Abstract:
The present invention provides systems and methods for improving efficiency of power transformers by capturing heat energy that is produced by air breathing heat engine (ABHE) or a feed water heater to produce chillant. The systems of the present invention may be used with step-down or step-up power transformers. A heat energy dissipation device is in communication with the transformer and may recover heat energy from the ABHE and transformer. A refrigeration system is coupled to the dissipation device to use recovered heat energy to produce chillant which is supplied to the transformer and ABHE. The system may also include a gas compressor and post-compression and pre-compression heat exchangers; steam turbine engines, and power generators.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention.  
           [0002]    The present invention relates to power transformers, which may be step-up or step-down transformers.  
           [0003]    2. Description of the Related Art  
           [0004]    The manufacturing of electricity begins at the power plant, where natural gas, oil, coal or other fuels are burned in a boiler producing steam under high pressure and/or in air breathing heat engines (ABHE), which turns a turbine connected to a generator having a large magnet surrounded by coiled copper wire. The turbine causes the magnet to rotate inside the coils and generate electricity by creating a current in each coil.  
           [0005]    From the generator, the power is “stepped up” to a very high voltage by a large power transformer for more economical transmission over long distances to different substations. A substation is comprised of electrical apparatus that generally transforms the voltage to lower levels. From the substations the power then travels to other distribution transformers. These transformers again reduce the voltage to the 120-volt and 240-volt levels required for appliances and equipment.  
           [0006]    From the distribution transformers, the power is channeled to distribution panels and home circuit breakers. It is at this point that the power is divided up into several circuits that serve different loads.  
           [0007]    Generally, transformers are highly efficient and can deliver practically the full power received in the primary coil to the secondary coil. However, transformer losses, typically in the form of heat, can reduce transformer efficiency, resulting in a reduction of load that the transformer can serve. Examples of transformer losses affected by heat and load which can be metered are: copper loss, hyteresis loss, eddy current loss, iron loss, no-load loss, and impedance loss. In addition, heat from transformer losses can degrade the insulation of the transformer, leading to reduced life of the transformer.  
           [0008]    It is prudent to manage transformer losses to prevent overheating. Known systems address the overheat problem of power transformer by using fans or other cooling mechanisms such as cooling oil baths or electric refrigeration systems. Traditionally, the fans or the electric refrigeration systems utilize external sources of energy, therefore, they are not very efficient.  
           [0009]    Further improvements in power transformer systems are needed.  
         SUMMARY OF THE INVENTION  
         [0010]    The invention provides a system and method for improving the inner workings of a power transformer and simultaneously conditioning the intake air to an air breathing heat engine (ABHE) as taught in U.S. Pat. No. 4,936,109 of the present inventor. The inventive system also may modulate the heat from losses described herein and provide for the ‘on-line’ conditioning of the heat from a power transformer.  
           [0011]    In one embodiment of the present invention, the system for improving efficiency of power transformers includes a power transformer, a device for dissipating the heat energy, and a refrigeration system that uses the dissipated heat energy to produce a chillant. The chillant is then re-circulated and used to lower the temperature of the power transformer system. The device for dissipating the heat energy may be a liquid to liquid heat exchanger or a liquid to air heat exchanger. The refrigeration system may be an absorption chiller that employs heat energy to produce a chillant by energizing a staged process of concentration, condensation, evaporation and absorption of a mixture of gas and liquid.  
           [0012]    In another embodiment, the system may further include a gas compressor that generates heat energy during gas compression, and a device for recovering the heat energy to supply to the refrigeration system producing a chillate. The device for recovering heat energy may include a post-compression heat exchanger. The chillant from the refrigeration system is used in a heat exchange process to condition the intake air to the compressor. In this particular embodiment, the gas compressor may further include a pre-compression heat exchanger, which also receives the chillant from the refrigeration system and an embodiment to provide chillant for reducing the heat related transformer losses. The pre-compression heat exchanger serves to cool the intake gas prior to the compression process, so that the energy used for gas compression can be reduced.  
