with the present disclosure.

BACKGROUND

[0002] Waste heat is often created as a byproduct of industrial processes where flowing streams of high-temperature liquids, gases, or fluids must be exhausted into the environment or removed in some way in an effort to maintain the operating temperatures of the industrial process equipment. Some industrial processes utilize heat exchanger devices to capture and recycle waste heat back into the process via other process streams. However, the capturing and recycling of waste heat is generally infeasible by industrial processes that utilize high temperatures or have insufficient mass flow or other unfavorable conditions.

[0003] Waste heat can be converted into useful energy by a variety of turbine generator or heat engine systems that employ thermodynamic methods, such as Rankine cycles. Rankine cycles and similar thermodynamic methods are typically steam-based processes that recover and utilize waste heat to generate steam for driving a turbine, turbo, or other expander connected to an electric generator.

[0004] An organic Rankine cycle utilizes an organic solvent as the working fluid instead of water, as used during a traditional Rankine cycle. The organic solvent has a lower boiling-point than water. Exemplary lower boiling-point working fluids include hydrocarbons, such as light hydrocarbons (e.g., propane or butane) and halogenated hydrocarbons, such as hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) (e.g., R245fa). More recently, in view of issues such as thermal instability, toxicity, flammability, and production cost of the lower boiling-point working fluids, some thermodynamic cycles have been modified to circulate non-hydrocarbon working fluids, such as ammonia.

[0005] The control of a power turbine coupled to an energy-producing component, such as a generator, is quite relevant to the operation and efficiency of the Rankine cycle process and to the generation of electrical energy. Generally, control of the power turbine is provided to synchronize the generator with a corresponding electrical grid and to provide electrical energy to the grid after the synchronization of the generator with the electrical grid. In many Rankine cycle processes, a pump or compressor may be used to initiate the cycle and build high system pressure before feeding the working fluid to a waste heat exchanger in fluid communication with the power turbine. In certain scenarios, the power turbine may experience thermal shock from the working fluid being heated in the waste heat exchanger and fed to the power turbine. Thus, the working fluid must typically be attemperated to reduce the likelihood of thermal shock to the power turbine. Generally, conventional methods are time-consuming and inefficient in stabilizing the system and reducing the likelihood of thermal shock of the power turbine in order to synchronize the generator to the grid and provide power to the grid.

[0006] Therefore, there is a need for a heat engine system and a method for generating electrical energy, whereby flow rates, temperatures, and pressures within a working fluid system are precisely and accurately controlled within acceptable limits in order to maximize the efficiency of the heat engine system to generate electricity.

SUMMARY

[0007] Embodiments of the disclosure may provide a method for synchronizing a generator of a heat engine system with an electrical grid. The method may include circulating, via a turbo pump, a working fluid within a working fluid circuit of the heat engine system. The working fluid circuit may have a high pressure side and a low pressure side, and at least a portion of the working fluid may be in a supercritical state. The method may also include transferring thermal energy from a heat source stream to the working fluid by at least a primary heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit. The method may further include feeding the working fluid into a power turbine and converting the thermal energy from the working fluid to mechanical energy of the power turbine, and converting the mechanical energy into electrical energy by a power generator coupled to the power turbine. The method may also include comparing at least one electrical energy parameter of the electrical energy converted by the power generator with at least one grid parameter of the electrical grid configured to be electrically coupled to the power generator. The method may further include modulating at least one valve of a plurality of valves operatively coupled to a process control system to change a flow rate of the working fluid fed into the power turbine, such that the at least one electrical energy parameter of the electrical energy converted by the power generator is substantially similar to the at least one grid parameter of the electrical grid, thereby synchronizing the power generator with the electrical grid.

[0008] Embodiments of the disclosure may further provide a method for synchronizing a generator of a heat engine system with an electrical grid. The method may include circulating, via a turbo pump, a working fluid within a working fluid circuit of the heat engine system. The working fluid circuit may have a high pressure side and a low pressure side, and at least a portion of the working fluid may be in a supercritical state. The method may also include transferring thermal energy from a heat source stream to the working fluid by at least a primary heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit. The method may further include feeding the working fluid into a power turbine and converting the thermal energy from the working fluid to mechanical energy of the power turbine, and converting the mechanical energy into electrical energy by a power generator coupled to the power turbine. The method may also include comparing a plurality of electrical energy parameters of the electrical energy converted by the power generator with a plurality of grid parameters of the electrical grid configured to be electrically coupled to the generator. The method may further include modulating at least one valve of a power turbine trim valve, a power turbine throttle valve, a power turbine bypass valve, a turbo pump bypass valve, and a drive turbine throttle valve, each operatively coupled to a process control system to change a flow rate of the working fluid fed into the power turbine, such that the plurality of electrical energy parameters of the electrical energy converted by the power generator is substantially similar to the plurality of grid parameters of the electrical grid, thereby synchronizing the power generator with the electrical grid. The method may also include closing the generator breaker, such that the power generator and electrical grid are electrically coupled, and the electrical energy is supplied to the electrical grid.

[0009] Embodiments of the disclosure may further provide a method for supplying electrical energy to an electrical grid from a heat engine system. The method may include starting a drive turbine from a working fluid including carbon dioxide being circulated via a start pump within a working fluid circuit of the heat engine system. The method may also include circulating, via a turbo pump coupled to the drive turbine, the working fluid within the working fluid circuit of the heat engine system. The working fluid circuit may have a high pressure side and a low pressure side, and at least a portion of the working fluid may be in a supercritical state. The method may also include transferring thermal energy from a heat source stream to the working fluid by at least a primary heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit. The method may further include feeding the working fluid into a power turbine and converting the thermal energy from the working fluid to mechanical energy of the power turbine, and converting the mechanical energy into electrical energy by a power generator coupled to the power turbine.

[0010] The method may also include comparing a plurality of electrical energy parameters of the electrical energy converted by the power generator with a plurality of grid parameters of the electrical grid configured to be electrically coupled to the generator. The plurality of electrical energy parameters may include voltage, phase sequence, phase angle, waveform, and frequency, and the plurality of grid parameters may include voltage, phase sequence, phase angle, waveform, and frequency. The method may further include modulating a power turbine trim valve, a power turbine throttle valve, a power turbine bypass valve, a turbo pump bypass valve, and a drive turbine throttle valve, each operatively coupled to a process control system to change a flow rate of the working fluid fed into the power turbine, such that the plurality of electrical energy parameters of the electrical energy converted by the power generator is substantially similar to the plurality of grid parameters of the electrical grid, thereby synchronizing the power generator with the electrical grid. The method may also include closing the generator breaker, such that the power generator and electrical grid are electrically coupled, and the electrical energy is supplied to the electrical grid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure is best understood from the following detailed description when read with the accompanying Figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0012] FIG. 1 illustrates an exemplary heat engine system, according to one or more embodiments disclosed herein.

[0013] FIG. 2 depicts a schematic diagram of a control system configured to operate a power turbine throttle valve, according to one or more embodiments disclosed herein.

[0014] FIG. 3 depicts a schematic diagram of a control system configured to operate a power turbine trim valve, according to one or more embodiments disclosed herein.

[0015] FIG. 4 depicts a schematic diagram of a control system configured to operate a power turbine bypass valve, according to one or more embodiments disclosed herein.

[0016] FIG. 5 depicts a schematic diagram of a control system configured to operate a drive turbine throttle valve, according to one or more embodiments disclosed herein.

[0017] FIG. 6 depicts a schematic diagram of a control system configured to operate a turbo pump bypass valve, according to one or more embodiments disclosed herein.

[0018] FIG. 7 is a flow chart depicting a method for synchronizing a generator of a heat engine system with an electrical grid, according to one or more embodiments disclosed herein.

[0019] Like numerals shown in the Figures and discussed herein represent like components throughout the multiple embodiments disclosed herein.

DETAILED DESCRIPTION

[0020] It is to be understood that the present disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described herein to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the present disclosure may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments described herein may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment without departing from the scope of the disclosure.

[0021] Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Further, in the following discussion and in the claims, the terms "including", "containing", and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to". All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B", unless otherwise expressly specified herein.

[0022] FIG. 1 depicts an exemplary heat engine system 200 that contains a process system 210 and a power generation system 220 fluidly coupled to and in thermal communication with a waste heat system 100 via a working fluid circuit 202, as described in one or more embodiments herein. The heat engine system 200 may be referred to as a thermal engine system, an electrical generation system, a waste heat or other heat recovery system, and/or a thermal to electrical energy system, as described in one or more embodiments herein. The heat engine system 200 may be generally configured to encompass one or more elements of a Rankine cycle, a derivative of a Rankine cycle, or another thermodynamic cycle for generating electrical energy from a wide range of thermal sources.

[0023] In one or more embodiments described herein, FIG. 1 depicts the working fluid circuit 202 containing the working fluid and having a high pressure side and a low pressure side, wherein at least a portion of the working fluid contains carbon dioxide in a supercritical state. In many examples, the working fluid contains carbon dioxide, and at least a portion of the carbon dioxide is in a supercritical state. FIG. 1 depicts the high and low pressure sides of the working fluid circuit 202 of the heat engine system 200 by representing the high pressure side with "______" and the low pressure side with "-.-.-."--as described in one or more embodiments. The heat engine system 200 also may have a heat exchanger 120 fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202, configured to be fluidly coupled to and in thermal communication with the heat source stream 110, and configured to transfer thermal energy from the heat source stream 110 to the working fluid within the working fluid circuit 202. The heat exchanger 120 may be fluidly coupled to the working fluid circuit 202 upstream of a power turbine 228 and downstream of a recuperator 216.

