Abstract:
Uninterruptible power is supplied to a load connected to a power line by connecting the power line to a rotatable member that includes a Rankine cycle turbine coupled to a device that operates as a motor when line power is operative thereby rotating the member at a standby rotational speed so that a predetermined amount of kinetic energy is stored in the rotating member, and that operates as a generator when the line power is inoperative and the member is rotated by the application of vaporized working fluid to the turbine. Working fluid is vaporized and maintained at an operational temperature level only when the line power is inoperative. The working fluid is held at a standby temperature level, preferably greater than the operational temperature level, while the power line is operative whereby the working fluid contains a predetermined amount of stored thermal energy while the power line is operative. In response to loss of line power, vaporized working fluid is applied to the turbine thereby rotating the rotatable member whereby the turbine rotates the member at a nominal operational speed that preferably is less than the standby rotational speed. Finally, in response to the loss of line power the device is connected to the load whereby the stored thermal energy in the working fluid and the stored kinetic energy in the rotating member are converted by the device to power for the load.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to a method of and apparatus for producing power, and more particularly, to a method of and apparatus for producing uninterruptible power for communication systems that are located in urban areas or in the vicinity of towns and also stand alone power systems for communication installations in remote areas.  
       BACKGROUND OF THE INVENTION  
       [0002]     Uninterruptible power systems particularly in communication systems often utilize photovoltaic systems, thermoelectric generators (TEG) or organic Rankine cycle energy converters. A diesel engine based uninterruptible power sources (UPS) utilizes batteries or a flywheel to supply an electrical load when line power drops out and until the diesel can start and bring the generator on line.  
         [0003]     In telecommunications systems, redundant organic Rankine cycle energy converters each operating at partial load have been used so that, failure of one converter causes the other converter to supply the full load. A transient period, until which the second energy converter delivers the full load, which can last from a few minutes up to about 20-50 minutes can be reduced by a standard battery that delivers a few ampere-hours.  
         [0004]     Since 1976, as part of the Trans-Alaska Pipeline Project, a large number of stations have been operating each using a single Organic Rankine cycle turbine unit as a warm standby unit to ensure the required reliability. In such a standby unit, a line-operated electric heater under themostatic control provides external heat to a vapor generator of the unit to maintain the working fluid at about 120° F. When power fails, the main burner is activated quickly bringing the organic vapor Rankine cycle turbine unit on line delivering full power to the station as described in Trans-Alaska Pipeline, Remote Gate Valve Equipment Buildings, Operation and Maintenance Manual, Volume II, Ormat Energy Converter Model 155, April 1976).  
         [0005]     In a related system disclosed in U.S. Pat. No. 4,982,569, the disclosure of which is hereby incorporated by reference, a hybrid power system is disclosed that includes an intermittently operable non-fuel consuming power generator, such as a photovoltaic cell array, or a wind generator, connected through a control circuit to a battery for changing the same and for supplying current to a timewise, substantially constant, electrical load. In addition, this hybrid power plant includes an electric generator connected to an intermittently operable prime mover, such as a Rankine cycle organic vapor turbogenerator, for charging the battery and supplying current to the electrical load when the prime mover is operated, and a sensor for sensing at least one electrical parameter of the power plant. With such an arrangement, the prime mover is operable only when the power generator is not operating.  
         [0006]     In another related system disclosed in U.S. Pat. No. 4,760,705, the disclosure of which is hereby incorporated by reference, the invention disclosed therein relates to a Rankine cycle power plant operating with an improved working fluid, the working fluid being a compound selected from the group consisting of bicyclic aromatic hydrocarbons, substituted bicyclic aromatic hydrocarbons, heterocyclic aromatic hydrocarbons, substituted heterocyclic aromatic hydrocarbons, bicyclic or heterobicyclic compounds where one ring is aromatic and the other condensed ring in a non-aromatic, and their mixtures. In a further aspect of the invention disclosed in this U.S. patent, a binary Rankine cycle power plant is provided in which the condenser of the high temperature and pressure turbine is cooled by a different working fluid which is vaporized thereby and supplied to a low temperature and pressure turbine.  
