Heat energy utilization system

Abstract

A power generation system includes a prime mover subsystem and a Rankine-cycle heat energy utilization subsystem. The waste heat stream from the prime mover subsystem provides sufficient thermal content to power the heat energy utilization subsystem. The heat energy utilization subsystem can include a hermetically sealed scroll device, which can expand the working fluid through a single or dual scroll pair configuration. The heat energy utilization subsystem may also include a load-splitting controller, quick-start features and a capacity control module to facilitate rapid response to variable load conditions, as well as provide stand-alone operational capability. The load-splitting controller may incorporate a fuzzy logic controller to coordinate operation between the two subsystems. Energy generated by the heat energy utilization subsystem can be in the form of heat for various domestic and process needs, or can provide supplemental electric current.

What is claimed is:  
     
         1 . A heat energy utilization system comprising: 
 a thermal circuit;    a pump to circulate a working fluid through said thermal circuit;    a power module comprising: 
 an expander; and  
 a load absorption device coupled to said expander such that at least a portion of the energy produced by the expansion of said working fluid in said expander operates said load absorption device;  
   a first heat exchanger including: 
 a first inlet and a first outlet together in fluid communication with said thermal circuit; and  
 a second inlet and a second outlet together in heat exchange relationship with said thermal circuit; and  
   a second heat exchanger, wherein said pump, power module, first heat exchanger and second heat exchanger are connected via said thermal circuit so as to be in fluid communication with one another such that, upon exchange of heat in said first heat exchanger, the increase in energy content in said working fluid is converted to useable work in said load absorption device.    
     
     
         2 . A heat energy utilization system according to  claim 1 , wherein said second inlet in said first heat exchanger is configured to accept an externally supplied heat stream.  
     
     
         3 . A heat energy utilization system according to  claim 2 , wherein said power module is hermetically sealed.  
     
     
         4 . A heat energy utilization system according to  claim 3 , further comprising: 
 a lubricant pump disposed within said power module and operatively responsive to said expander; and    a lubricant circuit in fluid communication with said lubricant pump, said lubricant circuit including a lubricant droplet separator, such that upon operation of a lubricant pump, said lubricant circuit can circulate a lubricant within said power module.    
     
     
         5 . A heat energy utilization system according to  claim 4 , further comprising a desuperheating heat exchanger disposed within said power module, said desuperheating heat exchanger in thermal communication with said expander, whereby said desuperheating heat exchanger reduces the thermal content of fluid exiting said expander.  
     
     
         6 . A heat energy utilization system according to  claim 5 , wherein said load absorption device is a generator comprising: 
 a field-generating rotor; and    a stator coil mounted to said hermetically sealed power module so that upon movement of said field-generating rotor, it electrically interacts with said stator coil to produce an electric potential.    
     
     
         7 . A heat energy utilization system according to  claim 6 , wherein said thermal circuit is a closed loop.  
     
     
         8 . A heat energy utilization system according to  claim 1 , wherein said working fluid is an organic refrigerant.  
     
     
         9 . A heat energy utilization system according to  claim 6 , wherein said expander is a scroll device defined by a scroll housing, said scroll device including at least one scroll pair comprising a pair of involute spiral wrap members and a rotatable shaft coupled to said at least one scroll pair such that the expansion of said working fluid through said at least one scroll pair causes said rotatable shaft to rotate.  
     
     
         10 . A heat energy utilization system according to  claim 9 , wherein said field-generating rotor is rotatably coupled to said rotatable shaft.  
     
     
         11 . A heat energy utilization system according to  claim 9 , further comprising a second scroll pair coupled to said first pair through said rotatable shaft.  
     
     
         12 . A heat energy utilization system according to  claim 11 , further including at least one process heat utilization module in thermal communication with said thermal circuit, said process heat utilization module configured to provide process heat to an external user.  
     
     
         13 . A heat energy utilization system according to  claim 12 , wherein said at least one process heat utilization module includes a first process heat utilization module and a second process heat utilization module, said first process heat utilization module configured to extract higher temperature energy than said second process heat utilization module.  
     
     
         14 . A heat energy utilization system according to  claim 1 , further comprising an auxiliary burner in thermal communication with said heat stream.  
     