[0024] The heat engine system 200 may further contain the power turbine 228 disposed between the high pressure side and the low pressure side of the working fluid circuit 202, fluidly coupled to and in thermal communication with the working fluid circuit, and configured to convert thermal energy to mechanical energy by a pressure drop in the working fluid flowing between the high and the low pressure sides of the working fluid circuit 202. The heat engine system 200 may also contain a power generator 240 coupled to the power turbine 228 and configured to convert the mechanical energy into electrical energy. A power outlet 242 may be electrically coupled to the power generator 240 and configured to transfer the electrical energy from the power generator 240 to an electrical grid 244. The electrical grid 244 may be electrically coupled to the power generator 240 via a generator breaker 243. The generator breaker 243 may be configured to be in an open position or a closed position, such that in the open position, the heat engine system 200 may be electrically decoupled from the electrical grid 244, and in a closed position, the heat engine system 200 may be electrically coupled to the electrical grid 244, thereby allowing for electrical energy to be transmitted to the electrical grid 244 from the heat engine system 200.

[0025] The heat engine system 200 may further contain a turbo pump 260, which may have a drive turbine 264 and a pump portion 262. The pump portion 262 of the turbo pump 260 may be fluidly coupled to the low pressure side of the working fluid circuit 202 by an inlet configured to receive the working fluid from the low pressure side of the working fluid circuit 202, fluidly coupled to the high pressure side of the working fluid circuit 202 by an outlet configured to release the working fluid into the high pressure side of the working fluid circuit 202, and configured to circulate the working fluid within the working fluid circuit 202. The drive turbine 264 of the turbo pump 260 may be fluidly coupled to the high pressure side of the working fluid circuit 202 by an inlet configured to receive the working fluid from the high pressure side of the working fluid circuit 202, fluidly coupled to the low pressure side of the working fluid circuit 202 by an outlet configured to release the working fluid into the low pressure side of the working fluid circuit 202, and configured to rotate the pump portion 262 of the turbo pump 260.

[0026] In some embodiments, the heat engine system 200 may further contain a heat exchanger 150 which may be generally fluidly coupled to and in thermal communication with the heat source stream 110 and independently fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202, such that thermal energy may be transferred from the heat source stream 110 to the working fluid. The heat exchanger 150 may be fluidly coupled to the working fluid circuit 202 downstream to the outlet of the pump portion 262 of the turbo pump 260 and upstream from the inlet of the drive turbine 264 of the turbo pump 260. A drive turbine throttle valve 263 may be fluidly coupled to the working fluid circuit 202 downstream of the heat exchanger 150 and upstream of the inlet of the drive turbine 264 of the turbo pump 260. The working fluid containing the absorbed thermal energy may flow from the heat exchanger 150 to the drive turbine 264 of the turbo pump 260 via the drive turbine throttle valve 263. Therefore, in some embodiments, the drive turbine throttle valve 263 may be utilized to control the flow rate of the heated working fluid flowing from the heat exchanger 150 to the drive turbine 264 of the turbo pump 260.

[0027] In some embodiments, a recuperator 216 may be fluidly coupled to the working fluid circuit 202 and configured to transfer thermal energy from the working fluid within the low pressure side to the working fluid within the high pressure side of the working fluid circuit 202. In other embodiments, a recuperator 218 may be fluidly coupled to the working fluid circuit 202 downstream of the outlet of the pump portion 262 of the turbo pump 260 and upstream of the heat exchanger 150 and configured to transfer thermal energy from the working fluid within the low pressure side to the working fluid within the high pressure side of the working fluid circuit 202.

[0028] FIG. 1 further depicts the waste heat system 100 of the heat engine system 200 having three heat exchangers (e.g., the heat exchangers 120, 130, and 150) fluidly coupled to the high pressure side of the working fluid circuit 202 and in thermal communication with the heat source stream 110. Such thermal communication provides the transfer of thermal energy from the heat source stream 110 to the working fluid flowing throughout the working fluid circuit 202. In one or more embodiments disclosed herein, two, three, or, optionally, four or more heat exchangers may be fluidly coupled to and in thermal communication with the working fluid circuit 202, such as a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, respectively the heat exchangers 120, 150, and 130, and/or an optional quaternary heat exchanger (not shown). For example, the heat exchanger 120 may be the primary heat exchanger fluidly coupled to the working fluid circuit 202 upstream of an inlet of the power turbine 228, the heat exchanger 150 may be the secondary heat exchanger fluidly coupled to the working fluid circuit 202 upstream of an inlet of the drive turbine 264 of the turbine pump 260, and the heat exchanger 130 may be the tertiary heat exchanger fluidly coupled to the working fluid circuit 202 upstream of an inlet of the heat exchanger 120.

[0029] The waste heat system 100 may also contain an inlet 104 for receiving the heat source stream 110 and an outlet 106 for passing the heat source stream 110 out of the waste heat system 100. The heat source stream 110 may flow through and from the inlet 104, through the heat exchanger 120, through one or more additional heat exchangers, if fluidly coupled to the heat source stream 110, and to and through the outlet 106. In some examples, the heat source stream 110 may flow through and from the inlet 104, through the heat exchangers 120, 150, and 130, respectively, and to and through the outlet 106. The heat source stream 110 may be routed to flow through the heat exchangers 120, 130, 150, and/or additional heat exchangers in other desired orders.

[0030] The heat source stream 110 may be a waste heat stream such as, but not limited to, gas turbine exhaust stream, industrial process exhaust stream, or other combustion product exhaust streams, such as furnace or boiler exhaust streams. The heat source stream 110 may be at a temperature within a range from about 100.degree. C. to about 1,000.degree. C., or greater than 1,000.degree. C., and in some examples, within a range from about 200.degree. C. to about 800.degree. C., more narrowly within a range from about 300.degree. C. to about 600.degree. C. The heat source stream 110 may contain air, carbon dioxide, carbon monoxide, water or steam, nitrogen, oxygen, argon, derivatives thereof, or mixtures thereof. In some embodiments, the heat source stream 110 may derive thermal energy from renewable sources of thermal energy, such as solar or geothermal sources.

[0031] In some embodiments, the types of working fluid that may be circulated, flowed, or otherwise utilized in the working fluid circuit 202 of the heat engine system 200 include carbon oxides, hydrocarbons, alcohols, ketones, halogenated hydrocarbons, ammonia, amines, aqueous, or combinations thereof. Exemplary working fluids that may be utilized in the heat engine system 200 include carbon dioxide, ammonia, methane, ethane, propane, butane, ethylene, propylene, butylene, acetylene, methanol, ethanol, acetone, methyl ethyl ketone, water, derivatives thereof, or mixtures thereof. Halogenated hydrocarbons may include hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) (e.g., 1,1,1,3,3-pentafluoropropane (R245fa)), fluorocarbons, derivatives thereof, or mixtures thereof.

[0032] In many embodiments described herein, the working fluid the working fluid circulated, flowed, or otherwise utilized in the working fluid circuit 202 of the heat engine system 200, and the other exemplary circuits disclosed herein, may be or may contain carbon dioxide (CO.sub.2) and mixtures containing carbon dioxide. Generally, at least a portion of the working fluid circuit 202 contains the working fluid in a supercritical state (e.g., sc-CO.sub.2). Carbon dioxide utilized as the working fluid or contained in the working fluid for power generation cycles has many advantages over other compounds typically used as working fluids, since carbon dioxide has the properties of being non-toxic and non-flammable and is also easily available and relatively inexpensive. Due in part to a relatively high working pressure of carbon dioxide, a carbon dioxide system may be much more compact than systems using other working fluids. The high density and volumetric heat capacity of carbon dioxide with respect to other working fluids makes carbon dioxide more "energy dense" meaning that the size of all system components can be considerably reduced without losing performance. It should be noted that use of the terms carbon dioxide (CO.sub.2), supercritical carbon dioxide (sc-CO.sub.2), or subcritical carbon dioxide (sub-CO.sub.2) is not intended to be limited to carbon dioxide of any particular type, source, purity, or grade. For example, industrial grade carbon dioxide may be contained in and/or used as the working fluid without departing from the scope of the disclosure.

[0033] In other exemplary embodiments, the working fluid in the working fluid circuit 202 may be a binary, ternary, or other working fluid blend. The working fluid blend or combination can be selected for the unique attributes possessed by the fluid combination within a heat recovery system, as described herein. For example, one such fluid combination includes a liquid absorbent and carbon dioxide mixture enabling the combined fluid to be pumped in a liquid state to high pressure with less energy input than required to compress carbon dioxide. In another exemplary embodiment, the working fluid may be a combination of carbon dioxide (e.g., sub-CO.sub.2 or sc-CO.sub.2) and one or more other miscible fluids or chemical compounds. In yet other exemplary embodiments, the working fluid may be a combination of carbon dioxide and propane, or carbon dioxide and ammonia, without departing from the scope of the disclosure.

[0034] The working fluid circuit 202 generally has a high pressure side and a low pressure side and contains a working fluid circulated within the working fluid circuit 202. The use of the term "working fluid" is not intended to limit the state or phase of matter of the working fluid. For instance, the working fluid or portions of the working fluid may be in a liquid phase, a gas phase, a fluid phase, a subcritical state, a supercritical state, or any other phase or state at any one or more points within the working fluid circuit 202, the heat engine system 200, or thermodynamic cycle. In one or more embodiments, the working fluid is in a supercritical state over certain portions of the working fluid circuit 202 of the heat engine system 200 (e.g., a high pressure side) and in a subcritical state over other portions of the working fluid circuit 202 of the heat engine system 200 (e.g., a low pressure side). FIG. 1 depicts the high and low pressure sides of the working fluid circuit 202 of the heat engine system 200 by representing the high pressure side with "______" and the low pressure side with "-.-.-."--as described in one or more embodiments. In other embodiments, the entire thermodynamic cycle may be operated such that the working fluid is maintained in either a supercritical or subcritical state throughout the entire working fluid circuit 202 of the heat engine system 200.