         [0007]     Israel Patent 43547 discloses a further related system and discloses a rotor for a homopolar electrical machine.  
         [0008]     Batteries are used in all the telecommunication projects to provide DC power to the telecom equipment and the reliability and availability of the system depends strongly on the battery characteristics.  
         [0009]     The batteries have a limited lifetime and if not properly charged and maintained they have to be replaced a few times during the life of a project estimated as 20-25 years.  
         [0010]     In addition, because the battery condition cannot be correctly assessed, battery failure occurs without any kind of advance notice, station shut-down often occurs unexpectedly. Moreover, the battery fails when they are actually needed so that, when there is an electrical grid power outage, the diesel generator fails when it is attempted to start it consequently causes the battery, UPS and diesel generator not to provide power.  
         [0011]     It is therefore an object of the present invention to provide a new and improved method of and apparatus for providing uninterruptible power wherein the disadvantages as outlined are reduced or substantially overcome.  
       SUMMARY OF THE INVENTION  
       [0012]     According to the present invention, an uninterruptible power supply associated with a power line for supplying a load includes a load circuit connected said power line to said load for powering the same while said power line is operative, and a rotatable member including a Rankine cycle turbine coupled to a device that operates as a motor when line power is inoperative and this member is rotated by the application of vaporized working fluid to the turbine. A driver circuit connects the power line to the device thereby rotating the rotatable member at a standby rotational speed while the power line is operative for storing a predetermined amount of kinetic energy in the rotating member. The power supply also includes a boiler containing working fluid, a burner associated with said boiler operable to produce vaporized working fluid and to maintain the same at an operational temperature level when the line power is inoperative, and resistance heater associated with the boiler and connected to the power line for holding the working fluid at a standby temperature level while the power lind is operative, the standby level of the boiler being preferably greater than the operational level of the boiler whereby the working fluid contains a predetermined amount of thermal energy while the power line is operative. A valve is operable to connect the boiler to the turbine for applying vaporized working fluid to the turbine thereby rotating the rotatable member, and a control is responsive to loss of line power (1) for operating the burner, which causes the boiler to produce vaporized working fluid, and for operating the valve, which supplies vaporized working fluid to the Rankine cycle turbine which thereby rotates the member at a nominal operational speed preferably that is less than the standby rotational speed, and (2) for connecting the device to the load whereby power is supplied to the load while the power line is inoperative, the thermal energy in the working fluid in the boiler and the predetermined amount of kinetic energy being converted by the device to power for the load upon loss of line power.  
         [0013]     In addition, the present invention includes a method for supplying uninterruptible power to a load connected to a power line comprising connecting the power line to a rotatable member comprising a Rankine cycle turbine coupled to a device that preferably operates as a motor when line power is applied to the device thereby rotating the member at a standby rotational speed for storing a predetermined amount of kinetic energy in the rotating member, and that operates as a generator when the line power is inoperative, the member being rotated by the application of vaporized working fluid to the turbine. Additionally, the method includes vaporizing working fluid and maintaining the same at an operational temperature level only when the line power is inoperable. Furthermore, the method includes holding working fluid at a standby temperature level while the power line is operative, the standby temperature level preferably being greater than the operational temperature level whereby the working fluid contains a predetermined amount of stored thermal energy while power line is operative. In addition, the method includes applying the vaporized working fluid to the turbine thereby rotating the rotatable member in response to loss of line power whereby the turbine rotates the member at a nominal operational speed that is preferably less than the standby rotational speed. Moreover, the method includes connecting the device to the load whereby power is supplied to the load while the power line is inoperative so that the stored thermal energy in the working fluid and the predetermined amount of kinetic energy are converted to power for the load upon loss of line power. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Embodiments of the present invention are described by way of example, and with reference to the accompanying drawings wherein:  
         [0015]      FIG. 1A-1B  are schematic diagrams of an embodiment of the present invention showing different modes or phases of operation;  
         [0016]      FIG. 2  is a schematic diagram of an embodiment of the present invention;  
         [0017]      FIG. 3  is a schematic diagram of a modification of the embodiment of the present invention shown in  FIG. 2 ;  
         [0018]      FIG. 4  is a schematic diagram of a further modification of the embodiment of the present invention shown in  FIG. 2 ;  
         [0019]      FIG. 5  is a schematic diagram of an additional embodiment of the present invention;  
         [0020]      FIG. 6  is a schematic diagram of still another embodiment of the present invention; and  
         [0021]      FIG. 7  is a schematic diagram of further embodiment of the present invention.  
