Air Source Heat Pump System and Method of Use for Industrial Steam Generation

This application is a continuation of U.S. patent application Ser. No. 18/324,066, filed May 25, 2023, which is a continuation of International Patent Application No. PCT/US2022/072937, filed Jun. 14, 2022, which claims the benefit of U.S. Provisional Application No. 63/211,297, filed Jun. 16, 2021, and U.S. Provisional Application No. 63/290,784, filed Dec. 17, 2021, each of which is hereby incorporated by reference in its entirety into the present application.

In the United States, the industrial sector accounts for 22% of greenhouse gas emissions, which equals approximately 1.5 gigatonnes of equivalent carbon dioxide per year (GtCO2e/year). Within the industrial sector, steam production for process heat is one of the largest energy consumers, accounting for almost 4 quads of U.S. primary energy consumption and emitting more than 200 MMtonnes of carbon dioxide (CO2) every year. Most of these emissions are generated from burning of fuels for conventional boilers, cogeneration, and process heating.

Accordingly, there is a need in the art for systems and methods of steam generation for industrial heat that are more efficient and generate less carbon emissions. It is with these thoughts in mind, among others, that the air source heat pump system and method of use for industrial steam generation were developed.

Aspects of the present disclosure include a system for generating steam. The system may include a first heat pump cycle and a second heat pump cycle. The first heat pump cycle is configured to circulate a first working fluid. The first heat pump cycle may include: first heat exchanger, a first compressor, a second heat exchanger, and a first expansion valve. The first heat exchanger is in fluid communication with the first expansion valve and configured to receive the first working fluid from the first expansion valve. The first working fluid absorbs heat in the first heat exchanger. The first compressor is in fluid communication with the first heat exchanger and configured to receive the first working fluid from the first exchanger. The first compressor is configured to increase the pressure and temperature of the first working fluid. The second heat exchanger is in fluid communication with the first compressor and configured to receive the first working fluid from the first compressor. The second heat exchanger is configured to reject heat from the first working fluid to a second working fluid of the second heat pump cycle. The first expansion valve is in fluid communication with the second heat exchanger and is configured to receive the first working fluid from the second heat exchanger. The first expansion valve is configured to expand the first working fluid to a lower pressure.

The second heat pump cycle is configured to circulate the second working fluid. The second heat pump cycle may include: the second heat exchanger, a second compressor, a third heat exchanger, and a second expansion valve. The second heat exchanger is in fluid communication with a second expansion valve and is configured to receive the second working fluid from the second expansion valve. The second working fluid absorbs heat from the first working fluid in the second heat exchanger. The second compressor is in fluid communication with the second heat exchanger and is configured to receive the second working fluid from the second heat exchanger. The second compressor is configured to increase the pressure and temperature of the second working fluid. The third heat exchanger is in fluid communication with the second compressor and is configured to receive the second working fluid from the second compressor. The third heat exchanger is in fluid communication with a third working fluid in a steam generation system. The third heat exchanger is configured to reject heat from the second working fluid to the third working fluid in the steam generation system, the third working fluid being water. The second expansion valve is in fluid communication with the third heat exchanger and configured to receive the second working fluid from the third heat exchanger. The second expansion valve is configured to expand the second working fluid to a lower pressure.

In certain instances, the system further includes: a first suction-line heat exchanger and a second suction-line heat exchanger. The first suction-line heat exchanger is in fluid communication with and between the first heat exchanger and the first compressor. The first suction-line heat exchanger is in fluid communication with and between the second heat exchanger and the first expansion valve. The first suction-line heat exchanger is configured to preheat the first working fluid prior to compressing the first working fluid with the outflow of the first working fluid from the second heat exchanger. The second suction-line heat exchanger is in fluid communication with and between the second heat exchanger and the second compressor. The second suction-line heat exchanger is in fluid communication with and between the third heat exchanger and the second expansion valve. The second suction-line heat exchanger is configured to preheat the second working fluid prior to compressing the second working fluid with the outflow of the second working fluid from the third heat exchanger.

