Abstract:
Apparatus for producing uninterruptible power upon loss of power from an electric grid, comprising at least one hot standby organic Rankine cycle turbine system including a vapor turbine and a generator for producing power upon loss of power from the electric grid; a control unit for sensing loss of power from the electric grid and activating the hot standby organic Rankine cycle turbine system; and means for rotating the turbine when power is available from the electric grid. In addition, a method for producing uninterruptible power upon loss of power from an electric grid, said method comprising the steps of: providing at least one hot organic Rankine cycle turbine system including a vapor turbine and a generator for producing power upon loss of power from the electric grid; sensing loss of power from the electric grid and activating the hot standby organic Rankine cycle turbine system; and rotating the turbine in the hot standby organic Rankine cycle turbine system when power is available from the electric grid.

Description:
TECHNICAL FIELD 
     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 such as communication systems that are also located in urban areas or in the vicinity of towns and also only stand alone systems. 
     BACKGROUND OF THE INVENTION 
     In systems provided for providing uninterruptible power particularly for communication systems several options have been available: photovoltaic systems, thermoelectric generators (TEG) or organic Rankine cycle energy converters (OEC). In addition, uninterruptible power sources (UPS) for short time periods as well as UPS&#39;s and diesel generators for long time use or diesel generators and a flywheel system. 
     In photovoltaic systems, batteries are used to compensate for the hours/days without solar radiation. Usually, the batteries are very large and, in most cases, the choice is for Nickel-Cadmium batteries. The reason is that the photovoltaic systems require batteries to work on deep discharge cycles, for which the Ni-Cad batteries are much better adapted than Lead Acid batteries. The problems are—very high cost for batteries and the need for maintenance of the batteries. In any case, in a 20-year project, the Ni-Cad batteries have to be replaced at least once. In telecommunication systems powered by photovoltaic cells need always batteries. 
     As far as thermoelectric generators (TEG) are concerned, since telecommunication equipment operates at varying load, and the TEG are continuously delivering full rated power, batteries are necessary for correcting the supply of power to the equipment. Moreover, the TEG requires use of dummy loads for dissipating the surplus of power delivered and not used by the telecommunications equipment. As TEG cannot trickle charge the batteries, additional battery chargers are required. If not, the battery will not be properly charged, and will require additional maintenance and manual charging during maintenance and the lifetime will decrease. The telecommunication systems powered by TEG always need batteries. 
     Turning to organic Rankine cycle energy converters (OEC), since they operate at varying load, they can trickle charge the batteries and thus increase their lifetime. In telecommunication systems, the OECs can be used in hot standby configuration. If one OEC fails, the second will deliver the full station load. The transient period until the second OEC will deliver the full load is of a few minutes (up to about 20-50 minutes) and could be reduced by either adding a very small standard battery to OECs to deliver a few AH during the transient period. 
     In a related system disclosed in U.S. Pat. No. 4,982,589, the disclosure of which is hereby incorporated by reference, a hybrid power plant 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 time-wise, 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. 
     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. 
     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. 
     In addition, the battery condition cannot be correctly assessed, and it will normally fail without any kind of advance notice, thus causing shut down of the stations. Moreover, the battery fails when they are actually needed so that, when there is an electric grid power outage, the diesel generator fails when it is attempted to start it consequently causing the battery, UPS and diesel generator not to provide power. 
     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 
     Apparatus for producing uninterruptible power according to the present invention comprises a hot standby organic Rankine cycle turbine system. No batteries are needed in the present invention. In one embodiment of the present invention apparatus for producing uninterruptible power according to the present invention includes a high-speed flywheel; and a single hot standby organic Rankine cycle turbine system. In another embodiment of the present invention apparatus for producing uninterruptible power according to the present invention includes two hot standby organic Rankine cycle turbine systems operating in parallel. In this embodiment both hot standby organic Rankine cycle turbine systems include a sonic nozzle for ensuring that the pressure in the boiler of the hot standby organic Rankine cycle turbine system operates at relatively high pressure. Furthermore in this embodiment one hot standby organic Rankine cycle turbine system includes a control valve for opening and closing in accordance with the output of the generator of the other hot standby organic Rankine cycle turbine system. In addition, here the other hot standby organic Rankine cycle turbine system also includes a control valve for opening and closing in accordance with the output of the generator of the other hot standby organic Rankine cycle turbine system. In this embodiment, the relatively high pressure of the boiler is suitable for producing full power output from the organic Rankine cycle turbine included in said hot standby organic Rankine cycle turbine system. 
     Furthermore in the embodiment of the present invention including a high-speed flywheel a motor is included for rotating the turbine when electric power is available from the electric grid. This embodiment also includes a heater comprising a burner for combusting fuel. In addition, the present embodiment includes an electric heater for heating to liquid organic working fluid when electric power is available from the electric grid. Moreover, in the present embodiment a three-way valve is included for supplying, when electric power is available from the electric grid, sufficient organic working fluid vapor for operation of the turbine bearings only. 