[0035] Generally, the high pressure side of the working fluid circuit 202 contains the working fluid (e.g., sc-CO.sub.2) at a pressure of about 15 MPa or greater, such as about 17 MPa or greater, or about 20 MPa or greater. In some examples, the high pressure side of the working fluid circuit 202 may have a pressure within a range from about 15 MPa to about 30 MPa, more narrowly within a range from about 16 MPa to about 26 MPa, more narrowly within a range from about 17 MPa to about 25 MPa, and more narrowly within a range from about 17 MPa to about 24 MPa, such as about 23.3 MPa. In other examples, the high pressure side of the working fluid circuit 202 may have a pressure within a range from about 20 MPa to about 30 MPa, more narrowly within a range from about 21 MPa to about 25 MPa, and more narrowly within a range from about 22 MPa to about 24 MPa, such as about 23 MPa.

[0036] The low pressure side of the working fluid circuit 202 contains the working fluid (e.g., CO.sub.2 or sub-CO.sub.2) at a pressure of less than 15 MPa, such as about 12 MPa or less, or about 10 MPa or less. In some examples, the low pressure side of the working fluid circuit 202 may have a pressure within a range from about 4 MPa to about 14 MPa, more narrowly within a range from about 6 MPa to about 13 MPa, more narrowly within a range from about 8 MPa to about 12 MPa, and more narrowly within a range from about 10 MPa to about 11 MPa, such as about 10.3 MPa. In other examples, the low pressure side of the working fluid circuit 202 may have a pressure within a range from about 2 MPa to about 10 MPa, more narrowly within a range from about 4 MPa to about 8 MPa, more narrowly within a range from about 5.2 MPa to about 8 MPa, and more narrowly within a range from about 5.2 MPa to about 7 MPa, such as about 6 MPa.

[0037] As stated above, the heat engine system 200 may further contain the power turbine 228 disposed between the high pressure side and the low pressure side of the working fluid circuit 202, disposed downstream of the heat exchanger 120, and fluidly coupled to and in thermal communication with the working fluid circuit. The power turbine 228 may be an expansion device capable of transforming a pressurized fluid into mechanical energy, generally, transforming high temperature and pressure fluid into mechanical energy, thereby rotating a shaft in an exemplary embodiment. The power turbine 228 may contain or be a turbine, a turbo, an expander, or another device for receiving and expanding the working fluid discharged from the heat exchanger 120. The power turbine 228 may have an axial construction or radial construction and may be a single-staged device or a multi-staged device. Exemplary devices that may be utilized in the power turbine 228 include an expansion device, a geroler, a gerotor, a valve, other types of positive displacement devices such as a pressure swing, a turbine, a turbo, or any other device capable of transforming a pressure or pressure/enthalpy drop in a working fluid into mechanical energy. A variety of expanding devices are capable of working within the inventive system and achieving different performance properties that may be utilized as the power turbine 228.

[0038] The power turbine 228 may be generally coupled to the power generator 240 by the driveshaft 230. A gearbox 232 may be generally disposed between the power turbine 228 and the power generator 240 and adjacent or encompassing the driveshaft 230. The driveshaft 230 may be a single piece or contain two or more pieces coupled together. In one example, a first segment of the driveshaft 230 extends from the power turbine 228 to the gearbox 232, a second segment of the driveshaft 230 extends from the gearbox 232 to the power generator 240, and multiple gears are disposed between and coupled to the two segments of the driveshaft 230 within the gearbox 232.

[0039] In some configurations, the heat engine system 200 may also provide for the delivery of a portion of the working fluid, seal gas, bearing gas, air, or other gas into a chamber or housing, such as a housing 238 within the power generation system 220 for purposes of cooling one or more parts of the power turbine 228. In other configurations, the driveshaft 230 may include a seal assembly (not shown) designed to prevent or capture any working fluid leakage from the power turbine 228. Additionally, a working fluid recycle system may be implemented along with the seal assembly to recycle seal gas back into the working fluid circuit 202 of the heat engine system 200.

[0040] The power generator 240 may be a generator, an alternator (e.g., permanent magnet alternator), or other device for generating electrical energy, such as transforming mechanical energy from the driveshaft 230 and the power turbine 228 to electrical energy. The power outlet 242 may be electrically coupled to the power generator 240 and configured to transfer the generated electrical energy from the power generator 240 to the electrical grid 244 via the generator breaker 243. The electrical grid 244 may be or include an electrical grid, an electrical bus (e.g., plant bus), power electronics, other electric circuits, or combinations thereof. The electrical grid 244 generally contains at least one alternating current bus, alternating current grid, alternating current circuit, or combinations thereof. In one example, the power generator 240 is a generator and is electrically and operably connected to the electrical grid 244 via the power outlet 242 and the generator breaker 243. In another example, the power generator 240 is an alternator and is electrically and operably connected to power electronics (not shown) via the power outlet 242. In another example, the power generator 240 is electrically connected to power electronics which are electrically connected to the power outlet 242.

[0041] The power electronics may be configured to convert the electrical power into desirable forms of electricity by modifying electrical properties, such as voltage, current, phase, or frequency. The power electronics may include converters or rectifiers, inverters, transformers, regulators, controllers, switches, resistors, storage devices, and other power electronic components and devices. In other embodiments, the power generator 240 may contain, be coupled with, or be other types of load receiving equipment, such as other types of electrical generation equipment, rotating equipment, a gearbox (e.g., gearbox 232), or other device configured to modify or convert the shaft work created by the power turbine 228. In one embodiment, the power generator 240 is in fluid communication with a cooling loop having a radiator and a pump for circulating a cooling fluid, such as water, thermal oils, and/or other suitable refrigerants. The cooling loop may be configured to regulate the temperature of the power generator 240 and power electronics by circulating the cooling fluid to draw away generated heat.

[0042] The heat engine system 200 may also provide for the delivery of a portion of the working fluid into a chamber or housing of the power turbine 228 for purposes of cooling one or more parts of the power turbine 228. In one embodiment, due to the potential need for dynamic pressure balancing within the power generator 240, the selection of the site within the heat engine system 200 from which to obtain a portion of the working fluid is critical because introduction of this portion of the working fluid into the power generator 240 should respect or not disturb the pressure balance and stability of the power generator 240 during operation. Therefore, the pressure of the working fluid delivered into the power generator 240 for purposes of cooling is the same or substantially the same as the pressure of the working fluid at an inlet of the power turbine 228. The working fluid is conditioned to be at a desired temperature and pressure prior to being introduced into the power turbine 228. A portion of the working fluid, such as the spent working fluid, exits the power turbine 228 at an outlet of the power turbine 228 and is directed to one or more heat exchangers or recuperators, such as recuperators 216 and 218. The recuperators 216 and 218 may be fluidly coupled to the working fluid circuit 202 in series with each other. The recuperators 216 and 218 are operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202.

[0043] In one embodiment, the recuperator 216 may be fluidly coupled to the low pressure side of the working fluid circuit 202, disposed downstream of a working fluid outlet on the power turbine 228, and disposed upstream of the recuperator 218 and/or the condenser 274. The recuperator 216 may be configured to remove at least a portion of thermal energy from the working fluid discharged from the power turbine 228. In addition, the recuperator 216 may also be fluidly coupled to the high pressure side of the working fluid circuit 202, disposed upstream of the heat exchanger 120 and/or a working fluid inlet on the power turbine 228, and disposed downstream of the heat exchanger 130. The recuperator 216 may be configured to increase the amount of thermal energy in the working fluid prior to flowing into the heat exchanger 120 and/or the power turbine 228. Therefore, the recuperator 216 may be operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202. In some examples, the recuperator 216 may be a heat exchanger configured to cool the low pressurized working fluid discharged or downstream of the power turbine 228 while heating the high pressurized working fluid entering into or upstream of the heat exchanger 120 and/or the power turbine 228.

[0044] Similarly, in another embodiment, the recuperator 218 may be fluidly coupled to the low pressure side of the working fluid circuit 202, disposed downstream of a working fluid outlet on the power turbine 228 and/or the recuperator 216, and disposed upstream of the condenser 274. The recuperator 218 may be configured to remove at least a portion of thermal energy from the working fluid discharged from the power turbine 228 and/or the recuperator 216. In addition, the recuperator 218 may also be fluidly coupled to the high pressure side of the working fluid circuit 202, disposed upstream of the heat exchanger 150 and/or a working fluid inlet on a drive turbine 264 of turbo pump 260, and disposed downstream of a working fluid outlet on a pump portion 262 of turbo pump 260. The recuperator 218 may be configured to increase the amount of thermal energy in the working fluid prior to flowing into the heat exchanger 150 and/or the drive turbine 264. Therefore, the recuperator 218 may be operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202. In some examples, the recuperator 218 may be a heat exchanger configured to cool the low pressurized working fluid discharged or downstream of the power turbine 228 and/or the recuperator 216 while heating the high pressurized working fluid entering into or upstream of the heat exchanger 150 and/or the drive turbine 264.