In certain instances, the first heat exchanger facilitates heat transfer from a first transfer fluid to the first working fluid, the first fluid being air.

In certain instances, the steam generation system may include a steam compressor in fluid communication with the third heat exchanger, the steam compressor configured to increase the pressure and temperature of the third working fluid so as to output steam. In certain instances, the system may further include the steam generation system.

In certain instances, the steam compressor may be configured to deliver steam at temperatures of greater than or equal to 120 degrees Celsius from heat delivered from the first and second heat pump cycles.

In certain instances, the system may further include a control system in electrical communication with the first and second heat pump cycles, the control system configured to control the delivery of heat to the third working fluid from at least one or both of a first heat source, and a second heat source, the first heat source including the first and second heat pump cycles, the second heat source including an alternate heat source.

In certain instances, the first and second compressors are centrifugal compressors. In certain instances, the first and second compressor are electrically powered.

In certain instances, the first working fluid may be one of a fluorocarbon, a hydrofluoroolefin, a hydrofluoroether, a hydrocarbon, carbon dioxide, ammonia, or water, and the second working fluid may be one of a fluorocarbon, a hydrofluoroolefin, a hydrofluoroether, a hydrocarbon, carbon dioxide, ammonia, or water.

Aspects of the present disclosure include a system for generating steam for industrial heat. The system may include a first heat pump cycle and a second heat pump cycle. The first heat pump cycle configured to circulate a first working fluid. The first heat pump cycle may include: an evaporator, a first compressor, a heat exchanger, and a first expansion valve. The evaporator is in fluid communication with the first expansion valve and configured to receive the first working fluid from the first expansion valve. The first working fluid absorbs heat in the evaporator. The first compressor is in fluid communication with the evaporator and configured to receive the first working fluid from the evaporator. The first compressor is configured to increase the pressure and temperature of the first working fluid. The heat exchanger is in fluid communication with the first compressor and configured to receive the first working fluid from the first compressor. The heat exchanger is configured to reject heat from the first working fluid to a second working fluid of the second heat pump cycle. The first expansion valve is in fluid communication with the heat exchanger and configured to receive the first working fluid from the heat exchanger, the first expansion valve configured to expand the first working fluid to a lower pressure.

The second heat pump cycle is configured to circulate the second working fluid. The second heat pump cycle may include: the heat exchanger, suction-line heat exchanger, a second compressor, a steam generator, and a second expansion valve. The heat exchanger is in fluid communication with a second expansion valve and configured to receive the second working fluid from the second expansion valve. The second working fluid absorbs heat from the first working fluid in the heat exchanger. The suction-line heat exchanger is in fluid communication with the heat exchanger and configured to receive the second working fluid from the heat exchanger. The suction-line heat exchanger is configured to preheat the second working fluid prior to compressing the second working fluid. The second compressor is in fluid communication with the suction-line heat exchanger and configured to receive the second-working fluid from the suction-line heat exchanger. The second compressor is configured to increase the pressure and temperature of the second working fluid. The steam generator is in fluid communication with the second compressor and configured to receive the second working fluid from the second compressor. The steam generator is configured to reject heat from the second working fluid to a transfer fluid. The suction-line heat exchanger is in fluid communication with the steam generator. The second expansion valve is in fluid communication with the suction-line heat exchanger and configured to receive the second working fluid from the suction-line heat exchanger. The second expansion valve is configured to expand the second working fluid to a lower pressure.

In certain instances, the system may further include: a third compressor and a fourth compressor. The third compressor is in the first heat pump cycle. The third compressor is in fluid communication with and positioned between the first compressor and the heat exchanger. The third compressor is configured to receive the first working fluid from the first compressor. The third compressor is configured to increase the pressure and temperature of the first working fluid. The fourth compressor is in the second heat pump cycle. The fourth compressor is in fluid communication with the second compressor and configured to receive the second-working fluid from the second compressor. The fourth compressor is configured to increase the pressure and temperature of the second working fluid.

