This invention relates to a more efficient and flexible method of providing Combined Cooling, Heating, and Power (CCHP); so-called Tri-generation. The invention embodies a mechanical/electrical power generation system that also produces selectable heating and cooling outputs in an environmentally clean and energy efficient way. A combined thermal separator/power generator uses the thermodynamic properties of natural working fluids to provide supplemental heating, cooling, and power without emitting any additional greenhouse gasses to the environment by use of waste or unused heat energy. This is accomplished through the combined operation of a Rankine cycle, using a refrigerant such as ammonia (NH3) as the working fluid for power production; and a carbon dioxide (CO2) heat pumping cycle. Simultaneous and usable energy output forms from this combined energy efficient cycle are mechanical power and/or electricity, and various options and combinations of usable thermal energy.
Cogeneration, also called combined heat and power (CHP), is the use of a heat engine or a power station to sequentially generate mechanical and/or electrical power as well as useful heat. Conventional Rankine (i.e., water/steam) and Brayton cycle (i.e. gas turbine) assemblies have been combined in various forms to increase efficiencies advantaging heat recovery principles. Practical temperatures for a steam plant span H2O boiling point to ˜1200° F. yielding actual efficiencies well below 50%. A Brayton cycle gas turbine generator utilizes much higher input temperatures and typically yields higher flue gas output temperatures (˜840° F. to ˜1220° F.). Therefore system efficiency may be improved substantially by utilizing recovered heat from the Brayton cycle, typically ˜1000° F., as a heat source for a “bottoming” Rankine steam cycle. These scenarios generally use higher quality (i.e. higher temperature) heat sources for operation.
A further conventional use for moderate quality heat (˜212° F. to ˜350° F.) that may be recovered from many processes is to drive absorption chillers for cooling. A plant which produces a combination of cooling, heating, and power (CCHP) is sometimes called trigeneration or more generally a polygeneration plant.
The efficient use and reclamation of prolifically available lower quality waste heat sources to help meet a facility's electrical, thermal, and mechanical power demands has become a global priority. Methods to apply medium grade waste heat (exampled hereafter 100° F.-400° F.) and much more abundant renewable low grade waste heat (<100° F.) to help meet the electrical, thermal, and mechanical power demands of society is a paramount need.
Due to increasing carbon emissions, and their contribution to global warming, there exists a parallel demand for low greenhouse gas (GHG) emission processes that rely on integrated, natural solutions. This is specifically evidenced by the high growth of two energy efficient market trends identified as vapor compression heat pump systems exampling those used in HVAC applications, as well as CHP systems. Little has been considered in relation to the combination of these two general systems due to practical considerations which have traditionally limited CHP to large scale, higher temperature operations.
Scenarios of CHP improvements for smaller scale, lower temperature (<400° F.) utilizations have been considered in recent art, however low temperature (<0° F. to 100° F.) thermal waste recovery is lesser applied in the capacity of use with CHP, as are small scale fixed or portable systems (<50 kW) using natural working fluids in lieu of water/steam or synthetic refrigerant working fluids. New trends building on this CHP background are integrated thermal use possibilities when a cold stream is provided as a by-product of the power producing cycle. Such CCHP tri-generation methods are exemplified as powered by exhaust heat from a prime mover or generator, etc. and the use of an absorption cycle using a refrigerant/absorbent pair such as ammonia/water. In such a system, a stream of medium to high temperature exhaust (waste) heat is utilized to generate a lower temperature cold stream. However, the known methods of CHP and CCHP have not lent sufficient consideration to other configurations utilizing natural refrigerants such as ammonia solely in the capacity of the power producing working fluid. Applicant's Thermal Separator/Power Generator (“TSPG”) invention seeks to effectively exploit the thermodynamic properties of natural substances such as carbon dioxide, ammonia, and/or hydrocarbons to provide supplemental heating, cooling and power without emitting additional greenhouse gases to the environment, and to the extent possible, use available waste or unused heat energy.