[0045] A cooler or a condenser 274 may be fluidly coupled to and in thermal communication with the low pressure side of the working fluid circuit 202 and may be configured or operative to control a temperature of the working fluid in the low pressure side of the working fluid circuit 202. The condenser 274 may be disposed downstream of the recuperators 216 and 218 and upstream of the start pump 280 and the turbopump 260. The condenser 274 receives the cooled working fluid from the recuperator 218 and further cools and/or condenses the working fluid which may be recirculated throughout the working fluid circuit 202. In many examples, the condenser 274 is a cooler and may be configured to control a temperature of the working fluid in the low pressure side of the working fluid circuit 202 by transferring thermal energy from the working fluid in the low pressure side to a cooling loop or system outside of the working fluid circuit 202.

[0046] A cooling media or fluid is generally utilized in the cooling loop or system by the condenser 274 for cooling the working fluid and removing thermal energy outside of the working fluid circuit 202. The cooling media or fluid flows through, over, or around while in thermal communication with the condenser 274. Thermal energy in the working fluid is transferred to the cooling fluid via the condenser 274. Therefore, the cooling fluid is in thermal communication with the working fluid circuit 202, but not fluidly coupled to the working fluid circuit 202. The condenser 274 may be fluidly coupled to the working fluid circuit 202 and independently fluidly coupled to the cooling fluid. The cooling fluid may contain one or multiple compounds and may be in one or multiple states of matter. The cooling fluid may be a media or fluid in a gaseous state, a liquid state, a subcritical state, a supercritical state, a suspension, a solution, derivatives thereof, or combinations thereof.

[0047] In many examples, the condenser 274 is generally fluidly coupled to a cooling loop or system (not shown) that receives the cooling fluid from a cooling fluid return 278a and returns the warmed cooling fluid to the cooling loop or system via a cooling fluid supply 278b. The cooling fluid may be water, carbon dioxide, or other aqueous and/or organic fluids (e.g., alcohols and/or glycols), air or other gases, or various mixtures thereof that is maintained at a lower temperature than the temperature of the working fluid. In other examples, the cooling media or fluid contains air or another gas exposed to the condenser 274, such as an air steam blown by a motorized fan or blower. A filter 276 may be disposed along and in fluid communication with the cooling fluid line at a point downstream of the cooling fluid supply 278b and upstream of the condenser 274. In some examples, the filter 276 may be fluidly coupled to the cooling fluid line within the process system 210.

[0048] The heat engine system 200 may further contain several pumps, such as a turbo pump 260 and a start pump 280, disposed within the working fluid circuit 202 and fluidly coupled between the low pressure side and the high pressure side of the working fluid circuit 202. The turbo pump 260 and the start pump 280 may be operative to circulate the working fluid throughout the working fluid circuit 202. The start pump 280 may be generally a motorized pump and may be utilized to initially pressurize and circulate the working fluid in the working fluid circuit 202. Once a predetermined pressure, temperature, and/or flow rate of the working fluid is obtained within the working fluid circuit 202, the start pump 280 may be taken off line, idled, or turned off and the turbo pump 260 is utilized to circulate the working fluid during the electricity generation process. The working fluid enters each of the turbo pump 260 and the start pump 280 from the low pressure side of the working fluid circuit 202 and exits each of the turbo pump 260 and the start pump 280 from the high pressure side of the working fluid circuit 202.

[0049] The start pump 280 may be a motorized pump, such as an electric motorized pump, a mechanical motorized pump, or other type of pump. Generally, the start pump 280 may be a variable frequency motorized drive pump and may contain a pump portion 282 and a motor-drive portion 284. The motor-drive portion 284 of the start pump 280 contains a motor and a drive including a driveshaft and gears (not shown). In some examples, the motor-drive portion 284 has a variable frequency drive, such that the speed of the motor may be regulated by the drive. The pump portion 282 of the start pump 280 is driven by the motor-drive portion 284 coupled thereto. The pump portion 282 has an inlet for receiving the working fluid from the low pressure side of the working fluid circuit 202, such as from the condenser 274 and/or the working fluid storage system 290. The pump portion 282 has an outlet for releasing the working fluid into the high pressure side of the working fluid circuit 202.

[0050] Start pump inlet valve 283 and start pump outlet valve 285 may be utilized to control the flow of the working fluid passing through the start pump 280. Start pump inlet valve 283 may be fluidly coupled to the low pressure side of the working fluid circuit 202 upstream of the pump portion 282 of the start pump 280 and may be utilized to control the flow rate of the working fluid entering the inlet of the pump portion 282. Start pump outlet valve 285 may be fluidly coupled to the high pressure side of the working fluid circuit 202 downstream of the pump portion 282 of the start pump 280 and may be utilized to control the flow rate of the working fluid exiting the outlet of the pump portion 282.

[0051] The turbo pump 260 may be generally a turbo-drive pump or a turbine-drive pump and utilized to pressurize and circulate the working fluid throughout the working fluid circuit 202. The turbo pump 260 may contain a pump portion 262 and a drive turbine 264 coupled together by a driveshaft 267 and an optional gearbox (not shown). The drive turbine 264 may be configured to rotate the pump portion 262 and the pump portion 262 may be configured to circulate the working fluid within the working fluid circuit 202.

[0052] The driveshaft 267 may be a single piece, as shown in FIG. 1, or may contain two or more pieces coupled together. In one example, a first segment of the driveshaft 267 extends from the drive turbine 264 to the gearbox, a second segment of the driveshaft 267 extends from the gearbox to the pump portion 262, and multiple gears are disposed between and coupled to the two segments of the driveshaft 267 within the gearbox.

[0053] The drive turbine 264 of the turbo pump 260 may be driven by heated working fluid, such as the working fluid flowing from the heat exchanger 150. The drive turbine 264 may be fluidly coupled to the high pressure side of the working fluid circuit 202 by an inlet configured to receive the working fluid from the high pressure side of the working fluid circuit 202, such as flowing from the heat exchanger 150. The drive turbine 264 may be fluidly coupled to the low pressure side of the working fluid circuit 202 by an outlet configured to release the working fluid into the low pressure side of the working fluid circuit 202.

[0054] The pump portion 262 of the turbo pump 260 may be driven by the driveshaft 267 coupled to the drive turbine 264. The pump portion 262 of the turbo pump 260 may be fluidly coupled to the low pressure side of the working fluid circuit 202 by an inlet configured to receive the working fluid from the low pressure side of the working fluid circuit 202. The inlet of the pump portion 262 is configured to receive the working fluid from the low pressure side of the working fluid circuit 202, such as from the condenser 274 and/or the working fluid storage system 290. Also, the pump portion 262 may be fluidly coupled to the high pressure side of the working fluid circuit 202 by an outlet configured to release the working fluid into the high pressure side of the working fluid circuit 202 and circulate the working fluid within the working fluid circuit 202.

[0055] In one configuration, the working fluid released from the outlet on the drive turbine 264 is returned into the working fluid circuit 202 downstream of the recuperator 216 and upstream of the recuperator 218. In one or more embodiments, the turbo pump 260, including piping and valves, is optionally disposed on a turbo pump skid 266, as depicted in FIG. 1. The turbo pump skid 266 may be disposed on or adjacent to the main process skid 212.

[0056] A drive turbine bypass valve 265 is generally coupled between and in fluid communication with a fluid line extending from the inlet on the drive turbine 264 with a fluid line extending from the outlet on the drive turbine 264. The drive turbine bypass valve 265 is generally opened to bypass the turbo pump 260 while using the start pump 280 during the initial stages of generating electricity with the heat engine system 200. Once a predetermined pressure and temperature of the working fluid is obtained within the working fluid circuit 202, the drive turbine bypass valve 265 is closed, and the heated working fluid is flowed through the drive turbine 264 to start the turbo pump 260.

[0057] The drive turbine throttle valve 263 may be coupled between and in fluid communication with a fluid line extending from the heat exchanger 150 to the inlet on the drive turbine 264 of the turbo pump 260. The drive turbine throttle valve 263 is configured to modulate the flow of the heated working fluid into the drive turbine 264, which in turn may be utilized to adjust the flow of the working fluid throughout the working fluid circuit 202. Additionally, valve 293 may be utilized to provide back pressure for the drive turbine 264 of the turbo pump 260.

[0058] A turbo pump attemperator valve 295 may be fluidly coupled to the working fluid circuit 202 via a bypass line 291 disposed between the outlet on the pump portion 262 of the turbo pump 260 and the inlet on the drive turbine 264 and/or disposed between the outlet on the pump portion 282 of the start pump 280 and the inlet on the drive turbine 264. The bypass line 291 and the turbo pump attemperator valve 295 may be configured to flow the working fluid from the pump portion 262 or 282, around and avoid the recuperator 218 and the heat exchanger 150, and to the drive turbine 264, such as during a warm-up or cool-down step of the turbo pump 260. The bypass line 291 and the turbo pump attemperator valve 295 may be utilized to warm the working fluid with the drive turbine 264 while avoiding the thermal heat from the heat source stream 110 via the heat exchangers, such as the heat exchanger 150.

[0059] A check valve 261 is disposed downstream of the outlet of the pump portion 262 of the turbo pump 260, and the check valve 281 is disposed downstream of the outlet of the pump portion 282 of the start pump 280. Check valves 261 and 281 are flow control safety valves and generally utilized to regulate the directional flow or to prohibit backflow of the working fluid within the working fluid circuit 202. Check valve 261 is configured to prevent the working fluid from flowing upstream towards or into the outlet of the pump portion 262 of the turbo pump 260. Similarly, check valve 281 is configured to prevent the working fluid from flowing upstream towards or into the outlet of the pump portion 282 of the start pump 280.

