Organic rankine cycle micro combined heat and power system

Abstract

A micro combined heat and power system includes at least a heat source, an expander, a condenser, a pump, recuperator and conduit for circulating a working fluid. After the working fluid is expanded, its thermodynamic properties allow it to remain in a superheated state so that it selectively can give up at least a portion of its excess heat first to the recuperator and then to the condenser, which can then subsequently exchange heat with a circulating air, water or related loop to provide space heat or domestic hot water that can be used, for example, to heat a dwelling. The amount of heat exchange in the recuperator can be adjusted to allow the output ratio of heat to electricity to be varied while maximizing overall system efficiency. Additional componentry, such as an accumulator, enhances system operability by smoothing out working fluid flow rates during transitional operation, such as start-up and shut-down.

We claim:  
     
         1 . A cogeneration system comprising: 
 a heat source;    a working fluid circuit comprising: 
 conduit configured to transport an organic working fluid through said working fluid circuit, at least a portion of said conduit disposed adjacent said heat source such that said organic working fluid disposed in said portion of said conduit is superheated during operation of said heat source;  
 an expander in fluid communication with said conduit such that said organic working fluid received therefrom remains superheated after expansion in said expander;  
 a condenser in fluid communication with said expander;  
 a pump configured to circulate said organic working fluid through at least said conduit, expander and condenser; and  
 a recuperator coupled to said conduit and configured to selectively increase the temperature of said organic working fluid entering said portion of said conduit disposed adjacent said heat source; and  
   at least one energy conversion circuit operatively responsive to said working fluid circuit such that upon operation of said cogeneration system, said at least one energy conversion circuit is configured to provide useable energy.    
     
     
         2 . A cogeneration system according to  claim 1 , wherein said recuperator comprises: 
 a first heat exchange passage disposed between said expander and said condenser; and    a second heat exchange passage disposed between said pump and said part of said conduit adjacent said heat source.    
     
     
         3 . A cogeneration system according to  claim 1 , wherein said at least one energy conversion circuit comprises: 
 a generator coupled to said expander to produce electricity; and    a circulating fluid medium in thermal communication with said condenser such that at least a portion of the heat given up by said organic working fluid in said condenser provides increased thermal content to said circulating fluid medium.    
     
     
         4 . A cogeneration system according to  claim 3 , wherein said expander is a scroll expander.  
     
     
         5 . A cogeneration system according to  claim 3 , wherein said circulating fluid medium is configured to transport a space heating fluid.  
     
     
         6 . A cogeneration system according to  claim 5 , wherein said space heating fluid is water.  
     
     
         7 . A cogeneration system according to  claim 5 , wherein said space heating fluid is forced air.  
     
     
         8 . A cogeneration system according to  claim 3 , wherein said circulating fluid medium is configured to transport domestic hot water.  
     
     
         9 . A cogeneration system according to  claim 1 , wherein said heat source is a burner.  
     
     
         10 . A cogeneration system according to  claim 1 , further comprising an accumulator responsive to pressure differences within said working fluid circuit such that under a first operating condition, said accumulator adds excess working fluid to said working fluid circuit, and under a second operating condition, said accumulator removes excess working fluid from said working fluid circuit.  
     
     
         11 . A cogeneration system according to  claim 10 , wherein said accumulator is intermediate said condenser and said pump.  
     
     
         12 . A cogeneration system according to  claim 10 , wherein said accumulator is situated at a higher elevation relative to said pump to promote the gravity flow of said additional working fluid from said accumulator to said pump during said first operating condition.  
     
     
         13 . A cogeneration system according to  claim 10 , further comprising a warming device thermally coupled to said accumulator such that during at least a portion of the period that said cogeneration system is not in operation, said accumulator is maintained at a higher temperature than the remainder of said working fluid circuit.  
     
     
         14 . A cogeneration system according to  claim 10 , further comprising a valve configured to selectively fluidly isolate said accumulator from the remainder of said working fluid circuit.  
     