This is accomplished through the combined operation of an ammonia (NH3) Rankine cycle, and a carbon dioxide (CO2) compressor/expander module arranged in a heat pumping cycle. The novel NH3 refrigerant Rankine cycle power generator is heat assisted by a CO2 heat pump with the total system supplying supplementary heat/cooling outputs. Simultaneous and usable energy output forms from this combined TSPG cycle are mechanical power and/or electricity, and various options and combinations of usable thermal energy. The TSPG unit is anticipated to conveniently serve the heating and cooling needs of a singular use or facility, or distributed uses. This can be directly and locally supplied, or distributed through a hydronic thermal grid (TG). This TG is a network which conveniently facilitates the transportation, amplification, and conversion of waste heat offering nearly limitless opportunities for the recovery and utilization of useful thermal energy that is typically thrown away. The benefits of the invention are made possible by a combination of two specific and sectional natural refrigerant systems. A Rankine cycle power generator (applicant's RPG) section might use synthetic refrigerant fluids or blends. A preferred embodiment would use a natural refrigerant working fluid such as ammonia (NH3), which is heat boosted by a choice of options to a superheated vapor state. Secondary temperatures are also produced in the power generation cycle which are sufficient for uses such as heating domestic hot water or moderate space heating.
A CO2 heat pump section thermally separates a hot and cold thermal stream from ambient or unused low temperature heat sources such as ambient air or geo-bodies. This thermal separation module (applicant's TSM) section when combined in a parallel preheat operation with the RPG section, adds a significant efficiency heat boost to the RPG cycle ultimately and optionally providing power, even for the TSM operation itself, as well as providing simultaneous space or process cooling. Applicant's TSM exploits the thermodynamic properties of carbon dioxide to efficiently provide full-time cooling sufficient for cooling applications and optionally (to electricity production) for off-the-electrical grid supplemental heating.
There is a need for, and applicant's invention provides a compact, modular product which is a type of natural refrigerant powered thermal and mechanical/electrical generator capable of supplying options of heating, cooling, refrigeration, hydraulic power, mechanical power, and electrical power in an integrated device serving both mobile and fixed off-the-electric grid applications. Applicant's invention will convert thermal energy from waste sources such as ambient air, geothermal or geoexchange, and solar sources into useable thermodynamic energy for mechanical applications such as power generation or for thermal uses.
Unlike fixed CHP utilities and/or other renewable and inflexible energy sources; applicant's unit could operate as a portable platform in harsh and variable conditions and be deployed in both fixed and mobile applications. As a “distributed” energy system, it can be brought online faster than central power plants, with increased system-wide reliability. Networked as a distributed node or as clustered arrays in concentrated locations to meet variable power growth capacities and thermal requirements, this concept promises to radically change the landscape of responsible and efficient thermal and electrical energy consumption, and the systems required to supply it. Even alternative heat sources such as solar and geo-exchange conveniently adapts and add even greater efficiency and power output.
Applicant's invention embodies a Thermal Separator/Power Generator (“TSPG”) for rapid user distribution and deployment as a standalone machine which might efficiently serve multiple simultaneous uses. Conveniently networked as a distributed node expandable with like machines via a thermal/electrical grid via rigid or flexible conduits for thermal/mechanical/electrical end-use applications; or also applied in arrays in concentrated locations, variable power growth capacities and thermal requirements may be met as needed in a modular fashion. Heating and cooling needs are advantaged as coexistent applications with power production. Hydraulic power inputs and/or outputs are options within the scope of mechanical power features. Increased efficiency benefits from boosted thermal gain which may be provided by modular ancillary add-on heat recovery components would directly access available heat sources such as solar, water bodies, and waste heat from vehicles or other processes.
Many studies have been completed comparing different refrigerants for use as working fluids for use in Rankine cycles, some of which have been commercialized. Most of these systems utilize synthetic derivative refrigerants and blends with toxic, flammable, or corrosive characteristics, although flammable hydrocarbon gases have also been considered.