[0060] A power turbine bypass line 208 may be fluidly coupled to the working fluid circuit 202 at a point upstream of an inlet of the power turbine 228 and at a point downstream of an outlet of the power turbine 228. The power turbine bypass line 208 is configured to flow the working fluid around and avoid the power turbine 228 when a power turbine bypass valve 219 is in an opened position. The flow rate and the pressure of the working fluid flowing into the power turbine 228 may be reduced or stopped by adjusting the power turbine bypass valve 219 to the opened position. Alternatively, the flow rate and the pressure of the working fluid flowing into the power turbine 228 may be increased or started by adjusting the power turbine bypass valve 219 to the closed position due to the backpressure formed through the power turbine bypass line 208.

[0061] In one or more embodiments, the working fluid circuit 202 provides a bypass flowpath for the start pump 280 via the start pump bypass line 224 and a start pump bypass valve 254, as well as a bypass flowpath for the turbo pump 260 via the turbo pump bypass line 226 and a turbo pump bypass valve 256. One end of the start pump bypass line 224 may be fluidly coupled to an outlet of the pump portion 282 of the start pump 280, and the other end of the start pump bypass line 224 may be fluidly coupled to a fluid line 226. Similarly, one end of a turbo pump bypass line 226 may be fluidly coupled to an outlet of the pump portion 262 of the turbo pump 260, and the other end of the turbo pump bypass line 226 is coupled to the start pump bypass line 229. In some configurations, the start pump bypass line 224 and the turbo pump bypass line 226 merge together as a single line upstream of coupling to a fluid line 229. The fluid line 229 extends between and may be fluidly coupled to the recuperator 218 and the condenser 274. The start pump bypass valve 254 is disposed along the start pump bypass line 224 and fluidly coupled between the low pressure side and the high pressure side of the working fluid circuit 202 when in a closed position. Similarly, the turbo pump bypass valve 256 is disposed along the turbo pump bypass line 226 and fluidly coupled between the low pressure side and the high pressure side of the working fluid circuit 202 when in a closed position.

[0062] FIG. 1 further depicts a power turbine throttle valve 250 fluidly coupled to a bypass line 246 on the high pressure side of the working fluid circuit 202 and upstream of the heat exchanger 120, as disclosed by at least one embodiment described herein. The power turbine throttle valve 250 may be fluidly coupled to the bypass line 246 and configured to modulate, adjust, or otherwise control the working fluid flowing through the bypass line 246 for controlling a general coarse flow rate of the working fluid within the working fluid circuit 202. The bypass line 246 may be fluidly coupled to the working fluid circuit 202 at a point upstream of the valve 293 and at a point downstream of the pump portion 282 of the start pump 280 and/or the pump portion 262 of the turbo pump 260. Additionally, a power turbine trim valve 252 may be fluidly coupled to a bypass line 248 on the high pressure side of the working fluid circuit 202 and upstream of the heat exchanger 150, as disclosed by another embodiment described herein. The power turbine trim valve 252 may be fluidly coupled to the bypass line 248 and configured to modulate, adjust, or otherwise control the working fluid flowing through the bypass line 248 for controlling a fine flow rate of the working fluid within the working fluid circuit 202. In an exemplary embodiment, the power turbine trim valve 252 may be used for controlling a fine flow rate of the working fluid to synchronize the power generator 240 with the electrical grid 244. The bypass line 248 may be fluidly coupled to the bypass line 246 at a point upstream of the power turbine throttle valve 250 and at a point downstream of the power turbine throttle valve 250.

[0063] The power turbine bypass valve 219, the drive turbine throttle valve 263, the power turbine throttle valve 250, the power turbine trim valve 252, and the turbo pump bypass valve 256 may be independently, and in combination, controlled by the process control system 204. The heat engine system 200 includes the process control system 204 communicably connected, wired and/or wirelessly, with numerous sets of sensors, valves, and pumps, in order to process the measured and reported temperatures, pressures, and mass flow rates of the working fluid at the designated points within the working fluid circuit 202. In response to these measured and/or reported parameters, the process control system 204 may be operable to selectively adjust the valves in accordance with a control program or algorithm, thereby maximizing operation of the heat engine system 200.

[0064] The process control system 204 may be communicably and operatively connected, wired and/or wirelessly, with the power turbine bypass valve 219, the drive turbine throttle valve 263, the power turbine throttle valve 250, the power turbine trim valve 252, the turbo pump bypass valve 256, and other parts of the heat engine system 200. The process control system 204 may be operatively connected to the working fluid circuit 202 and a mass management system 270 and may be enabled to monitor and control multiple process operation parameters of the heat engine system 200. Such operation parameters may include, for example, the pressure, temperature, and flow rate of the working fluid in various locations in the heat engine system 200.

[0065] The process control system 204 includes at least one controller 206, and in at least one embodiment, includes a plurality of controllers 206. In an exemplary embodiment, at least one controller 206 contains one or more algorithms utilized to control the drive turbine throttle valve 263, the power turbine bypass valve 219, the power turbine throttle valve 250, the power turbine trim valve 252, and the turbo pump bypass valve 256, as well as other valves, pumps, and sensors within the heat engine system 200. In an exemplary embodiment, the controller 206 includes one or more ramp profile algorithms. In one embodiment, the process control system 204, via the ramp profile algorithms embedded in one or more controllers 206, is enabled to move, adjust, manipulate, or otherwise control, the drive turbine throttle valve 263, the power turbine bypass valve 219, the power turbine throttle valve 250, the power turbine trim valve 252, and/or the turbo pump bypass valve 256 for adjusting or controlling the flow rate of the working fluid throughout the working fluid circuit 202. By controlling the flow rate of the working fluid, the process control system 204 is also operable to regulate the temperatures and pressures throughout the working fluid circuit 202, thereby maximizing operation of the heat engine system 200.

[0066] Further, in certain embodiments, the process control system 204, as well as any other controllers or processors disclosed herein, may include one or more non-transitory, tangible, machine-readable media, such as read-only memory (ROM), random access memory (RAM), solid state memory (e.g., flash memory), floppy diskettes, CD-ROMs, hard drives, universal serial bus (USB) drives, any other computer readable storage medium, or any combination thereof. The storage media may store encoded instructions, such as firmware, that may be executed by the process control system 204 or any of the other controllers disclosed herein (e.g., the one or more controllers 206) to operate the logic or portions of the logic presented in the methods disclosed herein. For example, in certain embodiments, the heat engine system 200 may include computer code disposed on a computer-readable storage medium or a process controller that includes such a computer-readable storage medium. The computer code may include instructions for initiating a control function to alternate the position of one or more of the drive turbine throttle valve 263, the power turbine bypass valve 219, the power turbine throttle valve 250, the power turbine trim valve 252, and/or the turbo pump bypass valve 256.

[0067] Additionally, the process control system 204 may operate with the heat engine system 200 semi-passively with the aid of several sets of sensors. The first set of sensors is arranged at or adjacent the suction inlet of the turbo pump 260 and the start pump 280 and the second set of sensors is arranged at or adjacent the outlet of the turbo pump 260 and the start pump 280. The first and second sets of sensors monitor and report the pressure, temperature, mass flow rate, or other properties of the working fluid within the low and high pressure sides of the working fluid circuit 202 adjacent the turbo pump 260 and the start pump 280. As shown in FIG. 1, the pressures adjacent the turbo pump 260 and the start pump 280, upstream and downstream, may be referred to as pressure P1 and pressure P2, respectively. The third set of sensors is arranged either inside or adjacent the working fluid storage vessel 292 of the working fluid storage system 290 to measure and report the pressure, temperature, mass flow rate, or other properties of the working fluid within the working fluid storage vessel 292. Additionally, an instrument air supply (not shown) may be coupled to sensors, devices, or other instruments within the heat engine system 200 including the mass management system 270 and/or other system components that may utilize a gaseous supply, such as nitrogen or air.

[0068] During operation of the heat engine system 200 in accordance with one embodiment, as shown in FIG. 7, a method 10 provides for synchronizing a generator of a heat engine system with an electrical grid. The method 10 may include circulating, via a turbo pump, a working fluid within a working fluid circuit of the heat engine system (block 12). The working fluid circuit may have a high pressure side and a low pressure side, and at least a portion of the working fluid may be in a supercritical state. The method 10 may also include transferring thermal energy from a heat source stream to the working fluid by at least a primary heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit (block 14). The method 10 may further include feeding the working fluid into a power turbine and converting the thermal energy from the working fluid to mechanical energy of the power turbine (block 16), and converting the mechanical energy into electrical energy by a power generator coupled to the power turbine (block 18). The method 10 may also include comparing at least one electrical energy parameter of the electrical energy converted by the power generator with at least one grid parameter of the electrical grid configured to be electrically coupled to the power generator (block 20). The method 10 may further include modulating at least one valve of a plurality of valves operatively coupled to a process control system to change a flow rate of the working fluid fed into the power turbine (block 22), such that the at least one electrical energy parameter of the electrical energy converted by the power generator is substantially similar to the at least one grid parameter of the electrical grid, thereby synchronizing the power generator with the electrical grid. Further, in certain embodiments, the method 10 may optionally also include closing the generator breaker such that the power generator and the electrical grid are electrically coupled, and the electrical energy is supplied to the electrical grid (block 24).

[0069] In an exemplary operation of the heat engine system 200, the start pump 280 may be utilized to initially pressurize and circulate the working fluid in the working fluid circuit 202. Once a predetermined pressure, temperature, and/or flow rate of the working fluid is obtained within the working fluid circuit 202, the start pump 280 may be taken off line, idled, or turned off, and the turbo pump 260 is utilized to circulate the working fluid during the electricity generation process. The working fluid may enter one of or both the turbo pump 260 and the start pump 280 from the low pressure side of the working fluid circuit 202 and exit the corresponding turbo pump 260 and/or the start pump 280 from the high pressure side of the working fluid circuit 202.