     
    
       [0022]     Like reference numerals and designations in the various drawings refer to like elements.  
       DETAILED DESCRIPTION  
       [0023]     Turning to the Figures,  FIGS. 1A and 1B  show shematically the main phases of operation of the preferred embodiment of the present invention, the phases being designated as Phases  0 ,  1   a ,  1   b  and  1   c  and representing the configuration of the apparatus as a function of events that occur in the operation of the apparatus. Phase  0  occurs when an electric utility supplies line power to a load, this phase lasting as long as line power is operative. In Phase  0 , the apparatus is in a hot standby rotational speed, and working fluid in boiler  53  is maintained at an operational temperature level by a resistance heater connected to the line.  
         [0024]     Phase  1   a  occurs in response to the loss of line power, and typically last for a few seconds as spin-down of turbine  57  causes generator  73  to deliver energy to the load. Upon loss of power, working fluid is applied to turbine  57  and fuel is delivered to burner  51 .  
         [0025]     Phase  1   b  typically last for a few minutes after loss of line power occurs as stored thermal energy in boiler  53  is converted to electricity and delivered to the load. At the end of phase  1   b , the burner is delivering sufficient heat to the boiler to maintain the same at an operational temperature level at which the turbine operation sustains the load. At this time, Phase  1   c  occurs as long as the line remains inoperative and the fuel is not exhausted.  
         [0026]     In phase  0  (see  FIG. 1A ) power is supplied by the electric utility to the load by rectifier  76  as well as the AC input being supplied to motor  52  that maintains or drives turbine  57  so that it is rotated. In this phase, electric heater  54 , supplied by AC line power supplied by the utility, preferably maintains the temperature of vapor generator or boiler  53  at a temperature above its normal operating temperature (normal operation or normal operating conditions being conditions during phase  1   c  described below). However, on the other hand, the temperature of boiler or vapor generator  53  can be maintained at the same temperature as that when normal operation takes place (see phase  3  described below). In addition, in phase  0 , if preferred, motor  52  maintains the speed of turbine  57  above its normal operating speed (normal operation or normal operating conditions being conditions during phase  1   c  described below). However, on the other hand, the speed of turbine  57  can be maintained at its normal operating speed i.e. during normal operation (see phase  1   c  described below). In phase  1   a  (see  FIG. 1B ), a utility failure occurs so that no line power is available and the power is supplied to the load for a short period of time (e.g. some seconds) by Rankine cycle turbine  57  utlitizing its inertia or kinetic energy via generator  73  and rectifier  76 . Thereafter, in phase  1   b  (see also  FIG. 1B ), power is supplied to the load by Rankine cycle turbine  57  via generator  73  and rectifier  76  utlizing the thermal energy present in boiler or vapor generator  53 . In phase  1   c  (see  FIG. 1B  as well), power is supplied by Rankine cycle turbine  57 , under its normal operating conditions, to the load via generator  73  and rectifier  76  wherein boiler or vapor generator  53  now supplies the vapors to Rankine cycle turbine  57  from heat supplied from the combustion gases produced by burner  51 .  
         [0027]     Thus, the Rankine cycle turbine is maintained at hot standby conditions wherein the hot standby Rankine cycle turbine is the rotating Rankine cycle turbine  57  and boiler or vapor generator  53  in a state of incipient rate flow of vaporized working fluid. In such a manner, the Rankine cycle turbine system, having the rotating Rankine cycle turbine  57  and hot boiler or vapor generator  53 , in phase  0 , is at hot standby ready to provide the required continuous operation to ensure that the load is continuously supplied with the required power.  