           [0013]    In yet another embodiment, the system of the present invention further includes an air breathing heat engine (ABHE) operably coupled to the gas compressor, whereby the gas compressor compresses air that flows through the ABHE. The compressed air is mixed with fuel, and ignited to create a combustion force to run the ABHE. At the same time, exhaust gas containing heat energy is produced. The ABHE has a device for recovering the heat energy from the exhaust gas. The device may be a post-combustion heat exchanger located downstream of the combustion area. The heat exchanger recovers heat energy from the exhaust gas by a heat exchange process. The recovered heat energy is then transferred to the refrigeration system for use in the production of chillant. The post-combustion heat exchanger is embodied to provide heat energy that can produce chillant from the refrigeration system to use in the heat exchange process. In a specific embodiment of the present invention, the ABHE may be connected, by a shaft, to a generator for power generation. The combustion force generated in the ABHE is used to drive the shaft, which in turn drives the generator.  
           [0014]    In an alternative embodiment, the system of the present invention includes a steam turbine, instead of the ABHE. The steam turbine receives pressurized steam from a steam source, such as a boiler. Once entering the steam turbine, the pressurized steam expands with an output of power that can drive a shaft to actuate a connected power generator. After complete expansion, the steam flows into a downstream condenser to be condensed and cooled. The steam changes to hot water carrying heat energy that can be transferred to the refrigeration system. The refrigeration system can use this additional heat energy for the production of chillant. The steam turbine may provide hot water to a connected hot water heater, which distributes hot water for various purposes.  
           [0015]    One advantage of the invention is that it provides the method for cooling the inner working of a transformer for all atmospheric and load conditions while other directed chillate is conditioning the ambient air stream to the ABHE which magnifies the amount of electrical energy for retail by 20-30% when ambient termperatures are around 95° F. (35° C.) compared to the through-put for turbine ISO or transformer nameplate rating. The chillate provides the means to protect the transformer against the damage of temperature rise due to the heat gain in the inherent losses. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0017]    [0017]FIG. 1 is a diagram showing an embodiment of the system of the present invention;  
         [0018]    [0018]FIG. 2 is a graph depicting rising transformer temperature and showing a zone in which chilled oil is used to augment ambient cooling;  
         [0019]    [0019]FIG. 3 is a diagram of another embodiment of the present invention, showing the heat generating section;  
         [0020]    [0020]FIG. 4 is a diagram of an alternative embodiment of the present invention, showing the heat generating section. 
     
    
       [0021]    Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplification set out herein illustrates an embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings.  
         [0023]    Referring now to FIG. 1, system  10  for improving a power transformer efficiency generally includes power transformer  20  generating heat through transformation losses such as heat due to resistance flow of current, heat due to hysteresis, heat due to eddy currents, and heat due to no-load. The efficiency of transformer  10  can be calculated in terms of energy units (kilowatt hour, Kwh):  
         Efficiency=Output/Input=Output ( Kwh )/[Output ( Kwh )+Heat loss ( Kwh )] 
         [0024]    The voltage regulation of transformer  20  is the percentage change in the output voltage from no-load to full-load. [% Regulation=(no-load voltage−load voltage)×100/load voltage)]. Ideally, there should be no change in the transformer&#39;s output voltage from no-load to full-load. In such a case, the voltage regulation is 0%. To get the best performance out of a transformer, it is necessary to have the lowest possible voltage regulation.  
         [0025]    Power transformer  20  may be any commercially available transformer, such as any one of the common classes of transformers listed in TABLE 1.  