     
         15 . A heat energy utilization system according to  claim 14 , further comprising: 
 a logic and control module in signal communication with each of said load absorption device, auxiliary burner, pump, and adapted to be in signal communication with said heat stream;    an energy storage device in electrical communication with said logic and control module; and    a recharging module in electrical communication with said load absorption device and said energy storage device such that said logic and control module is configured to initiate a start-up sequence for said heat energy utilization subsystem, and said recharging module recharges said energy storage device during normal operation of said heat energy utilization system.    
     
     
         16 . A heat energy utilization system according to  claim 15 , wherein said energy storage device is an electrical battery.  
     
     
         17 . A heat energy utilization system according to  claim 16 , further comprising: 
 an accumulator in fluid communication with said first heat exchanger and expander to collect and store at least a portion of excess energy from said heat stream;    a control valve in fluid communication with said accumulator; and    an isolation valve disposed within said thermal circuit, said isolation valve to be used to selectively isolate said first heat exchanger from said expander,    whereby, upon initiation and subsequent operation of said heat energy utilization system, it is capable of sustained operation.    
     
     
         18 . A heat energy utilization system adapted to be coupled to a heat source, said heat energy utilization system comprising: 
 a thermal circuit;    a pump to circulate a working fluid through said thermal circuit;    a hermetically sealed power module operating as a scroll expander, said hermetically sealed power module comprising: 
 a scroll housing;  
 a plurality of scroll pairs mounted in said scroll housing, each of which includes a pair of meshed axially extending involute spiral wrap members;  
 a rotatable shaft coupled to said plurality of scroll pairs such that the expansion of said working fluid through said plurality of scroll pairs causes said rotatable shaft to rotate;  
 a throttle valve disposed in said thermal circuit to permit a predetermined amount of said working fluid to enter said scroll expander; and  
 a generator operatively responsive to said rotatable shaft to produce work;  
   a first heat exchanger including: 
 a first inlet and a first outlet together in fluid communication with said thermal circuit; and  
 a second inlet and a second outlet together in heat exchange relationship with said first inlet and outlet; and  
   a second heat exchanger, wherein said pump, first heat exchanger, expander and second heat exchanger are connected via said thermal circuit so as to be in fluid communication with one another such that, upon exchange of heat between said first inlet and outlet and said second inlet and outlet, the increase in energy content in said working fluid is converted to electric potential in said generator.    
     
     
         19 . A power generation system for providing a primary and secondary source of output power comprising: 
 a prime mover subsystem including: 
 means for generating a primary source of power; and  
 means for generating a heat stream; and  
   a heat energy utilization subsystem for coupling to said prime mover subsystem, said heat energy utilization subsystem including: 
 a thermal circuit;  
 a pump to circulate a working fluid through said thermal circuit;  
 a power module comprising: 
 an expander;  
 a load absorption device coupled to said expander such that at least a portion of the energy produced by the expansion of said working fluid operates to produce power;  
 
 a first heat exchanger including: 
 a first inlet and a first outlet together in fluid communication with said thermal circuit; and  
 a second inlet and a second outlet together in heat exchange relationship with said first inlet and outlet; and  
 
 a second heat exchanger for cooling said working fluid,  
   wherein said pump, first heat exchanger, expander and second heat exchanger are connected via said thermal circuit so as to be in fluid communication with one another such that, upon introduction of said heat stream from said prime mover, at least a portion of the increase in energy content in said working fluid produces useable work in said load absorbing device.    
     
     
         20 . A power generation system according to  claim 19 , further including a throttle valve disposed in said thermal circuit to permit a predetermined amount of working fluid to enter said expander.  
     
     
         21 . A power generation system according to  claim 20 , wherein said power module is hermetically sealed in a hermetic shell.  
     
     
         22 . A power generation system according to  claim 21 , further comprising an auxiliary burner in thermal communication with said heat stream to augment the thermal content of said heat stream.  
     
     
         23 . A power generation system of  claim 22 , further comprising: 
 a logic and control module in electrical communication with each of said generator, auxiliary burner, pump, and means for generating a primary source of power;    an energy storage device in electrical communication with said logic and control circuit; and    a recharging module in electrical communication with said generator and said energy storage device such that said logic and control module can initiate a start-up sequence for said heat energy utilization subsystem, and said recharging module recharges said energy storage device during normal operation of said power generation system.    
     