     
         15 . A cogeneration system comprising: 
 a heat source;    a working fluid circuit comprising: 
 conduit configured to transport an organic working fluid through said working fluid circuit, at least a portion of said conduit disposed adjacent said heat source such that said organic working fluid disposed in said portion of said conduit is superheated during operation of said heat source;  
 an expander in fluid communication with said conduit such that said organic working fluid received therefrom remains superheated after expansion in said expander;  
 a condenser in fluid communication with said expander;  
 a pump configured to circulate said organic working fluid through at least said conduit, expander and condenser; and  
 an accumulator responsive to pressure differences within said working fluid circuit such that under a first operating condition, said accumulator adds excess working fluid to said working fluid circuit, and under a second operating condition, said accumulator removes excess working fluid from said working fluid circuit; and  
   at least one energy conversion circuit operatively responsive to said working fluid circuit such that upon operation of said cogeneration system, said at least one energy conversion circuit is configured to provide useable energy.    
     
     
         16 . A cogeneration system according to  claim 15 , wherein said accumulator is intermediate said condenser and said pump.  
     
     
         17 . A cogeneration system according to  claim 15 , wherein said accumulator is situated at a higher elevation relative to said pump to promote the gravity flow of said additional working fluid from said accumulator to said pump during said first operating condition.  
     
     
         18 . A cogeneration system according to  claim 15 , further comprising a warming device thermally coupled to said accumulator such that during at least a portion of the period that said cogeneration system is not in operation, said accumulator is maintained at a higher temperature than the remainder of said working fluid circuit.  
     
     
         19 . A cogeneration system according to  claim 15 , further comprising a valve configured to selectively fluidly isolate said accumulator from the remainder of said working fluid circuit.  
     
     
         20 . A Rankine cycle cogeneration system comprising: 
 a heat source;    a working fluid circuit comprising: 
 conduit configured to transport an organic working fluid through said working fluid circuit, at least a portion of said conduit disposed adjacent said heat source such that said organic working fluid disposed in said portion of said conduit disposed adjacent said heat source is heated during operation of said heat source;  
 an expander in fluid communication with said conduit such that said organic working fluid received therefrom remains superheated after said expansion in said expander;  
 a condenser in fluid communication with said expander;  
 a pump configured to circulate said organic working fluid through at least said conduit, expander and condenser;  
 a recuperator coupled to said conduit and configured to selectively increase the temperature of said organic working fluid entering said portion of said conduit disposed adjacent said heat source; and  
 an accumulator intermediate said condenser and said pump; and  
   at least one energy conversion circuit operatively responsive to said working fluid circuit such that upon operation of said cogeneration system, said at least one energy conversion circuit is configured to provide useable energy.    
     
     
         21 . A cogeneration system according to  claim 20 , wherein said accumulator is responsive to pressure differences within said working fluid circuit such that under a first operating condition, said accumulator adds excess working fluid to said working fluid circuit, and under a second operating condition, said accumulator removes excess working fluid from said working fluid circuit.  
     
     
         22 . A cogeneration system according to  claim 21 , wherein said accumulator is situated at a higher elevation relative to said pump to promote the gravity flow of said excess working fluid from said accumulator to said pump during said first operating condition.  
     
     
         23 . A Rankine cycle cogeneration system comprising: 
 an organic working fluid;    an evaporator capable of superheating said organic working fluid, said evaporator comprising: 
 a burner; and  
 conduit adjacently spaced relative to said burner such that during burner operation heat transferred therefrom is sufficient to superheat said organic working fluid disposed in said conduit;  
   a substantially closed-loop working fluid circuit in thermal communication with said burner, said substantially closed-loop working fluid circuit configured to transport said organic working fluid therethrough, said substantially closed-loop working fluid circuit comprising: 
 an expander in fluid communication with said conduit such that said organic working fluid received therefrom remains superheated after expansion in said expander;  
 a condenser in fluid communication with said expander;  
 a pump configured to circulate said organic working fluid through at least said conduit, expander and condenser;  
 a recuperator coupled to said conduit and configured to selectively increase the temperature of said organic working fluid entering said evaporator; and  
 an accumulator fluidly responsive to pressure differences within said working fluid circuit such that under a first operating condition, said accumulator adds excess working fluid to said working fluid circuit, and under a second operating condition, said accumulator removes excess working fluid from said working fluid circuit; and  
   at least one energy conversion circuit comprising: 
 a generator coupled to said expander to produce electricity; and  
 a circulating fluid medium in thermal communication with said condenser such that at least a portion of the heat given up by said organic working fluid in said condenser provides increased thermal content to said circulating fluid medium.  
   
