Abstract:
An integrated system provides electricity and heat from solar, waste heat, biomass and fossil fuel energy. The system operates with a volatile organic working fluid that circulates in a variable speed heat engine type cycle, that is heated either to its boiling point, to a saturated state or above its boiling point, or to a superheated gas state, expanded through an expander, with working fluid injected therein such that the fluid exiting the expander is cooled in a condenser in thermal communication with a facility&#39;s domestic hot water, space heating or process heating systems, and circulated by a pump. Heat exchange loops define hot water production capability for use in a facility while a generator is coupled to the expander to produce electricity and is connected to the utility grid at fixed frequency and voltage in either a paralleling or island mode.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to the onsite production of heat and power from sustainable resources such as solar, waste heat and biomass system for the supply of electrical power, domestic hot water and space heating operating either in parallel or in isolation from the central grid, and more specifically, to a modular, scalable systems that enables maximum harvesting of solar energy, waste heat energy and heat from the combustion of fuel, to produce electrical power and useable heat in a closed loop heat engine cycle using a volatile organic working fluid in a system dynamically responsive to the source temperature, sink temperature, facility&#39;s electrical and thermal loads and ambient conditions. 
         [0002]    In recent years, six major trends have emerged that are reshaping the energy industry. First, millions of consumers have experienced more frequent, more prolonged and more devastating electrical outages from failure of the central grid caused by more frequent, more severe and more costly hurricanes and storms and the increasing dependency of modern society on electrical devices including, computers, modems, televisions, and the like. Second, the cost of fossil fuel has spiked including gasoline, diesel fuel, natural gas and coal stimulated by the unprecedented demand for energy from emerging nations and the more severe storms. Third, the nearly universal acknowledgement of the detrimental impact caused by air pollution and specifically large fossil fuel plants in global warming. Fourth, the deregulation of the electrical industry has substantially reduced obstacles to interconnection by distributed generation resources. Fifth, substantial incentives from various governments spur more sustainable energy technologies. And, sixth, the increasing availability of real time pricing for all classes of electrical customers places a premium on technologies that can reduce grid electrical demand during high demand/high price situations. 
         [0003]    Although there is an abundance of solar energy received by the Earth, its intensity at the Earth&#39;s surface is actually very low and varying with the time of day, time of year and the conditions of the Earth&#39;s atmosphere. Conventional heat engine cycles have been analyzed based on the on the ideal heat engine cycle Carnot disclosed in 1824 which postulates an infinite heat source and an infinite heat sink. In such hypothesized system, the efficiency of the power systems is determined by: 
         [0004]    (i) the temperatures of the available heat source and sink; 
         [0005]    (ii) the selection of the state points, thereby describing the adopted thermodynamic cycle; 
         [0006]    (iii) the behavior of the working fluid used; 
         [0007]    (iv) the irreversibility&#39;s in the mechanical systems involved; and, 
         [0008]    (v) the temperature and pressure limitations of the materials used in the devices. 
         [0009]    In a similar fashion the more practical Rankine and its associated organic Rankine cycles (ORCs) also assume infinite source and sink temperature and requires the evaporation and typically superheating of the working fluid in the heating device before entering the expander. 
       DESCRIPTION OF THE PRIOR ART 
       [0010]    In 1977, S. S. Wilson &amp; M. S. Radwan in “Appropriate Thermodynamics for Heat Engine Analysis and Design” disclosed a modified organic heat engine cycle, called the trilateral flash cycle (TFCs) based on the matching and optimization of heat source and sink, cycle, working fluid, expander and load characteristics which heats the liquid working fluid only to the point of boiling, saturation, and expands the heated high pressure saturated working fluid using positive displacement expanders in a cycle that optimizes the amount of the finite heat energy recoverable and electricity produced from a finite heat source. All previous disclosed closed loop heat engine systems utilizing a volatile organic working fluid were designed to operate in one of the two distinct modes, super heated, (ORC) or saturated liquid, (TFC) and did not contemplate the advantages or the ability to dynamically switch between the two modes in response to changing fuel load and operating conditions. Clearly, it is desirable to overcome the limitations and deficiencies of the ORC and TFC to provide a method which dynamical adjusts the heating of the working liquid only up to its boiling point, TFC or beyond its boiling point, ORC depending on the fuel, load, and ambient conditions. 