     
         24 . A power generation system according to  claim 23 , wherein said energy storage device is an electrical battery.  
     
     
         25 . A power generation system according to  claim 24 , further comprising: 
 an accumulator in fluid communication with said first heat exchanger and expander to collect and store at least a portion of excess thermal energy from said heat stream;    a control valve in fluid communication with said accumulator; and    an isolation valve disposed within said thermal circuit, said isolation valve to be used to selectively isolate said first heat exchanger from said expander.    
     
     
         26 . A power generation system according to  claim 25 , further comprising a capacity control module to facilitate the responsiveness of said heat energy utilization subsystem, said capacity control module comprising: 
 a speed sensor coupled to said expander;    a feed-back controller operatively responsive to a signal from said speed sensor so as to actuate said isolation valve;    a bypass valve disposed within said heat stream to control the flow of said heat stream into said first heat exchanger module;    a plurality of sensors disposed in said thermal circuit to measure said working fluid temperature and pressure; and    a proportional integral differential logic controller to control said bypass valve, said pump and said auxiliary burner based on first heat exchanger sensor input signals.    
     
     
         27 . A power generation system according to  claim 26 , wherein said speed sensor and feed-back controller are packaged within said hermetic shell of said power module.  
     
     
         28 . A power generation system according to  claim 27 , further comprising a load splitting module to analyze and respond to varying load conditions such that it causes said prime mover subsystem and said heat energy utilization subsystem to provide substantially uniform and dynamic load components, respectively, to the composite electric generation profile.  
     
     
         29 . A power generation system according to  claim 28 , wherein said load splitting module includes a fuzzy logic controller.  
     
     
         30 . A power generation system according to  claim 19 , further comprising: 
 a lubricant pump disposed within said power module and operatively responsive to said expander; and    a lubricant circuit in fluid communication with said lubricant pump, said lubricant circuit including a lubricant droplet separator, such that upon operation of said lubricant pump, said lubricant circuit can circulate a lubricant within said power module.    
     
     
         31 . A power generation system according to  claim 19 , further comprising a desuperheating heat exchanger disposed within said power module, said desuperheating heat exchanger in thermal communication with said expander, whereby said desuperheating heat exchanger reduces the thermal content of said working fluid exiting said expander.  
     
     
         32 . A power generation system according to  claim 19 , wherein said load absorption device is a generator comprising: 
 a field-generating rotor; and    a stator coil mounted to said hermetically sealed power module so that upon movement of said field-generating rotor, it electrically interacts with said stator coil to produce an electric potential.    
     
     
         33 . A power generation system according to  claim 19 , wherein said thermal circuit is a closed loop.  
     
     
         34 . A power generation system according to  claim 19 , wherein said working fluid is an organic refrigerant.  
     
     
         35 . A power generation system according to  claim 19 , further including at least one process heat utilization module in thermal communication with said thermal circuit, said process heat utilization module configured to provide process heat to an external user.  
     
     
         36 . A power generation system according to  claim 35 , wherein said at least one process heat utilization module includes a first process heat utilization module and a second process heat utilization module, said first process heat utilization module configured to extract higher temperature energy than said second process heat utilization module.  
     
     
         37 . A power generation system according to  claim 19 , wherein said prime mover subsystem is a fuel cell.  
     
     
         38 . A power generation system according to  claim 19 , wherein said prime mover subsystem is a microturbine.  
     
     
         39 . A power generation system according to  claim 38 , where said microturbine further comprises a recuperator in thermal communication with said means for generating a heat stream, said recuperator adapted for preheating air prior to combustion of said air in said prime mover subsystem.  
     
     
         40 . A power generation system according to  claim 39 , wherein said combustion takes place in a catalytic combustor.  
     
     
         41 . A power generation system according to  claim 19 , wherein said expander of said heat energy utilization subsystem is a scroll device, and includes a scroll housing that contains at least one pair of meshed axially extending involute spiral wrap members and a rotatable shaft coupled to said at least one scroll pair such that the expansion of said working fluid through said at least one scroll pair causes said rotatable shaft to rotate.  
     
     
         42 . A power generation system according to  claim 41 , further comprising a second scroll pair of meshed axially extending involute spiral wrap members coupled to the first scroll pair of said at least one scroll pair.  
     