[0070] In one or more exemplary embodiments disclosed herein, during or subsequent to the turbo pump 260 being activated and thereby pumping the working fluid from the low pressure side to the high pressure side, the process control system 204 may transmit one or more control signals to the power turbine throttle valve 250 and/or the power turbine trim valve 252. Such control signals generally cause the power turbine throttle valve 250 and/or the power turbine trim valve 252 to gradually and independently open, via the ramp profile algorithm embedded in at least one controller in a portion of the process control system 204, as depicted in FIG. 2 for the power turbine throttle valve 250 and in FIG. 3 for the power turbine trim valve 252. Therefore, the working fluid flow rate passing through the power turbine throttle valve 250 and/or the power turbine trim valve 252 may be closely controlled and regulated, thereby controlling at least one electrical energy parameter generated by the power generator 240. The at least one electrical energy parameter may be voltage, phase sequence, phase angle, waveform, and/or frequency. In an exemplary embodiment, the electrical energy parameter includes frequency. The power turbine throttle valve 250 and/or the power turbine trim valve 252 may be independently manipulated, such that the flow rate through the power turbine throttle valve 250 and/or the power turbine trim valve 252 provides the power turbine 228 with a sufficient speed to synchronize the coupled power generator 240 with the corresponding electrical grid 244. Synchronization of the power generator 240 and electrical grid 244 may occur when the electrical energy parameters are substantially similar. The electrical grid parameters may include voltage, phase sequence, phase angle, waveform, and frequency. In an exemplary embodiment, the electrical energy parameters and electrical grid parameters may be compared. The generator breaker 243 may be manipulated into a closed position when the compared electrical grid parameters and the electrical energy parameters are substantially similar, thereby electrically coupling the heat engine system 200 and the electrical grid 244 and allowing for the electrical communication of energy from the heat engine system 200 to the electrical grid 244.

[0071] In some instances, the power turbine bypass valve 219 may be manipulated by a control signal generated by the process control system 204. Such instances may occur when the flow rate through the power turbine throttle valve 250 and/or the power turbine trim valve 252 provides the power turbine with a speed generating a frequency and/or other electrical energy parameter in the power generator 240, such that synchronization of the power generator 240 with the electrical grid 244 is unachievable. Thus, the power turbine bypass valve 219 may be gradually opened, via the ramp profile algorithm embedded in at least one controller in a portion of the process control system 204 shown in FIG. 4, to reduce the flow rate through the power turbine 228, thereby providing for an adjustment to the speed of the power turbine 228, thereby allowing for the proper frequency and/or other electrical energy parameters for the synchronization of the power generator 240 with the electrical grid 244. As shown in FIG. 1, the opening of the power turbine bypass valve 219 permits at least a portion of the working fluid fed from the heat exchanger 120 to be bypassed via power turbine bypass line 208 from flowing through the power turbine 228.

[0072] As stated above, the drive turbine throttle valve 263 and/or the turbo pump bypass valve 256 may be configured to modulate the flow of the heated working fluid into the drive turbine 264, which in turn may be utilized to adjust the flow of the working fluid throughout the working fluid circuit 202. Further, by modulating the flow of the heated working fluid into the drive turbine 264 via the drive turbine throttle valve 263 and/or the turbo pump bypass valve 256, the pressure P2 at the power turbine trim valve 252 is modulated accordingly. Thus, the drive turbine throttle valve 263 and/or the turbo pump bypass valve 256 may be used to modulate the pressure P2 at the power turbine trim valve 252 and the power turbine throttle valve 250. To provide relief in instances in which the pressure P2, downstream of the turbo pump 260 and upstream of each of the power turbine throttle valve 250 and power turbine trim valve 252, exceeds desired parameters associated with the corresponding pressure P1 upstream of the turbo pump 260, the turbo pump bypass valve 256 may be modulated to reduce pressure P2 in the heat engine system 200 in order to reduce risk of damage to the turbo pump 260.

[0073] In an exemplary embodiment, the process control system 204 may be operatively connected to the drive turbine throttle valve 263 and/or the turbo pump bypass valve 256 and configured to transmit a control signal to the drive turbine throttle valve 263 and/or the turbo pump bypass valve 256, thereby gradually opening, via the ramp profile algorithm embedded in at least one controller in a portion of the process control system 204 shown in FIG. 5, to maintain sufficient pressure P2 at the power turbine trim valve 252, such that the flow rate through the power turbine trim valve 252 is sufficient to synchronize the power generator 240 with the electrical grid 244. Further, the process control system may be operatively connected to the turbo pump bypass valve 256 and configured to transmit a control signal to the turbo pump bypass valve 256 to gradually open, via the ramp profile algorithm embedded in at least one controller in a portion of the process control system 204 shown in FIG. 6, to reduce the pressure at the power turbine trim valve 252 in instances in which the pressure P2 may be outside of a desired parameter in relation to the pressure P1 (turbo pump bearing differential P2-P1).

[0074] In addition to the foregoing, in an exemplary embodiment, upon synchronization of the power generator 240 with the electrical grid 244, the process control system 204 may be configured to transmit a command signal to the power turbine trim valve 252, such that the power turbine trim valve 252 is completely opened to allow working fluid to flow therethrough. In order to create a sufficient flow rate into the power turbine 228 to produce the necessary electrical energy in the power generator 240 required by the electrical grid 244, the process control system 204 may be further configured to transmit a control signal to the drive turbine throttle valve 263, thereby modulating the drive turbine throttle valve 263 to provide more flow through the drive turbine 264, thereby increasing the pressure P2 at the power turbine trim valve 252 and allowing for a higher flow rate into the power turbine 228 via the power turbine trim valve 252 and the power turbine throttle valve 250. In an exemplary embodiment, the process control system 204 may be further configured to transmit a command signal to the turbo pump bypass valve 256 when the pressure P2 at the power turbine trim valve 252 and the power turbine throttle valve 250 exceeds the desired parameters in relation to the pressure P1 as required to reduce the risk of damage to the turbo pump 260.

[0075] As stated above, the process control system 204 may be configured to operate the power turbine bypass valve 219, the drive turbine throttle valve 263, the power turbine trim valve 252, and the turbo pump bypass valve 256 independently or in combination, to provide electrical energy to the electrical grid 244 from the heat engine system 200. Accordingly, the modulation of any of the valves in the heat engine system 200 by the process control system 204 may require a correction or modulation of at least one other valve in the heat engine system 200. Thus, the modulation and operation of the power turbine bypass valve 219, the drive turbine throttle valve 263, the power turbine trim valve 252, and the turbo pump bypass valve 256 by the process control system may be a dynamic process including open-loop and/or closed-loop feedback systems, wherein the modulation of a valve may require a corresponding modulation of at least one other valve.

[0076] A bypass line 160 may be fluidly coupled to a fluid line 131 of the working fluid circuit 202 upstream of the heat exchangers 120, 130, and/or 150 by a bypass valve 162, as illustrated in FIG. 1. The bypass valve 162 may be a solenoid valve, a hydraulic valve, an electric valve, a manual valve, or derivatives thereof. In many examples, the bypass valve 162 is a solenoid valve and configured to be controlled by the process control system 204.

[0077] In one or more embodiments, the working fluid circuit 202 provides release valves 213a, 213b, 213c, and 213d, as well as release outlets 214a, 214b, 214c, and 214d, respectively, in fluid communication with each other. Generally, the release valves 213a, 213b, 213c, and 213d remain closed during the electricity generation process, but may be configured to automatically open to release an over-pressure at a predetermined value within the working fluid. Once the working fluid flows through the valve 213a, 213b, 213c, or 213d, the working fluid is vented through the respective release outlet 214a, 214b, 214c, or 214d. The release outlets 214a, 214b, 214c, and 214d may provide passage of the working fluid into the ambient surrounding atmosphere. Alternatively, the release outlets 214a, 214b, 214c, and 214d may provide passage of the working fluid into a recycling or reclamation step that generally includes capturing, condensing, and storing the working fluid.

[0078] The release valve 213a and the release outlet 214a may be fluidly coupled to the working fluid circuit 202 at a point disposed between the heat exchanger 120 and the power turbine 228. The release valve 213b and the release outlet 214b may be fluidly coupled to the working fluid circuit 202 at a point disposed between the heat exchanger 150 and the drive turbine 264 of the turbo pump 260. The release valve 213c and the release outlet 214c may be fluidly coupled to the working fluid circuit 202 via a bypass line that extends from a point between the valve 293 and the pump portion 262 of the turbo pump 260 to a point on the turbo pump bypass line 226 between the turbo pump bypass valve 256 and the fluid line 229. The release valve 213d and the release outlet 214d may be fluidly coupled to the working fluid circuit 202 at a point disposed between the recuperator 218 and the condenser 274.

[0079] In some embodiments, the overall efficiency of the heat engine system 200 and the amount of power ultimately generated can be influenced by the inlet or suction pressure at the pump when the working fluid contains supercritical carbon dioxide. In order to minimize or otherwise regulate the suction pressure of the pump, the heat engine system 200 may incorporate the use of a mass management system ("MMS") 270. The mass management system 270 controls the inlet pressure of the start pump 280 by regulating the amount of working fluid entering and/or exiting the heat engine system 200 at strategic locations in the working fluid circuit 202, such as at tie-in points, inlets/outlets, valves, or conduits throughout the heat engine system 200. Consequently, the heat engine system 200 becomes more efficient by increasing the pressure ratio for the start pump 280 to a maximum possible extent.