In certain instances, the first compressor and third compressor are rotatably coupled together on a shaft and electrically powered by a motor. In certain instances, the second compressor may be electrically powered by a first motor and the fourth compressor may be electrically powered by a second motor.

In certain instances, the first heat pump cycle includes a first economizer and a third expansion valve, the first economizer configured to receive a primary fluid stream of the first working fluid from the heat exchanger and reject heat therefrom in the first economizer, the third expansion valve configured to receive a secondary fluid stream of the first working fluid from the heat exchanger and expand the secondary fluid stream of the first working fluid to a lower pressure prior to entering the first economizer, and the secondary fluid stream of the first working fluid configured to absorb heat in the first economizer, wherein the secondary fluid stream of the first working fluid may be directed to an inflow of the third compressor, and wherein the primary fluid stream of the first working fluid may be directed to an inflow of the first expansion valve.

In certain instances, the first compressor is configured to receive the primary fluid stream of the first working fluid and the second compressor may be configured to receive the primary and secondary fluid streams of the first working fluid.

In certain instances, the second heat pump cycle includes a second economizer and a fourth expansion valve, the second economizer configured to receive a primary fluid stream of the second working fluid from the steam generator and reject heat therefrom in the second economizer, the fourth expansion valve configured to receive a secondary fluid stream of the second working fluid from the steam generator and expand the secondary fluid stream of the second working fluid to a lower pressure prior to entering the second economizer, and the secondary fluid stream of the second working fluid configured to absorb heat in the second economizer, wherein the secondary fluid stream of the second working fluid may be directed to an inflow of the fourth compressor, and wherein the primary fluid stream of the second working fluid may be directed to the suction-line heat exchanger to preheat the second working fluid exiting the heat exchanger.

In certain instances, the third compressor may be configured to receive the primary fluid stream of the second working fluid and the fourth compressor may be configured to receive the primary and secondary fluid streams of the second working fluid.

In certain instances, the steam generator may be configured to deliver steam at temperatures of greater than or equal to 150 degrees Celsius.

In certain instances, the evaporator may be configured to receive a first transfer fluid, the evaporator configured to reject heat from the first transfer fluid, wherein the first transfer fluid may be air.

Aspects of the present disclosure include a method for generating steam for industrial heat. The method may include: rejecting heat from a first circulating fluid to a first working fluid in a first heat exchanger; preheating the first working fluid in a first suction-line heat exchanger prior to compressing the first working fluid; compressing the first working fluid via a first compressor, thereby increasing the pressure of the first working fluid; rejecting heat from the first working fluid to a second working fluid in a second heat exchanger; expanding the first working fluid to a lower pressure via a first expansion valve; preheating the second working fluid in a second suction-line heat exchanger prior to compressing the second working fluid; compressing the second working fluid via a second compressor, thereby increasing the pressure of the second working fluid; rejecting heat from the second working fluid to a third working in a third heat exchanger, the third working fluid being part of a steam generation system; and expanding the second working fluid to a lower pressure via a second expansion valve.

In certain instances, the steam generation system includes a steam compressor configured to generate steam from the third working fluid. In certain instances, the steam compressor may be configured to deliver steam at temperatures of greater than or equal to 120 degrees Celsius. In certain instances, the first and second compressors are centrifugal compressors. In certain instances, the first and second compressor are electrically powered.