     
         43 . An integrated power generation system for providing a primary and secondary source of power, comprising: 
 a microturbine subsystem configured to generate a heat stream; and    a heat energy utilization subsystem coupled to said microturbine, providing said secondary source of power, including: 
 a closed-loop thermal circuit;  
 a pump to circulate a working fluid through said thermal circuit;  
 a first heat exchanger including: 
 a first inlet and outlet for said closed-loop thermal circuit;  
 a second inlet and outlet in heat exchange relationship with said first inlet and outlet, said second inlet and outlet in fluid communication with said heat stream;  
 
 a hermetically sealed power module comprising: 
 a scroll expander to convert the energy in said working fluid discharged from said first heat exchanger; and  
 a load absorption device coupled to said scroll expander such that at least a portion of the energy produced by the expansion of said working fluid in said scroll expander operates said load absorption device to produce work; and  
 
   a second heat exchanger in fluid communication with said scroll expander, wherein said pump, first heat exchanger, expander and second heat exchanger are connected via said thermal circuit so as to be in fluid communication with one another such that, upon introduction of said heat stream into said second inlet and outlet, the increase in energy content in said working fluid is converted to useable work in said load absorbing device.    
     
     
         44 . An integrated power generation system according to  claim 43 , further including a throttle valve disposed in said thermal circuit to permit a predetermined amount of working fluid to enter said expander.  
     
     
         45 . An integrated power generation system according to  claim 43 , wherein said load absorbing device is a generator rotatably responsive to said rotatable shaft to produce an electric potential.  
     
     
         46 . An integrated power generation system according to  claim 43 , where said microturbine subsystem further comprises a recuperator in thermal communication with said heat stream such that during microturbine operation, said recuperator preheats air prior to combustion of said air in said microturbine subsystem.  
     
     
         47 . An integrated power generation system according to  claim 46 , wherein said microturbine subsystem includes a catalytic combustor.  
     
     
         48 . An integrated power generation system according to  claim 43 , wherein said heat energy utilization subsystem further comprises an auxiliary burner in thermal communication with said heat stream to augment the thermal content thereof.  
     
     
         49 . An integrated power generation system according to  claim 43 , further comprising: 
 a lubricant pump disposed within said power module and operatively responsive to said expander; and    a lubricant circuit in fluid communication with said lubricant pump, said lubricant circuit including a lubricant droplet separator, such that upon operation of said lubricant pump, said lubricant circuit can circulate a lubricant within said power module.    
     
     
         50 . An integrated power generation system according to  claim 43 , further comprising a desuperheating heat exchanger disposed within said power module, said desuperheating heat exchanger in thermal communication with said expander, whereby said desuperheating heat exchanger reduces the thermal content of fluid exiting said expander.  
     
     
         51 . An integrated power generation system according to  claim 43 , further comprising a second pair of meshed axially extending involute spiral wrap members mechanically coupled to said first scroll pair.  
     
     
         52 . An integrated power generation system according to  claim 43 , further including at least one process heat utilization module in thermal communication with said thermal circuit, said process heat utilization module configured to provide process heat to an external user.  
     
     
         53 . An integrated power generation system according to  claim 52 , wherein said at least one process heat utilization module includes a first and second process heat utilization modules, said first process heat utilization module configured to extract higher temperature energy than said second process heat utilization module.  
     
     
         54 . An integrated power generation system according to  claim 48 , further comprising a quick-start mechanism in the heat energy utilization subsystem, said quick-start mechanism comprising: 
 a logic and control module in electrical communication with each of said generator, auxiliary burer, pump, and microturbine subsystem;    a battery in electrical communication with said logic and control module; and    a recharging module in electrical communication with said generator and said battery such that said logic and control module is configured to initiate a start-up sequence for said heat energy utilization subsystem, and said recharging module recharges said battery during normal operation of said heat energy utilization subsystem.    
     
     
         55 . An integrated power generation system according to  claim 54 , further comprising: 
 an accumulator in fluid communication with said first heat exchanger and expander to collect and store at least a portion of excess thermal energy from said heat stream;    a control valve in fluid communication with said accumulator; and    an isolation valve disposed within said thermal circuit, said isolation valve to be used to selectively isolate said first heat exchanger from said expander, whereby, upon initiation and subsequent operation of said heat energy utilization system, it is capable of sustained operation.    
     