     
     
         24 . A dwelling configured to provide at least a portion of the heat and power needs of occupants therein, said dwelling comprising: 
 a plurality of walls defining at least one room therebetween;    a roof situated above said plurality of walls;    at least one ingress/egress to facilitate passage into and out of said dwelling; and    a cogeneration system in heat and power communication with said at least one room, said cogeneration system comprising: 
 a heat source;  
 a working fluid circuit comprising: 
 conduit configured to transport an organic working fluid through said working fluid circuit, at least a portion of said conduit disposed adjacent said heat source such that said organic working fluid passing through said portion of said conduit disposed adjacent said heat source is superheated during operation of said heat source;  
 an expander in fluid communication with said conduit such that said organic working fluid received therefrom remains superheated after expansion in said expander;  
 a condenser in fluid communication with said expander;  
 a pump configured to circulate said organic working fluid through at least said conduit, expander and condenser; and  
 a recuperator coupled to said conduit and configured to selectively increase the temperature of said organic working fluid entering said portion of said conduit disposed adjacent said heat source; and  
 
 at least one energy conversion circuit operatively responsive to said working fluid circuit such that upon operation of said cogeneration system, said at least one energy conversion circuit is configured to provide useable energy.  
   
     
     
         25 . A dwelling according to  claim 24 , further comprising a controller to control at least the flow rate of said organic working fluid.  
     
     
         26 . A dwelling according to  claim 25 , wherein said controller is in signal communication with an outdoor sensor.  
     
     
         27 . A dwelling according to  claim 25 , wherein said controller is responsive to occupant input.  
     
     
         28 . A dwelling according to  claim 27 , wherein said controller responsive to occupant input is a thermostat.  
     
     
         29 . A dwelling according to  claim 24 , further comprising an accumulator responsive to pressure differences within said working fluid circuit such that under a first operating condition, said accumulator adds excess fluid to said working fluid circuit, and under a second operating condition, said accumulator removes excess working fluid from said working fluid circuit.  
     
     
         30 . A micro combined heat and power system comprising: 
 an electric production subsystem comprising: 
 an organic working fluid;  
 a burner for superheating said organic working fluid;  
 a scroll expander configured to receive and expand said organic working fluid in a superheated state;  
 a generator operatively coupled to said scroll expander to produce electricity;  
 a condenser disposed in fluid communication with said scroll expander;  
 a pump to circulate said organic working fluid through said electricity generating loop;  
 a recuperator in thermal communication with said expander such that during operation of said micro combined heat and power system, said superheated organic working fluid exiting said expander selectively gives up at least a portion of its excess heat to increase the temperature of said organic working fluid entering said burner; and  
 an accumulator intermediate said condenser and said pump; and  
   a heat production subsystem comprising an circulating fluid medium in thermal communication with said condenser.    
     
     
         31 . A method of producing heat and electrical power from a cogeneration device, the method comprising the steps of: 
 providing a heat source;    configuring a first circuit to transport an organic working fluid adjacent said heat source;    superheating said organic working fluid;    expanding said superheated organic working fluid to generate electricity;    maintaining said organic working fluid in said superheated state at least until said organic working fluid enters a recuperator;    giving up at least a portion of the excess heat from said superheated organic working fluid in said recuperator;    exchanging at least a portion of the excess heat from said organic working fluid that has passed through said recuperator in a condenser with a circulating fluid medium such that after passing through said condenser, said organic working fluid is no longer in a superheated state;    adding heat to said organic working fluid that is no longer in a superheated state in said recuperator; and    returning said organic working fluid such that it is adjacent said heat source.    
     
     
         32 . A method according to  claim 31 , wherein said circulating fluid medium is configured to transport a space heating fluid.  
     
     
         33 . A method according to  claim 32 , wherein said space heating fluid is water.  
     
     
         34 . A method according to  claim 31 , wherein said space heating fluid is forced air.  
     
     
         35 . A method according to  claim 31 , wherein said circulating fluid medium is configured to transport domestic hot water.  
     
     
         36 . A method according to  claim 31 , further comprising adjusting the flow rate of said organic working fluid through said recuperator in response to a set point condition in said circulating fluid medium.  
     
     
         37 . A method according to  claim 36 , wherein said set point condition is a hydronic fluid temperature in said circulating fluid medium.