Patent Application
20110296849
None.
Not applicable.
This invention relates to a method of integrating an electrical power generator and/or an electrical motor with a heat driven air conditioning and heating system to provide power, cooling, and heating to an environmentally controlled space, such as a building, vehicle, or shelter.
Many industrial processes produce waste heat of low temperature, such that little useful work is generally accomplished with this waste heat. It is well known that certain thermodynamic cycles, such as absorption cooling, can provide environmental cooling even from low grade heat sources, such as thermal solar, engine exhaust, and bottoming cycles for industrial steam generators, but absorption cooling suffers from low efficiencies. In addition, cycles, such as absorption cooling, cannot easily integrate electrical power generation.
Prior art has not completely integrated heating and cooling with electrical power generation, or alternatively with an electric motor/generator to supplement the thermodynamic cycle with the electric motor during periods of low thermal energy availability. Furthermore, a self-contained system that includes a prime mover, such as an internal combustion engine, combined with power generation and heat and cooling functions, which are further supplemented by waste heat recovery from the engine exhaust have not been described. In the prior art, some systems use refrigerant as the working fluid to generate electrical power (Edwards, U.S. Pat. No. 4,738,111), commonly referred to as an Organic Rankine Cycle. Other systems provide for power and cooling, but use an external combustor, instead of an internal combustion engine (McCullough, U.S. Pat. No. 5,228,309). Many do not consider the need for recuperation, which transfers the remaining usable heat at the output of the Rankine expander to pre-heat fluid entering the heater or boiler.
Prior art for the apparatus that provides the heating and cooling functions have been well described elsewhere (Benson, U.S. Pat. No. 6,581,384). It can be summarized that none have maximized the efficiency achievable with a combined Rankine and refrigeration cycle. Some approaches either do not recuperate heat from the working fluid (Steuart, U.S. Pat. No. 1,871,244) or do not recuperate heat in a fashion that maximizes the temperature of the working fluid entering the heating device (Brola, U.S. Pat. No. 4,118,934). Some systems attempt to only provide heating (Schafer, U.S. Pat. No. 4,271,679) or cooling (Horn, U.S. Pat. No. 2,875,589) but not both. Some add complexity by using separate working fluids for the power and heat pump cycles (Silvern, U.S. Pat. No. 3,153,442) (Schafer, U.S. Pat. No. 4,271,679).
Hence, there is a need for a single system of sufficient efficiency and simplicity to make the manufacture and operation economically attractive. Since the intent of the system is to operate from external heat source, or be supplemented by recovery of heat from an integrated prime mover, the integrated power, heating and cooling system must be flexible enough to accommodate variable electrical and air conditioning loads and allow simple controls with a minimum of sensors and actuators.
The expander 9 exhaust passes through the recuperator 14 and 17, where much of the heat is transferred from the expander exhaust gas to the liquid entering the heater 2. The compressor 13, using the same working fluid as the expander 9, compresses the working fluid from a low pressure, gaseous state to an intermediate pressure gas as part of a typical refrigeration cycle. The output from the compressor 13 is co-mingled with the outlet of the first recuperator 14. The combined outlet flows from the expander 9 and first recuperator 14 can then be optionally passed into recuperator 17 to extract as much heat from the working fluid as possible. The working fluid then passes through the five-way reversing valve 23 from port 18 to port 20 to the condenser heat exchanger 26. In an alternative embodiment, the condenser may be cooled by an externally chilled fluid as would be supplied by an evaporative type chiller.
The working fluid exits the condenser 26 as a intermediate pressure liquid and is split, where part of the liquid passes through the bi-directional, variable area expansion valve 37, and the other part of the liquid passes through check valve 32. Upon exiting the expansion valve 37, the intermediate pressure liquid becomes a low pressure liquid. The low pressure liquid enters the evaporator heat exchanger 43 to cool a space, such as a building. In an alternative embodiment, the evaporator may be used to cool another fluid, rather than directly cooling a building. The working fluid leaving the evaporator 43 is a low pressure vapor and is passed through the five-way reversing valve 23 from port 21 to port 22, where the working fluid returns to the compressor 13. Port 19 is not used in the cooling mode. The remainder of the working fluid not passing through the expansion valve 37 instead passes through check valve 32 and eventually returns to the liquid pump 47. Check valve 33 is checked closed.