         [0011]    During the expansion of volatile organic working fluid in an expander, almost invariably the working fluid leaves the expander in the superheated state and has to be cooled in the condenser or requires a recuperator heat exchanger to transfer the heat to preheat the relatively high pressure liquid. Everything else being equal the greater the superheat in the exhausted working fluid exiting the expander, the lower the efficiency of the mechanical/electrical generating heat engine cycle. Clearly dispensing with the need for a recuperator and producing more electrical energy from the same thermal energy is desirable through the injection of relatively high pressure liquid into the expansion volume of the expander and modulating the mass flow of the injected liquid such that the combined mass flow of the working fluid exits the expander in a saturated state and produces more net power. 
         [0012]    Combined heat and power (CHP) systems using internal combustion engines, turbines, micro turbines, and fuel cells have been known for some time as a way to improve overall efficiency by an order of magnitude in energy production systems. In a typical CHP system, heat and electricity are produced from a combustion process engine that drives an electric generator, as well as heat water, or air. Although historically CHP systems tend to be rather large, because of the six forces outline above, micro CHP systems consuming fossil fuel are emerging technologies. Because of the dramatic increase in power outages and fossil fuel prices, there is a huge market for dispatchable, sustainable energy systems. 
         [0013]    In view of the limitations of the existing art, the present invention fulfills the long felt need to optimize the production of electricity and heat in response to the varying availability of solar energy, waste heat and the varying load requirements of the facility, to dynamically optimize the electric power production by operating the system with a superheated working fluid entering the expander as in a Carnot or Rankine cycles or with a saturated liquid entering the expander in the trilateral flash cycle and minimizing the superheat of the working fluid exiting the expander and to provide a more reliable and secure source of electricity and heat not subject to the numerous power outages of central grid systems. The above and other objects and advantages of the present invention will become apparent from the following specifications, drawings and claims. It will be understood that the particular embodiments of the invention are shown by way of illustration only and not as limitation of the invention. The principle features of this invention may be employed in various embodiments without departing from the scope of the invention. 
         [0014]    While the above-described systems fulfill their respective, particular objectives and requirements, the aforementioned systems do not describe a system that uses beneficial portions of the Rankine and Carnot cycles to produce electricity and heat at minimal amounts of energy. Therefore, a need exists for a new and improved apparatus and method for producing sustainable power and heat that in its structure allows for multiple fuels to generate heat. The present invention substantially fulfills this need. Further, the present invention substantially departs from the conventional concepts and designs of the prior art. 
       SUMMARY OF THE INVENTION 
       [0015]    The present invention is an integrated system to provide both electric power and heat from various energy sources including solar, waste heat, biomass and fossil fuels. The combined heat and power system operates with a volatile organic working fluid that circulates in a variable speed heat engine type cycle, where the organic working fluid is heated to either its boiling point, a saturated state or past its boiling point, a superheated gas state, expanded through an expander, with relatively high pressure subcooled liquid working fluid injected into the expansion chambers of the expander such that the volatile organic working exiting the expander is in a saturated state, cooled in a condenser in thermal communication with the domestic hot water or space heating system, and pressurized and circulated by a pump. Heat exchange loops within the system define hot water production capability for use in space heating, domestic hot water, and/or process heat while the generator is coupled to the expander to produce electricity which is interconnected to the grid at fixed frequency and voltage in either a paralleling or island mode. 
         [0016]    The foregoing has outlined, in general, the physical aspects of the invention and has served as an aid to better understanding the detailed description. Thus, the present invention is not limited to the method or detail of construction, fabrication, material, or application of use described and illustrated herein. Any other variation of fabrication, use, or application should be considered apparent as an alternative embodiment of the present invention. 
         [0017]    There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. 
         [0018]    Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the drawings. In this respect, before explaining the current embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 
         [0019]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and devices for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and the scope of the present invention. 
         [0020]    It is therefore a principal object of the present invention to provide a method and apparatus which will maximize the overall energy efficiency of the energy process of harvesting and converting solar energy to usable electrical power and heat, while overcoming the disadvantages and drawbacks of known methods of solar photovoltaic, solar thermal electric, and solar thermal systems. 
         [0021]    Still another object of the present invention is to provide an integrated method and apparatus for operating the combined power and heat system in parallel when the grid is functioning and independently of the central grid system when the grid has failed. 