     In addition, the present invention includes a method for producing uninterruptible power and comprises the step of providing a hot standby organic Rankine cycle turbine system for producing uninterruptible power. In one embodiment of the method for producing uninterruptible power a high-speed flywheel is provided; and a hot standby organic Rankine cycle turbine system that produces power is provided. In a further embodiment of the method for producing uninterruptible power by providing a hot standby organic Rankine cycle turbine system two hot standby organic Rankine cycle turbine systems operating in parallel are provided. In this embodiment, relatively high pressure is maintained in the boiler of the hot standby organic Rankine cycle turbine system by using a sonic nozzle for supplying organic working fluid vapor to the organic turbine. Furthermore, in the present embodiment, a control valve is provided for supplying further working fluid vapor from the boiler to the organic turbine in response to a signal from the output of the generator of the other hot standby turbine when the output falls below a certain threshold such that the output of the first hot standby organic Rankine cycle turbine is substantially full power. In addition, in this embodiment relatively high pressure is maintained in the boiler of the other hot standby organic Rankine cycle turbine system by also using a sonic nozzle for supplying organic working fluid vapor-to the organic turbine of the other hot standby organic Rankine cycle turbine system. Moreover, in the present embodiment a control valve is provided for supplying further working fluid vapor from the boiler to the organic turbine contained in the other hot standby organic Rankine cycle turbine system in response to a signal from the output of the generator of the first hot standby turbine when the output falls below a certain threshold such that the output of the other hot standby organic Rankine cycle turbine is substantially full power. Additionally, in this embodiment, the relatively high pressure maintained in the boiler of the hot standby organic Rankine cycle turbine system is such that the relatively high pressure of the boiler is suitable for producing full power output from the organic Rankine cycle turbine included in said hot standby organic Rankine cycle turbine system. 
     Furthermore, in the embodiment of the method for producing uninterruptible power in which a high-speed flywheel; and a hot standby organic Rankine cycle turbine system that produces power are provided, an electric motor is operated for rotating the turbine when electric power is available from the electric grid. In this embodiment, sufficient organic working fluid vapor is supplied to the condenser for supplying organic working fluid condensate only to the bearings of the turbine when electric power is available from the electric grid. In addition, in the present embodiment, an electric heater is operated when electric power is available from the electric grid that heats the organic working fluid liquid present in a boiler such that sufficient organic working fluid vapor is produced for supplying organic working fluid condensate from the condenser only to the bearings of the turbine. Furthermore, in this embodiment, power is supplied to the electric grid using the high-speed flywheel when electric power is not available from the power grid. Moreover, in accordance with the present embodiment, organic working fluid vapor is supplied only to the nozzles of the turbine and the turbine is rotated using heat stored in the heated working fluid present in the boiler of the hot standby organic Rankine cycle turbine system when electric power is not available from the power grid. In addition, a burner for heating the organic working fluid liquid present in said boiler is switched on when electric power is not available from the power grid. Additionally, the electric heater is switched off when electric power is not available from the power grid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention are described by way of example, and with reference to the accompanying drawings wherein: 
     FIG. 1 is a schematic diagram of apparatus typical of the prior art; 
     FIG. 2 is a schematic diagram of an embodiment of the present invention; 
     FIG. 3 is a schematic diagram of a modification of the embodiment of the present invention shown in FIG. 2; 
     FIG. 4 is a schematic diagram of a further modification of the embodiment of the present invention shown in FIG. 2; 
     FIG. 5 is a schematic diagram of another embodiment of the present invention. 
    
    
     Like reference numerals and designations in the various drawings refer to like elements. 
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, reference numeral  10  designates a typical power producing station having a pair of organic Rankine cycle turbine systems  20  and  50 . In this system, both organic Rankine cycle turbine systems ate provided and operate at half power or half load in order to provide extra reliability to the system. Thus, if, e.g., maintenance needs to be carried out to one of the systems  20  or  50 , the other system can remain operating at full power or full load thus permitting the station to continue operating at full load capacity. Battery or batteries  40  are provided to permit the transfer from operation with both systems  20  and  50  operating to the operation of one system, system  20  or  50 , with full load capacity still being maintained at the station. 
     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 high-speed flywheel  20 A and single 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. This 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 power is available from the electric grid. Moreover, in the present embodiment, three-way valve  55 A is included that enables the supply, when electric power is available from the electric grid, of sufficient organic working fluid vapor only for operation of the bearings  56 A of turbine  57 A. 
     In operation, when the electric grid is supplying electric power, electric motor  52 A rotates turbine wheel  58 A of turbine  57 A via inverter  75 A that receives DC (bas) from uninterruptible power source (UPS)  80 A. Three-way valve  55 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 flap  68 A is maintained in a closed state by actuator  69 A. Thus, three-way valve  55 A supplies organic working fluid vapor from boiler  53 A via bleed conduit  58 A to exhaust block  59 A. These vapors are then supplied via conduit  61 A to condenser  62 A where they are cooled producing organic working fluid condensate. This condensate is supplied via conduit  63 A, header  64 A and conduits  65 A and  66 A to bearings  56 A. Condensate exiting the bearings is supplied via pump  67 A, e.g. a pitot pump, to a small reservoir 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 to boiler  53 A. 