                             TABLE 1                           The most common classes of transformer       THE MOST COMMON CLASSES OF TRANSFORMER            CLASS       COOLING METHOD               OA   OUTSIDE-AIR   SELF-COOLED (BY CONVECTION)       OA/FA   OUTSIDE-AIR/FAN-AIR   SELF-COOLED OR FAN COOLED       OA/FA/FA   OUTSIDE-AIR W/2 FAN   SELF-COOLED/FAN COOLED           COOLING SETS       OA/FA/FOA   OUTSIDE-AIR/FAN-AIR/FORCED (PUMPED) OIL   SELF-COOLED, FAN COOLED PUMPED OIL       FOA   FORCED OIL/FAN COOLED   PUMPED OIL WITH FANS       AA   AIR-AIR DRY TYPE (OR CAST INSULATION)   SELF COOLED (BY CONVECTION)       AA/FA   AIR-AIR/FAN-AIR IN DRY TYPE   SELF-COOLED WITH FANS                  
 
         [0026]    Transformer  20  may have transformer coil (not shown) that is made of any suitable material such as copper wire. In an oil cooled transformer where the hot spot temperature changes the heat of the coil, for example from 95° C. to  115 ° C., the resistance to current flow would be increased by: (115° C.-95° C.=) 20° C.×43%/100° C.=8.3%. The increased resistance produces lower voltage.  
         [0027]    By the theorem of Similar Triangles, calculations can be made for comparing power and energy lost in transformer due to increase in resistance within the secondary coil. For example (See FIG. 2), by limiting the rise in the oil temperature an average of 126° F. (52° C.) to 221° F. (105°) when ambient temperature is 95° F. (35° C.), and absolute zero is 459° F. (237.2° C.) these losses are reduced by 4.0% when compared to 248° F. (120° C.) hot spot (See calculation below):  
           R   248       R   221       =         459   +   153   +   95       459   +   126   +   95       =   1.04                           
 
         [0028]    Similarly when ambient is 50° F. (10° C.) and the oil temperature rise is limited to an average 110° .F (43.3° C.), the resistance to current flow is decreased by 14.0% and the current flow could be increased by 14.0% when compared to 248° F. (120° C.) hot spot (See calculation below):  
           R   248       R   160       =         459   +   153   +   95       459   +   110   +   50       =   1.14                           
 
         [0029]    Power transformer  20  may have various built-in overload capabilities, and existing cooling method as shown in TABLE 1. The existing cooling method requires a supply of external energy. For example, a cooling fan requires a connection to an outside electrical source. The existing cooling method may be replaced or complemented by system  10  of the present invention.  
         [0030]    System  10  further includes device for dissipating heat energy  30  in communication with power transformer  20 . According to FIG. 1, device for dissipating heat energy  30  includes heat exchanger  31 . Heat exchanger  31  may include elongated tube  29  defining interior space  32  and hollow coil  33  disposed within interior space  32  and extending from inlet connection  41  along the length of tube  29  to outlet connection  40 . Medium line  24  has first end  34  connected to power transformer  20 , and second end  35  open into interior space  32  at first end  36  of tube  29 . First end  34  of first medium line  24  is connected to power transformer  20  through valve  50 , which can open when the internal temperature of power transformer  20  reaches a predetermined temperature, and can close as the internal temperature of power transformer  20  drops below the predetermined temperature. Medium return line  25  has a first end  43  open into interior space  32  at second end  37  of tube  29 , and second end  44  in communication with power transformer  20 .  
         [0031]    First chillant line  52  and first chillant return line  53  are in communication with heat exchanger  31  and refrigeration system  60 . First chillant line  52  has first end  55  connected to and in communication with refrigeration system  60 , and second end  54  connected to and in communication with hollow coil  33  at inlet connection  41  of tube  29 . First chillant return line  53  has first end  57  connected to and in communication with hollow coil  33  at outlet connection  40  of tube  29 , and second end  56  connected to and in communication with refrigeration system  60 .  
         [0032]    Refrigeration system  60  may include any suitable absorption chiller or refrigeration generator available in the market. Examples of absorption chillers and refrigeration generators that can be used in system  10  are described in U.S. Pat. No. 4,936,109, the disclosure of which is herein fully incorporated by reference. Generally, an absorption chiller or a refrigeration generator employs heat energy to energize a staged process of concentration, condensation, evaporation and absorption to provide a chillant for cooling purposes. The chillant may be in a fluid form, such as water or gas.  