         [0022]    Still another object of the invention is to provide an integrated method and apparatus for dynamically controlling the amount and ratio of electrical to thermal output of the system. 
         [0023]    Still another object of the invention is to provide an integrated method and apparatus for optimizing the conversion of heat energy into electrical power and minimizing the power losses from the expansion of the working fluid to a superheated condition. 
         [0024]    Still another object is to provide an integrated method and apparatus for energy recovery system, utilizing the waste heat usually rejected from the condenser of a facility&#39;s air conditioning and refrigeration system, the facility&#39;s attic or other sources of waste heat, to generate electric power and useable heat. 
         [0025]    It is intended that any other advantages and objects of the present invention that become apparent or obvious from the detailed description or illustrations contained herein are within the scope of the present invention. 
         [0026]    These together with other objects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    In referring to the drawings, 
           [0028]      FIG. 1  indicates a schematic diagram for a single source directly heated combined heat and power system; and, 
           [0029]      FIG. 2  indicates a schematic diagram for a multiple source directly heated combined heat and power system. 
       
    
    
       [0030]    The same reference numerals refer to the same parts throughout the various figures. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    The present art overcomes the prior art limitations by providing a combined electricity and heat producing system fueled by various sources, primarily solar and other renewable sources integrated with combustion of fossil fuels for a supplemental heat source. With reference to the drawings,  FIG. 1  illustrates a possible configuration of the principal hardware components comprising a system embodying the operating mechanisms to affect the benefits described. It is noted however that variations in equipment may be made and would be within the ambit of a person skilled in the art. Referring initially to  FIG. 1 , one embodiment of the integrated Combined Heat and Power System  10  is a directly-heated, single closed loop system that includes a first (or primary) circuit thermal fluid conduit  15  and a secondary circuit thermal fluid conduit  78 . An advantage of the directly heated system is that it eliminates the inherent loss resulting from the pinch points of the various heat sources and sinks thus maximizing the efficiency of the cycle. First circuit  15  conducts the heated volatile organic working fluid from heating device  20  to the expander  30 . The expander  30  houses a positive displacement expander such as a rotary vane, scroll, screw, reciprocating or nutating engine. As the heated organic working fluid proceeds along an ideally isentropic path through the expander, its pressure and temperature fall, its volume expands, and accompanying those changes in state conditions, its enthalpy is converted to mechanical energy creating rotating shaft power which drives the alternator,  40 . Organic working fluid generally become drier and superheated because of the characteristic of their saturation envelope and the current practice is volatile organic working fluid exit the expander in a superheated state. The alternator,  40  delivers variable frequency and variable voltage output electric power to the transmission line,  42  connecting the alternator to the converter controller. The converter controller converts the variable frequency and variable voltage electric power to a fixed frequency and voltage that within tight parameters that enable the convert controller to synchronize its electric output with the electric grid or to maintain it within operating specifications if the grid has failed and the system is operating in an island mode. The conditioned power from the converter controller  45  is feed to the main circuit panel for distribution to the rest of the facility or the attached electric grid. Converter controller,  45  also monitors the temperature, pressure, electric power output and thermal output. Through sensors and control lines,  76 . The expander also features a port(s) for injection of subcooled liquid volatile organic working fluid. Injection of this subcooled liquid eliminates the superheat lo normally produce by expansion in organic Rankine cycle systems and enable useable mechanical power from the superheat created by expansion of the volatile organic working fluid. The combined mass flow of primary circuit  15  and secondary injection circuit  76  arrives at its exit conduit  16  at the saturation pressure and temperature for the volatile organic working fluid employed as the heat engine thermodynamic medium, a minimum approach difference above the temperature established in condenser  62 . The converter controller  45  determines the target condensing temperature based on ambient conditions, the available heat energy in heater  20 , the electrical and thermal load of the facility in real time. The converter controller can also be program to respond to “real time electric” pricing parameters that may present opportunities to arbitrage the real time price of electricity versus the cost of producing that same electricity from sustainable fuel. Spent ambient coolant is returned to the cooling tower or other ambient coolant source via conduit  38 . The spent saturate working fluid exiting the expander  30  is conducted by primary circuit  16  to condensing heat exchanger  62 . Condensing heat exchanger transfer the latent heat of condensation and the specific heat of subcooling to the facility&#39;s space heating system, or domestic hot water heating system or process heating system. The primary circuit  15  conducts the subcooled working fluid in a liquid state to the working fluid pump,  70 . where it is pumped to the operating of pressure of heater  20 , En route from working fluid pump  70 , a portion of the flow is separated from conduit  16  via secondary circuit,  78  to supply the injector valves  76  which modulate the mass flow of the liquid working fluid into the expansion volume of the expander  30 , such that the working fluid exits the expander  30  in a saturated state. It enters heater  20  via conduit  15  to repeat the heat engine with organic working fluid cycle. 