         [0028]     As far as  FIG. 2  is concerned, power unit system  10 A is provided according to an embodiment of the present invention for providing uninterruptible power and includes organic Rankine cycle turbine  57 A designed to operate as a hot standby organic Rankine cycle turbine system  50 A. In the present embodiment, hot standby organic Rankine cycle turbine system  50 A includes electric motor  52 A for rotating the turbine when electric power is available from the electric grid. The embodiment also includes boiler  53 A and heater  51 A comprising e.g. a burner for combusting fuel. In addition, the present embodiment includes electric heater  54 A for heating the liquid organic working fluid in the boiler when electric line power is available from the electric grid or utility. Moreover, in the present embodiment, valve  55 A is included that enables the supply of organic working fluid vapor to turbine  57 A for its nominal operation, when electric power is not available from the electric grid.  
         [0029]     In operation, when the electric grid or utility is supplying electric line power, electric motor  52 A rotates turbine  57 A via driver  75 A that receives power from the grid. Line  66 A receives sufficient organic working fluid vapor from boiler  53 A, heated by electric heater  54 A, for supplying fluid only to bearings  56 A. Heater, i.e. burner,  51 A is not operated and preferably a flap located on the stack of boiler  53 A is maintained in a closed state by an actuator. Thus, liquid supplied via line  66 A is supplied to reservoir  64 A. This condensate is supplied via line  65 A where it is cooled to bearings  56 A. Condensate exiting the bearings is supplied via pump  67 A, e.g. a pitot pump, to reservoir  64 A from where it is returned to bearings  56 A. Electric heater  54 A continues to supply heat to organic working fluid in boiler  53 A for compensating for fluid finding its way back via line  68 A to vessel  69 A in heat relationship with boiler  53 A. Thus, under such conditions, the electric grid supplies power to the load and the organic Rankine cycle turbine system is maintained at hot standby.  
         [0030]     When the electric grid does not supply electric power, kinetic energy present in turbine  57 A permits power unit  10 A to continue to supply electric power even though no electric power is supplied to electric motor  52 A from the electric grid or utility. Valve  55 A is opened by control unit  85 A, which senses the state of the line power, in order that organic working fluid vapor is supplied from boiler  53 A via conduit  71 A to turbine nozzle block  70 A. Consequently, power is now produced by the rotation of organic Rankine cycle turbine  57 A rotated by organic working fluid vapor produced by heat present in the hot organic working fluid present in boiler  53 A. At the same time, the actuator opens the flap and heater, i.e. burner,  51 A, commences operation with the receipt of a control signal from control unit  85 A that also sends a control signal to open fuel valve  72 A. In addition, control unit  85 A sends a control signal to electric heater  54 A to stop operation. The rotation of organic Rankine cycle Turbine  57 A results in generator  73 A producing electric power that can be supplied to the load. Thus, now the heat produced by the combustion gasses from burner  51 A heats the working fluid in boiler  53 A that produces vapors for supply to turbine  57 A.  
         [0031]     When electric power becomes available from the electric grid once again, control  85 A senses the electric power and sends control signals to heater, i.e. burner,  51 A, to switch off, to the flap to open, to electric heater  54 A to switch on and to close valve  55 A so that no organic working fluid vapor is supplied via this valve to organic Rankine cycle turbine  57 A. Organic working fluid liquid continues to be suppied to  56 A of turbine  57 A as previously described via line  66 A, reservoir  64 A and line  65 A.  
         [0032]     Thus, in accordance with the present invention and with reference to  FIG. 2 , in standby mode or Phase  0  (see  FIG. 1A ) when line or utility power is available to supply the load, turbine  57 A is driven by motor  52 A. Also in this mode, boiler  53 A is heated by resistance or electric heater  54 A receiving line power from the utility or electric grid. Working fluid liquid supplied to reservoir  64 A is cooled in line  65 A and is supplied to bearings  56 A for providing lubrication of the bearings during rotation of turbine  57 A.  