         [0033]    As depicted in FIG. 1, refrigeration system  60  produces chillant  62  that is transferred through first chillant line  52  into hollow coil  33  at inlet connection  41  of heat exchanger  31 . At the same time, heat energy from transformer losses is transferred to medium  21 , which may be an oil, water, a gas, or any other cooling fluid that circulates inside power transformer  20 . Medium  21  becomes heated medium  22  as the temperature rises. When the temperature of heated medium  22  reaches a pre-determined temperature, valve  50  opens to release heated medium  22  into medium line  24 . The ambient temperature may affect the temperature of medium  21 , but will not influence the operation of valve  50 .  
         [0034]    Heated medium  22  from medium line  24  enters interior space  32  of tube  29  at first end  36 . While in tube  29 , heat energy is transferred to chillant  62  in hollow coil  33  by a heat transfer process, resulting in cool medium  21 , and heated chillant  64 . The initial temperature of chillant  62  may be about 50° F. (10° C.). After the heat transfer process, the temperature of heated chillant  64  may reach a about 80° F. (29.4° C.). Cool medium  21  exits tube  29  from second end  37  and enters medium return line  25  to travel back to power transformer  20 . Cool medium  21  circulates inside power transformer  20  to capture additional heat energy released from power transformer  20 . Simultaneously, heat energy captured in heated chillant  64  is transferred to refrigeration system  60  to energize a staged process of concentration, condensation, evaporation and absorption to produce chillant  62  having a sufficiently cool temperature.  
         [0035]    In another embodiment of the present invention, as shown in FIG. 3 in addition to all components of system  10  in FIG. 1, system  70  further includes gas compressor  72 , and post-compression heat exchanger  80  positioned downstream of gas compression area  75  within gas compressor  72 . Post-compression heat exchanger  80  may include sensible cooling coil  78  which receives chillant  62  from refrigeration system  60 . Sensible cooling coil  78  extends within compressor  72 . When gas is compressed, a certain amount of heat energy is released. The heat energy is transferred to chillant  62  within sensible cooling coil  78  by a heat exchange process. As a result, chillant  62  becomes heated chillant  64 , which is transferred back to refrigeration system  60 . Refrigeration system  60  uses the heat energy in the staged process of concentration, condensation, evaporation, and absorption to produce another chillant  62 , as described hereinabove.  
         [0036]    System  70  further includes second chillant line  82 , and second chillant return line  83 . Second chillant line  82  is connected to and in communication with refrigerator system  60  and post-compression heat exchanger  80 . Second chillant line  82  may have a first end  84  branching from first chillant line  52 . First end  84  and first chillant line  52  may form a T-position  85 , allowing chillant  62  produced by refrigeration system  60  to move in two directions, one within first chillant line  52  toward heat exchanger  31  (see FIGS. 1 and 3), another within second chillant line  83  toward post-compression heat exchanger  80 . Second end  88  of chillant line  82  connects to first end  89  of sensible cooling coil  78 .  
         [0037]    Second chillant return line  83  is connected to and in communication with post-compression heat exchanger  80  and refrigeration system  60 , allowing heated chillant  64  to be transferred from post-compression heat exchanger  80  to refrigeration system  60 . Second chillant return line  83  has first end  90  connected to second end  92  of sensible cooling coil  78 . Second end  91  of second chillant return line  83  may form a T-position  86  with first chillant return line  53 . Heated chillant  64  from first chillant return line  53  and second chillant return line  83  combine at T position  86  before moving along chillant return line  53  toward refrigeration system  60 .  
         [0038]    In an alternative embodiment (not shown), first end  84  of second chillant line  82  may be in direct communication with refrigeration system  60 , without first joining first chillant line  52 . Similarly, second end  91  of second chillant return line  83  may be in direct communication with refrigeration system  60 , without first joining first chillant return line  53 . In this specific embodiment, chillant  62  from refrigeration  60  will be transferred through a separate second chillant line  82  all the way to post-compression heat exchanger  80 . Likewise, heated chillant  64  from post-compression heat exchanger  80  will be transferred through a separate second chillant return line  83  all the way to refrigeration system  60 .  