     
         56 . An integrated power generation system according to  claim 54 , further comprising a capacity control module to facilitate the responsiveness of said heat energy utilization subsystem, said capacity control module comprising: 
 a speed sensor coupled to said expander;    a feed-back controller operatively responsive to a signal from said speed sensor so as to actuate said isolation valve;    a bypass valve disposed within said heat stream to control the flow of said heat stream into said first heat exchanger module;    a plurality of sensors disposed in said thermal circuit to measure said working fluid temperature and pressure; and    a proportional integral differential logic controller to control said bypass valve, said pump and said auxiliary burner based on first heat exchanger sensor input signals.    
     
     
         57 . An integrated power generation system according to  claim 56 , further comprising a load splitting module to analyze and respond to varying load conditions such that it causes said prime mover subsystem and said heat energy utilization subsystem to provide substantially uniform and dynamic load components, respectively, to the composite electric generation profile.  
     
     
         58 . An integrated power generation system according to  claim 57 , wherein said load splitting module includes a fuzzy logic controller.  
     
     
         59 . A method of producing power by using a power generation system that has a prime mover subsystem and a secondary power generation subsystem, the method comprising the steps of: 
 operating said prime mover subsystem to energize a first load absorption device;    arranging at least a pump, first heat exchanger, expander and second heat exchanger to be in fluid communication with one another via circulated working fluid routed through a thermal circuit as part of said secondary power generation subsystem, whereby said first heat exchanger is placed in thermal communication with said prime mover subsystem;    exchanging heat between said prime mover subsystem and said first heat exchanger;    transferring at least a portion of the thermal content of said heat in said first heat exchanger to said working fluid, thereby producing an increase in temperature of said working fluid;    regulating the flow of said working fluid to said expander;    coupling said expander to a second load absorption device;    expanding said working fluid in said expander such that the energy released by said expansion energizes said second load absorption device;    condensing at least a portion of said expanded working fluid in a second heat exchanger; and    pressurizing the condensed portion of said working fluid with a pump coupled to said expander.    
     
     
         60 . A method according to  claim 59 , wherein a throttle valve is used in said step of regulating the flow of said working fluid to said expander.  
     
     
         61 . A method according to  claim 59 , wherein said second load absorbing device is an electric generator.  
     
     
         62 . A method according to  claim 59 , further comprising the step of hermetically sealing said expander and said second load absorption device in a power module.  
     
     
         63 . A method according to  claim 62 , wherein the expander is a scroll expander.  
     
     
         64 . A method according to  claim 63 , wherein said scroll expander includes a plurality of scroll pairs.  
     
     
         65 . A method according to  claim 59 , further comprising the additional step of operating a lubricant pump and a lubricant droplet separator in fluid communication with said lubricant pump, both disposed within said power module and operatively responsive to said expander such that, upon operation of said lubricant pump, a lubricant circulates within said power module.  
     
     
         66 . A method according to  claim 59 , further comprising the additional step of operating a desuperheating heat exchanger disposed within said power module, said desuperheating heat exchanger in thermal communication with said expander such that said desuperheating heat exchanger reduces the thermal content of fluid exiting said expander.  
     
     
         67 . A method according to  claim 59 , wherein the prime mover subsystem comprises a microturbine.  
     
     
         68 . A method according to  claim 67 , comprising the additional step of arranging an auxiliary burner to be in thermal communication with said first heat exchanger.  
     
     
         69 . A method according to  claim 59 , further comprising the additional steps of: 
 arranging at least one process heat utilization module to be in thermal communication with said working fluid;    extracting at least a portion of the thermal content of said working fluid from said thermal circuit; and    heating a fluid medium in said at least one process heat utilization module with said extracted thermal content.    
     
     
         70 . A method according to  claim 69 , wherein said process heat utilization module is in thermal communication with said working fluid at a location between where said working fluid is discharged from said first heat exchanger and expanded in said expander.  
     
     
         71 . A method according to  claim 70 , wherein said process heat utilization module is in thermal communication with said working fluid at a location between where said working fluid is expanded in said expander and where it enters said second heat exchanger.  
     
     
         72 . A method according to  claim 71 , wherein a first of said at least one process heat utilization module is in thermal communication with said working fluid at a location between where said working fluid is discharged from said first heat exchanger and expanded in said expander, and a second of said at least one heat recovery module is in thermal communication with said working fluid at a location between where said working fluid is expanded in said expander and where it enters said second heat exchanger.  
     