[0080] The mass management system 270 may contain at least one vessel or tank, such as a storage vessel (e.g., working fluid storage vessel 292), a fill vessel, and/or a mass control tank (e.g., mass control tank 286), fluidly coupled to the low pressure side of the working fluid circuit 202 via one or more valves, such as the valve 287. In one exemplary configuration, the valve 287 is a fluid (e.g., CO.sub.2) transfer pump inlet valve. The valves are moveable--as being partially opened, fully opened, and/or closed--to either remove working fluid from the working fluid circuit 202 or add working fluid to the working fluid circuit 202. Exemplary embodiments of the mass management system 270, and a range of variations thereof, are found in U.S. application Ser. No. 13/278,705, filed Oct. 21, 2011, published as U.S. Pub. No. 2012-0047892, and issued as U.S. Pat. No. 8,613,195, the contents of which are incorporated herein by reference to the extent consistent with the present disclosure. Briefly, however, the mass management system 270 may include a plurality of valves and/or connection points, each in fluid communication with the mass control tank 286. The valves may be characterized as termination points where the mass management system 270 is operatively connected to the heat engine system 200. The connection points and valves may be configured to provide the mass management system 270 with an outlet for flaring excess working fluid or pressure, or to provide the mass management system 270 with additional/supplemental working fluid from an external source, such as a fluid fill system.

[0081] In some embodiments, the mass control tank 286 may be configured as a localized storage tank for additional/supplemental working fluid that may be added to the heat engine system 200 when needed in order to regulate the pressure or temperature of the working fluid within the working fluid circuit 202 or otherwise supplement escaped working fluid. By controlling the valves, the mass management system 270 adds and/or removes working fluid mass to/from the heat engine system 200 with or without the need of a pump, thereby reducing system cost, complexity, and maintenance.

[0082] In some examples, a working fluid storage vessel 292 is part of a working fluid storage system 290 and may be fluidly coupled to the working fluid circuit 202. At least one connection point, such as a working fluid feed 288, may be a fluid fill port for the working fluid storage vessel 292 of the working fluid storage system 290 and/or the mass management system 270. Additional or supplemental working fluid may be added to the mass management system 270 from an external source, such as a fluid fill system via the working fluid feed 288. Exemplary fluid fill systems are described and illustrated in U.S. Pat. No. 8,281,593, the contents of which are incorporated herein by reference to the extent consistent with the present disclosure.

[0083] In another embodiment described herein, bearing gas and seal gas may be supplied to the turbo pump 260 or other devices contained within and/or utilized along with the heat engine system 200. One or multiple streams of bearing gas and/or seal gas may be derived from the working fluid within the working fluid circuit 202 and contain carbon dioxide in a gaseous, subcritical, or supercritical state. In some examples, the bearing gas or fluid is flowed by the start pump 280, from a bearing gas supply 296a and/or a bearing gas supply 296b, into the working fluid circuit 202, through a bearing gas supply line (not shown), and to the bearings within the power generation system 220. In other examples, the bearing gas or fluid is flowed by the start pump 280, from the working fluid circuit 202, through a bearing gas supply line (not shown), and to the bearings within the turbo pump 260. In some examples, the seal gas supply 298 is a connection point or valve that feeds into a seal gas system. A gas return 294 is generally coupled to a discharge, recapture, or return of bearing gas, seal gas, and other gases. The gas return 294 provides a feed stream into the working fluid circuit 202 of recycled, recaptured, or otherwise returned gases--generally derived from the working fluid. The gas return is generally fluidly coupled to the working fluid circuit 202 upstream of the condenser 274 and downstream of the recuperator 218.

[0084] In some embodiments described herein, the waste heat system 100 is disposed on or in a waste heat skid 102 fluidly coupled to the working fluid circuit 202, as well as other portions, sub-systems, or devices of the heat engine system 200. The waste heat skid 102 may be fluidly coupled to a source of and an exhaust for the heat source stream 110, a main process skid 212, a power generation skid 222, and/or other portions, sub-systems, or devices of the heat engine system 200.

[0085] In one or more configurations, the waste heat system 100 disposed on or in the waste heat skid 102 generally contains inlets 122, 132, and 152 and outlets 124, 134, and 154 fluidly coupled to and in thermal communication with the working fluid within the working fluid circuit 202. The inlet 122 is disposed upstream of the heat exchanger 120, and the outlet 124 is disposed downstream of the heat exchanger 120. The working fluid circuit 202 is configured to flow the working fluid from the inlet 122, through the heat exchanger 120, and to the outlet 124 while transferring thermal energy from the heat source stream 110 to the working fluid by the heat exchanger 120. The inlet 152 is disposed upstream of the heat exchanger 150, and the outlet 154 is disposed downstream of the heat exchanger 150. The working fluid circuit 202 is configured to flow the working fluid from the inlet 152, through the heat exchanger 150, and to the outlet 154 while transferring thermal energy from the heat source stream 110 to the working fluid by the heat exchanger 150. The inlet 132 is disposed upstream of the heat exchanger 130 and the outlet 134 is disposed downstream of the heat exchanger 130. The working fluid circuit 202 is configured to flow the working fluid from the inlet 132, through the heat exchanger 130, and to the outlet 134 while transferring thermal energy from the heat source stream 110 to the working fluid by the heat exchanger 130.

[0086] In one or more configurations, the power generation system 220 is disposed on or in the power generation skid 222 generally contains inlets 225a, 225b and an outlet 227 fluidly coupled to and in thermal communication with the working fluid within the working fluid circuit 202. The inlets 225a, 225b are upstream of the power turbine 228 within the high pressure side of the working fluid circuit 202 and are configured to receive the heated and high pressure working fluid. In some examples, the inlet 225a may be fluidly coupled to the outlet 124 of the waste heat system 100 and configured to receive the working fluid flowing from the heat exchanger 120 and the inlet 225b may be fluidly coupled to the outlet 241 of the process system 210 and configured to receive the working fluid flowing from the turbo pump 260 and/or the start pump 280. The outlet 227 is disposed downstream of the power turbine 228 within the low pressure side of the working fluid circuit 202 and is configured to provide the low pressure working fluid. In some examples, the outlet 227 may be fluidly coupled to the inlet 239 of the process system 210 and configured to flow the working fluid to the recuperator 216.

[0087] A filter 215a may be disposed along and in fluid communication with the fluid line at a point downstream of the heat exchanger 120 and upstream of the power turbine 228. In some examples, the filter 215a may be fluidly coupled to the working fluid circuit 202 between the outlet 124 of the waste heat system 100 and the inlet 225a of the process system 210.

[0088] The portion of the working fluid circuit 202 within the power generation system 220 is fed the working fluid by the inlets 225a and 225b. A power turbine stop valve 217 may be fluidly coupled to the working fluid circuit 202 between the inlet 225a and the power turbine 228. The power turbine stop valve 217 is configured to control the working fluid flowing from the heat exchanger 120, through the inlet 225a, and into the power turbine 228 while in an opened position. Alternatively, the power turbine stop valve 217 may be configured to cease the flow of working fluid from entering into the power turbine 228 while in a closed position.

[0089] A power turbine attemperator valve 223 may be fluidly coupled to the working fluid circuit 202 via a bypass line 211 disposed between the outlet on the pump portion 262 of the turbo pump 260 and the inlet on the power turbine 228 and/or disposed between the outlet on the pump portion 282 of the start pump 280 and the inlet on the power turbine 228. The bypass line 211 and the power turbine attemperator valve 223 may be configured to flow the working fluid from the pump portion 262 or 282, around and avoid the recuperator 216 and the heat exchangers 120 and 130, and to the power turbine 228, such as during a warm-up or cool-down step. The bypass line 211 and the power turbine attemperator valve 223 may be utilized to warm the working fluid with heat coming from the power turbine 228 while avoiding the thermal heat from the heat source stream 110 flowing through the heat exchangers, such as the heat exchangers 120 and 130. In some examples, the power turbine attemperator valve 223 may be fluidly coupled to the working fluid circuit 202 between the inlet 225b and the power turbine stop valve 217 upstream of a point on the fluid line that intersects the incoming stream from the inlet 225a. The power turbine attemperator valve 223 may be configured to control the working fluid flowing from the start pump 280 and/or the turbo pump 260, through the inlet 225b, and to a power turbine stop valve 217, the power turbine bypass valve 219, and/or the power turbine 228.

[0090] The power turbine bypass valve 219 may be fluidly coupled to a turbine bypass line that extends from a point of the working fluid circuit 202 upstream of the power turbine stop valve 217 and downstream of the power turbine 228. Therefore, the bypass line and the power turbine bypass valve 219 are configured to direct the working fluid around and avoid the power turbine 228. If the power turbine stop valve 217 is in a closed position, the power turbine bypass valve 219 may be configured to flow the working fluid around and avoid the power turbine 228 while in an opened position. In one embodiment, the power turbine bypass valve 219 may be utilized while warming up the working fluid during a start-up operation of the electricity generating process. An outlet valve 221 may be fluidly coupled to the working fluid circuit 202 between the outlet on the power turbine 228 and the outlet 227 of the power generation system 220.