Although natural refrigerant hydrocarbons are cited and studied, it is noteworthy that little work has been accomplished in the art in consideration of ammonia and carbon dioxide natural refrigerants combined in new ways for CCHP systems.
With new and increasing knowledge concerning the detrimental aspects of manmade synthetic refrigerants, natural refrigerants will serve the future in ever increasing energy management capacities. The use of natural refrigerant systems will be preferred for thermal, mechanical, or electrical utilizations if efficiencies of cost and performance can be provided. An object of the invention is to provide an improved efficiency thermodynamic system which provides all of the following attributes in a singular platform:
The selection of a refrigerant for use of the power producing cycle of the RPG is a primary need. The unique properties of natural refrigerants must be taken into consideration for practical use. Apart from air and water, natural refrigerants basically divide into hydrocarbons, ammonia, and carbon dioxide. The most challenging characteristic of the hydrocarbon family refrigerants is their high flammability. Propane (R290), propylene (R1270), butane (R600) and isobutane (R600a) are examples. Such fluids have proved effective refrigerants, but safety design concerns for flammability may exclude them from practical consideration encompassing the mechanical/electrical complexities necessary for the RPG encompassing electrical output. The dominant characteristics of ammonia are a penetrating odor and toxicity. Despite these downsides, ammonia has been widely used for well over 100 years and has a good safety record. This may be partly due to the pungent smell made evident by even a small leak which helps assure proper maintenance of a sealed system.
Carbon dioxide is present in the soda we drink and the air we breathe and is non-flammable and non-toxic. Despite the high pressures associated with its use, carbon dioxide has been used as a refrigerant since 1862. Its use in an RPG cycle has not been seriously considered given its low critical temperature of <85° F.
The graphs illustrated in
Thermodynamic modeling of the TSPG system indicates that by supplementing a modest heat level input of <400 degrees Fahrenheit the full potential of the proposed features described can be attained. This would be accomplished by waste heat recovered from engine stacks or other on-site sources. However consideration has been given encompassing any condition whereby sufficient waste heat is not available for full power output, and conventional on-board combustion fuel (biodiesel, diesel, natural gas, propane, etc.) might be employed to assure full capabilities under all conditions.
The RPG section of the TSPG will not only produce electrical power, but will also simultaneously produce secondary (water or air) heating ˜100° F. to ˜130° F., which otherwise must be rejected, for use in applications such as domestic water heating. In operation, the TSM section of the TSPG generates hot liquid such as water at (˜130° F. to ˜200° F.) while simultaneously providing for (water or air) cooling ˜35° F. to ˜55° F. Combining the RPG and TSM sections together with a heat exchanger common to both sections allows construction of a Thermal Separator Power Generator (TSPG) package whereby thermal energy may extracted by the TSM from low temperature sources (<100 F) and used to efficiently boost temperature of the working fluid used in the RPG section which has a higher boiling point temperature. Applicant's TSPG invention results in mechanical/electrical power, heat, and cool at low energy consumed, if any, as additional purchased fuel/electrical energy consumption. This is based on available waste heat resources and priorities selected for the use of the energy reclaimed and used in whatever form.
Applicant's TSM is a modular, lightweight and extremely energy efficient portable packaged platform using environmentally responsible CO2 as the refrigerant compound. The TSM provides hot and cold high-pressure CO2 fluid energy streams from which to transfer thermal temperatures to low pressure, safe, easily handled and low cost hot and cold simultaneously available liquid (such as water) base thermal streams. These low-pressure water-base lines offer unlimited potential for meeting heating, cooling, and refrigeration first responder needs for emergency and disaster relief applications.
The TSM utilizes a CO2 heat pumping cycle, whereby low quality thermal energy is efficiently elevated to significantly higher heat quality than is possible with conventional vapor compression technology using toxic HFC or other refrigerants.