     
         73 . A method according to  claim 72 , further comprising the additional steps of: 
 inserting elevated temperature and pressure working fluid into an accumulator; and    storing said elevated temperature and pressure working fluid in said accumulator.    
     
     
         74 . A method according to  claim 68 , further comprising the additional step of initiating a start-up sequence in said secondary power generation subsystem by: 
 providing electric current to a control module;    sending start-up signals from said control module to at least one of said auxiliary burner, said pump, said first heat exchanger or said first load absorption device; and    energizing said thermal circuit by operating said auxiliary burner such that the thermal content produced by said combustor enables the self-sustaining operation of said heat energy utilization subsystem.    
     
     
         75 . A method according to  claim 68 , further comprising the additional step of initiating a start-up sequence in said heat energy utilization subsystem by: 
 providing electric current to a control module;    sending start-up signals from said control module to at least one of said auxiliary burner, said pump, said isolation valve, said first heat exchanger or said first load absorption device; and    energizing said thermal circuit by releasing said elevated temperature and pressure working fluid stored in said accumulator.    
     
     
         76 . A method according to  claim 68 , further comprising the additional steps of: 
 providing a load-splitting module that accumulates, through a load-splitting controller, the steady-state and dynamic load requirements of an end-user; and    sending out signals to determine what portion of the supplied power will be supplied by said heat energy utilization subsystem, and what portion will be supplied by said prime mover.    
     
     
         77 . A method according to  claim 76 , further comprising the additional step of providing a capacity control module that, based on temperature and pressure data gathered from said first heat exchanger, calculates said heat energy utilization subsystem response to changes in power requirements.  
     
     
         78 . A method according to  claim 76 , further comprising the additional step of incorporating a fuzzy logic controller into said load-splitting module, said fuzzy logic controller configured to provide output signals to said prime mover and secondary power generation subsystems.  
     
     
         79 . A method of operating a heat energy utilization subsystem using a quick-start mechanism, the method comprising the steps of: 
 arranging at least a pump, first heat exchanger, expander and second heat exchanger to be in fluid communication with one another via circulated working fluid routed through a thermal circuit;    arranging an auxiliary burner, fuel supply and an auxiliary burner exhaust line such that said auxiliary burner exhaust line is placed in thermal communication with said thermal circuit;    initiating a start-up sequence in said heat energy utilization subsystem by: 
 providing electric current to a control module;  
 sending start-up signals from said control module to at least one of said auxiliary burner, said pump, said first heat exchanger or said first load absorption device; and  
 energizing said thermal circuit by operating said auxiliary burner such that the thermal content produced by said auxiliary burner enables the self-sustaining operation of said heat energy utilization subsystem;  
   transferring at least a portion of the thermal content of said auxiliary burner exhaust line to said working fluid, said transfer of said thermal content producing an increase in temperature of said working fluid;    regulating the flow of said working fluid to said expander;    expanding said working fluid in an expander such that the energy released by said expansion turns said load absorbing device;    condensing said expanded working fluid in a condenser; and    pressurizing said working fluid with a pump coupled to said expander, whereby said heat energy utilization subsystem is capable of sustained, stand-alone operation.    
     
     
         80 . A method according to  claim 79 , wherein a throttle valve disposed within said first thermal circuit is used in said step of regulating the flow of working fluid to said expander.  
     
     
         81 . A method according to  claim 79 , further comprising the step of hermetically sealing said expander and said first load absorption device in a power module.  
     
     
         82 . A method according to  claim 81 , wherein the expander is a scroll expander.  
     
     
         83 . A method according to  claim 82 , wherein said step of expanding said working fluid is through a plurality of scroll pairs.  
     
     
         84 . A method according to  claim 82 , further comprising the additional step of operating a lubricant pump and a lubricant droplet separator in fluid communication with said lubricant pump, both disposed within said power module and operatively responsive to said expander such that, upon operation of said lubricant pump, a lubricant circulates within said power module.  
     
     
         85 . A method according to  claim 81 , further comprising the additional step of operating a desuperheating heat exchanger disposed within said power module, said desuperheating heat exchanger in thermal communication with said expander such that said desuperheating heat exchanger reduces the thermal content of fluid exiting said expander.