Aspects of the present disclosure include a method for generating steam for industrial heat. The method may include: absorbing heat in a first working fluid in an evaporator, the first working fluid circulating in a first heat pump cycle; compressing the first working fluid in a first compressor, thereby increasing the pressure of the first working fluid; compressing the first working fluid in a second compressor, thereby increasing the pressure of the first working fluid; rejecting heat from the first working fluid to a second working fluid in a heat exchanger, the second working fluid circulating in a second heat pump cycle; expanding the first working fluid to a lower pressure via a first expansion valve; preheating the second working fluid in a suction-line heat exchanger prior to compressing the second working fluid in a third compressor; compressing the second working fluid in the third compressor, thereby increasing the pressure of the second working fluid; compressing the second working fluid in a fourth compressor, thereby increasing the pressure of the second working fluid; rejecting heat from the second working fluid in a steam generator; rejecting heat from the second working fluid in the suction-line heat exchanger after exiting the steam generator; and expanding the second working fluid to a lower pressure via a second expansion valve.

In certain instances, the system may further include splitting the first working fluid into a primary fluid stream and a secondary fluid stream; expanding the secondary fluid stream of the first working fluid to a lower pressure via a third expansion valve; absorbing heat in the secondary fluid stream of the first working fluid in a first economizer; and rejecting heat from the primary fluid stream of the first working fluid to the secondary fluid stream of the first working fluid in the first economizer.

In certain instances, the system further may include directing the primary fluid stream of the first working fluid to the first expansion valve; and directing the secondary fluid stream of the first working fluid to an inflow of the second compressor.

In certain instances, the first and second compressors are rotatably coupled together via a shaft and are powered by a motor.

In certain instances, heat may be absorbed in the evaporator from ambient air, and the steam generator may be configured to deliver steam at 150 degrees Celsius or greater.

Aspects of the present disclosure include a system for generating steam for industrial heat. The system may include a plurality of heat pump cycles in thermal communication with each other and in thermal communication with a steam generation cycle. The plurality of heat pump cycles may include a first heat pump cycle and a second heat pump cycle. The first heat pump is configured to circulate a first a working fluid and include a first heat exchanger and a first suction-line heat exchanger. The second heat pump cycle is configured to circulate a second working fluid and include a second heat exchanger and a second suction-line heat exchanger. The first suction-line heat exchanger is configured to preheat the first working fluid prior to compressing the first working fluid. The first heat exchanger is configured to transfer heat from the first working fluid to the second working fluid. The second suction-line heat exchanger is configured to preheat the second working fluid prior to compressing the second working fluid. The second heat exchanger is configured to transfer heat from the second working fluid a third working fluid in the steam generation cycle.

Aspects of the present disclosure include an energy arbitrage system including a cascading heat pump system that generates steam. The energy arbitrage system further includes a computing device in communication with the cascading heat pump system for generating steam and with a boiler configured to generate steam. The computing device includes a processing device and a computer-readable medium with one or more executable instructions stored thereon, wherein the processing device of the computing device executes the one or more instructions to perform the operations of: receive steam demands from a facility; sends instructions to the cascading heat pump system for generating steam to provide for the steam demands from the facility; and sends instructions to the boiler to provide for a remaining portion of the steam demands from the facility if the cascading heat pump system for generating steam cannot fulfill all of the steam demands.

In certain instances, the computing device is in further communication with a renewable energy source configured to provide electricity to the electric grid and to the cascading heat pump system. The processing device of the computing device executes the one or more instructions to perform the further operations of: receiving information associated with an amount of electricity produced by the renewable energy source; sending instructions to the renewable energy source to supply electricity to the system for generating steam; sending instructions to the renewable energy source to supply excess electricity that is not required by the cascading heat pump system for generating steam to the electric grid; and sending instructions to the cascading heat pump system for generating steam to draw electricity from the electric grid if the renewable energy source supplies an insufficient amount of electricity.

Aspects of the present disclosure include an energy arbitrage system including a cascading heat pump system that generates steam. The energy arbitrage system further includes a computing device in communication with the cascading heat pump system for generating steam and with a renewable energy source configured to provide electricity to the electric grid and to the system for generating steam. The computing device includes a processing device and a computer-readable medium with one or more executable instructions stored thereon, wherein the processing device of the computing device executes the one or more instructions to perform the operations of: receiving information associated with an amount of electricity produced by the renewable energy source; sending instructions to the renewable energy source to supply electricity to the system for generating steam; sending instructions to the renewable energy source to supply excess electricity that is not required by the cascading heat pump system for generating steam to the electric grid; and sending instructions to the cascading heat pump system for generating steam to draw electricity from the electric grid if the renewable energy source supplies an insufficient amount of electricity.