The proposed technical departure utilizing the proposed methods would serve many thermal/electrical/mechanical processes simultaneously leaving a cold thermal stream for cooling applications. Heat energy generated with the TSM in this manner can recover more than three times the BTU's compared with electrical kW power equivalent BTU's, yielding a heating Coefficient of Performance efficiency >3, which is three or more times the electrical input to obtain it; a COP of 1. This equates to >300% efficiency compared with electricity assumed as 100%. When compared with fueled combustion equipment, the method additionally averts a preponderance of the inherent BTU efficiency stack losses resulting in COP efficiencies <1 and the inevitable, wasteful fuel consumption and supply logistics.
The TSM may integrate an Energy Recovery Module (“ERM”) which utilizes the fluid-mechanical expansive properties of high pressure CO2 gas to increase heat pumping efficiency by as much as one third. The net result would incorporate a CO2 compressor with an expansion engine or ERM in an efficient TSM system design, which would increase heat pumping efficiency to a COP>3.5 or higher. Combined heating/cooling COP efficiencies may be six (6) or even higher. The outcome is a portable field deployable device, or a fixed heating and cooling unit with myriad applications/utilizations and very high efficiency.
Diverse power applications are available for shaft-coupling machinery such as hydraulic or pneumatic devices as well as electric generators. Potential layered applications are made possible by combining CO2 transcritical heat pump technology with the power production capabilities of a Rankine Cycle Power Generator.
Turning to
There is a drive motor 38 and compressor 40 to power a CO2 vapor compression cycle in the TSM 10 by any of a number of power sources indicated at 12. These can be various forms of hydraulic power such as hydraulic power packs, wind hydraulics, farm implements, or other hydraulic means. The drive motor can also be conventionally powered by means of electrical energy.
As can be seen in
The RPG) section is illustrated in
At block 30, unused warm/hot fluid such as water is diverted at valve 32 for undefined thermal regeneration uses or for heat rejection as and if necessary. However, alternatively and preferably, the warm/hot water may be used at block 34 for warm/hot water applications such as domestic hot water uses, storage, or processes, etc.
This process is described as high pressure gas of high temperature exchanging thermal energy to a high pressure Rankine refrigerant fluid of lower temperature. The refrigerant boiler 44 is similar to and more fully described in PCT/US2008/006827 filed May 30, 2008 which is incorporated herein by reference. However, in this dual high pressure embodiment, both TSM fluid 41 and the Rankine refrigerant fluid circuit are at high pressures; therefore, the entire heat exchanger shell must also be designed to safely handle these pressures. Other types and styles of heat exchangers can also be configured for use as known to those skilled in the art.
Thus, the high pressure fluid 41 (which is in a gaseous state) passes through a channel tube array in the heat exchanger gas boiler 44 where the fluid 41 is cooled to a warm gas 47 and discharged at the gas boiler 44 discharge 48. As seen in
In lieu of temperature boost from fluid 41 exchanged to the second Rankine refrigerant fluid 46, there exists still another alternative, i.e., of hot liquid applications >130° F. in block 18. As well known in the art, by diverting the hot gas around gas boiler 44 to a high pressure to low pressure gas cooler heat exchanger as previously described (exchanger, pipe/valving not shown) alternate thermal applications may be attained such as hot water >130° F. but must be realized at the expense of boost heat (efficiency) for the power generation circuit.
The warm gas 47 is then is routed to the expansion engine 54 and throttle/expansion valve 50 exiting either or both as a cold mixed gas/fluid 52 and into a high pressure to low pressure heat exchanger evaporator 56 where it is evaporated back to gas. In this process the cold gas 52 is warmed (as will be explained below) and exits the evaporator 56 as warmed gas 57. The gas remains at close to the inlet pressure which is a pressure of approximately 300-700 psi, with a very small pressure drop through the evaporator 56. The warmed gas 57 enters the compressor 40 at a low temperature but at pressure and temperature which assures the fluid is in a gaseous state as the cycle repeats.