In
The working fluid exits the condenser as a intermediate pressure liquid and is split where part of the liquid passes through the variable area, bi-directional expansion valve 37, and the other part of the liquid passes through check valve 33. The intermediate pressure liquid becomes a low pressure liquid, upon exiting the expansion valve 37. The low pressure liquid enters heat exchanger 26, which is being used as an evaporator. The working fluid leaving the evaporator is a low pressure vapor and is passed into port 20 of the five-way valve 23 and out of port 22, where the working fluid returns to the compressor 13. The remainder of the working fluid not passing through the expansion valve 37 instead passes through check valve 33 eventually returns to the high pressure liquid pump 47. Check valve 32 is checked closed.
The present invention provides a process and apparatus for utilizing waste heat to power a reconfigurable thermodynamic cycle that can be used to selectively cool or heat an environmentally controlled space, such as a room or a building, plus generate electrical power. Alternative configurations will be presented that incorporate a motor/generator, such that the heat pump cycle can be supplemented with electrical power, during times when thermodynamic energy may not be sufficient. Another alternative configuration includes incorporation of a prime mover, such as an internal combustion engine, to mechanically drive the integrated power, cooling, and heating system, and the heat generated by the prime mover is recovered to supply heat to help drive the heating and cooling cycle. The system provides a design which reasonably balances the need to maximize efficiency, while also keeping the design cost effective.
The thermodynamic cycle of this invention is a combination of a Rankine cycle to provide power and a refrigeration and heating cycle, commonly known as a heat pump. The system uses a single working fluid in both liquid and gaseous phases. The advantage of a single working fluid is that the system can tolerate some seal leakage between the expander and compressor and simplification of the overall system by reducing the total number of components required. The working fluid has desirable properties of low critical point pressure (<1000 psia) and temperature (<300° F.). Several common refrigerants are candidate working fluids.
Although, the combined Rankine and heat pump cycles are core to each integrated system, there are four typical configurations in which the thermodynamic core system is used. These are understood to be exemplary only and that other combinations can be obtained.
Accordingly, besides the objects and advantages of the cooling and heating apparatus described above, several objects and advantages of the present invention are:
(a) to provide cooling and heating and electrical power apparatus and process which is powered by heat energy from low temperature, waste heat sources, such as thermal solar, internal combustion engine exhaust, residual energy from steam generators, or any one of many other similar sources.
(b) to provide a cooling and heating system which can accommodate variable amounts of input energy with wide variations of temperature of that input energy, and can be supplemented by an electric motor.
(c) to provide a self-contained system with a prime mover which can provide direct shaft power, where that shaft horsepower can easily be apportioned between providing heating or cooling and providing electrical power.
(d) to provide a means for supplementing the prime mover shaft power with shaft power from an expander, where the energy to drive the expander is scavenged from the prime mover and/or optionally supplemented by an external source.
(e) to provide a cooling, heating, and electrical power system which is simple in design and, therefore, is more cost effective to manufacture.
(f) to provide a system which is efficient, flexible in accommodating a variety of load conditions, and easy to control.
The novel features which are believed to be characteristic of the invention will be better understood from the following description, both to its organization and method of operation. Further objects and advantages will be apparent, when considered in connection with the accompanying drawings, in which presently preferred embodiments of the invention are illustrated by way of example. It is expressly understood that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention.
The embodiments described herein are for the purposes of illustration only, and it is understood by those familiar in the art that numerous other embodiments are possible. In one embodiment of the invention, as illustrated in
The engine exhaust 3 can often exceed 500° C. and is shown in
One of the major benefits of this system arrangement of combined shaft power is that all the power from the engine 1 and expander 9 can be applied as needed to any combination of air conditioning (or heating) load and electrical load demand, if the system includes an electrical machine 12 that can operate as a generator. For electrical power supplied by the system, the engine 1 can be controlled to operate at a constant speed, and therefore supply the electrical power at a constant frequency. As either the compressor 13 or generator 12 load increases, the fuel supply to the engine 1 is increased to increase the engine 1 output torque, but the speed can be maintained as constant to keep the electrical output frequency constant. An increase in the fuel flow to the engine 1 will also increase the heat supplied to the heater 2, which increases the amount of supplemental shaft horsepower supplied to the system from the expander 9.
Although the figures depict the rotating components on a common shaft, in some applications it may be beneficial to have one or more of the components rotating at different speeds through use of a gearbox or other speed reducing or speed increasing device.
The present invention provides an apparatus for utilizing waste heat to drive a reconfigurable thermodynamic cycle that can be used to selectively cool or heat an environmentally controlled space, such as a room, building, or vehicle, can provide electrical power, and optionally can be coupled to a prime mover. The system provides a design which reasonably balances the need to maximize efficiency, while also keeping the design cost effective.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