Aspects of the present disclosure include an energy arbitrage system including a cascading heat pump system that generates steam. The energy arbitrage system further includes a computing device in communication with: the system for generating steam; a thermal storage unit configured to deliver steam; and a renewable energy source configured to provide electricity to the thermal storage unit and to the system for generating steam. The computing device includes a processing device and a computer-readable medium with one or more executable instructions stored thereon, wherein the processing device of the computing device executes the one or more instructions to perform the operations of: receiving information associated with an amount of electricity produced by the renewable energy source; sending instructions to the renewable energy source to supply electricity to the system for generating steam; and sending instructions to the renewable energy source to supply excess electricity that is not required by the cascading heat pump system for generating steam to the thermal storage unit.

In certain instances, the processing device of the computing device executes the one or more instructions to perform the further operations of: when the amount of electricity produced by the renewable energy source is insufficient to operate the system for generating steam, sending instructions to the thermal storage units to supply steam to the facility.

It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein. As such, elements of one system can be incorporated into any of the systems described herein. And, elements can be subtracted from any of the systems described herein without limitation.

Several definitions that apply throughout this disclosure will now be presented.

The term “conduit” is defined as a tube, pipe, or channel to convey, channel, or otherwise flow fluid. The conduit may be a system conduit or may connect two elements within the system, thereby establishing fluid communication between the two elements.

The term “coupled” is defined as connected, whether directly, or indirectly, through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently or releasably connected.

illustrates an exemplary steam generation systemin an industrial application. A specific example of the components of such a system will be shown and described in more detail in reference to.provides an overview of the system, which includes a two-stage air-source heat pump comprising a bottoming heat pump(i.e., a first heat pump) and a topping heat pump(i.e., a second heat pump) that are thermally coupled together by an intermediate heat exchanger (i.e., a heat exchanger). The steam generation systemmay also include a steam compressor. In the intermediate heat exchanger, the working fluid in the bottoming heat pumprejects heat to the working fluid in the topping heat pump. Then, in a steam generator (i.e., a heat exchanger) the working fluid of the topping heat pumprejects heat to a third working fluid. In some instances, the third working fluidmay pass through a steam compressorafter absorbing heat from steam generator.

Each of the heat pumps,are used to “pump” lower temperature heat to a higher temperature by using an electrical energy source. Currently available heat pumps either do not generate a large enough temperature lift to produce steam or they require the use of a higher temperature waste heat stream as the energy source. As described herein, the systemutilizes a “cascading” or series of heat pump cycles in thermal connection with each other that progressively raise the temperatures to deliver decarbonized steam at a lower cost than alternative sources. The systemdoes not require waste heat to deliver high temperature steam.

The steam generation systemofmay be generally applicable to a variety of industrial processes and/or manufacturing environments. For example, the steam generation systemmay be used to generate industrial steam. In one instance, the bottoming heat pumpand the topping heat pumpmay be modular, electric-powered air-source heat pumps arranged in a thermally cascading manner. This modularity may enable industry-specific needs, such as different steam pressures and capacities. While the systems in this application illustrate two heat pump cycles (i.e., topping heat pump and bottoming heat pump), the system is scalable and can be modified to include additional heat pumps. In certain instances, the system may include three heat pump cycles. In certain instances, the system may include four heat pump cycles. In certain instances, the system may include five heat pump cycles. In one instance, the steam generation systemmay generate steam at a temperature of approximately 150-degrees Celsius and at a pressure of approximately 4.5 bar, which may satisfy a majority of industrial steam production needs including the food, paper, and chemical industries.