     When the electric grid does not supply electric power, power stored in flywheel  20 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. Three-way valve  55 A os switched 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, with the supply of vapors via conduit  58 A to exhaust block  59 A being shut. Consequently, power is now produced by the rotation of turbine wheel  58 A rotated by organic working fluid vapor produced by heat stored in the hot organic working fluid present in boiler  53 A. At the same time, actuator  69 A opens flap  68 A 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 turbine wheel  58 A results in generator  73 A producing electric power. 
     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 flap  68 A to close, to electric heater  58 A to switch on and to three-way valve  55 A to supply organic working fluid vapor only to exhaust block  60 A for operation of the bearings  56 A of turbine  57 A. 
     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 and comprises a power unit system very similar to the embodiment described with reference to FIG.  2 . 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 electric grid. 
     As far as FIG. 4 is concerned, numeral  10 C designates an additional embodiment of the present invention for supplying uninterruptible power in accordance to the present invention. Also here, this embodiment is similar to the embodiment described with reference to FIG.  2  and in particular to the embodiment described with reference to FIG.  3 . In the present embodiment rather than using three-way valve  55 A or  55 B as shown in FIGS. 2 and 3 respectively, conduit  59 C feeds one turbine nozzle out of several or tens present in nozzle block  70 C so that a few percent of the organic working fluid vapors are fed to turbine wheel  58 C via conduit  59 C for rotating it. 
     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 wheel  58 C for rotating the turbine wheel. As a result, there is no need in this embodiment for an electric motor for rotating turbine wheel  58 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 wheel  58 C at full power. 
     In these embodiments, if preferred, turbine wheel  58 A,  58 B and  58 C can function as a flywheel such that flywheel  20 A can be eliminated. Furthermore, electric generator  73 A in FIG. 1 can be a synchronous, homopolar, induction or permanent magnet generator, while motor  52 A can be an induction, synchronous or permanent magnet motor. 
     Thus, in these embodiments, the use of flywheel  20 A,  20 B and  20 C or turbine wheel  58 A,  58 B and  58 C operating as a flywheel, eliminates the need for using a battery or batteries. 
     Turning to FIG. 5, power producing station  10 D is provided in accordance with a still further embodiment of the present invention in order that uninterruptible power can be produced at all times. Organic Rankine cycle turbine systems  20 D and  50 D are provided in accordance with the present invention with sonic nozzles  22 D and  52 D respectively that permit the pressure in boilers  23 D and  53 D to be maintained at a relatively high pressure so that any one of systems  20 D or  50 D can quickly provide full power when needed. The pressure maintained in boilers  23 D and  53 D is substantially the pressure needed to operate either of organic turbine  24 D and  54 D at full power or full load capacity of load  40 D. Each system  20 D or  50 D is also provided with control valve  25 D and  55 D respectively so that sufficient vapors can be supplied from boilers  23 D and  53 D to organic turbine  24 D and  54 D in order that the turbines whenever required can quickly produce full power. 
     In normal operation, organic Rankine cycle turbine systems  20 D and  50 D operate so that organic turbines  24 D and  54 D receive sufficient organic working fluid vapors from boilers  23 D and  53 D respectively via sonic nozzles  22 D and  52 D to drive electric generators  26 D and  56 D in order that each of them produce half power or half load capacity. As can be seen from FIG. 5, heat is supplied to boilers  23 D and  53 D by use of heaters  21 D and  51 D, for example burners, the operations of which are controlled by fuel valves  28 D and  58 D regulated by controls  30 D and  60 D respectively. Expanded organic working fluid exiting each organic turbine  24 D and  54 D is supplied to organic working fluid condensers  27 D and  57 D respectively so that organic working fluid condensate produced therein is supplied via, for example, pump  29 D or  59 D, to boilers  23 D and  53 D. When one of systems  20 D and  50 D begins to reduce its power output, control line  28 D or  58 D senses the drop in the power output of one of electric generators  26 D or  56 D and one of controls  30 D or  60 D supplies a control signal to one of control valves  25 D and  55 D so that these valves are opened. Consequently, sufficient organic working fluid is now supplied to one of organic turbines  24 D and  54 D so that one of electric generators  26 D and  56 D produces full power. Once the other organic Rankine cycle turbine system, either  20 D or  50 D returns to half power or half load capacity, line  28 D or  58 D senses the increase in the power output of the respective electric generator,  26 D and  56 D, and thus a control signal is supplied by control  30 D or  60 D to the respective control valve,  25 D and  55 D, so that this valve is now closed ensuring that only sufficient organic working fluid vapor is supplied to the respective organic turbine  24 D and  54 D in order that half power or half load capacity is now produced by the organic turbine. 
     Thus, according to the embodiment of the present invention described with reference to FIG. 5, due to the pressure of high pressure in boilers  23 D and  53 D, no battery or batteries are needed or necessary in the operation of this embodiment. 
     Furthermore, 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. 
     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.