         [0033]     In transient mode, phase  1   a  (see  FIG. 1B ), when utility failure occurs and line power is interrupted, kinetic energy present in turbine  57 A permits the turbine to continue rotating so that generator  73 A produces power that is supplied to the load via rectifier  76 A. Also, at the same time, valve  55 A begins to open so that organic working vapor can be supplied from boiler  53 A via conduit  71 A to turbine nozzle block  70 A in order that vapors are supplied to turbine  57 A for rotating it. In addition, simultaneously, ignition of burner  51 A commences while electric heater  54 A is switched off. Thereafter, in phase  1   b  (see  FIG. 1B ), valve  55 A having completed opening and continues to supplie vapors to turbine  57 A using heat present in boiler or vapor generator  53 A, generator  73 A produces power that is supplied to the load, fuel valve  72 A opens and burner  51 A. Consequently, boiler  53 A quickly produces rated flow of vaporized working fluid.  
         [0034]     Subsequently, when line power is unavailable, phase  1   c  (see  FIG. 1B ), in an active mode, boiler  53 A, heated by the continuous operation of burner  51 A, supplies rated flow of vaporized working fluid to turbine  57 A that drives generator  73 A for supplying power to the load.  
         [0035]     Turning to  FIG. 3 , numeral  10 B designates a further embodiment of a power unit system provided for supplying uninterruptible power in accordance to the present invention. It comprises a power unit system very similar to the embodiment described with reference to  FIG. 2  and operates on an organic working fluid. However, in the embodiment described with reference to  FIG. 3 , motor/generator  52 B is included such that when electric power is available at the electric grid motor/generator  52 B operates as a motor for rotating turbine  57 B. On the other hand, when no electric power is available on the electric grid, motor/generator  52 B operates as an electric generator in order that the rotation of turbine  57 B results in motor/generator  52 B producing electric power that can be supplied to the load.  
         [0036]     As far as  FIG. 4  is concerned, numeral  10 C designates an additional embodiment of the present invention wherein a power unit system is provided for supplying uninterruptible power in accordance to the present invention. Also here, this embodiment is similar to the embodiment described with reference to  FIG. 1  and in particular to the embodiment described with reference to  FIG. 2  and operates on an organic working fluid. In the present embodiment rather than using on-off valve  55 A or  55 B as shown in  FIGS. 1 and 2  respectively, conduit  59 C feeds one turbine nozzle out several or tens present in nozzle block  70 C so that a few percent of the organic working fluid vapors are fed to turbine  57 C via conduit  59 C for rotating it.  
         [0037]     Consequently, when electric power is available at the electric grid, a small amount of organic working fluid vapor is supplied via conduit  59 C and one nozzle of nozzle block  70 C to turbine  57 C for rotating the turbine. As a result, there is no need in this embodiment for an electric motor for rotating turbine  57 C when electric power is available from the electric grid. In addition, when no electric power is available on the electric grid, control valve  86 C that receives control signals from control unit  85 C supplies organic working fluid vapor to the rest of the nozzles in nozzle block  70 C for rotating turbine  57 C at full power.  
         [0038]     In these embodiments, if preferred, electric generator  73 A in  FIG. 2  can be a synchronous, homopolar, induction or permanent magnet generator, while motor  52 A can be an induction, synchronous or permanent magnet motor.  
         [0039]     Thus, in these embodiments, the use of organic Rankine cycle turbine  57 ,  57 A,  57 B and  57 C rotating when the line power is available, eliminates the need for using a battery or batteries.  
         [0040]     In addition, while the above description refers to the working fluid as an organic working fluid, the present includes water and its use in the Rankine cycle turbine system. In addition, of course, the water can be used as the working fluid in the Rankine cycle power plant systems that form part of the previously described embodiments.  