In addition to RPG heat boost, when in operation the TSM vapor compression cycle heat extraction function therefore serves to leave a resultant full time supplemental cooling loop exampled and shown, supplied as a water or water/glycol cooling or refrigeration loop but may use other gas or liquid fluids. In this case, the cooling loop 16 provides cooled air 60 to a living or temperature cooled environment. It can also serve other low temperature applications such as previously described at block 20. There is a low pressure liquid circulation pump 62 that pumps a water/glycol or similar solution at a low pressure and low temperature 64. The solution 64 passes through a second stage heat exchanger 66 where ambient warm air forced by a fan 68 is blown over or through the heat exchanger 66. Alternatively, a liquid (i.e., water based) heat exchanger 67 shown supplying block 20 for optional cooling uses. Warmed water/glycol solution 70 leaves the heat exchanger 66 and/or 67 and is pumped to the low pressure section of the evaporator 56. The warmed water glycol solution 70 is cooled in the evaporator 56 and exits at discharge end 72 as a low pressure and low temperature solution 64. The water/glycol solution in the heat exchanger 56 is physically separated from the cold Rankine cycle refrigerant 52 that is passing through the evaporator 56. However, they are in thermal communication with each other so that the heat is removed from the warmed water/glycol solution 70 as it passes through the evaporator 56. The cold water/glycol solution 64 is discharged at 72 and is then recirculated by the pump 62.
The RPG 22 is illustrated in the top half of
The NH3 gas 78 exits the pre heater 80 at 82. At this point, and only if necessary, the gas 82 is further heated by means of a heat source 84 to assure full capacity temperature and pressure adequate to power a turbine, piston machine, or other prime mover 86. In this way further heat may be added only as required from conventional processes such as fueled combustion. The heat source 84 can be a standby fueled steam boiler, direct fire to the Rankine circuit, or other appropriate heat generating source and means of generating a topping temperature suitable to reach the superheated vapor heat thresholds desired. The fuel source can be an on-board fuel tank which allows the system to be portable. The benefit of this combined cycle is that approximately one quarter to one third of the heat input requirements of the RPG can be supplied by the CO2 heat pump, from low temperature waste sources, and the balance required for full power production derived from medium and high temperature waste heat sources with provision for conventional heat topping of the Rankine cycle only as and if necessary/required. The sum waste heat recovery potentials would be anticipated to dramatically reduce or even eliminate the BTU heat input that typically comes from sources such as natural gas or bio or diesel fuel as conventionally supplied.
The prime mover 86 is powered by the NH3 and drives a generator 88. This generates electrical power 90. Alternatively, the prime mover 86 may be any form of electrical or mechanical power generator that can be powered by the high temperature high pressure NH3. Thus, mechanical, hydraulic or electric power can be produced. Another form of utilization of the gas 78 may be made by the expansion engine as disclosed in both US2006/030759 and PCT/US2008/006845.
A warm gas 92 exiting prime mover 86 at a mid pressure enters a high pressure side 94 of a high pressure fluid to low pressure fluid heat exchanger 96 which is a NH3 condenser or gas cooler providing heat rejection of the power cycle. This cools and liquefies the NH3 and, in this embodiment, discharges it at 98 as a mixed fluid or liquid to enter liquid storage tank receiver 100 for re-circulation by the pump 76.
The last loop to consider is an RPG condenser loop 102. Generally water 104 will be the heat transfer fluid medium. A pump, not illustrated, pumps the water 104 through the loop. Cool water 106 enters the heat exchanger 96 at 98. Heat from the warm gas 92 is transferred to the cool water 106 as it passes through the exchanger 96. When the water is discharged from the heat exchanger 96 at 108, it is warm/hot water that may be heat rejected as described at block 30 but is also suitable for many domestic warm water applications as described at block 34.
Thus there has been provided a Thermal Separator Power Generator that incorporates a thermal separator heat pump cycle and a Rankine power generator cycle. While the invention has been described in conjunction with a specific embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and scope of the appended claims.
This application is based on and claims priority of U.S. provisional patent application 61/284,936 filed Dec. 28, 2009.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/US10/03255 | 12/28/2010 | WO | 00 | 6/13/2012 |
Number | Date | Country | |
---|---|---|---|
61284936 | Dec 2009 | US |