         [0039]    As further shown in FIG. 3, system  70  may include pre-compression heat exchanger  71  positioned within compressor  72  upstream of post-compression heat exchanger  80  for cooling the gas that enters compressor  72  prior to or at the same time as gas compression. Lowering the temperature of the gas, prior to or simultaneously with the gas compression, reduces the energy required to compress the gas.  
         [0040]    Heat exchanger  71  may include air condition coil  74  in communication with second chillant line  82  through extension line  94 , and second chillant return line  83  through extension line  95 . Air condition coil  74  receives chillant  62  from refrigeration system  60  through second chillant line  82  and extension line  94 , and returns heated chillant  64  to refrigeration system  60  through extension line  95  and second chillant return line  83 .  
         [0041]    In operation, compressor  72  may be driven by any power engine, such as a steam turbine engine, an electric motor, internal combustion engine. Air supplied through gas intake  73  flows through pre-compression heat exchanger  71 , whereby heat energy in the air is transferred by a heat exchange process into chillant  62  contained in air condition coil  74 . The air is compressed in compressor  72 , releasing heat energy. The compressed air then passes post-compression heat exchanger  80 , and through compressed gas line  76  to a place where the compressed air is to be used or stored. Post-compression heat exchanger  80  recovers heat energy by a process of heat exchange, wherein heat energy is transferred to chillant  62  in sensible cooling coil  78 , producing heated chillant  64 . Heated chillant  64  from pre-compression heat exchanger  71  combined with that from post-compression heat exchanger  80  is transferred to refrigeration system  60 , which uses the combined heat energy to produce chillant  62 , in the same way as what described herein above. Chillant  62  is circulated back to air condition coil  74  and sensible cooling coil  78 . In one example, chillant  62  has a temperature of 42° F. (5.6° C.) when it is supplied to sensible cooling coil  78  and air condition coil  74 , whereas, heated chillant  64  may have a temperature of 52° F. (11° C.) when heated chillant  64  returns to refrigeration system  60 .  
         [0042]    In FIG. 3, system  70  further includes air breathing heat engine (ABHE)  100 . As is conventional, air breathing heat engine  100  includes combustor  101  and turbine  102  which utilizes combustion force from combustor  101  to drive shaft  103 . Shaft  103  is drivingly connected to a generator  106  for power generation.  
         [0043]    Air breathing heat engine  100  is positioned downstream of compressed gas line  76 . Compressed air from compressor  72  is mixed with injected fuel in combustor  101  and the air and fuel mixture is ignited resulting in a combustion force that drives shaft  103  to actuate generator  106 . Exhaust gas  107  is produced as a result of the combustion is ported via conduit  108  to a waste heat recovery unit  111 , having combustion heat exchanger  112  positioned within flue  117  of heat recovery unit  111 . Combustion heat exchanger  112  includes at least one chillant coil  113  receiving chillant  62  from refrigeration system  60 . As demonstrated in FIG. 3, combustion heat exchanger  112  includes top chillant coil  114  stacked above bottom chillant coil  115 . Both top chillant coil  114  and bottom chillant coil  115  are connected to and in communication with chillant supply line  116  and chillant return line  118 .  
         [0044]    In operation, heat energy from exhaust gas  107  in waste recovery unit  111  is captured in chillant  62  within top chillant coil  114  and bottom chillant coil  115 . Chillant  62  becomes heated chillant  64 , leaving waste recovery unit  111  through chillant return line  118  to refrigeration system  60 . The heat energy is used by refrigeration system  60  to produce chillant  62 , as described above. Chillant  62  circulates back to top chillant coil  114  and bottom chillant coil  115  via chillant supply line  116 .  