         [0041]     As far as  FIG. 5  is concerned, numeral  10 D designates an additional embodiment of the present invention for supplying uninterruptible power in accordance to the present invention. Basically, this embodiment is similar to previous described embodiments of the present invention, except that, in the present embodiment, the water working fluid is supplied from water storage tank  90 D via pump  56 D to boiler  53 D. Water storage tank  90 D itself is preferably supplied with treated water from water treatment system  91 D furnished with make-up water. In addition, in this embodiment the low-pressure steam exiting turbine  57 D, connected to high frequency asynchronous generator/motor  73 D, is supplied from turbine exhaust manifold  60 D via conduit  92 D to stack or chimney  94 D for exit to the atmosphere. Thus, turbine  57 D has an atmospheric exhaust, and comprises consequently a back-pressure steam turbine. Furthermore, in an alternative according to the present invention, conduit or line  92 D is preferably tapered at its outlet to stack  94 D in order to assist the draft produced in the stack or chimney. In such a case, flap F 3  can be connected externally to conduit or line  92 D at its outlet  93 D. In a further alternative, according to the present invention, portion of the exhaust steam exhausting turbine  57 D present in conduit or line  92 D can be mixed with treated water supplied to boiler  53 D in order to directly preheat the water supplied to the boiler. In a still further alternative, according to the present invention, exhaust steam exhausting turbine  57 D present in conduit or line  92 D can be used to indirectly preheat the treated water supplied to boiler  53 D. Condensate produced during such preheating can be supplied to water storage tank  90 D.  
         [0042]     Numeral  10 E in  FIG. 6  designates a still further embodiment of the present invention for supplying uninterruptible power in accordance to the present invention. Basically, this embodiment is also similar to the previous described embodiments of the present invention, and in particular to the embodiment, generator/motor  73 E is a synchronous or a homopolar generator/motor.  
         [0043]     Turning now to  FIG. 7 , numeral  10 F a still further embodiment of the present invention for supplying uninterruptible power in accordance to the present invention. Basically, this embodiment is similar to previous described embodiments of the present invention, except that, in the present embodiment, the working fluid, specifically water, is circulated in power unit  50 F with the aid of pump  56 F. In this embodiment, the low-pressure steam exiting turbine  57 F is supplied to turbine exhaust manifold  60 F and then to condenser  62 F, preferably an air-cooled condenser having a fan for supplying air to the condenser tubes, for producing steam condensate that is supplied using pump  56 F to boiler  53 F. In this embodiment, generator/motor  52 F connected to turbine  57 F can be a high frequency asynchronous generator/motor or alternatively a synchronous or a homopolar generator/motor.  
         [0044]     In operation, when the electric grid or utility is supplying electric line power, electric motor/generator  52 F operating as a motor rotates turbines  57 F via driver  75 F that receives power from the grid. Line  66 F receives sufficient organic working fluid vapor from boiler  53 F, heated by electric heater  54 F, for supplying fluid only to bearings  56 F. Heater, i.e. burner,  51 F is not operated and preferably a flap located on the stack of boiler  53 F is maintained in a closed state by an actuator. Thus, liquid supplied via line  66 A is supplied to reservoir  64 F. This condensate is supplied via line  65 A where it is cooled to bearings  56 F. Condensate exiting the bearings is supplied via pump  67 F, e.g. a pitot pump, to reservoir  64 F from where it is returned to bearings  56 F. Electric heater  54 F continues to supply heat to organic working fluid in boiler  53 AF for compensating for fluid finding its way back via line  68 F to vessel  69 F in heat relationship with boiler  53 F. Thus, under such conditions, the electric grid supplies power to the load and the organic Rankine cycle turbine system is maintained at hot standby.  
         [0045]     When the electric grid does not supply electric power, kinetic energy present in turbine  57 F permits power unit  10 F to continue to supply electric power even though no electric power is supplied to electric motor  52 F from the electric grid or utility. Valve  55 F is opened by control unit  85 F, which senses the state of the line power, in order that organic working fluid vapor is supplied from boiler  53 F via conduit  71 F to turbine nozzle block  70 F. Consequently, power is now produced by the rotation of organic Rankine cycle turbine  57 F rotated by organic working fluid vapor produced by heat present in the hot organic working fluid present in boiler  53 F. At the same time, the actuator opens the flap and heater, i.e. burner,  51 F, commences operation with the receipt of a control signal from control unit  85 F that also sends a control signal to open fuel valve  72 F. In addition, control unit  85 A sends a control signal to electric heater  54 F to stop operation. The rotation of organic Rankine cycle turbine  57 F results in motor/generator  52 F, now operating as a generator, producing electric power that can be supplied to the load. Thus, now the heat produced by the combustion gases from the burner  51 F heats the working fluid in boiler  53 F that produces vapors for supply to turbine  57 F.  