[0091] In one or more configurations, the process system 210 is disposed on or in the main process skid 212 generally contains inlets 235, 239, and 255 and outlets 231, 237, 241, 251, and 253 fluidly coupled to and in thermal communication with the working fluid within the working fluid circuit 202. The inlet 235 is upstream of the recuperator 216, and the outlet 154 is downstream of the recuperator 216. The working fluid circuit 202 is configured to flow the working fluid from the inlet 235, through the recuperator 216, and to the outlet 237 while transferring thermal energy from the working fluid in the low pressure side of the working fluid circuit 202 to the working fluid in the high pressure side of the working fluid circuit 202 by the recuperator 216. The outlet 241 of the process system 210 is downstream of the turbo pump 260 and/or the start pump 280, upstream of the power turbine 228, and configured to provide a flow of the high pressure working fluid to the power generation system 220, such as to the power turbine 228. The inlet 239 is upstream of the recuperator 216, downstream of the power turbine 228, and configured to receive the low pressure working fluid flowing from the power generation system 220, such as to the power turbine 228. The outlet 251 of the process system 210 is downstream of the recuperator 218, upstream of the heat exchanger 150, and configured to provide a flow of working fluid to the heat exchanger 150. The inlet 255 is downstream of the heat exchanger 150, upstream of the drive turbine 264 of the turbo pump 260, and configured to provide the heated high pressure working fluid flowing from the heat exchanger 150 to the drive turbine 264 of the turbo pump 260. The outlet 253 of the process system 210 is downstream of the pump portion 262 of the turbo pump 260 and/or the pump portion 282 of the start pump 280, couples a bypass line disposed downstream of the heat exchanger 150 and upstream of the drive turbine 264 of the turbo pump 260, and configured to provide a flow of working fluid to the drive turbine 264 of the turbo pump 260.

[0092] Additionally, a filter 215c may be disposed along and in fluid communication with the fluid line at a point downstream of the heat exchanger 150 and upstream of the drive turbine 264 of the turbo pump 260. In some examples, the filter 215c may be fluidly coupled to the working fluid circuit 202 between the outlet 154 of the waste heat system 100 and the inlet 255 of the process system 210.

[0093] In another embodiment described herein, as illustrated in FIG. 1, the heat engine system 200 contains the process system 210 disposed on or in a main process skid 212, the power generation system 220 disposed on or in a power generation skid 222, the waste heat system 100 disposed on or in a waste heat skid 102. The working fluid circuit 202 extends throughout the inside, the outside, and between the main process skid 212, the power generation skid 222, the waste heat skid 102, as well as other systems and portions of the heat engine system 200. In some embodiments, the heat engine system 200 contains the bypass line 160 and the bypass valve 162 disposed between the waste heat skid 102 and the main process skid 212. A filter 215b may be disposed along and in fluid communication with the fluid line 135 at a point downstream of the heat exchanger 130 and upstream of the recuperator 216. In some examples, the filter 215b may be fluidly coupled to the working fluid circuit 202 between the outlet 134 of the waste heat system 100 and the inlet 235 of the process system 210.

[0094] The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

1. A method for synchronizing a generator of a heat engine system with an electrical grid, comprising: circulating, via a turbo pump, a working fluid within a working fluid circuit of the heat engine system, wherein the working fluid circuit has a high pressure side and a low pressure side and at least a portion of the working fluid is in a supercritical state; transferring thermal energy from a heat source stream to the working fluid by at least a primary heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit; feeding the working fluid into a power turbine and converting the thermal energy from the working fluid to mechanical energy of the power turbine; converting the mechanical energy into electrical energy by the generator coupled to the power turbine; comparing at least one electrical energy parameter of the electrical energy converted by the generator with at least one grid parameter of the electrical grid configured to be electrically coupled to the generator; and modulating at least one valve of a plurality of valves operatively coupled to a process control system to change a flow rate of the working fluid fed into the power turbine, such that the at least one electrical energy parameter of the electrical energy converted by the generator is substantially similar to the at least one grid parameter of the electrical grid, thereby synchronizing the generator with the electrical grid.

2. The method of claim 1, wherein the plurality of valves comprises at least one valve selected from a power turbine trim valve, a power turbine throttle valve, a power turbine bypass valve, a drive turbine throttle valve, a turbo pump bypass valve, or combinations of valves thereof.

3. The method of claim 1, wherein the at least one electrical energy parameter is selected from the group consisting of voltage, phase sequence, phase angle, waveform, and frequency.

4. The method of claim 1, wherein the at least one grid parameter is selected from the group consisting of voltage, phase sequence, phase angle, waveform, and frequency.

5. The method of claim 1, wherein the heat engine system comprises a plurality of sensors, at least one sensor of the plurality of sensors being disposed adjacent each of the plurality of valves and further being operatively coupled to the process control system and configured to detect at least one system parameter.

6. The method of claim 5, further comprising transmitting from the at least one sensor a sensor signal based on the at least one system parameter to the process control system.

7. The method of claim 6, wherein the process control system includes at least one controller including a ramp profile algorithm, such that the at least one controller is configured to manipulate the at least one valve to a predetermined valve position over a predetermined time period based on at least one of the sensor signals.

8. The method of claim 1, wherein the at least one valve is a power turbine trim valve, a power turbine bypass valve, a drive turbine throttle valve, and a turbo pump bypass valve.

9. The method of claim 1, wherein the working fluid comprises carbon dioxide.

10. A method for generating electrical energy for an electrical grid with a heat engine system comprising a power generator, comprising: synchronizing the power generator with the electrical grid in accordance with the method of claim 1; closing a generator breaker, thereby electrically coupling the power generator and the electrical grid; and feeding the electrical energy generated by the power generator to the electrical grid.

11. The method of claim 10, wherein the at least one valve is a power turbine trim valve, a power turbine throttle valve, a power turbine bypass valve, a drive turbine throttle valve, a turbo pump bypass valve, or combinations of valves thereof.

12. The method of claim 11, wherein the at least one electrical energy parameter is selected from the group consisting of voltage, phase sequence, phase angle, waveform, and frequency.

13. The method of claim 12, wherein the at least one grid parameter is selected from the group consisting of voltage, phase sequence, phase angle, waveform, and frequency.

14. A method for supplying electrical energy to an electrical grid from a heat engine system, comprising: circulating via a turbo pump a working fluid within a working fluid circuit of the heat engine system, wherein the working fluid circuit has a high pressure side and a low pressure side and at least a portion of the working fluid is in a supercritical state; transferring thermal energy from a heat source stream to the working fluid by at least a primary heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit; feeding the working fluid into a power turbine and converting the thermal energy from the working fluid to mechanical energy of the power turbine; converting the mechanical energy into electrical energy by a power generator coupled to the power turbine; comparing a plurality of electrical energy parameters of the electrical energy converted by the power generator with a plurality of grid parameters of the electrical grid configured to be electrically coupled to the power generator; modulating at least one valve selected from a power turbine trim valve, a power turbine throttle valve, a power turbine bypass valve, a drive turbine throttle valve, a turbo pump bypass valve, or combinations of valves thereof, each operatively coupled to a process control system to change a flow rate of the working fluid fed into the power turbine, such that the a plurality of electrical energy parameters of the electrical energy converted by the power generator is substantially similar to the plurality of grid parameters of the electrical grid, thereby synchronizing the power generator with the electrical grid; and closing the generator breaker, such that the power generator and electrical grid are electrically coupled and the electrical energy is supplied to the electrical grid.

15. The method of claim 14, wherein the plurality of electrical energy parameters includes voltage, phase sequence, phase angle, waveform, and frequency.

16. The method of claim 14, wherein the plurality of grid parameters includes voltage, phase sequence, phase angle, waveform, and frequency.

17. The method of claim 14, wherein the heat engine system comprises a plurality of sensors, at least one sensor of the plurality of sensors being disposed adjacent each of the power turbine trim valve, the power turbine throttle valve, the power turbine bypass valve, the turbo pump bypass valve, and the drive turbine throttle valve, and further being operatively coupled to the process control system and configured to detect at least one system parameter, and the method further comprises transmitting from the at least one sensor a sensor signal based on the at least one system parameter to the process control system.

18. The method of claim 17, wherein the process control system includes at least one controller including a ramp profile algorithm, such that the at least one controller is configured to manipulate one or more of the power turbine trim valve, the power turbine throttle valve, the power turbine bypass valve, the turbo pump bypass valve, and the drive turbine throttle valve to a predetermined valve position over a predetermined time period based on at least one of the sensor signals.

19. The method of claim 14, wherein the working fluid comprises carbon dioxide.

20. A method for supplying electrical energy to an electrical grid from a heat engine system, comprising: starting a drive turbine from a working fluid including carbon dioxide being circulated via a start pump within a working fluid circuit of the heat engine system; circulating via a turbo pump coupled to the drive turbine the working fluid within the working fluid circuit of the heat engine system, wherein the working fluid circuit has a high pressure side and a low pressure side and at least a portion of the working fluid is in a supercritical state; transferring thermal energy from a heat source stream to the working fluid by at least a primary heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit; feeding the working fluid into a power turbine and converting the thermal energy from the working fluid to mechanical energy of the power turbine; converting the mechanical energy into electrical energy by a power generator coupled to the power turbine; comparing a plurality of electrical energy parameters of the electrical energy converted by the power generator with a plurality of grid parameters of the electrical grid configured to be electrically coupled to the power generator, wherein the plurality of electrical energy parameters includes voltage, phase sequence, phase angle, waveform, and frequency; and the plurality of grid parameters includes voltage, phase sequence, phase angle, waveform, and frequency; modulating a power turbine trim valve, a power turbine throttle valve, a power turbine bypass valve, a turbo pump bypass valve, a drive turbine throttle valve, or combinations of valves thereof, each operatively coupled to a process control system to change a flow rate of the working fluid fed into the power turbine, such that the plurality of electrical energy parameters of the electrical energy converted by the power generator is substantially similar to the plurality of grid parameters of the electrical grid, thereby synchronizing the power generator with the electrical grid; and closing the generator breaker, such that the power generator and electrical grid are electrically coupled and the electrical energy is supplied to the electrical grid.