         [0045]    In a specific embodiment of the present invention (not shown), air breathing heat engine  100  may further include an acoustic enclosure, as described in U.S. Pat. No. 6,082,094, the disclosure of which is herein incorporated by reference. Refrigeration  60  may supply chillant  62  for ventilating the acoustic enclosure via appropriate chillant supply line connection (not shown) or through an additional heat exchanger placed within the acoustic enclosure, or as described in U.S. Pat. No. 6,082,094.  
         [0046]    Returning to FIGS. 1 and 3, refrigeration system  60  of system  10  and  70  may simultaneously receive heat energy from power transformer  20 , compressor  72 , and air breathing heat engine  100 , and use the combined heat energy to generate chillant  62 . Chillant  62  may be supplied to one or more heat exchangers for various cooling purposes as described above.  
         [0047]    In another embodiment shown in FIG. 4, system  120  includes steam turbine  121  connected to and in communication with refrigeration  60 . Refrigeration system  60  is connected to power transformer  20  in the same fashion, as shown in FIG. 1. Generally, steam turbine  121  releases heat energy which is transferred to refrigeration system  60  for use in the production of chillant  62 , similar to what discussed hereinabove.  
         [0048]    Steam turbine  121  may be any known steam turbine that has a suitable configuration. For example, as depicted in FIG. 4, steam turbine  121  includes steam condenser  122  in communication with turbine engine  123 . Turbine engine  123  includes shaft  125  connected to power generator  126 , or other machine or equipment that is operable using power from an engine. Steam turbine  121  receives condensed steam from a source, which can be a boiler of a compatible capacity. The condensed steam enters steam turbine  121  through steam inlet pipe  128  and expands in turbine engine  123 , with an output of power driving shaft  125  to actuate power generator  126 . After complete expansion, the expanded steam flows to steam condenser  122  from turbine engine  123  through an appropriate exhaust steam casing (not shown), and is condensed to hot water. Expanded steam or hot water can be returned to the steam source or the boiler through return pipe  129 . Some excess hot water  130  containing heat energy which may be at a temperature of about 210° F. (98.9° C.), may flow through first hot water pipe  132  from condenser  122  to refrigeration system  60 . Refrigeration system  60  uses the heat energy for the production of chillant  62  for cooling power transformer  20  (see FIG. 1).  
         [0049]    Additional hot water or working fluid  133  may flow through second hot water pipe  134  to hot water heater  140 , which is connected to steam turbine  121 . It is also possible to have excess steam from turbine engine  123  to flow through steam pipe  136  to supply heat to hot water heater  140 .  
         [0050]    Hot water or working fluid  141 , which is a residual hot water derived from hot water  130  flowing through refrigeration system  60 , wherein a portion of heat is extracted from hot water  130  for the production of chillant  62 , may be supplied to hot water heater  140  through third hot water pipe  142 . Output hot water  150  from hot water heater  140  can be distributed for various heating purposes.  
         [0051]    In a specific embodiment (not shown), condenser  122  may contain a heat exchanger that can capture heat energy from condensing the steam. The captured heat energy can then be transferred to refrigeration system  60 , similar to what have been discussed above as relating to gas compressor  72 .  
         [0052]    Further, it is possible to combine the embodiments shown in FIGS. 3 and 4, so that both steam turbine  121  and air breathing heat engine  100  are components of the same system. Both turbine  121  and air breathing heat engine  100  may produce heat energy that together can be supplied to refrigeration system  60 . In addition, if air breathing heat engine  100  produces excess heat, the heat energy may be used to heat the water in the connected hot water heater  140 . For particular applications and circumstances, the amount of generated heat apportioned to refrigeration system and hot water heater  140  may be adjusted.  
         [0053]    It is one advantage of the present invention to protect power transformer  20  by keeping power transformer  20  at a suitable temperature, regardless of the ambient temperature. It is another advantage of the present invention to use one on-line refrigeration system  60  to produce chillant  62  for cooling different components of a power generation system. Refrigeration system  60  takes advantage of heat energy that is released from internal sources within the system, and minimizes external energy requirements.  
         [0054]    While the present invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.