         [0046]     When electric power becomes available from the electric grid once again, control  85 F senses the electric power and sends control signals to heater, i.e. burner,  51 F, to switch off, to the flap to open, to electric heater  54 F to switch on and to close valve  55 F so that no steam is supplied via this valve to organic Rankine cycle turbine  57 F. Liquid water continues to be supplied to bearings  56 F of turbine  57 F as previously described via line  66 F, reservoir  64 F and line  65 F.  
         [0047]     While the embodiment described with reference to  FIGS. 5, 6  and  7  describe a generator/motor driven by turbine  57 D,  57 E and  57 F, if preferred, a separate generator and motor, e.g. like motor  52 A and generator  73 A described with reference to  FIG. 1 , can be used instead of the generator/motor.  
         [0048]     In addition, it should be pointed out that the present invention includes as well the method for operating the apparatus disclosed with reference to above-described figures.  
         [0049]     Moreover, it should be pointed out that, at present, the embodiment of the present invention described with reference to  FIG. 3  is considered the best mode for carrying out the present invention.  
         [0050]     Furthermore, when an organic working fluid is used as the working fluid in the Rankine cycle turbine system or systems, the working fluid is preferably chosen from the group chlorobenzene-dichlorobenzene, trichlorobenzene; bicyclic aromatic hydrocarbons; substituted bicyclic aromatic hydrocarbons, heterocyclic aromatic hydrocarbons, substituted heterocyclic aromatic hydrocarbons, bicyclic or heterobicyclic compounds where one ring is aromatic and the other condensed ring is non-aromatic, and their mixtures such as naphthalene, 1-methyl-napthalene, 1-methyl-napthalene, tetralin, quinolene, benzothiophene; an organic, alkylated heat transfer liquid fluid or a synthetic alkylated aromatic heat transfer fluid, e.g. thermal oils such as Therminol LT fluid (an alkyl substituted aromatic fluid), Dowtherm J (a mixture of isomers of an alkylated aromatic fluid), isomers of diethyl benzene and mixtures of the isomers and butyl benzene.  
         [0051]     Furthermore, while the above description refers to a hot standby mode of operation, the present invention is also operational in a warm standby mode wherein a battery is provided in addition to the Rankine cycle turbine system described above and detailed in the above-mentioned embodiments. In the warm standby mode, the battery provides power to the load after the line power has stopped supplying power to the load or the electric utility had failed and until the Rankine cycle turbine supplies the required power to the load. In this embodiment, the boiler is maintained warm (e.g. at about 60° C.) by e.g. an electric heater, like  54 A shown in  FIG. 2 , described above so that the period of time needed for the Rankine cycle turbine to start supplying the required power level to the load is relatively short (e.g. up to a half hour). Thus, the battery used in this configuration is relatively small.  
         [0052]     In addition, the units described in accordance with the present invention, can be used in a cold standby configuration, wherein a large battery is provided for supply power to the load when line power fails until nominal power is produced by the power unit. In such a system, the power until will commence operation when line power drops out.  
         [0053]     Furthermore, in accordance with the present invention, the power produced by the generator of the Rankine cycle turbine unit, e.g.  73 A of  FIG. 2 , etc., is preferably supplied to the load so that it threshold voltage is lower than that supplied to the load when line power is available. This permits the power produced by the Rankine cycle turbine unit to be supplied automatically to the load once the power from the grid or power utility had dropped below a certain predetermined threshold value. In the arrangement provided in accordance with the present invention, the need for using an additional or external rectifier can be saved. However, on the other hand, the line power can be supplied to the load via an additional or external rectifier.  
         [0054]     In addition, in accordance with the present invention, it should be pointed out that operation of Rankine cycle turbine unit using Therminol or Dowtherm J permits the unit to operate at a relatively high temperature. When operating with these working fluids, low losses in particular during standby operation when grid or utility power is rotating the turbine are achieved. In addition, such high temperature operation can reduce the size of the condenser.  
         [0055]     It is believed that the advantages and improved results furnished by the method and apparatus of the present invention are apparent from the foregoing description of the invention. Various changes and modifications may be made without departing from the spirit and scope of the invention as described in the claims that follow.