In the steam generation systemof, the bottoming heat pumpmay utilize ambient air as a heat source (i.e., air sourced). The evaporator (i.e., heat exchanger) of the bottoming heat pumpcaptures heat from the ambient air. The heat is absorbed by the evaporator of the bottoming heat pump, thereby evaporating the working fluid within the bottoming heat pump.

The topping heat pumpis thermally coupled to the bottoming heat pumpby an intermediate heat exchanger. In one instance, the intermediate heat exchanger comprises the condenser of the bottoming heat pumpand the evaporator of the topping heat pump. Thus, within the intermediate heat exchanger, the condenser of the bottoming heat pumprejects heat and the evaporator of the topping heat pumpabsorbs heat.

The conduit (i.e., fluid flow path) for a third working fluidis coupled to the topping heat pumpby a steam generator (i.e., heat exchanger). In one instance, the steam generator comprises the condenser of the topping heat pumpand the conduit for a third working fluid. Thus, within the steam generator, the condenser of the topping heat pumprejects heat and the third working fluidabsorbs heat.

Before entering the steam generator, a mechanical pump may be used to increase the pressure of the third working fluid. After the third working fluidexits the steam generator, a steam compressormay be used to increase the pressure and the temperature of the third working fluid. Thus, a mechanical pump may be installed before the steam generator, a steam compressormay be installed after the steam generator, or both.

In one instance, the third working fluidis water. Within the steam generator, the water absorbs heat from the working fluid of the topping heat pump. In one example, the pressure of the water may be greater than or equal to the target steam saturation temperature. In other words, the water may absorb sufficient heat from the topping heat pumpto evaporate into steam. After the steam generator, a steam compressormay be used to directly increase the pressure and temperature of the steam. In one example, the pressure of the water may be less than the target steam saturation temperature after exiting the steam generator and, therefore, the steam compressormay be used to increase the pressure of the water to the required saturation temperature. The systemmay be retrofitted to existing steam generation systems within facilities. Alternatively, the systemmay include a steam generation system as part of the overall system.

The steam generation systemmay be powered by electricity. In other words, electricityis input into the steam generation systemin order to generate steam. For example, the steam generation systemmay be powered through grid electricity, onsite renewable energy, or a combination thereof. The steam generation systemmay enable economic decarbonization of industrial steam production, as steam energy in the industrial sectoraccounts for almost 4 quads of U.S. primary energy consumption and emits more than 200 MMtonnes of COevery year.

In some instances, the steam generation systemmay incorporate energy arbitrage. In other words, energy arbitrage may be used in conjunction with the steam generation systemby incorporating additional systems that can provide heating to the steam generation systemand/or provide electricity to the heat pump systems described herein. The additional systems could include solar arrays, thermal storage systems, and fuel boilers (e.g., natural gas, coal, waste products, or biomass), among other systems. These systems can be coupled to the steam generation systemand/or the heat pump systems and selectively actuated to provide heat to the systemand/or electricity to the heat pump systems. The specific system that provides heat to the steam generation systemand/or electricity to the heat pump systems can be determined by the availability, the price of the energy source of the system applying heat or electricity, as well as other factors including the requirements of the steam generation system. By incorporating energy arbitrage, the steam generation systemis capable of generating consistent steam delivery while significantly reducing carbon emissions.

In some instances, the steam generation systemmay include more than two heat pumps arranged in a thermal cascading manner to heat pump air to generate steam. In one instance, the steam generation systemmay include three heat pumps. For example, the steam generation systemmay include a bottoming heat pump (i.e., a first heat pump), an intermediate heat pump (i.e., a second heat pump), and a topping heat pump (i.e., a third heat pump). In another instance, the steam generation systemmay include four heat pumps. For example, the steam generation systemmay include a bottoming heat pump (i.e., a first heat pump), a first intermediate heat pump (i.e., a second heat pump), a second intermediate heat pump (i.e., a third heat pump), and a topping heat pump (i.e., a fourth heat pump). In another instance, the steam generation systemmay include five heat pumps.