         [0032]    Converter Controller  45  controls the temperature of the working fluid exits the heater,  20 . Although the Carnot cycle proves that the maximum power that lo can be generated from a heat engine cycle is the maximum delta temperature between the source and the sink temperature, this optimization does not necessarily hold true for integrated combine heat and power systems. For instance the greater the delta temperature difference of the conduits leading up to heater  20  the greater the heat losses from the entire system so that the amount of available energy at heater  20  is substantially less that it would be if the circuit was operated at a lower temperature but with more available energy to convert to power and useable heat. Moreover, the Carnot and Rankine cycles require superheating the fluid which means that the amount of heat energy available below the temperature of evaporation is not available to the power cycle. However, the trilateral flash cycle captures the heat available down to the condensing temperature and produces power from it. Based on the thermodynamic, economic parameters and the load profile converter controller,  45  can modulate the speed of the working fluid pump,  70  such that the working fluid exiting the heater  20  can be in a saturate or superheated state. 
         [0033]    Referring next to  FIG. 2 , an alternate embodiment of the directly heated integrated combined heat and Power system  2  is shown. Here, waste heating device,  80  consist of a heat exchanger in the refrigerant loop of the facility&#39;s air conditioner or refrigeration equipment located between the compressor and condenser of said system. This waste heating device,  80  can transfer the cooling BTUs as well as the heat of compression from the compressor to preheat the liquid volatile organic working fluid. Conduit  82  conducts the preheated liquid working fluid from the waste heating device  80  to high temperature solar collectors,  20 . The higher temperature solar collectors can be various style solar collectors designed to produce heat above 200° F. As the solar collectors,  80  heats the fluid the velocity of the working fluid through the expanders can be controlled by the speed of the variable speed working fluid pump,  70 . By controlling the speed of this pump, the converter controller can determine if the working fluid will leave the solar collectors by a conduit  82  in a saturated bi-phase state or in a superheated state. The working fluid exiting the collectors can be either directed to the combustion heater,  90  via conduits  82  and  83 , or directed to bypass the combustion heater,  90  via conduit  87 . If the working fluid is directed to the combustion heater  90 , the energy output of the combustion heater  90  can be modulated to produce either saturated working fluid or superheated working fluid as determined by converter controller  45  by controlling the modulation of the combustion heater  90  and the speed of the variable speed pump  70 . The heated working fluid exiting the combustion heater,  90  can be directed by conduit  84  directly to the expander or directed by conduit  85  to bypass the expander. Upon enter the expander,  30 , the heated organic working fluid proceeds along an ideally isentropic path through the expander, its pressure and temperature fall, its volume expands, and accompanying those changes in state conditions, its enthalpy is converted to mechanical energy creating rotating shaft power which drives the alternator,  40 . Organic working fluid generally becomes drier and superheated because of the characteristic of their saturation envelope. The current practice in organic Rankine cycle systems is to have the volatile organic working fluid exit the expander in a superheated state. The alternator,  40  delivers variable frequency and variable voltage output electric power to the transmission line,  42  connecting the alternator to the converter controller. The converter controller converts the variable frequency and variable voltage electric power to a fixed frequency and voltage that within tight parameters that enable the convert controller to synchronize its electric output with the electric grid or to maintain it within operating specifications if the grid has failed and the system is operating in an island mode. The conditioned power from the converter controller  45  is feed to the main circuit panel for distribution to the rest of the facility or the attached electric grid. Converter controller,  45  also monitors the temperature, pressure, electric power output and thermal output. Through sensors and control lines,  76 . The expander also features a port(s) for injection of subcooled liquid volatile organic working fluid. Injection of this subcooled liquid working fluid eliminates the superheat normally produce by expansion in organic Rankine cycle systems and produces useable mechanical power from the superheat energy created by expansion of the volatile organic working fluid. The combined mass flow of primary circuit  84  and secondary injection circuit  76  arrives at its exit conduit  16  at the saturation pressure and temperature for the volatile organic working fluid employed as the heat engine thermodynamic medium, a minimum approach difference above the temperature established in condenser  60 . The converter controller  45  determines the target condensing temperature based on ambient conditions, the available heat energy in heater  20 , the electrical and thermal load of the facility, and real time pricing information. The converter controller can also be program to respond to “real time electric” pricing parameters that may present opportunities to arbitrage the real time price of electricity versus the cost of producing that same electricity from onsite electric generation. Spent ambient coolant is returned to the cooling tower or other ambient coolant source can transfer all or a portion of the heat of the spent working fluid depending on the load of the facility, ambient conditions and operating parameters of the building. The spent saturate working fluid exiting the expander  30  is conducted by first circuit  34  to space heating heat exchanger,  62 . Space heating heat exchanger  62 , can transfer all or a portion of the heat of the spent working fluid depending on the load of the facility, ambient conditions and operating parameters of the building. The spent working fluid exiting heat exchanger,  62  is conducted by first circuit  34  to domestic hot water heat exchanger  64 . Domestic hot water heat exchanger  64  can transfer all or a portion of the heat of the spent working fluid depending on the load of the facility, ambient conditions and operating parameters of the building. The spent working fluid exiting domestic hot water heat exchanger  64  is conducted by first circuit  34  to ambient condenser,  60 . Ambient condenser  60  removes heat from the spent working fluid so that the working fluid condenses in to a liquid and is slightly subcooled. The condensed liquid working fluid exits the ambient condenser  60  and is conducted by first circuit  34  to a receiving vessel,  65 . Receiving vessel stores excess working fluid to compensate for the dynamic operating conditions of the system. The liquid working fluid exiting the condenser,  65  is conducted by primary circuit  34  to the variable speed working fluid pump. The variable speed working fluid pump pressurizes the working liquid working fluid to a pressure above the pressure produced in the hottest of the heat sources  80 ,  20 , or  90 . The pressurized liquid working fluid leaves the working fluid pump,  70  and is conducted by conduit  16  to an oil separator,  75  were substantially all of the oil is removed from the working fluid. The oil removed by the oil separator  75  is conducted by conduit  74  back to the expander where it is injected into the oil port of the expander using the pressure developed by the working fluid pump. The evaporation temperature produced by the condensing heat exchanger transfers the latent heat of condensation and the specific heat of subcooling to the facility&#39;s space heating system, or domestic hot water heating system or process heating system. The primary circuit  15  conducts the subcooled working fluid in a liquid state to the working fluid pump,  70 . where it is pumped to the operating of pressure of the heater  20 , En route from working fluid pump  70 , a portion of the flow is separated from conduit  16  via secondary circuit,  78  to supply the injector valves  76  which modulate the mass flow of the liquid working fluid into the expansion volume of the expander  30 , such that the working fluid exits the expander  30  in a saturated state. It enters heater  20  via conduit  15  to repeat the heat engine with organic working fluid cycle. The expander  30  houses a positive displacement expander such as a rotary vane, scroll, screw, reciprocating or nutating engine. As the heated organic converter controller  45  can control the system such that the volatile organic working fluid exiting the solar collectors,  20  is either in a saturate state or a superheated state. working fluid proceeds along an ideally isentropic path through the expander, its pressure and temperature fall, its volume expands, and accompanying those changes in state conditions, its enthalpy is converted to mechanical energy creating rotating shaft power which drives the alternator,  40 . 
         [0034]    From the aforementioned description, an apparatus and its method for producing sustainable electricity and heat has been described. The apparatus, as a system, is uniquely capable of producing both electricity and heat from sustainable fuels at minimal energy input. The apparatus as described and its various components may be manufactured from many materials, including but not limited to aluminum, steel, polymers, high density polyethylene, nylon, ferrous and non-ferrous metals, their alloys, and composites. 
         [0035]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. Therefore, the claims include such equivalent constructions insofar as they do not depart from the spirit and the scope of the present invention.